Merge pull request #4656 from hthh/cmpr-fixes

TextureDecoder: Fix off-by-one errors in CMPR

1 files changed, 7 insertions, 22 deletions

diff --git a/Source/Core/VideoCommon/TextureDecoder_Generic.cpp b/Source/Core/VideoCommon/TextureDecoder_Generic.cpp
index bb48d1aca8..eb7ed141ef 100644
--- a/Source/Core/VideoCommon/TextureDecoder_Generic.cpp
+++ b/Source/Core/VideoCommon/TextureDecoder_Generic.cpp
@@ -10,6 +10,7 @@
 #include "Common/CommonTypes.h"
 #include "VideoCommon/LookUpTables.h"
 #include "VideoCommon/TextureDecoder.h"
+#include "VideoCommon/TextureDecoder_Util.h"
 //#include "VideoCommon/VideoCommon.h" // to get debug logs
 #include "VideoCommon/VideoConfig.h"
 
@@ -140,18 +141,6 @@ static inline void DecodeBytes_RGBA8(u32* dst, const u16* src, const u16* src2)
 #endif
 }
 
-struct DXTBlock
-{
-  u16 color1;
-  u16 color2;
-  u8 lines[4];
-};
-
-static inline u32 MakeRGBA(int r, int g, int b, int a)
-{
-  return (a << 24) | (b << 16) | (g << 8) | r;
-}
-
 static void DecodeDXTBlock(u32* dst, const DXTBlock* src, int pitch)
 {
   // S3TC Decoder (Note: GCN decodes differently from PC so we can't use native support)
@@ -169,21 +158,17 @@ static void DecodeDXTBlock(u32* dst, const DXTBlock* src, int pitch)
   colors[1] = MakeRGBA(red2, green2, blue2, 255);
   if (c1 > c2)
   {
-    // Approximation of x/3: 3/8 (1/2 - 1/8)
-    int blue3 = ((blue2 - blue1) >> 1) - ((blue2 - blue1) >> 3);
-    int green3 = ((green2 - green1) >> 1) - ((green2 - green1) >> 3);
-    int red3 = ((red2 - red1) >> 1) - ((red2 - red1) >> 3);
-    colors[2] = MakeRGBA(red1 + red3, green1 + green3, blue1 + blue3, 255);
-    colors[3] = MakeRGBA(red2 - red3, green2 - green3, blue2 - blue3, 255);
+    colors[2] =
+        MakeRGBA(DXTBlend(red2, red1), DXTBlend(green2, green1), DXTBlend(blue2, blue1), 255);
+    colors[3] =
+        MakeRGBA(DXTBlend(red1, red2), DXTBlend(green1, green2), DXTBlend(blue1, blue2), 255);
   }
   else
   {
     // color[3] is the same as color[2] (average of both colors), but transparent.
     // This differs from DXT1 where color[3] is transparent black.
-    colors[2] =
-        MakeRGBA((red1 + red2 + 1) / 2, (green1 + green2 + 1) / 2, (blue1 + blue2 + 1) / 2, 255);
-    colors[3] =
-        MakeRGBA((red1 + red2 + 1) / 2, (green1 + green2 + 1) / 2, (blue1 + blue2 + 1) / 2, 0);
+    colors[2] = MakeRGBA((red1 + red2) / 2, (green1 + green2) / 2, (blue1 + blue2) / 2, 255);
+    colors[3] = MakeRGBA((red1 + red2) / 2, (green1 + green2) / 2, (blue1 + blue2) / 2, 0);
   }
 
   for (int y = 0; y < 4; y++)