Initial version of grid atlas packer, CLI integration

README.md

@@ -88,11 +88,22 @@ Use the following command line arguments for the standalone version of the atlas
 Alternativelly, the minimum possible dimensions may be selected automatically if a dimensions constraint is set instead:
 
 - `-pots` – a power-of-two square
-- `-potr` – a power-of-two square or rectangle (2:1)
+- `-potr` – a power-of-two square or rectangle (typically 2:1 aspect ratio)
 - `-square` – any square dimensions
 - `-square2` – square with even side length
 - `-square4` (default) – square with side length divisible by four
 
+### Uniform grid atlas
+
+By default, glyphs in the atlas have different dimensions and are bin-packed in an irregular fashion to maximize use of space.
+With the `-uniformgrid` switch, you can instead force all glyphs to have identical dimensions and be laid out in a grid.
+In that case, these additional options are available to customize the layout:
+
+- `-uniformcols <N>` &ndash; sets the number of columns
+- `-uniformcell <width> <height>` &ndash; sets the dimensions of the grid's cells
+- `-uniformcellconstraint <none / pots / potr / square / square2 / square4>` &ndash; sets constraint for cell dimensions (see explanation of options above)
+- `-uniformorigin <yes / no / horizontal / vertical>` &ndash; sets whether the glyph's origin point should be fixed at the same position in each cell
+
 ### Outputs
 
 Any non-empty subset of the following may be specified:
@@ -105,9 +116,9 @@ Any non-empty subset of the following may be specified:
 
 ### Glyph configuration
 
-- `-size <EM size>` &ndash; sets the size of the glyphs in the atlas in pixels per EM
-- `-minsize <EM size>` &ndash; sets the minimum size. The largest possible size that fits the same atlas dimensions will be used
-- `-emrange <EM range>` &ndash; sets the distance field range in EM's
+- `-size <em size>` &ndash; sets the size of the glyphs in the atlas in pixels per em
+- `-minsize <em size>` &ndash; sets the minimum size. The largest possible size that fits the same atlas dimensions will be used
+- `-emrange <em range>` &ndash; sets the distance field range in em's
 - `-pxrange <pixel range>` (default = 2) &ndash; sets the distance field range in output pixels
 - `-pxalign <on / off / horizontal / vertical>` (default = vertical) &ndash; enables or disables alignment of glyph's origin point with the pixel grid
 

msdf-atlas-gen/GlyphGeometry.cpp

@@ -92,6 +92,37 @@ void GlyphGeometry::wrapBox(double scale, double range, double miterLimit, bool
     }
 }
 
+void GlyphGeometry::frameBox(double scale, double range, double miterLimit, int width, int height, const double *fixedX, const double *fixedY) {
+    scale *= geometryScale;
+    range /= geometryScale;
+    box.range = range;
+    box.scale = scale;
+    box.rect.w = width;
+    box.rect.h = height;
+    if (fixedX && fixedY) {
+        box.translate.x = *fixedX/geometryScale;
+        box.translate.y = *fixedY/geometryScale;
+    } else {
+        double l = bounds.l, b = bounds.b, r = bounds.r, t = bounds.t;
+        l -= .5*range, b -= .5*range;
+        r += .5*range, t += .5*range;
+        if (miterLimit > 0)
+            shape.boundMiters(l, b, r, t, .5*range, miterLimit, 1);
+        if (fixedX)
+            box.translate.x = *fixedX/geometryScale;
+        else {
+            double w = scale*(r-l);
+            box.translate.x = -l+.5*(box.rect.w-w)/scale;
+        }
+        if (fixedY)
+            box.translate.y = *fixedY/geometryScale;
+        else {
+            double h = scale*(t-b);
+            box.translate.y = -b+.5*(box.rect.h-h)/scale;
+        }
+    }
+}
+
 void GlyphGeometry::placeBox(int x, int y) {
     box.rect.x = x, box.rect.y = y;
 }
@@ -122,10 +153,18 @@ int GlyphGeometry::getIdentifier(GlyphIdentifierType type) const {
     return 0;
 }
 
+double GlyphGeometry::getGeometryScale() const {
+    return geometryScale;
+}
+
 const msdfgen::Shape & GlyphGeometry::getShape() const {
     return shape;
 }
 
+const msdfgen::Shape::Bounds & GlyphGeometry::getShapeBounds() const {
+    return bounds;
+}
+
 double GlyphGeometry::getAdvance() const {
     return advance;
 }

msdf-atlas-gen/GlyphGeometry.h

@@ -22,6 +22,8 @@ public:
     /// Computes the dimensions of the glyph's box as well as the transformation for the generator function
     void wrapBox(double scale, double range, double miterLimit, bool alignOrigin = false);
     void wrapBox(double scale, double range, double miterLimit, bool alignOriginX, bool alignOriginY);
+    /// Computes the glyph's transformation and alignment (unless specified) for given dimensions
+    void frameBox(double scale, double range, double miterLimit, int width, int height, const double *fixedX, const double *fixedY);
     /// Sets the glyph's box's position in the atlas
     void placeBox(int x, int y);
     /// Sets the glyph's box's rectangle in the atlas
@@ -34,8 +36,12 @@ public:
     unicode_t getCodepoint() const;
     /// Returns the glyph's identifier specified by the supplied identifier type
     int getIdentifier(GlyphIdentifierType type) const;
+    /// Returns the glyph's geometry scale
+    double getGeometryScale() const;
     /// Returns the glyph's shape
     const msdfgen::Shape & getShape() const;
+    /// Returns the glyph's shape's raw bounds
+    const msdfgen::Shape::Bounds & getShapeBounds() const;
     /// Returns the glyph's advance
     double getAdvance() const;
     /// Returns the glyph's box in the atlas

msdf-atlas-gen/GridAtlasPacker.cpp

@@ -0,0 +1,537 @@
+
+#include "GridAtlasPacker.h"
+
+#include <algorithm>
+
+namespace msdf_atlas {
+
+static int floorPOT(int x) {
+    int y = 1;
+    while (x >= y)
+        y <<= 1;
+    return y>>1;
+}
+
+static int ceilPOT(int x) {
+    int y = 1;
+    while (x > y)
+        y <<= 1;
+    return y;
+}
+
+static bool squareConstraint(DimensionsConstraint constraint) {
+    switch (constraint) {
+        case DimensionsConstraint::SQUARE:
+        case DimensionsConstraint::EVEN_SQUARE:
+        case DimensionsConstraint::MULTIPLE_OF_FOUR_SQUARE:
+        case DimensionsConstraint::POWER_OF_TWO_SQUARE:
+            return true;
+        case DimensionsConstraint::NONE:
+        case DimensionsConstraint::POWER_OF_TWO_RECTANGLE:
+            return false;
+    }
+    return true;
+}
+
+void GridAtlasPacker::lowerToConstraint(int &width, int &height, DimensionsConstraint constraint) {
+    if (squareConstraint(constraint))
+        width = height = std::min(width, height);
+    switch (constraint) {
+        case DimensionsConstraint::NONE:
+        case DimensionsConstraint::SQUARE:
+            break;
+        case DimensionsConstraint::EVEN_SQUARE:
+            width &= ~1;
+            height &= ~1;
+            break;
+        case DimensionsConstraint::MULTIPLE_OF_FOUR_SQUARE:
+            width &= ~3;
+            height &= ~3;
+            break;
+        case DimensionsConstraint::POWER_OF_TWO_RECTANGLE:
+        case DimensionsConstraint::POWER_OF_TWO_SQUARE:
+            if (width > 0)
+                width = floorPOT(width);
+            if (height > 0)
+                height = floorPOT(height);
+            break;
+    }
+}
+
+void GridAtlasPacker::raiseToConstraint(int &width, int &height, DimensionsConstraint constraint) {
+    if (squareConstraint(constraint))
+        width = height = std::max(width, height);
+    switch (constraint) {
+        case DimensionsConstraint::NONE:
+        case DimensionsConstraint::SQUARE:
+            break;
+        case DimensionsConstraint::EVEN_SQUARE:
+            width += width&1;
+            height += height&1;
+            break;
+        case DimensionsConstraint::MULTIPLE_OF_FOUR_SQUARE:
+            width += -width&3;
+            height += -height&3;
+            break;
+        case DimensionsConstraint::POWER_OF_TWO_RECTANGLE:
+        case DimensionsConstraint::POWER_OF_TWO_SQUARE:
+            if (width > 0)
+                width = ceilPOT(width);
+            if (height > 0)
+                height = ceilPOT(height);
+            break;
+    }
+}
+
+double GridAtlasPacker::dimensionsRating(int width, int height, bool aligned) const {
+    return ((double) width*width+(double) height*height)*(aligned ? 1-alignedColumnsBias : 1);
+}
+
+GridAtlasPacker::GridAtlasPacker() :
+    columns(-1), rows(-1),
+    width(-1), height(-1),
+    cellWidth(-1), cellHeight(-1),
+    padding(0),
+    dimensionsConstraint(DimensionsConstraint::NONE),
+    cellDimensionsConstraint(DimensionsConstraint::NONE),
+    hFixed(false), vFixed(false),
+    scale(-1),
+    minScale(1),
+    fixedX(0), fixedY(0),
+    unitRange(0),
+    pxRange(0),
+    miterLimit(0),
+    scaleMaximizationTolerance(.001),
+    alignedColumnsBias(.125)
+{ }
+
+msdfgen::Shape::Bounds GridAtlasPacker::getMaxBounds(double &maxWidth, double &maxHeight, GlyphGeometry *glyphs, int count, double scale, double range) const {
+    static const double LARGE_VALUE = 1e240;
+    msdfgen::Shape::Bounds maxBounds = { +LARGE_VALUE, +LARGE_VALUE, -LARGE_VALUE, -LARGE_VALUE };
+    for (GlyphGeometry *glyph = glyphs, *end = glyphs+count; glyph < end; ++glyph) {
+        if (!glyph->isWhitespace()) {
+            double geometryScale = glyph->getGeometryScale();
+            double shapeRange = range/geometryScale;
+            geometryScale *= scale;
+            const msdfgen::Shape::Bounds &shapeBounds = glyph->getShapeBounds();
+            double l = shapeBounds.l, b = shapeBounds.b, r = shapeBounds.r, t = shapeBounds.t;
+            l -= .5*shapeRange, b -= .5*shapeRange;
+            r += .5*shapeRange, t += .5*shapeRange;
+            if (miterLimit > 0)
+                glyph->getShape().boundMiters(l, b, r, t, .5*shapeRange, miterLimit, 1);
+            l *= geometryScale, b *= geometryScale;
+            r *= geometryScale, t *= geometryScale;
+            maxBounds.l = std::min(maxBounds.l, l);
+            maxBounds.b = std::min(maxBounds.b, b);
+            maxBounds.r = std::max(maxBounds.r, r);
+            maxBounds.t = std::max(maxBounds.t, t);
+            maxWidth = std::max(maxWidth, r-l);
+            maxHeight = std::max(maxHeight, t-b);
+        }
+    }
+    if (maxBounds.l >= maxBounds.r || maxBounds.b >= maxBounds.t)
+        maxBounds = msdfgen::Shape::Bounds();
+    if (hFixed)
+        maxWidth = maxBounds.r-maxBounds.l;
+    if (vFixed)
+        maxHeight = maxBounds.t-maxBounds.b;
+    return maxBounds;
+}
+
+double GridAtlasPacker::scaleToFit(GlyphGeometry *glyphs, int count, int cellWidth, int cellHeight, msdfgen::Shape::Bounds &maxBounds, double &maxWidth, double &maxHeight) const {
+    static const int BIG_VALUE = 1<<28;
+    if (cellWidth <= 0)
+        cellWidth = BIG_VALUE;
+    if (cellHeight <= 0)
+        cellHeight = BIG_VALUE;
+    cellWidth -= padding, cellHeight -= padding;
+    bool lastResult = false;
+    #define TRY_FIT(scale) (maxWidth = 0, maxHeight = 0, maxBounds = getMaxBounds(maxWidth, maxHeight, glyphs, count, (scale), unitRange+pxRange/(scale)), lastResult = maxWidth <= cellWidth && maxHeight <= cellHeight)
+    double minScale = 1, maxScale = 1;
+    if (TRY_FIT(1)) {
+        while (maxScale < 1e+32 && ((maxScale = 2*minScale), TRY_FIT(maxScale)))
+            minScale = maxScale;
+    } else {
+        while (minScale > 1e-32 && ((minScale = .5*maxScale), !TRY_FIT(minScale)))
+            maxScale = minScale;
+    }
+    if (minScale == maxScale)
+        return 0;
+    while (minScale/maxScale < 1-scaleMaximizationTolerance) {
+        double midScale = .5*(minScale+maxScale);
+        if (TRY_FIT(midScale))
+            minScale = midScale;
+        else
+            maxScale = midScale;
+    }
+    if (!lastResult)
+        TRY_FIT(minScale);
+    return minScale;
+}
+
+// Ultra spaghetti
+int GridAtlasPacker::pack(GlyphGeometry *glyphs, int count) {
+    bool cellHeightFinal = cellHeight > 0;
+    bool explicitRows = rows > 0;
+    int cellCount = count;
+    if (!cellCount)
+        return 0;
+
+    if (columns > 0 && rows > 0)
+        cellCount = columns*rows;
+    else if (columns > 0)
+        rows = (cellCount+columns-1)/columns;
+    else if (rows > 0)
+        columns = (cellCount+rows-1)/rows;
+    else if (width > 0 && cellWidth > 0) {
+        columns = (width+padding)/cellWidth;
+        rows = (cellCount+columns-1)/columns;
+    }
+
+    bool dimensionsChanged = false;
+    if (width < 0 && cellWidth > 0 && columns > 0) {
+        width = columns*cellWidth-padding;
+        dimensionsChanged = true;
+    }
+    if (height < 0 && cellHeight > 0 && rows > 0) {
+        height = rows*cellHeight-padding;
+        dimensionsChanged = true;
+    }
+    if (dimensionsChanged)
+        raiseToConstraint(width, height, dimensionsConstraint);
+
+    dimensionsChanged = false;
+    if (cellWidth < 0 && width > 0 && columns > 0) {
+        cellWidth = (width+padding)/columns;
+        dimensionsChanged = true;
+    }
+    if (cellHeight < 0 && height > 0 && rows > 0) {
+        cellHeight = (height+padding)/rows;
+        dimensionsChanged = true;
+    }
+    if (dimensionsChanged)
+        lowerToConstraint(cellWidth, cellHeight, cellDimensionsConstraint);
+
+    if ((cellWidth > 0 && cellWidth-padding <= pxRange) || (cellHeight > 0 && cellHeight-padding <= pxRange)) // cells definitely too small
+        return -1;
+
+    if (scale <= 0) {
+        // If both pxRange and miterLimit is non-zero, miter bounds have to be computed for all potential scales
+        if (pxRange && miterLimit > 0) {
+            double maxWidth = 0, maxHeight = 0;
+            msdfgen::Shape::Bounds maxBounds;
+
+            if (cellWidth > 0 || cellHeight > 0) {
+                scale = scaleToFit(glyphs, count, cellWidth, cellHeight, maxBounds, maxWidth, maxHeight);
+                if (scale < minScale)
+                    return -1;
+            }
+
+            else if (width > 0 && height > 0) {
+                double bestAlignedScale = 0;
+                int bestCols = 0, bestAlignedCols = 0;
+                for (int q = (int) sqrt(cellCount)+1; q > 0; --q) {
+                    int cols = q;
+                    int rows = (cellCount+cols-1)/cols;
+                    int tWidth = (width+padding)/cols;
+                    int tHeight = (height+padding)/rows;
+                    if (!(tWidth > 0 && tHeight > 0))
+                        continue;
+                    lowerToConstraint(tWidth, tHeight, cellDimensionsConstraint);
+                    double curScale = scaleToFit(glyphs, count, tWidth, tHeight, maxBounds, maxWidth, maxHeight);
+                    if (curScale > scale) {
+                        scale = curScale;
+                        bestCols = cols;
+                    }
+                    if (cols*tWidth == width && curScale > bestAlignedScale) {
+                        bestAlignedScale = curScale;
+                        bestAlignedCols = cols;
+                    }
+
+                    cols = (cellCount+q-1)/q;
+                    rows = (cellCount+cols-1)/cols;
+                    tWidth = (width+padding)/cols;
+                    tHeight = (height+padding)/rows;
+                    if (!(tWidth > 0 && tHeight > 0))
+                        continue;
+                    lowerToConstraint(tWidth, tHeight, cellDimensionsConstraint);
+                    curScale = scaleToFit(glyphs, count, tWidth, tHeight, maxBounds, maxWidth, maxHeight);
+                    if (curScale > scale) {
+                        scale = curScale;
+                        bestCols = cols;
+                    }
+                    if (cols*tWidth == width && curScale > bestAlignedScale) {
+                        bestAlignedScale = curScale;
+                        bestAlignedCols = cols;
+                    }
+                }
+                if (!bestCols)
+                    return -1;
+                // If columns can be aligned with total width at a slight cost to glyph scale, use that number of columns instead
+                if (bestAlignedScale >= minScale && (alignedColumnsBias+1)*bestAlignedScale >= scale) {
+                    scale = bestAlignedScale;
+                    bestCols = bestAlignedCols;
+                }
+
+                columns = bestCols;
+                rows = (cellCount+columns-1)/columns;
+                cellWidth = (width+padding)/columns;
+                cellHeight = (height+padding)/rows;
+                lowerToConstraint(cellWidth, cellHeight, cellDimensionsConstraint);
+                scale = scaleToFit(glyphs, count, cellWidth, cellHeight, maxBounds, maxWidth, maxHeight);
+            }
+
+            else {
+                maxBounds = getMaxBounds(maxWidth, maxHeight, glyphs, count, minScale, unitRange+pxRange/minScale);
+                cellWidth = (int) ceil(maxWidth)+padding;
+                cellHeight = (int) ceil(maxHeight)+padding;
+                raiseToConstraint(cellWidth, cellHeight, cellDimensionsConstraint);
+                scale = scaleToFit(glyphs, count, cellWidth, cellHeight, maxBounds, maxWidth, maxHeight);
+                if (scale < minScale)
+                    maxBounds = getMaxBounds(maxWidth, maxHeight, glyphs, count, scale = minScale, unitRange+pxRange/minScale);
+            }
+
+            if (!explicitRows && !cellHeightFinal)
+                cellHeight = (int) ceil(maxHeight)+padding;
+            fixedX = (-maxBounds.l+.5*(cellWidth-padding-maxWidth))/scale;
+            fixedY = (-maxBounds.b+.5*(cellHeight-padding-maxHeight))/scale;
+
+        } else {
+
+            double maxWidth = 0, maxHeight = 0;
+            msdfgen::Shape::Bounds maxBounds = getMaxBounds(maxWidth, maxHeight, glyphs, count, 1, unitRange);
+
+            double hScale = 0, vScale = 0;
+            if (cellWidth > 0)
+                hScale = (cellWidth-padding-pxRange)/maxWidth;
+            if (cellHeight > 0)
+                vScale = (cellHeight-padding-pxRange)/maxHeight;
+            if (hScale || vScale) {
+                if (hScale && vScale)
+                    scale = std::min(hScale, vScale);
+                else
+                    scale = hScale+vScale;
+                if (scale < minScale)
+                    return -1;
+            }
+
+            else if (width > 0 && height > 0) {
+                double bestAlignedScale = 0;
+                int bestCols = 0, bestAlignedCols = 0;
+                // TODO sqrtize
+                for (int cols = 1; cols < width; ++cols) {
+                    int rows = (cellCount+cols-1)/cols;
+                    int tWidth = (width+padding)/cols;
+                    int tHeight = (height+padding)/rows;
+                    if (!(tWidth > 0 && tHeight > 0))
+                        continue;
+                    lowerToConstraint(tWidth, tHeight, cellDimensionsConstraint);
+                    hScale = (tWidth-padding-pxRange)/maxWidth;
+                    vScale = (tHeight-padding-pxRange)/maxHeight;
+                    double curScale = std::min(hScale, vScale);
+                    if (curScale > scale) {
+                        scale = curScale;
+                        bestCols = cols;
+                    }
+                    if (cols*tWidth == width && curScale > bestAlignedScale) {
+                        bestAlignedScale = curScale;
+                        bestAlignedCols = cols;
+                    }
+                }
+                if (!bestCols)
+                    return -1;
+                // If columns can be aligned with total width at a slight cost to glyph scale, use that number of columns instead
+                if (bestAlignedScale >= minScale && (alignedColumnsBias+1)*bestAlignedScale >= scale) {
+                    scale = bestAlignedScale;
+                    bestCols = bestAlignedCols;
+                }
+
+                columns = bestCols;
+                rows = (cellCount+columns-1)/columns;
+                cellWidth = (width+padding)/columns;
+                cellHeight = (height+padding)/rows;
+                lowerToConstraint(cellWidth, cellHeight, cellDimensionsConstraint);
+            }
+
+            else {
+                cellWidth = (int) ceil(minScale*maxWidth+pxRange)+padding;
+                cellHeight = (int) ceil(minScale*maxHeight+pxRange)+padding;
+                raiseToConstraint(cellWidth, cellHeight, cellDimensionsConstraint);
+                hScale = (cellWidth-padding-pxRange)/maxWidth;
+                vScale = (cellHeight-padding-pxRange)/maxHeight;
+                scale = std::min(hScale, vScale);
+            }
+
+            if (!explicitRows && !cellHeightFinal)
+                cellHeight = (int) ceil(scale*maxHeight+pxRange)+padding;
+            fixedX = -maxBounds.l+.5*((cellWidth-padding)/scale-maxWidth);
+            fixedY = -maxBounds.b+.5*((cellHeight-padding)/scale-maxHeight);
+
+        }
+    } else {
+        double maxWidth = 0, maxHeight = 0;
+        msdfgen::Shape::Bounds maxBounds = getMaxBounds(maxWidth, maxHeight, glyphs, count, scale, unitRange+pxRange/scale);
+
+        if (cellWidth < 0 || cellHeight < 0) {
+            cellWidth = (int) ceil(maxWidth)+padding;
+            cellHeight = (int) ceil(maxHeight)+padding;
+            raiseToConstraint(cellWidth, cellHeight, cellDimensionsConstraint);
+        }
+
+        fixedX = (-maxBounds.l+.5*(cellWidth-padding-maxWidth))/scale;
+        fixedY = (-maxBounds.b+.5*(cellHeight-padding-maxHeight))/scale;
+    }
+
+    if (width < 0 || height < 0) {
+        if (columns <= 0) {
+            double bestRating = -1;
+            for (int q = (int) sqrt(cellCount)+1; q > 0; --q) {
+                int cols = q;
+                int rows = (cellCount+cols-1)/cols;
+                int curWidth = cols*cellWidth, curHeight = rows*cellHeight;
+                raiseToConstraint(curWidth, curHeight, dimensionsConstraint);
+                double rating = dimensionsRating(curWidth, curHeight, cols*cellWidth == curWidth);
+                if (rating < bestRating || bestRating < 0) {
+                    bestRating = rating;
+                    columns = cols;
+                }
+                rows = q;
+                cols = (cellCount+rows-1)/rows;
+                curWidth = cols*cellWidth, curHeight = rows*cellHeight;
+                raiseToConstraint(curWidth, curHeight, dimensionsConstraint);
+                rating = dimensionsRating(curWidth, curHeight, cols*cellWidth == curWidth);
+                if (rating < bestRating || bestRating < 0) {
+                    bestRating = rating;
+                    columns = cols;
+                }
+            }
+            rows = (cellCount+columns-1)/columns;
+        }
+        width = columns*cellWidth, height = rows*cellHeight;
+        raiseToConstraint(width, height, dimensionsConstraint);
+    }
+
+    if (columns < 0) {
+        columns = (width+padding)/cellWidth;
+        rows = (cellCount+columns-1)/columns;
+    }
+
+    int col = 0, row = 0;
+    for (GlyphGeometry *glyph = glyphs, *end = glyphs+count; glyph < end; ++glyph) {
+        if (!glyph->isWhitespace()) {
+            Rectangle rect = { };
+            glyph->frameBox(scale, unitRange+pxRange/scale, miterLimit, cellWidth-padding, cellHeight-padding, hFixed ? &fixedX : nullptr, vFixed ? &fixedY : nullptr);
+            glyph->placeBox(col*cellWidth, height-(row+1)*cellHeight);
+            if (++col >= columns) {
+                if (++row >= rows) {
+                    return end-glyph-1;
+                }
+                col = 0;
+            }
+        }
+    }
+
+    if (columns*rows < cellCount) {
+        // TODO return lower number
+    }
+    return 0;
+}
+
+void GridAtlasPacker::setFixedOrigin(bool horizontal, bool vertical) {
+    hFixed = horizontal, vFixed = vertical;
+}
+
+void GridAtlasPacker::setCellDimensions(int width, int height) {
+    cellWidth = width, cellHeight = height;
+}
+
+void GridAtlasPacker::unsetCellDimensions() {
+    cellWidth = -1, cellHeight = -1;
+}
+
+void GridAtlasPacker::setCellDimensionsConstraint(DimensionsConstraint dimensionsConstraint) {
+    cellDimensionsConstraint = dimensionsConstraint;
+}
+
+void GridAtlasPacker::setColumns(int columns) {
+    this->columns = columns;
+}
+
+void GridAtlasPacker::setRows(int rows) {
+    this->rows = rows;
+}
+
+void GridAtlasPacker::unsetColumns() {
+    columns = -1;
+}
+
+void GridAtlasPacker::unsetRows() {
+    rows = -1;
+}
+
+void GridAtlasPacker::setDimensions(int width, int height) {
+    this->width = width, this->height = height;
+}
+
+void GridAtlasPacker::unsetDimensions() {
+    width = -1, height = -1;
+}
+
+void GridAtlasPacker::setDimensionsConstraint(DimensionsConstraint dimensionsConstraint) {
+    this->dimensionsConstraint = dimensionsConstraint;
+}
+
+void GridAtlasPacker::setPadding(int padding) {
+    this->padding = padding;
+}
+
+void GridAtlasPacker::setScale(double scale) {
+    this->scale = scale;
+}
+
+void GridAtlasPacker::setMinimumScale(double minScale) {
+    this->minScale = minScale;
+}
+
+void GridAtlasPacker::setUnitRange(double unitRange) {
+    this->unitRange = unitRange;
+}
+
+void GridAtlasPacker::setPixelRange(double pxRange) {
+    this->pxRange = pxRange;
+}
+
+void GridAtlasPacker::setMiterLimit(double miterLimit) {
+    this->miterLimit = miterLimit;
+}
+
+void GridAtlasPacker::getDimensions(int &width, int &height) const {
+    width = this->width, height = this->height;
+}
+
+void GridAtlasPacker::getCellDimensions(int &width, int &height) const {
+    width = cellWidth, height = cellHeight;
+}
+
+int GridAtlasPacker::getColumns() const {
+    return columns;
+}
+
+int GridAtlasPacker::getRows() const {
+    return rows;
+}
+
+double GridAtlasPacker::getScale() const {
+    return scale;
+}
+
+double GridAtlasPacker::getPixelRange() const {
+    return pxRange;
+}
+
+void GridAtlasPacker::getFixedOrigin(double &x, double &y) {
+    x = fixedX-.5/scale;
+    y = fixedY-.5/scale;
+}
+
+}

msdf-atlas-gen/GridAtlasPacker.h

@@ -0,0 +1,86 @@
+
+#pragma once
+
+#include "GlyphGeometry.h"
+
+namespace msdf_atlas {
+
+/**
+ * This class computes the layout of a static uniform grid atlas and may optionally
+ * also find the minimum required dimensions and/or the maximum glyph scale
+ */
+class GridAtlasPacker {
+
+public:
+    GridAtlasPacker();
+
+    /// Computes the layout for the array of glyphs. Returns 0 on success
+    int pack(GlyphGeometry *glyphs, int count);
+
+    /// Sets whether the origin point should be at the same position in each glyph, separately for horizontal and vertical dimension
+    void setFixedOrigin(bool horizontal, bool vertical);
+    void setCellDimensions(int width, int height);
+    void unsetCellDimensions();
+    void setCellDimensionsConstraint(DimensionsConstraint dimensionsConstraint);
+    void setColumns(int columns);
+    void setRows(int rows);
+    void unsetColumns();
+    void unsetRows();
+
+    /// Sets the atlas's fixed dimensions
+    void setDimensions(int width, int height);
+    /// Sets the atlas's dimensions to be determined during pack
+    void unsetDimensions();
+    /// Sets the constraint to be used when determining dimensions
+    void setDimensionsConstraint(DimensionsConstraint dimensionsConstraint);
+    /// Sets the padding between glyph boxes
+    void setPadding(int padding);
+    /// Sets fixed glyph scale
+    void setScale(double scale);
+    /// Sets the minimum glyph scale
+    void setMinimumScale(double minScale);
+    /// Sets the unit component of the total distance range
+    void setUnitRange(double unitRange);
+    /// Sets the pixel component of the total distance range
+    void setPixelRange(double pxRange);
+    /// Sets the miter limit for bounds computation
+    void setMiterLimit(double miterLimit);
+
+    /// Outputs the atlas's final dimensions
+    void getDimensions(int &width, int &height) const;
+    void getCellDimensions(int &width, int &height) const;
+    int getColumns() const;
+    int getRows() const;
+    /// Returns the final glyph scale
+    double getScale() const;
+    /// Returns the final combined pixel range (including converted unit range)
+    double getPixelRange() const;
+    void getFixedOrigin(double &x, double &y);
+
+private:
+    int columns, rows;
+    int width, height;
+    int cellWidth, cellHeight;
+    int padding;
+    DimensionsConstraint dimensionsConstraint;
+    DimensionsConstraint cellDimensionsConstraint;
+    bool hFixed, vFixed;
+    double scale;
+    double minScale;
+    double fixedX, fixedY;
+    double unitRange;
+    double pxRange;
+    double miterLimit;
+    double scaleMaximizationTolerance;
+    double alignedColumnsBias;
+
+    static void lowerToConstraint(int &width, int &height, DimensionsConstraint constraint);
+    static void raiseToConstraint(int &width, int &height, DimensionsConstraint constraint);
+
+    double dimensionsRating(int width, int height, bool aligned) const;
+    msdfgen::Shape::Bounds getMaxBounds(double &maxWidth, double &maxHeight, GlyphGeometry *glyphs, int count, double scale, double range) const;
+    double scaleToFit(GlyphGeometry *glyphs, int count, int cellWidth, int cellHeight, msdfgen::Shape::Bounds &maxBounds, double &maxWidth, double &maxHeight) const;
+
+};
+
+}

msdf-atlas-gen/TightAtlasPacker.cpp

@@ -62,6 +62,7 @@ int TightAtlasPacker::tryPack(GlyphGeometry *glyphs, int count, DimensionsConstr
                 dimensions = packRectangles<SquareSizeSelector<2> >(rectangles.data(), rectangles.size(), padding);
                 break;
             case DimensionsConstraint::SQUARE:
+            default:
                 dimensions = packRectangles<SquareSizeSelector<> >(rectangles.data(), rectangles.size(), padding);
                 break;
         }

msdf-atlas-gen/TightAtlasPacker.h

@@ -1,32 +1,24 @@
 
 #pragma once
 
+#include "types.h"
 #include "GlyphGeometry.h"
 
 namespace msdf_atlas {
 
 /**
- * This class computes the layout of a static atlas and may optionally
+ * This class computes the layout of a static tightly packed atlas and may optionally
  * also find the minimum required dimensions and/or the maximum glyph scale
  */
 class TightAtlasPacker {
 
 public:
-    /// Constraints for the atlas's dimensions - see size selectors for more info
-    enum class DimensionsConstraint {
-        POWER_OF_TWO_SQUARE,
-        POWER_OF_TWO_RECTANGLE,
-        MULTIPLE_OF_FOUR_SQUARE,
-        EVEN_SQUARE,
-        SQUARE
-    };
-
     TightAtlasPacker();
 
     /// Computes the layout for the array of glyphs. Returns 0 on success
     int pack(GlyphGeometry *glyphs, int count);
 
-    /// Sets the atlas's dimensions to be fixed
+    /// Sets the atlas's fixed dimensions
     void setDimensions(int width, int height);
     /// Sets the atlas's dimensions to be determined during pack
     void unsetDimensions();

msdf-atlas-gen/json-export.cpp

@@ -58,7 +58,7 @@ static const char * imageTypeString(ImageType type) {
     return nullptr;
 }
 
-bool exportJSON(const FontGeometry *fonts, int fontCount, double fontSize, double pxRange, int atlasWidth, int atlasHeight, ImageType imageType, YDirection yDirection, const char *filename, bool kerning) {
+bool exportJSON(const FontGeometry *fonts, int fontCount, ImageType imageType, const JsonAtlasMetrics &metrics, const char *filename, bool kerning) {
     FILE *f = fopen(filename, "w");
     if (!f)
         return false;
@@ -68,11 +68,31 @@ bool exportJSON(const FontGeometry *fonts, int fontCount, double fontSize, doubl
     fputs("\"atlas\":{", f); {
         fprintf(f, "\"type\":\"%s\",", imageTypeString(imageType));
         if (imageType == ImageType::SDF || imageType == ImageType::PSDF || imageType == ImageType::MSDF || imageType == ImageType::MTSDF)
-            fprintf(f, "\"distanceRange\":%.17g,", pxRange);
-        fprintf(f, "\"size\":%.17g,", fontSize);
-        fprintf(f, "\"width\":%d,", atlasWidth);
-        fprintf(f, "\"height\":%d,", atlasHeight);
-        fprintf(f, "\"yOrigin\":\"%s\"", yDirection == YDirection::TOP_DOWN ? "top" : "bottom");
+            fprintf(f, "\"distanceRange\":%.17g,", metrics.distanceRange);
+        fprintf(f, "\"size\":%.17g,", metrics.size);
+        fprintf(f, "\"width\":%d,", metrics.width);
+        fprintf(f, "\"height\":%d,", metrics.height);
+        fprintf(f, "\"yOrigin\":\"%s\"", metrics.yDirection == YDirection::TOP_DOWN ? "top" : "bottom");
+        if (metrics.grid) {
+            fputs(",\"grid\":{", f);
+            fprintf(f, "\"cellWidth\":%d,", metrics.grid->cellWidth);
+            fprintf(f, "\"cellHeight\":%d,", metrics.grid->cellHeight);
+            fprintf(f, "\"columns\":%d,", metrics.grid->columns);
+            fprintf(f, "\"rows\":%d", metrics.grid->rows);
+            if (metrics.grid->originX)
+                fprintf(f, ",\"originX\":%.17g", *metrics.grid->originX);
+            if (metrics.grid->originY) {
+                switch (metrics.yDirection) {
+                    case YDirection::BOTTOM_UP:
+                        fprintf(f, ",\"originY\":%.17g", *metrics.grid->originY);
+                        break;
+                    case YDirection::TOP_DOWN:
+                        fprintf(f, ",\"originY\":%.17g", (metrics.grid->cellHeight-metrics.grid->padding-1)/metrics.size-*metrics.grid->originY);
+                        break;
+                }
+            }
+            fputs("}", f);
+        }
     } fputs("},", f);
 
     if (fontCount > 1)
@@ -89,14 +109,14 @@ bool exportJSON(const FontGeometry *fonts, int fontCount, double fontSize, doubl
 
         // Font metrics
         fputs("\"metrics\":{", f); {
-            double yFactor = yDirection == YDirection::TOP_DOWN ? -1 : 1;
-            const msdfgen::FontMetrics &metrics = font.getMetrics();
-            fprintf(f, "\"emSize\":%.17g,", metrics.emSize);
-            fprintf(f, "\"lineHeight\":%.17g,", metrics.lineHeight);
-            fprintf(f, "\"ascender\":%.17g,", yFactor*metrics.ascenderY);
-            fprintf(f, "\"descender\":%.17g,", yFactor*metrics.descenderY);
-            fprintf(f, "\"underlineY\":%.17g,", yFactor*metrics.underlineY);
-            fprintf(f, "\"underlineThickness\":%.17g", metrics.underlineThickness);
+            double yFactor = metrics.yDirection == YDirection::TOP_DOWN ? -1 : 1;
+            const msdfgen::FontMetrics &fontMetrics = font.getMetrics();
+            fprintf(f, "\"emSize\":%.17g,", fontMetrics.emSize);
+            fprintf(f, "\"lineHeight\":%.17g,", fontMetrics.lineHeight);
+            fprintf(f, "\"ascender\":%.17g,", yFactor*fontMetrics.ascenderY);
+            fprintf(f, "\"descender\":%.17g,", yFactor*fontMetrics.descenderY);
+            fprintf(f, "\"underlineY\":%.17g,", yFactor*fontMetrics.underlineY);
+            fprintf(f, "\"underlineThickness\":%.17g", fontMetrics.underlineThickness);
         } fputs("},", f);
 
         // Glyph mapping
@@ -116,7 +136,7 @@ bool exportJSON(const FontGeometry *fonts, int fontCount, double fontSize, doubl
             double l, b, r, t;
             glyph.getQuadPlaneBounds(l, b, r, t);
             if (l || b || r || t) {
-                switch (yDirection) {
+                switch (metrics.yDirection) {
                     case YDirection::BOTTOM_UP:
                         fprintf(f, ",\"planeBounds\":{\"left\":%.17g,\"bottom\":%.17g,\"right\":%.17g,\"top\":%.17g}", l, b, r, t);
                         break;
@@ -127,12 +147,12 @@ bool exportJSON(const FontGeometry *fonts, int fontCount, double fontSize, doubl
             }
             glyph.getQuadAtlasBounds(l, b, r, t);
             if (l || b || r || t) {
-                switch (yDirection) {
+                switch (metrics.yDirection) {
                     case YDirection::BOTTOM_UP:
                         fprintf(f, ",\"atlasBounds\":{\"left\":%.17g,\"bottom\":%.17g,\"right\":%.17g,\"top\":%.17g}", l, b, r, t);
                         break;
                     case YDirection::TOP_DOWN:
-                        fprintf(f, ",\"atlasBounds\":{\"left\":%.17g,\"top\":%.17g,\"right\":%.17g,\"bottom\":%.17g}", l, atlasHeight-t, r, atlasHeight-b);
+                        fprintf(f, ",\"atlasBounds\":{\"left\":%.17g,\"top\":%.17g,\"right\":%.17g,\"bottom\":%.17g}", l, metrics.height-t, r, metrics.height-b);
                         break;
                 }
             }

msdf-atlas-gen/json-export.h

@@ -8,7 +8,21 @@
 
 namespace msdf_atlas {
 
+struct JsonAtlasMetrics {
+    struct GridMetrics {
+        int cellWidth, cellHeight;
+        int columns, rows;
+        const double *originX, *originY;
+        int padding;
+    };
+    double distanceRange;
+    double size;
+    int width, height;
+    YDirection yDirection;
+    const GridMetrics *grid;
+};
+
 /// Writes the font and glyph metrics and atlas layout data into a comprehensive JSON file
-bool exportJSON(const FontGeometry *fonts, int fontCount, double fontSize, double pxRange, int atlasWidth, int atlasHeight, ImageType imageType, YDirection yDirection, const char *filename, bool kerning);
+bool exportJSON(const FontGeometry *fonts, int fontCount, ImageType imageType, const JsonAtlasMetrics &metrics, const char *filename, bool kerning);
 
 }

msdf-atlas-gen/main.cpp

@@ -83,6 +83,16 @@ ATLAS CONFIGURATION
   -pots / -potr / -square / -square2 / -square4
       Picks the minimum atlas dimensions that fit all glyphs and satisfy the selected constraint:
       power of two square / ... rectangle / any square / square with side divisible by 2 / ... 4
+  -uniformgrid
+      Lays out the atlas into a uniform grid. Enables following options starting with -uniform:
+    -uniformcols <N>
+        Sets the number of grid columns.
+    -uniformcell <width> <height>
+        Sets fixed dimensions of the grid's cells.
+    -uniformcellconstraint <none / pots / potr / square / square2 / square4>
+        Constrains cell dimensions to the given rule (see -pots / ... above)
+    -uniformorigin <yes / no / horizontal / vertical>
+        Sets whether the glyph's origin point should be fixed at the same position in each cell
   -yorigin <bottom / top>
       Determines whether the Y-axis is oriented upwards (bottom origin, default) or downwards (top origin).
 
@@ -103,12 +113,12 @@ R"(
       Generates a Shadron script that uses the generated atlas to draw a sample text as a preview.
 
 GLYPH CONFIGURATION
-  -size <EM size>
-      Specifies the size of the glyphs in the atlas bitmap in pixels per EM.
-  -minsize <EM size>
+  -size <em size>
+      Specifies the size of the glyphs in the atlas bitmap in pixels per em.
+  -minsize <em size>
       Specifies the minimum size. The largest possible size that fits the same atlas dimensions will be used.
-  -emrange <EM range>
-      Specifies the SDF distance range in EM's.
+  -emrange <em range>
+      Specifies the SDF distance range in em's.
   -pxrange <pixel range>
       Specifies the SDF distance range in output pixels. The default value is 2.
   -pxalign <on / off / horizontal / vertical>
@@ -253,6 +263,11 @@ struct Configuration {
     double angleThreshold;
     double miterLimit;
     bool alignOriginX, alignOriginY;
+    struct {
+        int cellWidth, cellHeight;
+        int cols, rows;
+        bool hFixed, vFixed;
+    } grid;
     void (*edgeColoring)(msdfgen::Shape &, double, unsigned long long);
     bool expensiveColoring;
     unsigned long long coloringSeed;
@@ -319,10 +334,12 @@ int main(int argc, const char * const *argv) {
     config.imageType = ImageType::MSDF;
     config.imageFormat = ImageFormat::UNSPECIFIED;
     config.yDirection = YDirection::BOTTOM_UP;
+    config.grid.vFixed = true;
     config.edgeColoring = msdfgen::edgeColoringInkTrap;
     config.kerning = true;
     const char *imageFormatName = nullptr;
     int fixedWidth = -1, fixedHeight = -1;
+    int fixedCellWidth = -1, fixedCellHeight = -1;
     config.preprocessGeometry = (
         #ifdef MSDFGEN_USE_SKIA
             true
@@ -334,13 +351,15 @@ int main(int argc, const char * const *argv) {
     config.generatorAttributes.scanlinePass = !config.preprocessGeometry;
     double minEmSize = 0;
     enum {
-        /// Range specified in EMs
+        /// Range specified in ems
         RANGE_EM,
         /// Range specified in output pixels
         RANGE_PIXEL,
     } rangeMode = RANGE_PIXEL;
     double rangeValue = 0;
-    TightAtlasPacker::DimensionsConstraint atlasSizeConstraint = TightAtlasPacker::DimensionsConstraint::MULTIPLE_OF_FOUR_SQUARE;
+    PackingStyle packingStyle = PackingStyle::TIGHT;
+    DimensionsConstraint atlasSizeConstraint = DimensionsConstraint::NONE;
+    DimensionsConstraint cellSizeConstraint = DimensionsConstraint::NONE;
     config.angleThreshold = DEFAULT_ANGLE_THRESHOLD;
     config.miterLimit = DEFAULT_MITER_LIMIT;
     config.alignOriginX = false, config.alignOriginY = true;
@@ -491,31 +510,31 @@ int main(int argc, const char * const *argv) {
             continue;
         }
         ARG_CASE("-pots", 0) {
-            atlasSizeConstraint = TightAtlasPacker::DimensionsConstraint::POWER_OF_TWO_SQUARE;
+            atlasSizeConstraint = DimensionsConstraint::POWER_OF_TWO_SQUARE;
             fixedWidth = -1, fixedHeight = -1;
             ++argPos;
             continue;
         }
         ARG_CASE("-potr", 0) {
-            atlasSizeConstraint = TightAtlasPacker::DimensionsConstraint::POWER_OF_TWO_RECTANGLE;
+            atlasSizeConstraint = DimensionsConstraint::POWER_OF_TWO_RECTANGLE;
             fixedWidth = -1, fixedHeight = -1;
             ++argPos;
             continue;
         }
         ARG_CASE("-square", 0) {
-            atlasSizeConstraint = TightAtlasPacker::DimensionsConstraint::SQUARE;
+            atlasSizeConstraint = DimensionsConstraint::SQUARE;
             fixedWidth = -1, fixedHeight = -1;
             ++argPos;
             continue;
         }
         ARG_CASE("-square2", 0) {
-            atlasSizeConstraint = TightAtlasPacker::DimensionsConstraint::EVEN_SQUARE;
+            atlasSizeConstraint = DimensionsConstraint::EVEN_SQUARE;
             fixedWidth = -1, fixedHeight = -1;
             ++argPos;
             continue;
         }
         ARG_CASE("-square4", 0) {
-            atlasSizeConstraint = TightAtlasPacker::DimensionsConstraint::MULTIPLE_OF_FOUR_SQUARE;
+            atlasSizeConstraint = DimensionsConstraint::MULTIPLE_OF_FOUR_SQUARE;
             fixedWidth = -1, fixedHeight = -1;
             ++argPos;
             continue;
@@ -534,7 +553,7 @@ int main(int argc, const char * const *argv) {
         ARG_CASE("-size", 1) {
             double s;
             if (!(parseDouble(s, argv[++argPos]) && s > 0))
-                ABORT("Invalid EM size argument. Use -size <EM size> with a positive real number.");
+                ABORT("Invalid em size argument. Use -size <em size> with a positive real number.");
             config.emSize = s;
             ++argPos;
             continue;
@@ -542,7 +561,7 @@ int main(int argc, const char * const *argv) {
         ARG_CASE("-minsize", 1) {
             double s;
             if (!(parseDouble(s, argv[++argPos]) && s > 0))
-                ABORT("Invalid minimum EM size argument. Use -minsize <EM size> with a positive real number.");
+                ABORT("Invalid minimum em size argument. Use -minsize <em size> with a positive real number.");
             minEmSize = s;
             ++argPos;
             continue;
@@ -550,7 +569,7 @@ int main(int argc, const char * const *argv) {
         ARG_CASE("-emrange", 1) {
             double r;
             if (!(parseDouble(r, argv[++argPos]) && r >= 0))
-                ABORT("Invalid range argument. Use -emrange <EM range> with a positive real number.");
+                ABORT("Invalid range argument. Use -emrange <em range> with a positive real number.");
             rangeMode = RANGE_EM;
             rangeValue = r;
             ++argPos;
@@ -587,6 +606,63 @@ int main(int argc, const char * const *argv) {
             argPos += 2;
             continue;
         }
+        ARG_CASE("-uniformgrid", 0) {
+            packingStyle = PackingStyle::GRID;
+            ++argPos;
+            continue;
+        }
+        ARG_CASE("-uniformcols", 1) {
+            packingStyle = PackingStyle::GRID;
+            unsigned c;
+            if (!(parseUnsigned(c, argv[argPos+1]) && c))
+                ABORT("Invalid number of grid columns. Use -uniformcols <N> with a positive integer.");
+            config.grid.cols = c;
+            argPos += 2;
+            continue;
+        }
+        ARG_CASE("-uniformcell", 2) {
+            packingStyle = PackingStyle::GRID;
+            unsigned w, h;
+            if (!(parseUnsigned(w, argv[argPos+1]) && parseUnsigned(h, argv[argPos+2]) && w && h))
+                ABORT("Invalid cell dimensions. Use -uniformcell <width> <height> with two positive integers.");
+            fixedCellWidth = w, fixedCellHeight = h;
+            argPos += 3;
+            continue;
+        }
+        ARG_CASE("-uniformcellconstraint", 1) {
+            packingStyle = PackingStyle::GRID;
+            if (!strcmp(argv[argPos+1], "none") || !strcmp(argv[argPos+1], "rect"))
+                cellSizeConstraint = DimensionsConstraint::NONE;
+            else if (!strcmp(argv[argPos+1], "pots"))
+                cellSizeConstraint = DimensionsConstraint::POWER_OF_TWO_SQUARE;
+            else if (!strcmp(argv[argPos+1], "potr"))
+                cellSizeConstraint = DimensionsConstraint::POWER_OF_TWO_RECTANGLE;
+            else if (!strcmp(argv[argPos+1], "square"))
+                cellSizeConstraint = DimensionsConstraint::SQUARE;
+            else if (!strcmp(argv[argPos+1], "square2"))
+                cellSizeConstraint = DimensionsConstraint::EVEN_SQUARE;
+            else if (!strcmp(argv[argPos+1], "square4"))
+                cellSizeConstraint = DimensionsConstraint::MULTIPLE_OF_FOUR_SQUARE;
+            else
+                ABORT("Unknown dimensions constaint. Use -uniformcellconstraint with one of: none, pots, potr, square, square2, or square4.");
+            argPos += 2;
+            continue;
+        }
+        ARG_CASE("-uniformorigin", 1) {
+            packingStyle = PackingStyle::GRID;
+            if (!strcmp(argv[argPos+1], "no") || !strcmp(argv[argPos+1], "0") || !strcmp(argv[argPos+1], "none") || !strcmp(argv[argPos+1], "false") || !strcmp(argv[argPos+1], "disabled"))
+                config.grid.hFixed = false, config.grid.vFixed = false;
+            else if (!strcmp(argv[argPos+1], "yes") || !strcmp(argv[argPos+1], "1") || !strcmp(argv[argPos+1], "both") || !strcmp(argv[argPos+1], "true") || !strcmp(argv[argPos+1], "enabled"))
+                config.grid.hFixed = true, config.grid.vFixed = true;
+            else if (!strcmp(argv[argPos+1], "horizontal") || !strcmp(argv[argPos+1], "h"))
+                config.grid.hFixed = true, config.grid.vFixed = false;
+            else if (!strcmp(argv[argPos+1], "vertical") || !strcmp(argv[argPos+1], "v") || !strcmp(argv[argPos+1], "default"))
+                config.grid.hFixed = false, config.grid.vFixed = true;
+            else
+                ABORT("Unknown option for -uniformorigin. Use one of: yes, no, horizontal, vertical.");
+            argPos += 2;
+            continue;
+        }
         ARG_CASE("-errorcorrection", 1) {
             msdfgen::ErrorCorrectionConfig &ec = config.generatorAttributes.config.errorCorrection;
             if (!memcmp(argv[argPos+1], "disable", 7) || !strcmp(argv[argPos+1], "0") || !strcmp(argv[argPos+1], "none")) {
@@ -762,11 +838,13 @@ int main(int argc, const char * const *argv) {
         fontInputs.push_back(fontInput);
 
     // Fix up configuration based on related values
+    if (packingStyle == PackingStyle::TIGHT && atlasSizeConstraint == DimensionsConstraint::NONE)
+        atlasSizeConstraint = DimensionsConstraint::MULTIPLE_OF_FOUR_SQUARE;
     if (!(config.imageType == ImageType::PSDF || config.imageType == ImageType::MSDF || config.imageType == ImageType::MTSDF))
         config.miterLimit = 0;
     if (config.emSize > minEmSize)
         minEmSize = config.emSize;
-    if (!(fixedWidth > 0 && fixedHeight > 0) && !(minEmSize > 0)) {
+    if (!(fixedWidth > 0 && fixedHeight > 0) && !(fixedCellWidth > 0 && fixedCellHeight > 0) && !(minEmSize > 0)) {
         fputs("Neither atlas size nor glyph size selected, using default...\n", stderr);
         minEmSize = MSDF_ATLAS_DEFAULT_EM_SIZE;
     }
@@ -851,6 +929,9 @@ int main(int argc, const char * const *argv) {
         config.imageFormat == ImageFormat::BINARY_FLOAT ||
         config.imageFormat == ImageFormat::BINARY_FLOAT_BE
     );
+    // TODO: In this case (if padding is -1), the border pixels of each glyph are black, but still computed. For floating-point output, this may play a role.
+    int padding = config.imageType == ImageType::MSDF || config.imageType == ImageType::MTSDF ? 0 : -1;
+    double uniformOriginX, uniformOriginY;
 
     // Load fonts
     std::vector<GlyphGeometry> glyphs;
@@ -975,38 +1056,108 @@ int main(int argc, const char * const *argv) {
         }
         bool fixedDimensions = fixedWidth >= 0 && fixedHeight >= 0;
         bool fixedScale = config.emSize > 0;
-        TightAtlasPacker atlasPacker;
-        if (fixedDimensions)
-            atlasPacker.setDimensions(fixedWidth, fixedHeight);
-        else
-            atlasPacker.setDimensionsConstraint(atlasSizeConstraint);
-        atlasPacker.setPadding(config.imageType == ImageType::MSDF || config.imageType == ImageType::MTSDF ? 0 : -1);
-        // TODO: In this case (if padding is -1), the border pixels of each glyph are black, but still computed. For floating-point output, this may play a role.
-        if (fixedScale)
-            atlasPacker.setScale(config.emSize);
-        else
-            atlasPacker.setMinimumScale(minEmSize);
-        atlasPacker.setPixelRange(pxRange);
-        atlasPacker.setUnitRange(unitRange);
-        atlasPacker.setMiterLimit(config.miterLimit);
-        atlasPacker.setOriginAlignment(config.alignOriginX, config.alignOriginY);
-        if (int remaining = atlasPacker.pack(glyphs.data(), glyphs.size())) {
-            if (remaining < 0) {
-                ABORT("Failed to pack glyphs into atlas.");
-            } else {
-                fprintf(stderr, "Error: Could not fit %d out of %d glyphs into the atlas.\n", remaining, (int) glyphs.size());
-                return 1;
+        switch (packingStyle) {
+
+            case PackingStyle::TIGHT: {
+                TightAtlasPacker atlasPacker;
+                if (fixedDimensions)
+                    atlasPacker.setDimensions(fixedWidth, fixedHeight);
+                else
+                    atlasPacker.setDimensionsConstraint(atlasSizeConstraint);
+                atlasPacker.setPadding(padding);
+                if (fixedScale)
+                    atlasPacker.setScale(config.emSize);
+                else
+                    atlasPacker.setMinimumScale(minEmSize);
+                atlasPacker.setPixelRange(pxRange);
+                atlasPacker.setUnitRange(unitRange);
+                atlasPacker.setMiterLimit(config.miterLimit);
+                atlasPacker.setOriginAlignment(config.alignOriginX, config.alignOriginY);
+                if (int remaining = atlasPacker.pack(glyphs.data(), glyphs.size())) {
+                    if (remaining < 0) {
+                        ABORT("Failed to pack glyphs into atlas.");
+                    } else {
+                        fprintf(stderr, "Error: Could not fit %d out of %d glyphs into the atlas.\n", remaining, (int) glyphs.size());
+                        return 1;
+                    }
+                }
+                atlasPacker.getDimensions(config.width, config.height);
+                if (!(config.width > 0 && config.height > 0))
+                    ABORT("Unable to determine atlas size.");
+                config.emSize = atlasPacker.getScale();
+                config.pxRange = atlasPacker.getPixelRange();
+                if (!fixedScale)
+                    printf("Glyph size: %.9g pixels/em\n", config.emSize);
+                if (!fixedDimensions)
+                    printf("Atlas dimensions: %d x %d\n", config.width, config.height);
+                break;
             }
+
+            case PackingStyle::GRID: {
+                GridAtlasPacker atlasPacker;
+                atlasPacker.setFixedOrigin(config.grid.hFixed, config.grid.vFixed);
+                if (fixedCellWidth >= 0 && fixedCellHeight >= 0)
+                    atlasPacker.setCellDimensions(fixedCellWidth, fixedCellHeight);
+                else
+                    atlasPacker.setCellDimensionsConstraint(cellSizeConstraint);
+                if (config.grid.cols > 0)
+                    atlasPacker.setColumns(config.grid.cols);
+                if (fixedDimensions)
+                    atlasPacker.setDimensions(fixedWidth, fixedHeight);
+                else
+                    atlasPacker.setDimensionsConstraint(atlasSizeConstraint);
+                atlasPacker.setPadding(padding);
+                if (fixedScale)
+                    atlasPacker.setScale(config.emSize);
+                else
+                    atlasPacker.setMinimumScale(minEmSize);
+                atlasPacker.setPixelRange(pxRange);
+                atlasPacker.setUnitRange(unitRange);
+                atlasPacker.setMiterLimit(config.miterLimit);
+                //atlasPacker.setOriginAlignment(config.alignOriginX, config.alignOriginY);
+                if (int remaining = atlasPacker.pack(glyphs.data(), glyphs.size())) {
+                    if (remaining < 0) {
+                        ABORT("Failed to pack glyphs into atlas.");
+                    } else {
+                        fprintf(stderr, "Error: Could not fit %d out of %d glyphs into the atlas.\n", remaining, (int) glyphs.size());
+                        return 1;
+                    }
+                }
+                atlasPacker.getDimensions(config.width, config.height);
+                if (!(config.width > 0 && config.height > 0))
+                    ABORT("Unable to determine atlas size.");
+                config.emSize = atlasPacker.getScale();
+                config.pxRange = atlasPacker.getPixelRange();
+                atlasPacker.getCellDimensions(config.grid.cellWidth, config.grid.cellHeight);
+                config.grid.cols = atlasPacker.getColumns();
+                config.grid.rows = atlasPacker.getRows();
+                if (!fixedScale)
+                    printf("Glyph size: %.9g pixels/em\n", config.emSize);
+                if (config.grid.hFixed || config.grid.vFixed) {
+                    atlasPacker.getFixedOrigin(uniformOriginX, uniformOriginY);
+                    printf("Grid cell origin: ");
+                    if (config.grid.hFixed)
+                        printf("X = %.9g", uniformOriginX);
+                    if (config.grid.hFixed && config.grid.vFixed)
+                        printf(", ");
+                    if (config.grid.vFixed) {
+                        switch (config.yDirection) {
+                            case YDirection::BOTTOM_UP:
+                                printf("Y = %.9g", uniformOriginY);
+                                break;
+                            case YDirection::TOP_DOWN:
+                                printf("Y = %.9g", (config.grid.cellHeight-padding-1)/config.emSize-uniformOriginY);
+                                break;
+                        }
+                    }
+                    printf("\n");
+                }
+                printf("Grid cell dimensions: %d x %d\n", config.grid.cellWidth, config.grid.cellHeight);
+                printf("Atlas dimensions: %d x %d (%d columns x %d rows)\n", config.width, config.height, config.grid.cols, config.grid.rows);
+                break;
+            }
+
         }
-        atlasPacker.getDimensions(config.width, config.height);
-        if (!(config.width > 0 && config.height > 0))
-            ABORT("Unable to determine atlas size.");
-        config.emSize = atlasPacker.getScale();
-        config.pxRange = atlasPacker.getPixelRange();
-        if (!fixedScale)
-            printf("Glyph size: %.9g pixels/EM\n", config.emSize);
-        if (!fixedDimensions)
-            printf("Atlas dimensions: %d x %d\n", config.width, config.height);
     }
 
     // Generate atlas bitmap
@@ -1075,8 +1226,25 @@ int main(int argc, const char * const *argv) {
             fputs("Failed to write CSV output file.\n", stderr);
         }
     }
+
     if (config.jsonFilename) {
-        if (exportJSON(fonts.data(), fonts.size(), config.emSize, config.pxRange, config.width, config.height, config.imageType, config.yDirection, config.jsonFilename, config.kerning))
+        JsonAtlasMetrics jsonMetrics = { };
+        JsonAtlasMetrics::GridMetrics gridMetrics = { };
+        jsonMetrics.distanceRange = config.pxRange;
+        jsonMetrics.size = config.emSize;
+        jsonMetrics.width = config.width, jsonMetrics.height = config.height;
+        jsonMetrics.yDirection = config.yDirection;
+        if (packingStyle == PackingStyle::GRID) {
+            gridMetrics.cellWidth = config.grid.cellWidth, gridMetrics.cellHeight = config.grid.cellHeight;
+            gridMetrics.columns = config.grid.cols, gridMetrics.rows = config.grid.rows;
+            if (config.grid.hFixed)
+                gridMetrics.originX = &uniformOriginX;
+            if (config.grid.vFixed)
+                gridMetrics.originY = &uniformOriginY;
+            gridMetrics.padding = padding;
+            jsonMetrics.grid = &gridMetrics;
+        }
+        if (exportJSON(fonts.data(), fonts.size(), config.imageType, jsonMetrics, config.jsonFilename, config.kerning))
             fputs("Glyph layout and metadata written into JSON file.\n", stderr);
         else {
             result = 1;

msdf-atlas-gen/msdf-atlas-gen.h

@@ -26,6 +26,7 @@
 #include "AtlasStorage.h"
 #include "BitmapAtlasStorage.h"
 #include "TightAtlasPacker.h"
+#include "GridAtlasPacker.h"
 #include "AtlasGenerator.h"
 #include "ImmediateAtlasGenerator.h"
 #include "DynamicAtlas.h"

msdf-atlas-gen/types.h

@@ -49,4 +49,20 @@ enum class YDirection {
     TOP_DOWN
 };
 
+/// The method of computing the layout of the atlas
+enum class PackingStyle {
+    TIGHT,
+    GRID
+};
+
+/// Constraints for the atlas's dimensions - see size selectors for more info
+enum class DimensionsConstraint {
+    NONE,
+    SQUARE,
+    EVEN_SQUARE,
+    MULTIPLE_OF_FOUR_SQUARE,
+    POWER_OF_TWO_RECTANGLE,
+    POWER_OF_TWO_SQUARE
+};
+
 }