Change FreeType lcd filter to provide better results.
https://codereview.appspot.com/6652046/
Will require rebaselines on systems using lcd smoothed FreeType.
git-svn-id: http://skia.googlecode.com/svn/trunk@5944 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/ports/SkFontHost_FreeType.cpp b/src/ports/SkFontHost_FreeType.cpp
index ce8f409..dc7666e 100644
--- a/src/ports/SkFontHost_FreeType.cpp
+++ b/src/ports/SkFontHost_FreeType.cpp
@@ -86,6 +86,8 @@
static bool gLCDSupport; // true iff LCD is supported by the runtime.
static int gLCDExtra; // number of extra pixels for filtering.
+/////////////////////////////////////////////////////////////////////////
+
// FT_Library_SetLcdFilterWeights was introduced in FreeType 2.4.0.
// The following platforms provide FreeType of at least 2.4.0.
// Ubuntu >= 11.04 (previous deprecated April 2013)
@@ -95,8 +97,6 @@
// Android >= Gingerbread (good)
typedef FT_Error (*FT_Library_SetLcdFilterWeightsProc)(FT_Library, unsigned char*);
-/////////////////////////////////////////////////////////////////////////
-
// Caller must lock gFTMutex before calling this function.
static bool InitFreetype() {
FT_Error err = FT_Init_FreeType(&gFTLibrary);
@@ -106,18 +106,20 @@
// Setup LCD filtering. This reduces color fringes for LCD smoothed glyphs.
#ifdef FT_LCD_FILTER_H
- //Use light as default, as FT_LCD_FILTER_DEFAULT adds up to 0x110.
- err = FT_Library_SetLcdFilter(gFTLibrary, FT_LCD_FILTER_LIGHT);
+ // Use default { 0x10, 0x40, 0x70, 0x40, 0x10 }, as it adds up to 0x110, simulating ink spread.
+ // SetLcdFilter must be called before SetLcdFilterWeights.
+ err = FT_Library_SetLcdFilter(gFTLibrary, FT_LCD_FILTER_DEFAULT);
if (0 == err) {
gLCDSupport = true;
gLCDExtra = 2; //Using a filter adds one full pixel to each side.
- static unsigned char gaussianLikeWeights[] = { 0x17, 0x40, 0x52, 0x40, 0x17 };
- //static unsigned char triangleLikeWeights[] = { 0x1C, 0x39, 0x56, 0x39, 0x1C };
+#ifdef SK_FONTHOST_FREETYPE_USE_NORMAL_LCD_FILTER
+ // This also adds to 0x110 simulating ink spread, but provides better results than default.
+ static unsigned char gGaussianLikeHeavyWeights[] = { 0x1A, 0x43, 0x56, 0x43, 0x1A, };
#if defined(SK_FONTHOST_FREETYPE_RUNTIME_VERSION) && \
SK_FONTHOST_FREETYPE_RUNTIME_VERSION > 0x020400
- err = FT_Library_SetLcdFilterWeights(gFTLibrary, gaussianLikeWeights);
+ err = FT_Library_SetLcdFilterWeights(gFTLibrary, gGaussianLikeHeavyWeights);
#elif defined(SK_CAN_USE_DLOPEN) && SK_CAN_USE_DLOPEN == 1
//The FreeType library is already loaded, so symbols are available in process.
void* self = dlopen(NULL, RTLD_LAZY);
@@ -128,10 +130,11 @@
dlclose(self);
if (NULL != setLcdFilterWeights) {
- err = setLcdFilterWeights(gFTLibrary, gaussianLikeWeights);
+ err = setLcdFilterWeights(gFTLibrary, gGaussianLikeHeavyWeights);
}
}
#endif
+#endif
}
#else
gLCDSupport = false;