1 2XXX - Not complete. 3 4Name 5 6 SGIX_ycrcba 7 8Name Strings 9 10 GL_SGIX_ycrcba 11 12Version 13 14 Last Modified Date: 01/16/1998 15 $Date: 1998/01/16 21:47:41 $ $Revision: 1.2 $ 16 17Number 18 19 203 20 21Dependencies 22 23 This extension, combined with the subsample.spec 24 (SGIX_subsample) extension obsoletes the current ycrcb.spec 25 (SGIX_ycrcb) extension. Support of SGIX_ycrcb should be 26 accomplished using the SGIX_subsample and SGIX_ycrcba. 27 28 EXT_texture3D affects the definition of this extension 29 EXT_subtexture affects the definition of this extension 30 EXT_histogram affects the definition of this extension 31 EXT_convolution affects the definition of this extension 32 SGI_color_table affects the definition of this extension 33 34 35Overview 36 37 This extension provides a method for OpenGL to read and store 38 images that are defined in standard YCRCB and YCRCBA video color 39 spaces. As with the CYMK extension, conversion to RGBA takes place 40 immediately following the unpack pixel store, and preceding the 41 pack pixel store operations, and is only available on transfers to 42 and from memory. The algorithms that convert between YCRCB and 43 RGBA are "black-box" in nature, and left undefined by the 44 extension, however it is recommended that conversion comply with 45 the CCIR standard. This extension specifies the format of a pixel 46 rectangle independent of component subsampling. Component 47 subsampling is specified using a separate extension. 48 49 Two new formats are added, YCRCB_SGIX and YCRCBA_SGIX. 50 51 YCRCB_SGIX is defined as a 3 component format representing the Cb, 52 Y, and Cr values per pixel. YCRCBA_SGIX is defined as a 4 component 53 format representing Cb, Y, Cr, and A values per pixel. 54 55 As with the CMYK extension, this extension doesn't preclude the 56 possibility of other higher quality conversion methods. 57 58 59New Procedures and Functions 60 61 None 62 63New Tokens 64 65 Accepted by the <format> parameter of DrawPixels, ReadPixels, 66 TexImage1D, TexImage2D, TexImage3DEXT, TexImage4DSGIS, TexSubImage1DEXT, 67 TexSubImage2DEXT, TexSubImage3DEXT, TexSubImage4DSGIS, GetTexImage, 68 ColorTableSGI, GetColorTableSGI, ConvolutionFilter1DEXT, 69 ConvolutionFilter2DEXT, ConvolutionFilter3DEXT, GetConvolutionFilterEXT, 70 SeparableFilter2DEXT, SeparableFilter3DEXT, GetSeparableFilterEXT, 71 GetHistogramEXT, and GetMinmaxEXT: 72 73 YCRCB_SGIX 0x8318 74 YCRCBA_SGIX 0x8319 75 76Additions to Chapter 2 of the 1.0 Specification (OpenGL Operation) 77 78 None 79 80Additions to Chapter 3 of the 1.0 Specification (Rasterization) 81 82 Two entries are added to table 3.5 (DrawPixels and ReadPixels formats): 83 84 Target 85 Name Type Elements Buffer 86 ---- ---- -------- ------ 87 YCRCB_SGIX Component Cb chroma value, Color 88 Y luminance value, 89 Cr chroma value 90 91 YCRCBA_SGIX Component Cb chroma value, Color 92 Y luminance value, 93 Cr chroma value, 94 A 95 96 Table 3.5: DrawPixels and ReadPixels formats. The third column 97 gives a description of and the number and order of elements in a 98 group. 99 100 The new formats YCRCB_SGIX and YCRCBA_SGIX are added to the 101 discussion of Conversion to RGB. If the format is either of these two 102 values, then the chroma and luminance values in each group are converted 103 to R, G, and B values using an undefined algorithm. 104 105Additions to Chapter 4 of the 1.0 Specification (Per-Fragment Operations 106and the Framebuffer) 107 108 The new formats are added to the discussion of Obtaining Pixels from the 109 Framebuffer. 110 111 The new formats are added to the discussion of Index Lookup. 112 113 A new section, "Conversion to YCrCb," is added immediately 114 following the section "Conversion to L." Or "Conversion to L" is 115 expanded to cover conversion to L, YCrCb, and CMYK 116 117 118Additions to Chapter 5 of the 1.0 Specification (Special Functions) 119 120 None 121 122Additions to Chapter 6 of the 1.0 Specification (State and State Requests) 123 124 None 125 126Additions to the GLX Specification 127 128 None 129 130GLX Protocol 131 132 None 133 134Errors 135 136 None 137 138New State 139 140 None 141 142New Implementation Dependent State 143 144 None 145 146