Add skia to the repository.

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@16 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 49 insertions, 0 deletions

diff --git a/skia/sgl/SkDither.cpp b/skia/sgl/SkDither.cpp
new file mode 100644
index 0000000..53a8573
--- /dev/null
+++ b/skia/sgl/SkDither.cpp
@@ -0,0 +1,49 @@
+#include "SkDither.h"
+
+/*  The base dither matrix we use to derive optimized ones for 565 and 4444
+ 
+    { 0,  32, 8,  40, 2,  34, 10, 42 },
+    { 48, 16, 56, 24, 50, 18, 58, 26 },
+    { 12, 44, 4,  36, 14, 46, 6,  38 },
+    { 60, 28, 52, 20, 62, 30, 54, 22 },
+    { 3,  35, 11, 43, 1,  33, 9,  41 },
+    { 51, 19, 59, 27, 49, 17, 57, 25 },
+    { 15, 47, 7,  39, 13, 45, 5,  37 },
+    { 63, 31, 55, 23, 61, 29, 53, 21 }
+
+    The 4444 version only needs 4 bits, and given that we can reduce its size
+    since the other 4x4 sub pieces all look the same once we truncate the bits.
+
+    The 565 version only needs 3 bits for red/blue, and only 2 bits for green.
+    For simplicity, we store 3 bits, and have the dither macros for green know
+    this, and they shift the dither value down by 1 to make it 2 bits.
+ */
+
+#ifdef ENABLE_DITHER_MATRIX_4X4
+
+const uint8_t gDitherMatrix_4Bit_4X4[4][4] = {
+    {  0,  8,  2, 10 },
+    { 12,  4, 14,  6 },
+    {  3, 11,  1,  9 },
+    { 15,  7, 13,  5 }
+};
+
+const uint8_t gDitherMatrix_3Bit_4X4[4][4] = {
+    {  0,  4,  1,  5 },
+    {  6,  2,  7,  3 },
+    {  1,  5,  0,  4 },
+    {  7,  3,  6,  2 }
+};
+
+#else   // used packed shorts for a scanlines worth of dither values
+
+const uint16_t gDitherMatrix_4Bit_16[4] = {
+    0xA280, 0x6E4C, 0x91B3, 0x5D7F
+};
+
+const uint16_t gDitherMatrix_3Bit_16[4] = {
+    0x5140, 0x3726, 0x4051, 0x2637
+};
+
+#endif
+