255 lines
7.3 KiB
C++
255 lines
7.3 KiB
C++
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///////////////////////////////////////////////////////////////////////////////
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// Copyright (C) Microsoft Corporation, 1998.
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//
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// dxtn.cpp
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//
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// Direct3D Reference Rasterizer - DXTn texture compression functions
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//
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///////////////////////////////////////////////////////////////////////////////
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#include "pch.cpp"
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// Primary color components (use DirextX byte ordering)
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#undef RED
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#define RED 0
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#undef GRN
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#define GRN 1
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#undef BLU
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#define BLU 2
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#undef ALFA
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#define ALFA 3
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typedef struct
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{
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float rgba[4];
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} FCOLOR; // internal color format
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//
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// Processing all primaries is such a common idiom
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// that we define a macro for this action.
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// Any self-respecting C compiler should easily optimize
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// this by unrolling the loop!
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//
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#define ForAllPrimaries for( primary = 0; primary < NUM_PRIMARIES; ++primary)
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// Similarly, processing all pixels in a block is a common idiom.
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#define ForAllPixels for(pixel=0; pixel < DXT_BLOCK_PIXELS; ++pixel)
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#define NUM_PRIMARIES 3
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#define NUM_COMPONENTS 4
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//
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// Quantization constants for RGB565
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//
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#define PRIMARY_BITS 8
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#define RED_BITS 5
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#define GRN_BITS 6
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#define BLU_BITS 5
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#define RED_SHIFT (PRIMARY_BITS-RED_BITS)
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#define GRN_SHIFT (PRIMARY_BITS-GRN_BITS)
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#define BLU_SHIFT (PRIMARY_BITS-BLU_BITS)
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#if 0
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#define RED_MASK 0xf8
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#define GRN_MASK 0xfc
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#define BLU_MASK 0xf8
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#endif
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// Weighting for each primary based on NTSC luminance
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static float wtPrimary[NUM_PRIMARIES] =
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{
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0.0820f, // blue
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0.6094f, // green
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0.3086f // red
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};
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//-----------------------------------------------------------------------------
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//
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// unpack a fixed point color
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//
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//-----------------------------------------------------------------------------
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static void RGBToColor (RGB565 *prgb, DXT_COLOR *pcolor)
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{
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WORD rgb;
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DXT_COLOR color;
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rgb = *((WORD *)prgb);
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// pick off bits in groups of 5, 6, and 5
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color.rgba[BLU] = (unsigned char) rgb;
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rgb >>= BLU_BITS;
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color.rgba[GRN] = (unsigned char) rgb;
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rgb >>= GRN_BITS;
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color.rgba[RED] = (unsigned char) rgb;
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// shift primaries into the appropriate LSBs
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color.rgba[BLU] <<= BLU_SHIFT;
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color.rgba[GRN] <<= GRN_SHIFT;
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color.rgba[RED] <<= RED_SHIFT;
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// replicate primaries MSBs into LSBs
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color.rgba[BLU] |= color.rgba[BLU] >> BLU_BITS;
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color.rgba[GRN] |= color.rgba[GRN] >> GRN_BITS;
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color.rgba[RED] |= color.rgba[RED] >> RED_BITS;
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*pcolor = color;
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}
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//-----------------------------------------------------------------------------
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//
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// DecodeBlockRGB - decompress a color block
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//
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//-----------------------------------------------------------------------------
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void DecodeBlockRGB (DXTBlockRGB *pblockSrc, DXT_COLOR colorDst[DXT_BLOCK_PIXELS])
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{
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int lev;
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DXT_COLOR clut[4];
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PIXBM pixbm;
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int pixel;
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int primary;
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// if source block is invalid, ...
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if (pblockSrc == NULL)
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return;
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// determine the number of color levels in the block
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lev = (pblockSrc->rgb0 <= pblockSrc->rgb1) ? 2 : 3;
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// Fill extrema values into pixel code lookup table.
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RGBToColor(&pblockSrc->rgb0, &clut[0]);
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RGBToColor(&pblockSrc->rgb1, &clut[1]);
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clut[0].rgba[ALFA] =
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clut[1].rgba[ALFA] =
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clut[2].rgba[ALFA] = 255;
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if (lev == 3)
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{ // No transparency info present, all color info.
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ForAllPrimaries
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{
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WORD temp0 = clut[0].rgba[primary]; // jvanaken fixed overflow bug
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WORD temp1 = clut[1].rgba[primary];
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clut[2].rgba[primary] = (BYTE)((2*temp0 + temp1 + 1)/3);
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clut[3].rgba[primary] = (BYTE)((temp0 + 2*temp1 + 1)/3);
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}
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clut[3].rgba[ALFA] = 255;
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}
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else
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{ // transparency info.
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ForAllPrimaries
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{
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WORD temp0 = clut[0].rgba[primary]; // jvanaken fixed overflow bug
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WORD temp1 = clut[1].rgba[primary];
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clut[2].rgba[primary] = (BYTE)((temp0 + temp1)/2);
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clut[3].rgba[primary] = 0; // jvanaken added this
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}
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clut[3].rgba[ALFA] = 0;
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}
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// munge a local copy
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pixbm = pblockSrc->pixbm;
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// Look up the actual pixel color in the table.
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ForAllPixels
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{
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// lookup color from pixel bitmap
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ForAllPrimaries
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colorDst[pixel].rgba[primary] = clut[pixbm & 3].rgba[primary];
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colorDst[pixel].rgba[ALFA] = clut[pixbm & 3].rgba[ALFA];
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// prepare to extract next index
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pixbm >>= 2;
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}
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}
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//-----------------------------------------------------------------------------
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// DecodeBlockAlpha4 - decompress a block with alpha at 4 BPP
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//-----------------------------------------------------------------------------
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void DecodeBlockAlpha4(DXTBlockAlpha4 *pblockSrc, DXT_COLOR colorDst[DXT_BLOCK_PIXELS])
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{
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int row, col;
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WORD alpha;
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DecodeBlockRGB(&pblockSrc->rgb, colorDst);
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for (row = 0; row < 4; ++row)
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{
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alpha = pblockSrc->alphabm[row];
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for (col = 0; col < 4; ++col)
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{
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colorDst[4 * row + col].rgba[ALFA] =
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((alpha & 0xf) << 4)
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| (alpha & 0xf);
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alpha >>= 4;
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}
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}
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}
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//-----------------------------------------------------------------------------
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//
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// DecodeBlockAlpha3 - decompress a block with alpha at 3 BPP
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//
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//-----------------------------------------------------------------------------
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void DecodeBlockAlpha3(DXTBlockAlpha3 *pblockSrc, DXT_COLOR colorDst[DXT_BLOCK_PIXELS])
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{
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int pixel;
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int alpha[8]; // alpha lookup table
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DWORD dwBM = 0; // alpha bitmap in DWORD cache
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DecodeBlockRGB(&pblockSrc->rgb, colorDst);
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alpha[0] = pblockSrc->alpha0;
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alpha[1] = pblockSrc->alpha1;
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if (alpha[0] > alpha[1]) // 8 alpha ramp
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{ // interpolate intermediate colors
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alpha[2] = (6 * alpha[0] + 1 * alpha[1]) / 7;
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alpha[3] = (5 * alpha[0] + 2 * alpha[1]) / 7;
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alpha[4] = (4 * alpha[0] + 3 * alpha[1]) / 7;
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alpha[5] = (3 * alpha[0] + 4 * alpha[1]) / 7;
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alpha[6] = (2 * alpha[0] + 5 * alpha[1]) / 7;
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alpha[7] = (1 * alpha[0] + 6 * alpha[1]) / 7;
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}
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else // else 6 alpha ramp with 0 and 255
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{ // interpolate intermediate colors
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alpha[2] = (4 * alpha[0] + 1 * alpha[1]) / 5;
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alpha[3] = (3 * alpha[0] + 2 * alpha[1]) / 5;
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alpha[4] = (2 * alpha[0] + 3 * alpha[1]) / 5;
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alpha[5] = (1 * alpha[0] + 4 * alpha[1]) / 5;
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alpha[6] = 0;
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alpha[7] = 255;
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}
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ForAllPixels
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{ // reload bitmap dword cache every 8 pixels
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if ((pixel & 7) == 0)
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{
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if (pixel == 0)
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{ // pack 3 bytes into dword
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dwBM = pblockSrc->alphabm[2];
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dwBM <<= 8;
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dwBM |= pblockSrc->alphabm[1];
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dwBM <<= 8;
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dwBM |= pblockSrc->alphabm[0];
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}
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else // pixel == 8
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{ // pack 3 bytes into dword
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dwBM = pblockSrc->alphabm[5];
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dwBM <<= 8;
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dwBM |= pblockSrc->alphabm[4];
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dwBM <<= 8;
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dwBM |= pblockSrc->alphabm[3];
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}
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}
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// unpack bitmap dword 3 bits at a time
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colorDst[pixel].rgba[ALFA] = (BYTE)alpha[(dwBM & 7)];
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dwBM >>= 3;
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}
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}
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///////////////////////////////////////////////////////////////////////////////
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// end
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