add optional decolorization value for lcd text
git-svn-id: http://skia.googlecode.com/svn/trunk@1358 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/ports/SkFontHost_FreeType.cpp b/src/ports/SkFontHost_FreeType.cpp
index b3cc783..8928b1e 100644
--- a/src/ports/SkFontHost_FreeType.cpp
+++ b/src/ports/SkFontHost_FreeType.cpp
@@ -72,6 +72,13 @@
using namespace skia_advanced_typeface_metrics_utils;
+// SK_FREETYPE_LCD_LERP should be 0...256, where 0 means no color reduction
+// and 256 means 100% color reduction (e.g. gray)
+//
+#ifndef SK_FREETYPE_LCD_LERP
+ #define SK_FREETYPE_LCD_LERP 128
+#endif
+
//////////////////////////////////////////////////////////////////////////
struct SkFaceRec;
@@ -979,6 +986,21 @@
using namespace skia_freetype_support;
#endif
+static int lerp(int start, int end, int percent) {
+ return start + ((end - start) * percent >> 8);
+}
+
+static uint16_t packTriple(unsigned r, unsigned g, unsigned b) {
+ if (SK_FREETYPE_LCD_LERP) {
+ SkASSERT((unsigned)SK_FREETYPE_LCD_LERP <= 256);
+ unsigned sum = r + 2 * g + b >> 2;
+ r = lerp(r, sum, SK_FREETYPE_LCD_LERP);
+ g = lerp(g, sum, SK_FREETYPE_LCD_LERP);
+ b = lerp(b, sum, SK_FREETYPE_LCD_LERP);
+ }
+ return SkPackRGB16(r >> 3, g >> 2, b >> 3);
+}
+
static void copyFT2LCD16(const SkGlyph& glyph, const FT_Bitmap& bitmap) {
SkASSERT(glyph.fWidth * 3 == bitmap.width - 6);
SkASSERT(glyph.fHeight == bitmap.rows);
@@ -991,7 +1013,7 @@
for (int y = 0; y < glyph.fHeight; y++) {
const uint8_t* triple = src;
for (int x = 0; x < width; x++) {
- dst[x] = SkPackRGB16(triple[0] >> 3, triple[1] >> 2, triple[2] >> 3);
+ dst[x] = packTriple(triple[0], triple[1], triple[2]);
triple += 3;
}
src += bitmap.pitch;