fglColorTableSGI(3G)
fglColorTableSGI - define a color lookup table
As shipped in IRIX 6.5. First release of IRIX 6.5.
NAME fglColorTableSGI - define a color lookup table FORTRAN SPECIFICATION SUBROUTINE fglColorTableSGI( INTEGER*4 target, INTEGER*4 internalformat, INTEGER*4 width, INTEGER*4 format, INTEGER*4 type, CHARACTER*8 table ) PARAMETERS target Must be GL_TEXTURE_COLOR_TABLE_SGI, GL_COLOR_TABLE_SGI, GL_POST_CONVOLUTION_COLOR_TABLE_SGI, GL_POST_COLOR_MATRIX_COLOR_TABLE_SGI, GL_PROXY_TEXTURE_COLOR_TABLE_SGI, GL_PROXY_COLOR_TABLE_SGI, GL_PROXY_POST_CONVOLUTION_COLOR_TABLE_SGI, or GL_PROXY_POST_COLOR_MATRIX_COLOR_TABLE_SGI. internalformat The internal format of the color table. The allowable values are GL_ALPHA, GL_ALPHA4_EXT, GL_ALPHA8_EXT, GL_ALPHA12_EXT, GL_ALPHA16_EXT, GL_LUMINANCE, GL_LUMINANCE4_EXT, GL_LUMINANCE8_EXT, GL_LUMINANCE12_EXT, GL_LUMINANCE16_EXT, GL_LUMINANCE_ALPHA, GL_LUMINANCE4_ALPHA4_EXT, GL_LUMINANCE6_ALPHA2_EXT, GL_LUMINANCE8_ALPHA8_EXT, GL_LUMINANCE12_ALPHA4_EXT, GL_LUMINANCE12_ALPHA12_EXT, GL_LUMINANCE16_ALPHA16_EXT, GL_INTENSITY_EXT, GL_INTENSITY4_EXT, GL_INTENSITY8_EXT, GL_INTENSITY12_EXT, GL_INTENSITY16_EXT, GL_RGB, GL_RGB2_EXT, GL_RGB4_EXT, GL_RGB5_EXT, GL_RGB8_EXT, GL_RGB10_EXT, GL_RGB12_EXT, GL_RGB16_EXT, GL_RGBA, GL_RGBA2_EXT, GL_RGBA4_EXT, GL_RGB5_A1_EXT, GL_RGBA8_EXT, GL_RGB10_A2_EXT, GL_RGBA12_EXT, and GL_RGBA16_EXT. width The number of entries in the color lookup table specified by table. format The format of the pixel data in table. The allowable values are GL_RED, GL_GREEN, GL_BLUE, GL_ALPHA, GL_LUMINANCE, GL_LUMINANCE_ALPHA, GL_RGB, GL_RGBA, and GL_ABGR_EXT. type The type of the pixel data in table. The allowable values are GL_UNSIGNED_BYTE, GL_BYTE, GL_UNSIGNED_SHORT, GL_SHORT, GL_UNSIGNED_INT, GL_INT, GL_FLOAT, GL_UNSIGNED_BYTE_3_3_2_EXT, GL_UNSIGNED_SHORT_4_4_4_4_EXT, GL_UNSIGNED_SHORT_5_5_5_1_EXT, GL_UNSIGNED_INT_8_8_8_8_EXT, and GL_UNSIGNED_INT_10_10_10_2_EXT. table Pointer to a one-dimensional array of pixel data that is processed to build the color table. DESCRIPTION fglColorTableSGI is part of the SGI_color_table extension, and is also used by the SGI_texture_color_table extension. fglColorTableSGI may be used in two ways: to test the actual size and color resolution of a lookup table given a particular set of parameters, or to load the contents of a color lookup table. Use the targets GL_PROXY_* for the first case and the other targets for the second case. If target is GL_TEXTURE_COLOR_TABLE_SGI, GL_COLOR_TABLE_SGI, GL_POST_CONVOLUTION_COLOR_TABLE_SGI, or GL_POST_COLOR_MATRIX_COLOR_TABLE_SGI, fglColorTableSGI builds a color lookup table from an array of pixels. The pixel array specified by width, format, type, and table is extracted from memory and processed just as if fglDrawPixels were called, but processing stops after the final expansion to RGBA is completed. The four scale parameters and the four bias parameters that are defined for the table are then used to scale and bias the R, G, B, and A components of each pixel. (Use fglColorTableParameterSGI to set these scale and bias parameters.) Next, the R, G, B, and A values are clamped to the range [0,1]. Each pixel is then converted to the internal format specified by internalformat. This conversion simply maps the component values of the pixel (R, G, B, and A) to the values included in the internal format (red, green, blue, alpha, luminance, and intensity). The mapping is as follows: Internal Format Red Green Blue Alpha Luminance Intensity _______________________________________________________________________ GL_ALPHA A GL_LUMINANCE R GL_LUMINANCE_ALPHA A R GL_INTENSITY_EXT R GL_RGB R G B GL_RGBA R G B A Finally, the red, green, blue, alpha, luminance, and/or intensity components of the resulting pixels are stored in the color table. They form a one-dimensional table with indices in the range [0, width - 1]. If target is GL_PROXY_*, fglColorTableSGI recomputes and stores the values of the proxy color table's state variables GL_COLOR_TABLE_FORMAT_SGI, GL_COLOR_TABLE_WIDTH_SGI, GL_COLOR_TABLE_RED_SIZE_SGI, GL_COLOR_TABLE_GREEN_SIZE_SGI, GL_COLOR_TABLE_BLUE_SIZE_SGI, GL_COLOR_TABLE_ALPHA_SIZE_SGI, GL_COLOR_TABLE_LUMINANCE_SIZE_SGI, and GL_COLOR_TABLE_INTENSITY_SIZE_SGI. There is no effect on the image or state of any actual color table. If the specified color table is too large to be supported, then all the proxy state variables listed above are set to zero. Otherwise, the color table could be supported by fglColorTableSGI using the corresponding non-proxy target, and the proxy state variables are set as if that target were being defined. The proxy state variables can be retrieved by calling fglGetColorTableParameterSGI with a target of GL_PROXY_*. This allows the application to decide if a particular fglColorTableSGI command would succeed, and determine what the resulting color table attributes would be. If a color table is enabled, and its width is non-zero, then its contents are used to replace a subset of the components of each RGBA pixel group, based on the internal format of the table. Each pixel group has color components (R, G, B, A) which are in the range [0.0, 1.0]. The color components are rescaled to the size of the color lookup table to form an index. Then a subset of the components based on the internal format of the table are replaced by the table entry selected by that index. If the color components and contents of the table are represented as follows: Representation Meaning _________________________________________________ r Table index computed from R g Table index computed from G b Table index computed from B a Table index computed from A L[i] Luminance value at table index i I[i] Intensity value at table index i R[i] Red value at table index i G[i] Green value at table index i B[i] Blue value at table index i A[i] Alpha value at table index i Then the result of color table lookup is as follows: Resulting Texture Components Table Internal Format R G B A _____________________________________________________ GL_ALPHA R G B A[a] GL_LUMINANCE L[r] L[g] L[b] At GL_LUMINANCE_ALPHA L[r] L[g] L[b] A[a] GL_INTENSITY I[r] I[g] I[b] I[a] GL_RGB R[r] G[g] B[b] A GL_RGBA R[r] G[g] B[b] A[a] When GL_TEXTURE_COLOR_TABLE_SGI is enabled, the filtered colors resulting from texturing are mapped by the texture color lookup table. The result of the table lookup is passed to the texture environment function to be applied to pixel fragments. The texture color table can be used to expand the range of colors represented by small texels, to select a small ``window'' from a texture image with larger dynamic range, to provide simple lighting for volume rendering, to implement a restricted kind of color-index texture, or to linearize the results of color-space conversions performed by multidimensional texturing. When GL_COLOR_TABLE_SGI is enabled, the colors resulting from the pixel map operation (if it is enabled) are mapped by the color lookup table before being passed to the convolution operation. The colors resulting from the convolution operation are modified by the post convolution color lookup table when GL_POST_CONVOLUTION_COLOR_TABLE_SGI is enabled. These modified colors are then sent to the color matrix operation. Finally, if GL_POST_COLOR_MATRIX_COLOR_TABLE_SGI is enabled, the colors resulting from the color matrix operation are mapped by the post color matrix color lookup table before being used by the histogram operation. NOTES If target is set to GL_TEXTURE_COLOR_TABLE_SGI, GL_COLOR_TABLE_SGI, GL_POST_CONVOLUTION_COLOR_TABLE_SGI or GL_POST_COLOR_MATRIX_COLOR_TABLE_SGI then width must be a power of two or a GL_INVALID_VALUE error is generated. All machines support table widths up to and including 256; some machines also support larger tables. If target is set to GL_TEXTURE_COLOR_TABLE_SGI and the SGI_texture_color_table extension is not supported then an GL_INVALID_ENUM error is generated. If target is set to GL_COLOR_TABLE_SGI, GL_POST_CONVOLUTION_COLOR_TABLE_SGI, or GL_POST_COLOR_MATRIX_COLOR_TABLE_SGI and the SGI_color_table extension is not supported then an GL_INVALID_ENUM error is generated. If type is set to GL_UNSIGNED_BYTE_3_3_2_EXT, GL_UNSIGNED_SHORT_4_4_4_4_EXT, GL_UNSIGNED_SHORT_5_5_5_1_EXT, GL_UNSIGNED_INT_8_8_8_8_EXT, or GL_UNSIGNED_INT_10_10_10_2_EXT and the EXT_packed_pixels extension is not supported then a GL_INVALID_ENUM error is generated. See fglIntro for more information on using extensions. ERRORS GL_INVALID_ENUM is generated if target is not one of the allowable values. GL_INVALID_ENUM is generated if internalformat is not one of the allowable values. GL_INVALID_VALUE is generated if width is less than zero. GL_INVALID_ENUM is generated if format is not one of the allowable values. GL_INVALID_ENUM is generated if type is not one of the allowable values. GL_TABLE_TOO_LARGE_EXT is generated if the requested color table is too large to be supported by the implementation, and target is not a GL_PROXY_* target. GL_INVALID_OPERATION is generated if fglColorTableSGI is executed between the execution of fglBegin and the corresponding execution of fglEnd. ASSOCIATED GETS fglGetColorTableParameterSGI MACHINE DEPENDENCIES On RealityEngine, RealityEngine2, and VTX systems, SGI_color_table is supported with these restrictions: 1. Only the texture color table is supported. The target color table must be GL_TEXTURE_COLOR_TABLE_SGI or GL_PROXY_TEXTURE_COLOR_TABLE_SGI. 2. The maximum image width is 256 pixels. 3. Only image types GL_UNSIGNED_BYTE and GL_UNSIGNED_SHORT are supported. 4. The GL_UNPACK_SWAP_BYTES pixel storage mode is not supported. Calling fglColorTableSGI when GL_UNPACK_SWAP_BYTES is GL_TRUE results in a GL_INVALID_OPERATION error. 5. The packed pixel types GL_UNSIGNED_BYTE_3_3_2_EXT, GL_UNSIGNED_SHORT_4_4_4_4_EXT, GL_UNSIGNED_SHORT_5_5_5_1_EXT, GL_UNSIGNED_INT_8_8_8_8_EXT, and GL_UNSIGNED_INT_10_10_10_2_EXT are not supported. The SGI_texture_color_table extension is supported on RealityEngine, RealityEngine2, and VTX systems and on InfiniteReality systems. The SGI_texture_color_table extension is supported on High Impact and Maximum Impact. However, on Indigo2 systems certain combinations of texture internal format and texture color table internal format do not work: Texture Texture Color Table ________________________________________ GL_LUMINANCE GL_RGB GL_LUMINANCE_ALPHA GL_RGB all formats GL_RGBA all formats GL_INTENSITY High Impact and Maximum Impact on Octane systems support all texture color table formats except GL_RGBA, or GL_INTENSITY with texture format GL_RGBA. On High Impact and Maximum Impact systems, the texture color table will give incorrect results if GL_FOG_FUNC_SGIS is enabled. SEE ALSO fglColorTableParameterSGI, fglCopyColorTableSGI, fglGetColorTableSGI.