Fix GLES2 Red Green Texture Decompression

Replaced broken decompression code with two calls to DXT5 decompression.

This should fix some issues with normal maps as they usually are stored
as RG Textures and were decompressed incorrectly.

1 files changed, 13 insertions, 76 deletions

diff --git a/thirdparty/squish/colourblock.cpp b/thirdparty/squish/colourblock.cpp
index 3de46382c0..3d87adaa77 100644
--- a/thirdparty/squish/colourblock.cpp
+++ b/thirdparty/squish/colourblock.cpp
@@ -24,6 +24,9 @@
    -------------------------------------------------------------------------- */
 
 #include "colourblock.h"
+// -- Godot start --
+#include "alpha.h"
+// -- Godot end --
 
 namespace squish {
 
@@ -214,83 +217,17 @@ void DecompressColour( u8* rgba, void const* block, bool isDxt1 )
 // -- Godot start --
 void DecompressColourBc5( u8* rgba, void const* block)
 {
-    // get the block bytes
-    u8 const* bytes = reinterpret_cast< u8 const* >( block );
-
-    // unpack the endpoints
-    u8 codes[16];
-    int red_0 = bytes[0];
-    int red_1 = bytes[1];
-
-    codes[0] = red_0;
-    codes[1] = red_1;
-    codes[6] = 0.0f;
-    codes[7] = 1.0f;
-    // generate the midpoints
-    if(red_0 > red_1)
-    {
-        for( int i = 2; i < 8; ++i )
-        {
-            codes[i] = ((8-i)*red_0 + (i-1)*red_1)/7;
-        }
-    }
-    else
-    {
-        for( int i = 2; i < 6; ++i )
-        {
-            codes[i] = ((6-i)*red_0 + (i-1)*red_1)/5;
-        }
-    }
-
-    int green_0 = bytes[8];
-    int green_1 = bytes[9];
-
-    codes[0 + 8] = green_0;
-    codes[1 + 8] = green_1;
-    codes[6 + 8] = 0.0f;
-    codes[7 + 8] = 1.0f;
-    // generate the midpoints
-    if(green_0 > green_1)
-    {
-        for( int i = 2; i < 8; ++i )
-        {
-            codes[i + 8] = ((8-i)*green_0 + (i-1)*green_1)/7;
-        }
-    }
-    else
-    {
-        for( int i = 2; i < 6; ++i )
-        {
-            codes[i + 8] = ((6-i)*green_0 + (i-1)*green_1)/5;
-        }
-    }
-
-    u8 indices[32];
-    for( int i = 0; i < 4; ++i )
-    {
-        u8 packed = bytes[2 + i];
-        u8* red_ind = indices + 4*i;
-
-        red_ind[0] = packed & 0x3;
-        red_ind[1] = ( packed >> 2 ) & 0x3;
-        red_ind[2] = ( packed >> 4 ) & 0x3;
-        red_ind[3] = ( packed >> 6 ) & 0x3;
-
-        packed = bytes[8 + i];
-        u8* green_ind = indices + 4*i + 16;
-        green_ind[0] = packed & 0x3;
-        green_ind[1] = ( packed >> 2 ) & 0x3;
-        green_ind[2] = ( packed >> 4 ) & 0x3;
-        green_ind[3] = ( packed >> 6 ) & 0x3;
+    void const* rblock = block;
+    void const* gblock = reinterpret_cast< u8 const* >( block ) + 8;
+    DecompressAlphaDxt5(rgba,rblock);
+    for ( int i = 0; i < 16; ++i ) {
+        rgba[i*4] = rgba[i*4 + 3];
     }
-
-    // store out the colours
-    for( int i = 0; i < 16; ++i )
-    {
-        rgba[4*i] = codes[indices[i]];
-        rgba[4*i +1] = codes[indices[i + 16] + 8];
-        rgba[4*i +2] = 0;
-        rgba[4*i +3] = 255;
+    DecompressAlphaDxt5(rgba,gblock);
+    for ( int i = 0; i < 16; ++i ) {
+        rgba[i*4+1] = rgba[i*4 + 3];
+        rgba[i*4 + 2] = 0;
+        rgba[i*4 + 3] = 255;
     }
 }
 // -- GODOT end --