From Johannes Baeuerele, "I have extended the pvr reader plugin to support etc1 compression(GL_ETC1_RGB8_OES). The changes attached to this submission are based on today's trunk.

The pvr format which can be used as a wrapper for different compressed and uncompressed formats supports this compression algorithm. The original pvr compression uses the pvrtc format. The handling of pvrtc is already implemented in the pvr plugin. PVR provides wrapper functionality for some formats, e.g. etc or even dxt/dds.

Our target system (gles2) is able to use the etc compression format. With minor changes in the submitted files, there is no need to write a separate plugin. However the original pvr texture compression formats are not supported on our target, which is the reason for this extension.

The changes mainly consist in the definition on new enum values in the classes and headers of ReaderWriterPVR,Image and Texture. I also found some locations where the handling of the original pvr textures was not implemented. These are also part of this submission."

include/osg/Texture

@@ -71,6 +71,10 @@
     #define GL_COMPRESSED_RGBA_PVRTC_2BPPV1_IMG     0x8C03
 #endif
 
+#ifndef GL_OES_compressed_ETC1_RGB8_texture
+    #define GL_ETC1_RGB8_OES                            0x8D64   
+#endif
+
 #ifndef GL_ARB_INTERNAL_TEXTURE_FORMAT
     #define GL_RGBA32F_ARB                           0x8814
     #define GL_RGB32F_ARB                            0x8815
@@ -446,6 +450,9 @@ class OSG_EXPORT Texture : public osg::StateAttribute
             USE_S3TC_DXT1_COMPRESSION,
             USE_S3TC_DXT3_COMPRESSION,
             USE_S3TC_DXT5_COMPRESSION,
+            USE_PVRTC_2BPP_COMPRESSION,
+            USE_PVRTC_4BPP_COMPRESSION,
+            USE_ETC_COMPRESSION,
             USE_RGTC1_COMPRESSION,
             USE_RGTC2_COMPRESSION,
             USE_S3TC_DXT1c_COMPRESSION,
@@ -644,6 +651,15 @@ class OSG_EXPORT Texture : public osg::StateAttribute
                 void setTextureCompressionS3TCSupported(bool flag) { _isTextureCompressionS3TCSupported=flag; }
                 bool isTextureCompressionS3TCSupported() const { return _isTextureCompressionS3TCSupported; }
 
+                void setTextureCompressionPVRTC2BPPSupported(bool flag) { _isTextureCompressionPVRTC2BPPSupported=flag; }
+                bool isTextureCompressionPVRTC2BPPSupported() const { return _isTextureCompressionPVRTC2BPPSupported; }
+                
+                void setTextureCompressionPVRTC4BPPSupported(bool flag) { _isTextureCompressionPVRTC4BPPSupported=flag; }
+                bool isTextureCompressionPVRTC4BPPSupported() const { return _isTextureCompressionPVRTC4BPPSupported; }
+                
+                void setTextureCompressionETCSupported(bool flag) { _isTextureCompressionETCSupported=flag; }
+                bool isTextureCompressionETCSupported() const { return _isTextureCompressionETCSupported; }
+
                 void setTextureCompressionRGTCSupported(bool flag) { _isTextureCompressionRGTCSupported=flag; }
                 bool isTextureCompressionRGTCSupported() const { return _isTextureCompressionRGTCSupported; }
 
@@ -748,6 +764,9 @@ class OSG_EXPORT Texture : public osg::StateAttribute
                 bool    _isTextureFilterAnisotropicSupported;
                 bool    _isTextureCompressionARBSupported;
                 bool    _isTextureCompressionS3TCSupported;
+                bool    _isTextureCompressionPVRTC2BPPSupported;
+                bool    _isTextureCompressionPVRTC4BPPSupported;
+                bool    _isTextureCompressionETCSupported;
                 bool    _isTextureCompressionRGTCSupported;
                 bool    _isTextureCompressionPVRTCSupported;
                 bool    _isTextureMirroredRepeatSupported;

src/osg/Image.cpp

@@ -311,6 +311,7 @@ unsigned int Image::computeNumComponents(GLenum pixelFormat)
         case(GL_COMPRESSED_RGB_PVRTC_2BPPV1_IMG): return 3;
         case(GL_COMPRESSED_RGBA_PVRTC_4BPPV1_IMG): return 4;
         case(GL_COMPRESSED_RGBA_PVRTC_2BPPV1_IMG): return 4;
+        case(GL_ETC1_RGB8_OES): return 3;
         case(GL_COLOR_INDEX): return 1;
         case(GL_STENCIL_INDEX): return 1;
         case(GL_DEPTH_COMPONENT): return 1;
@@ -415,17 +416,15 @@ unsigned int Image::computePixelSizeInBits(GLenum format,GLenum type)
         case(GL_COMPRESSED_RGBA_S3TC_DXT1_EXT): return 4;
         case(GL_COMPRESSED_RGBA_S3TC_DXT3_EXT): return 8;
         case(GL_COMPRESSED_RGBA_S3TC_DXT5_EXT): return 8;
-
         case(GL_COMPRESSED_SIGNED_RED_RGTC1_EXT): return 4;
         case(GL_COMPRESSED_RED_RGTC1_EXT):   return 4;
         case(GL_COMPRESSED_SIGNED_RED_GREEN_RGTC2_EXT): return 8;
         case(GL_COMPRESSED_RED_GREEN_RGTC2_EXT): return 8;
-
         case(GL_COMPRESSED_RGB_PVRTC_4BPPV1_IMG): return 4;
         case(GL_COMPRESSED_RGB_PVRTC_2BPPV1_IMG): return 2;
         case(GL_COMPRESSED_RGBA_PVRTC_4BPPV1_IMG): return 4;
         case(GL_COMPRESSED_RGBA_PVRTC_2BPPV1_IMG): return 2;
-        
+        case(GL_ETC1_RGB8_OES): return 4;
         default: break;
     }
 
@@ -564,6 +563,7 @@ bool Image::isCompressed() const
         case(GL_COMPRESSED_RGB_PVRTC_2BPPV1_IMG):
         case(GL_COMPRESSED_RGBA_PVRTC_4BPPV1_IMG):
         case(GL_COMPRESSED_RGBA_PVRTC_2BPPV1_IMG):
+        case(GL_ETC1_RGB8_OES):
             return true;
         default:
             return false;
@@ -604,6 +604,11 @@ unsigned int Image::getTotalSizeInBytesIncludingMipmaps() const
            break;
         case(GL_COMPRESSED_RGBA_S3TC_DXT3_EXT):
         case(GL_COMPRESSED_RGBA_S3TC_DXT5_EXT):
+        case(GL_COMPRESSED_RGB_PVRTC_2BPPV1_IMG):
+        case(GL_COMPRESSED_RGBA_PVRTC_2BPPV1_IMG):
+        case(GL_COMPRESSED_RGB_PVRTC_4BPPV1_IMG):
+        case(GL_COMPRESSED_RGBA_PVRTC_4BPPV1_IMG):
+        case(GL_ETC1_RGB8_OES):
            sizeOfLastMipMap = maximum(sizeOfLastMipMap, 16u); // block size of 16
            break;
         case(GL_COMPRESSED_SIGNED_RED_RGTC1_EXT):

src/osg/Texture.cpp

@@ -138,6 +138,8 @@ void Texture::TextureProfile::computeSize()
         case(GL_COMPRESSED_RGBA_PVRTC_2BPPV1_IMG): numBitsPerTexel = 2; break;
         case(GL_COMPRESSED_RGB_PVRTC_4BPPV1_IMG):  numBitsPerTexel = 4; break;
         case(GL_COMPRESSED_RGBA_PVRTC_4BPPV1_IMG): numBitsPerTexel = 4; break;
+
+        case(GL_ETC1_RGB8_OES):                       numBitsPerTexel = 4; break;
     }
 
     _size = (unsigned int)(ceil(double(_width * _height * _depth * numBitsPerTexel)/8.0));
@@ -1358,7 +1360,40 @@ void Texture::computeInternalFormatWithImage(const osg::Image& image) const
             }
             else internalFormat = image.getInternalTextureFormat();
             break;
-        
+        case(USE_PVRTC_2BPP_COMPRESSION):
+            if (extensions->isTextureCompressionPVRTC2BPPSupported())
+            {
+                switch(image.getPixelFormat())
+                {
+                case(3):
+                case(GL_RGB):   internalFormat = GL_COMPRESSED_RGB_PVRTC_2BPPV1_IMG; break;
+                case(4):
+                case(GL_RGBA):  internalFormat = GL_COMPRESSED_RGBA_PVRTC_2BPPV1_IMG; break;
+                default:        internalFormat = image.getInternalTextureFormat(); break;
+                }
+            }
+        case(USE_PVRTC_4BPP_COMPRESSION):
+            if (extensions->isTextureCompressionPVRTC4BPPSupported())
+            {
+                switch(image.getPixelFormat())
+                {
+                case(3):
+                case(GL_RGB):   internalFormat = GL_COMPRESSED_RGB_PVRTC_4BPPV1_IMG; break;
+                case(4):
+                case(GL_RGBA):  internalFormat = GL_COMPRESSED_RGBA_PVRTC_4BPPV1_IMG; break;
+                default:        internalFormat = image.getInternalTextureFormat(); break;
+                }
+            }
+        case(USE_ETC_COMPRESSION):
+            if (extensions->isTextureCompressionETCSupported())
+            {
+                switch(image.getPixelFormat())
+                {
+                case(3):
+                case(GL_RGB):   internalFormat = GL_ETC1_RGB8_OES; break;
+                default:        internalFormat = image.getInternalTextureFormat(); break;
+                }
+            }
         case(USE_RGTC1_COMPRESSION):
             if (extensions->isTextureCompressionRGTCSupported())
             {
@@ -1505,6 +1540,7 @@ bool Texture::isCompressedInternalFormat(GLint internalFormat)
         case(GL_COMPRESSED_RED_RGTC1_EXT):
         case(GL_COMPRESSED_SIGNED_RED_GREEN_RGTC2_EXT):
         case(GL_COMPRESSED_RED_GREEN_RGTC2_EXT):
+        case(GL_ETC1_RGB8_OES):  
         case(GL_COMPRESSED_RGB_PVRTC_4BPPV1_IMG):
         case(GL_COMPRESSED_RGB_PVRTC_2BPPV1_IMG):
         case(GL_COMPRESSED_RGBA_PVRTC_4BPPV1_IMG):
@@ -1521,6 +1557,8 @@ void Texture::getCompressedSize(GLenum internalFormat, GLint width, GLint height
         blockSize = 8;
     else if (internalFormat == GL_COMPRESSED_RGBA_S3TC_DXT3_EXT || internalFormat == GL_COMPRESSED_RGBA_S3TC_DXT5_EXT)
         blockSize = 16;
+    else if (internalFormat == GL_ETC1_RGB8_OES)
+        blockSize = 16;
     else if (internalFormat == GL_COMPRESSED_RED_RGTC1_EXT || internalFormat == GL_COMPRESSED_SIGNED_RED_RGTC1_EXT)
         blockSize = 8;
     else if (internalFormat == GL_COMPRESSED_RED_GREEN_RGTC2_EXT || internalFormat == GL_COMPRESSED_SIGNED_RED_GREEN_RGTC2_EXT)
@@ -1777,10 +1815,15 @@ void Texture::applyTexImage2D_load(State& state, GLenum target, const Image* ima
         switch(_internalFormat)
         {
             case GL_COMPRESSED_RGB_S3TC_DXT1_EXT:
+            case GL_COMPRESSED_RGB_PVRTC_2BPPV1_IMG:
+            case GL_COMPRESSED_RGB_PVRTC_4BPPV1_IMG:
+            case GL_ETC1_RGB8_OES:
             case GL_COMPRESSED_RGB: _internalFormat = GL_RGB; break;
             case GL_COMPRESSED_RGBA_S3TC_DXT1_EXT:
             case GL_COMPRESSED_RGBA_S3TC_DXT3_EXT:
             case GL_COMPRESSED_RGBA_S3TC_DXT5_EXT:
+            case GL_COMPRESSED_RGBA_PVRTC_2BPPV1_IMG:
+            case GL_COMPRESSED_RGBA_PVRTC_4BPPV1_IMG:
             case GL_COMPRESSED_RGBA: _internalFormat = GL_RGBA; break;
             case GL_COMPRESSED_ALPHA: _internalFormat = GL_ALPHA; break;
             case GL_COMPRESSED_LUMINANCE: _internalFormat = GL_LUMINANCE; break;
@@ -2413,6 +2456,13 @@ Texture::Extensions::Extensions(unsigned int contextID)
     
     _isTextureCompressionS3TCSupported = isGLExtensionSupported(contextID,"GL_EXT_texture_compression_s3tc");
 
+    _isTextureCompressionPVRTC2BPPSupported = isGLExtensionSupported(contextID,"GL_IMG_texture_compression_pvrtc");
+
+    _isTextureCompressionPVRTC4BPPSupported = _isTextureCompressionPVRTC2BPPSupported;//covered by same extension
+
+    _isTextureCompressionETCSupported = isGLExtensionSupported(contextID,"GL_OES_compressed_ETC1_RGB8_texture");
+    
+
     _isTextureCompressionRGTCSupported = isGLExtensionSupported(contextID,"GL_EXT_texture_compression_rgtc");
 
     _isTextureCompressionPVRTCSupported = isGLExtensionSupported(contextID,"GL_IMG_texture_compression_pvrtc");

src/osgPlugins/pvr/ReaderWriterPVR.cpp

@@ -45,7 +45,8 @@ enum
   kPVRTextureFlagTypePVRTC_2 = 12,
   kPVRTextureFlagTypePVRTC_4,
   kPVRTextureFlagTypeOGLPVRTC_2 = 24,
-  kPVRTextureFlagTypeOGLPVRTC_4
+  kPVRTextureFlagTypeOGLPVRTC_4,
+  kPVRTextureFlagTypeETC = 54
 };
 
 typedef struct _PVRTexHeader
@@ -154,11 +155,14 @@ public:
         bool hasAlpha;
         
         if(formatFlags == kPVRTextureFlagTypePVRTC_4 || formatFlags == kPVRTextureFlagTypePVRTC_2 ||
-           formatFlags == kPVRTextureFlagTypeOGLPVRTC_4 || formatFlags == kPVRTextureFlagTypeOGLPVRTC_2){
+           formatFlags == kPVRTextureFlagTypeOGLPVRTC_4 || formatFlags == kPVRTextureFlagTypeOGLPVRTC_2 ||
+           formatFlags == kPVRTextureFlagTypeETC){
             if(formatFlags == kPVRTextureFlagTypePVRTC_4 || formatFlags == kPVRTextureFlagTypeOGLPVRTC_4)
                 internalFormat = GL_COMPRESSED_RGBA_PVRTC_4BPPV1_IMG;
             else if(formatFlags == kPVRTextureFlagTypePVRTC_2 || formatFlags == kPVRTextureFlagTypeOGLPVRTC_2)
                 internalFormat = GL_COMPRESSED_RGBA_PVRTC_2BPPV1_IMG;
+            else if(formatFlags == kPVRTextureFlagTypeETC)
+                internalFormat = GL_ETC1_RGB8_OES;
             
             width = header.width;
             height = header.height;
@@ -193,6 +197,11 @@ public:
                     widthBlocks = width / 4;
                     heightBlocks = height / 4;
                     bpp = 4;
+                }else if(formatFlags == kPVRTextureFlagTypeETC){
+                    blockSize = 4 * 4; // Pixel by pixel block size for 4bpp
+                    widthBlocks = width / 4;
+                    heightBlocks = height / 4;
+                    bpp = 4;
                 }else{
                     blockSize = 8 * 4; // Pixel by pixel block size for 2bpp
                     widthBlocks = width / 8;