Add new module for distance field generation.

src/gpu/GrTextStrike.cpp

Index: src/gpu/GrTextStrike.cpp
diff --git a/src/gpu/GrTextStrike.cpp b/src/gpu/GrTextStrike.cpp
index e303a23df8d2b851800d4a2c25b40f84e540894b..0d7fcafe678ebb9cc1fb96f0e32d4c5cea17dc0a 100644
--- a/src/gpu/GrTextStrike.cpp
+++ b/src/gpu/GrTextStrike.cpp
@@ -13,7 +13,7 @@
 #include "SkString.h"
 
 #if SK_DISTANCEFIELD_FONTS
-#include "edtaa3.h"
+#include "SkDistanceFieldGen.h"
 #endif
 
 ///////////////////////////////////////////////////////////////////////////////
@@ -199,8 +199,9 @@ void GrFontCache::dump() const {
 #endif
 
 #if SK_DISTANCEFIELD_FONTS
-#define DISTANCE_FIELD_PAD   4
-#define DISTANCE_FIELD_RANGE (4.0)
+// this acts as the max magnitude for the distance field,
+// as well as the pad we need around the glyph
+#define DISTANCE_FIELD_RANGE   4
 #endif
 
 /*
@@ -253,10 +254,10 @@ GrGlyph* GrTextStrike::generateGlyph(GrGlyph::PackedID packed,
 #if SK_DISTANCEFIELD_FONTS
     // 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;
+        bounds.fLeft   -= DISTANCE_FIELD_RANGE;
+        bounds.fRight  += DISTANCE_FIELD_RANGE;
+        bounds.fTop    -= DISTANCE_FIELD_RANGE;
+        bounds.fBottom += DISTANCE_FIELD_RANGE;
     }
 #endif
     glyph->init(packed, bounds);
@@ -294,15 +295,13 @@ bool GrTextStrike::addGlyphToAtlas(GrGlyph* glyph, GrFontScaler* scaler) {
     GrPlot* plot;
 #if SK_DISTANCEFIELD_FONTS
     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;
+        int width = dfWidth - 2*DISTANCE_FIELD_RANGE;
+        int height = dfHeight - 2*DISTANCE_FIELD_RANGE;
+        int stride = width*bytesPerPixel;
 
         size_t size = width * height * bytesPerPixel;
         SkAutoSMalloc<1024> storage(size);
@@ -313,71 +312,28 @@ bool GrTextStrike::addGlyphToAtlas(GrGlyph* glyph, GrFontScaler* scaler) {
         // alloc storage for distance field glyph
         size_t dfSize = dfWidth * dfHeight * bytesPerPixel;
         SkAutoSMalloc<1024> dfStorage(dfSize);
-
-        // copy glyph into distance field storage
-        sk_bzero(dfStorage.get(), 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
-        SkAutoSMalloc<1024> distXStorage(dfWidth*dfHeight*sizeof(short));
-        SkAutoSMalloc<1024> distYStorage(dfWidth*dfHeight*sizeof(short));
-        SkAutoSMalloc<1024> outerDistStorage(dfWidth*dfHeight*sizeof(double));
-        SkAutoSMalloc<1024> innerDistStorage(dfWidth*dfHeight*sizeof(double));
-        SkAutoSMalloc<1024> gxStorage(dfWidth*dfHeight*sizeof(double));
-        SkAutoSMalloc<1024> gyStorage(dfWidth*dfHeight*sizeof(double));
-
-        short* distX = (short*) distXStorage.get();
-        short* distY = (short*) distYStorage.get();
-        double* outerDist = (double*) outerDistStorage.get();
-        double* innerDist = (double*) innerDistStorage.get();
-        double* gx = (double*) gxStorage.get();
-        double* gy = (double*) gyStorage.get();
-
-        dfPtr = (unsigned char*) dfStorage.get();
-        EDTAA::computegradient(dfPtr, dfWidth, dfHeight, gx, gy);
-        EDTAA::edtaa3(dfPtr, gx, gy, dfWidth, dfHeight, distX, distY, outerDist);
-
-        for (int i = 0; i < dfWidth*dfHeight; ++i) {
-            *dfPtr = 255 - *dfPtr;
-            dfPtr++;
-        }
-        dfPtr = (unsigned char*) dfStorage.get();
-        sk_bzero(gx, sizeof(double)*dfWidth*dfHeight);
-        sk_bzero(gy, sizeof(double)*dfWidth*dfHeight);
-        EDTAA::computegradient(dfPtr, dfWidth, dfHeight, gx, gy);
-        EDTAA::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);
+        
+        if (1 == bytesPerPixel) {
+            (void) SkGenerateDistanceFieldFromImage((unsigned char*)dfStorage.get(),
+                                                    (unsigned char*)storage.get(),
+                                                    width, height, DISTANCE_FIELD_RANGE);
+        } else {
+            // TODO: Fix color emoji
+            // for now, copy glyph into distance field storage
+            // this is not correct, but it won't crash
+            sk_bzero(dfStorage.get(), dfSize);
+            unsigned char* ptr = (unsigned char*) storage.get();
+            unsigned char* dfPtr = (unsigned char*) dfStorage.get();
+            size_t dfStride = dfWidth*bytesPerPixel;
+            dfPtr += DISTANCE_FIELD_RANGE*dfStride;
+            dfPtr += DISTANCE_FIELD_RANGE*bytesPerPixel;
+
+            for (int i = 0; i < height; ++i) {
+                memcpy(dfPtr, ptr, stride);
+
+                dfPtr += dfStride;
+                ptr += stride;
             }
-            *dfPtr++ = val;
         }
 
         // copy to atlas