Hook in rough distance field support for fonts

src/gpu/GrTextStrike.cpp

Index: src/gpu/GrTextStrike.cpp
diff --git a/src/gpu/GrTextStrike.cpp b/src/gpu/GrTextStrike.cpp
index a96aab16c8f640f18905d82766590b9104c55563..85e2b5021e9394ce0582776a928a9836e5d044c3 100644
--- a/src/gpu/GrTextStrike.cpp
+++ b/src/gpu/GrTextStrike.cpp
@@ -12,6 +12,8 @@
 #include "GrTextStrike_impl.h"
 #include "SkString.h"
 
+#include "edtaa3.h"
+
 SK_DEFINE_INST_COUNT(GrFontScaler)
 SK_DEFINE_INST_COUNT(GrKey)
 
@@ -193,6 +195,9 @@ void GrFontCache::dump() const {
     static int gCounter;
 #endif
 
+#define DISTANCE_FIELD_PAD   4
+#define DISTANCE_FIELD_RANGE (4.0)
+
 /*
     The text strike is specific to a given font/style/matrix setup, which is
     represented by the GrHostFontScaler object we are given in getGlyph().
@@ -246,6 +251,13 @@ GrGlyph* GrTextStrike::generateGlyph(GrGlyph::PackedID packed,
     }
 
     GrGlyph* glyph = fPool.alloc();
+    // expand bounds to hold full distance field data
+    if (fUseDistanceField) {
+        bounds.fLeft   -= DISTANCE_FIELD_PAD;
+        bounds.fRight  += DISTANCE_FIELD_PAD;
+        bounds.fTop    -= DISTANCE_FIELD_PAD;
+        bounds.fBottom += DISTANCE_FIELD_PAD;
+    }
     glyph->init(packed, bounds);
     fCache.insert(packed, glyph);
     return glyph;
@@ -256,6 +268,7 @@ bool GrTextStrike::removeUnusedPlots() {
     return fAtlasMgr->removeUnusedPlots(&fAtlas);
 }
 
+
 bool GrTextStrike::getGlyphAtlas(GrGlyph* glyph, GrFontScaler* scaler) {
 #if 0   // testing hack to force us to flush our cache often
     static int gCounter;
@@ -270,18 +283,105 @@ bool GrTextStrike::getGlyphAtlas(GrGlyph* glyph, GrFontScaler* scaler) {
     SkAutoRef ar(scaler);
 
     int bytesPerPixel = GrMaskFormatBytesPerPixel(fMaskFormat);
-    size_t size = glyph->fBounds.area() * bytesPerPixel;
-    SkAutoSMalloc<1024> storage(size);
-    if (!scaler->getPackedGlyphImage(glyph->fPackedID, glyph->width(),
-                                     glyph->height(),
-                                     glyph->width() * bytesPerPixel,
-                                     storage.get())) {
-        return false;
+
+    GrPlot* plot;
+    if (fUseDistanceField) {
+        SkASSERT(1 == bytesPerPixel);
+
+        // we've already expanded the glyph dimensions to match the final size
+        // but must shrink back down to get the packed glyph data
+        int dfwidth = glyph->width();
+        int dfheight = glyph->height();
+        int width = dfwidth - 2*DISTANCE_FIELD_PAD;
+        int height = dfheight - 2*DISTANCE_FIELD_PAD;
+        size_t stride = width*bytesPerPixel;
+
+        size_t size = width * height * bytesPerPixel;
+        SkAutoSMalloc<1024> storage(size);
+        if (!scaler->getPackedGlyphImage(glyph->fPackedID, width, height, stride, storage.get())) {
+            return false;
+        }
+
+        // alloc storage for distance field glyph
+        size_t dfsize = dfwidth * dfheight * bytesPerPixel;
+        SkAutoSMalloc<1024> dfstorage(dfsize);
+
+        // copy glyph into distance field storage
+        memset(dfstorage.get(), 0, dfsize);
+
+        unsigned char* ptr = (unsigned char*) storage.get();
+        unsigned char* dfptr = (unsigned char*) dfstorage.get();
+        size_t dfstride = dfwidth*bytesPerPixel;
+        dfptr += DISTANCE_FIELD_PAD*dfstride;
+        dfptr += DISTANCE_FIELD_PAD*bytesPerPixel;
+
+        for (int i = 0; i < height; ++i) {
+            memcpy(dfptr, ptr, stride);
+
+            dfptr += dfstride;
+            ptr += stride;
+        }
+
+        // generate distance field data
+        short* distx = new short[dfwidth*dfheight];
+        short* disty = new short[dfwidth*dfheight];
+        double* outerdist = new double[dfwidth*dfheight];
+        double* gx = new double[dfwidth*dfheight];
+        double* gy = new double[dfwidth*dfheight];
+        dfptr = (unsigned char*) dfstorage.get();
+        computegradient(dfptr, dfwidth, dfheight, gx, gy);
+        edtaa3(dfptr, gx, gy, dfwidth, dfheight, distx, disty, outerdist);
+
+        for (int i = 0; i < dfwidth*dfheight; ++i) {
+            *dfptr++ = 255 - *dfptr;
+        }
+        double* innerdist = new double[dfwidth*dfheight];
+        dfptr = (unsigned char*) dfstorage.get();
+        memset(gx, 0, sizeof(double)*dfwidth*dfheight);
+        memset(gy, 0, sizeof(double)*dfwidth*dfheight);
+        computegradient(dfptr, dfwidth, dfheight, gx, gy);
+        edtaa3(dfptr, gx, gy, dfwidth, dfheight, distx, disty, innerdist);
+
+        for (int i = 0; i < dfwidth*dfheight; ++i) {
+            unsigned char val;
+            double outerval = outerdist[i];
+            if (outerval < 0.0) { outerval = 0.0; }
+            double innerval = innerdist[i];
+            if (innerval < 0.0) { innerval = 0.0; }
+            double dist = outerval - innerval;
+            if (dist <= -DISTANCE_FIELD_RANGE) {
+                val = 255;
+            } else if (dist > DISTANCE_FIELD_RANGE) {
+                val = 0;
+            } else {
+                val = (unsigned char)((DISTANCE_FIELD_RANGE-dist)*128.0/DISTANCE_FIELD_RANGE);
+            }
+            *dfptr++ = val;
+        }
+
+        delete [] distx;
+        delete [] disty;
+        delete [] innerdist;
+        delete [] outerdist;
+        
+        // copy to atlas
+        plot = fAtlasMgr->addToAtlas(&fAtlas, dfwidth, dfheight, dfstorage.get(), 
+                                             &glyph->fAtlasLocation);
+
+    } else {
+        size_t size = glyph->fBounds.area() * bytesPerPixel;
+        SkAutoSMalloc<1024> storage(size);
+        if (!scaler->getPackedGlyphImage(glyph->fPackedID, glyph->width(),
+                                         glyph->height(),
+                                         glyph->width() * bytesPerPixel,
+                                         storage.get())) {
+            return false;
+        }
+
+        plot = fAtlasMgr->addToAtlas(&fAtlas, glyph->width(), glyph->height(), storage.get(), 
+                                             &glyph->fAtlasLocation);
     }
 
-    GrPlot* plot = fAtlasMgr->addToAtlas(&fAtlas, glyph->width(),
-                                         glyph->height(), storage.get(),
-                                         &glyph->fAtlasLocation);
     if (NULL == plot) {
         return false;
     }
@@ -289,3 +389,4 @@ bool GrTextStrike::getGlyphAtlas(GrGlyph* glyph, GrFontScaler* scaler) {
     glyph->fPlot = plot;
     return true;
 }
+