don't flip the fractional bits (low 4) for bilerp when in kMirror_TileMode

Review URL: https://codereview.appspot.com/5795043

git-svn-id: http://skia.googlecode.com/svn/trunk@3357 2bbb7eff-a529-9590-31e7-b0007b416f81

1 files changed, 30 insertions, 7 deletions

diff --git a/src/core/SkBitmapProcState_matrixProcs.cpp b/src/core/SkBitmapProcState_matrixProcs.cpp
index bda24385c7..9a15ad2098 100644
--- a/src/core/SkBitmapProcState_matrixProcs.cpp
+++ b/src/core/SkBitmapProcState_matrixProcs.cpp
@@ -56,15 +56,17 @@ void decal_filter_scale(uint32_t dst[], SkFixed fx, SkFixed dx, int count);
 
 #define MAKENAME(suffix)        GeneralXY ## suffix
 #define PREAMBLE(state)         SkBitmapProcState::FixedTileProc tileProcX = (state).fTileProcX; \
-                                SkBitmapProcState::FixedTileProc tileProcY = (state).fTileProcY
-#define PREAMBLE_PARAM_X        , SkBitmapProcState::FixedTileProc tileProcX
-#define PREAMBLE_PARAM_Y        , SkBitmapProcState::FixedTileProc tileProcY
-#define PREAMBLE_ARG_X          , tileProcX
-#define PREAMBLE_ARG_Y          , tileProcY
+                                SkBitmapProcState::FixedTileProc tileProcY = (state).fTileProcY; \
+                                SkBitmapProcState::FixedTileLowBitsProc tileLowBitsProcX = (state).fTileLowBitsProcX; \
+                                SkBitmapProcState::FixedTileLowBitsProc tileLowBitsProcY = (state).fTileLowBitsProcY
+#define PREAMBLE_PARAM_X        , SkBitmapProcState::FixedTileProc tileProcX, SkBitmapProcState::FixedTileLowBitsProc tileLowBitsProcX
+#define PREAMBLE_PARAM_Y        , SkBitmapProcState::FixedTileProc tileProcY, SkBitmapProcState::FixedTileLowBitsProc tileLowBitsProcY
+#define PREAMBLE_ARG_X          , tileProcX, tileLowBitsProcX
+#define PREAMBLE_ARG_Y          , tileProcY, tileLowBitsProcY
 #define TILEX_PROCF(fx, max)    (tileProcX(fx) * ((max) + 1) >> 16)
 #define TILEY_PROCF(fy, max)    (tileProcY(fy) * ((max) + 1) >> 16)
-#define TILEX_LOW_BITS(fx, max) ((tileProcX(fx) * ((max) + 1) >> 12) & 0xF)
-#define TILEY_LOW_BITS(fy, max) ((tileProcY(fy) * ((max) + 1) >> 12) & 0xF)
+#define TILEX_LOW_BITS(fx, max) tileLowBitsProcX(fx, (max) + 1)
+#define TILEY_LOW_BITS(fy, max) tileLowBitsProcY(fy, (max) + 1)
 #include "SkBitmapProcState_matrix.h"
 
 static inline U16CPU fixed_clamp(SkFixed x)
@@ -108,6 +110,25 @@ static SkBitmapProcState::FixedTileProc choose_tile_proc(unsigned m)
     return fixed_mirror;
 }
 
+static inline U16CPU fixed_clamp_lowbits(SkFixed x, int) {
+    return (x >> 12) & 0xF;
+}
+
+static inline U16CPU fixed_repeat_or_mirrow_lowbits(SkFixed x, int scale) {
+    return ((x * scale) >> 12) & 0xF;
+}
+
+static SkBitmapProcState::FixedTileLowBitsProc choose_tile_lowbits_proc(unsigned m) {
+    if (SkShader::kClamp_TileMode == m) {
+        return fixed_clamp_lowbits;
+    } else {
+        SkASSERT(SkShader::kMirror_TileMode == m ||
+                 SkShader::kRepeat_TileMode == m);
+        // mirror and repeat have the same behavior for the low bits.
+        return fixed_repeat_or_mirrow_lowbits;
+    }
+}
+
 static inline U16CPU int_clamp(int x, int n) {
 #ifdef SK_CPU_HAS_CONDITIONAL_INSTR
     if (x >= n)
@@ -522,6 +543,8 @@ SkBitmapProcState::chooseMatrixProc(bool trivial_matrix) {
     
     fTileProcX = choose_tile_proc(fTileModeX);
     fTileProcY = choose_tile_proc(fTileModeY);
+    fTileLowBitsProcX = choose_tile_lowbits_proc(fTileModeX);
+    fTileLowBitsProcY = choose_tile_lowbits_proc(fTileModeY);
     return GeneralXY_Procs[index];
 }