Refactor texture compressors into separate files

src/utils/SkTextureCompressor.cpp

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkTextureCompressor.h"
+#include "SkTextureCompressor_R11EAC.h"
+#include "SkTextureCompressor_LATC.h"
 
 #include "SkBitmap.h"
 #include "SkData.h"
 #include "SkEndian.h"
 
 #include "SkTextureCompression_opts.h"
 
 ////////////////////////////////////////////////////////////////////////////////
-//
-// Utility Functions
-//
-////////////////////////////////////////////////////////////////////////////////
-
-// Absolute difference between two values. More correct than SkTAbs(a - b)
-// because it works on unsigned values.
-template <typename T> inline T abs_diff(const T &a, const T &b) {
-    return (a > b) ? (a - b) : (b - a);
-}
-
-static bool is_extremal(uint8_t pixel) {
-    return 0 == pixel || 255 == pixel;
-}
-
-typedef uint64_t (*A84x4To64BitProc)(const uint8_t block[]);
-
-// This function is used by both R11 EAC and LATC to compress 4x4 blocks
-// of 8-bit alpha into 64-bit values that comprise the compressed data.
-// For both formats, we need to make sure that the dimensions of the 
-// src pixels are divisible by 4, and copy 4x4 blocks one at a time
-// for compression.
-static bool compress_4x4_a8_to_64bit(uint8_t* dst, const uint8_t* src,
-                                     int width, int height, int rowBytes,
-                                     A84x4To64BitProc proc) {
-    // Make sure that our data is well-formed enough to be considered for compression
-    if (0 == width || 0 == height || (width % 4) != 0 || (height % 4) != 0) {
-        return false;
-    }
-
-    int blocksX = width >> 2;
-    int blocksY = height >> 2;
-
-    uint8_t block[16];
-    uint64_t* encPtr = reinterpret_cast<uint64_t*>(dst);
-    for (int y = 0; y < blocksY; ++y) {
-        for (int x = 0; x < blocksX; ++x) {
-            // Load block
-            for (int k = 0; k < 4; ++k) {
-                memcpy(block + k*4, src + k*rowBytes + 4*x, 4);
-            }
-
-            // Compress it
-            *encPtr = proc(block);
-            ++encPtr;
-        }
-        src += 4 * rowBytes;
-    }
-
-    return true;
-}
-
-////////////////////////////////////////////////////////////////////////////////
-//
-// LATC compressor
-//
-////////////////////////////////////////////////////////////////////////////////
-
-// LATC compressed texels down into square 4x4 blocks
-static const int kLATCPaletteSize = 8;
-static const int kLATCBlockSize = 4;
-static const int kLATCPixelsPerBlock = kLATCBlockSize * kLATCBlockSize;
-
-// Generates an LATC palette. LATC constructs
-// a palette of eight colors from LUM0 and LUM1 using the algorithm:
-//
-// LUM0,              if lum0 > lum1 and code(x,y) == 0
-// LUM1,              if lum0 > lum1 and code(x,y) == 1
-// (6*LUM0+  LUM1)/7, if lum0 > lum1 and code(x,y) == 2
-// (5*LUM0+2*LUM1)/7, if lum0 > lum1 and code(x,y) == 3
-// (4*LUM0+3*LUM1)/7, if lum0 > lum1 and code(x,y) == 4
-// (3*LUM0+4*LUM1)/7, if lum0 > lum1 and code(x,y) == 5
-// (2*LUM0+5*LUM1)/7, if lum0 > lum1 and code(x,y) == 6
-// (  LUM0+6*LUM1)/7, if lum0 > lum1 and code(x,y) == 7
-//
-// LUM0,              if lum0 <= lum1 and code(x,y) == 0
-// LUM1,              if lum0 <= lum1 and code(x,y) == 1
-// (4*LUM0+  LUM1)/5, if lum0 <= lum1 and code(x,y) == 2
-// (3*LUM0+2*LUM1)/5, if lum0 <= lum1 and code(x,y) == 3
-// (2*LUM0+3*LUM1)/5, if lum0 <= lum1 and code(x,y) == 4
-// (  LUM0+4*LUM1)/5, if lum0 <= lum1 and code(x,y) == 5
-// 0,                 if lum0 <= lum1 and code(x,y) == 6
-// 255,               if lum0 <= lum1 and code(x,y) == 7
-
-static void generate_latc_palette(uint8_t palette[], uint8_t lum0, uint8_t lum1) {
-    palette[0] = lum0;
-    palette[1] = lum1;
-    if (lum0 > lum1) {
-        for (int i = 1; i < 7; i++) {
-            palette[i+1] = ((7-i)*lum0 + i*lum1) / 7;
-        }
-    } else {
-        for (int i = 1; i < 5; i++) {
-            palette[i+1] = ((5-i)*lum0 + i*lum1) / 5;
-        }
-        palette[6] = 0;
-        palette[7] = 255;
-    }
-}
-
-// Compress a block by using the bounding box of the pixels. It is assumed that
-// there are no extremal pixels in this block otherwise we would have used
-// compressBlockBBIgnoreExtremal.
-static uint64_t compress_latc_block_bb(const uint8_t pixels[]) {
-    uint8_t minVal = 255;
-    uint8_t maxVal = 0;
-    for (int i = 0; i < kLATCPixelsPerBlock; ++i) {
-        minVal = SkTMin(pixels[i], minVal);
-        maxVal = SkTMax(pixels[i], maxVal);
-    }
-
-    SkASSERT(!is_extremal(minVal));
-    SkASSERT(!is_extremal(maxVal));
-
-    uint8_t palette[kLATCPaletteSize];
-    generate_latc_palette(palette, maxVal, minVal);
-
-    uint64_t indices = 0;
-    for (int i = kLATCPixelsPerBlock - 1; i >= 0; --i) {
-
-        // Find the best palette index
-        uint8_t bestError = abs_diff(pixels[i], palette[0]);
-        uint8_t idx = 0;
-        for (int j = 1; j < kLATCPaletteSize; ++j) {
-            uint8_t error = abs_diff(pixels[i], palette[j]);
-            if (error < bestError) {
-                bestError = error;
-                idx = j;
-            }
-        }
-
-        indices <<= 3;
-        indices |= idx;
-    }
-
-    return
-        SkEndian_SwapLE64(
-            static_cast<uint64_t>(maxVal) |
-            (static_cast<uint64_t>(minVal) << 8) |
-            (indices << 16));
-}
-
-// Compress a block by using the bounding box of the pixels without taking into
-// account the extremal values. The generated palette will contain extremal values
-// and fewer points along the line segment to interpolate.
-static uint64_t compress_latc_block_bb_ignore_extremal(const uint8_t pixels[]) {
-    uint8_t minVal = 255;
-    uint8_t maxVal = 0;
-    for (int i = 0; i < kLATCPixelsPerBlock; ++i) {
-        if (is_extremal(pixels[i])) {
-            continue;
-        }
-
-        minVal = SkTMin(pixels[i], minVal);
-        maxVal = SkTMax(pixels[i], maxVal);
-    }
-
-    SkASSERT(!is_extremal(minVal));
-    SkASSERT(!is_extremal(maxVal));
-
-    uint8_t palette[kLATCPaletteSize];
-    generate_latc_palette(palette, minVal, maxVal);
-
-    uint64_t indices = 0;
-    for (int i = kLATCPixelsPerBlock - 1; i >= 0; --i) {
-
-        // Find the best palette index
-        uint8_t idx = 0;
-        if (is_extremal(pixels[i])) {
-            if (0xFF == pixels[i]) {
-                idx = 7;
-            } else if (0 == pixels[i]) {
-                idx = 6;
-            } else {
-                SkFAIL("Pixel is extremal but not really?!");
-            }
-        } else {
-            uint8_t bestError = abs_diff(pixels[i], palette[0]);
-            for (int j = 1; j < kLATCPaletteSize - 2; ++j) {
-                uint8_t error = abs_diff(pixels[i], palette[j]);
-                if (error < bestError) {
-                    bestError = error;
-                    idx = j;
-                }
-            }
-        }
-
-        indices <<= 3;
-        indices |= idx;
-    }
-
-    return
-        SkEndian_SwapLE64(
-            static_cast<uint64_t>(minVal) |
-            (static_cast<uint64_t>(maxVal) << 8) |
-            (indices << 16));
-}
-
-
-// Compress LATC block. Each 4x4 block of pixels is decompressed by LATC from two
-// values LUM0 and LUM1, and an index into the generated palette. Details of how
-// the palette is generated can be found in the comments of generatePalette above.
-//
-// We choose which palette type to use based on whether or not 'pixels' contains
-// any extremal values (0 or 255). If there are extremal values, then we use the
-// palette that has the extremal values built in. Otherwise, we use the full bounding
-// box.
-
-static uint64_t compress_latc_block(const uint8_t pixels[]) {
-    // Collect unique pixels
-    int nUniquePixels = 0;
-    uint8_t uniquePixels[kLATCPixelsPerBlock];
-    for (int i = 0; i < kLATCPixelsPerBlock; ++i) {
-        bool foundPixel = false;
-        for (int j = 0; j < nUniquePixels; ++j) {
-            foundPixel = foundPixel || uniquePixels[j] == pixels[i];
-        }
-
-        if (!foundPixel) {
-            uniquePixels[nUniquePixels] = pixels[i];
-            ++nUniquePixels;
-        }
-    }
-
-    // If there's only one unique pixel, then our compression is easy.
-    if (1 == nUniquePixels) {
-        return SkEndian_SwapLE64(pixels[0] | (pixels[0] << 8));
-
-    // Similarly, if there are only two unique pixels, then our compression is
-    // easy again: place the pixels in the block header, and assign the indices
-    // with one or zero depending on which pixel they belong to.
-    } else if (2 == nUniquePixels) {
-        uint64_t outBlock = 0;
-        for (int i = kLATCPixelsPerBlock - 1; i >= 0; --i) {
-            int idx = 0;
-            if (pixels[i] == uniquePixels[1]) {
-                idx = 1;
-            }
-
-            outBlock <<= 3;
-            outBlock |= idx;
-        }
-        outBlock <<= 16;
-        outBlock |= (uniquePixels[0] | (uniquePixels[1] << 8));
-        return SkEndian_SwapLE64(outBlock);
-    }
-
-    // Count non-maximal pixel values
-    int nonExtremalPixels = 0;
-    for (int i = 0; i < nUniquePixels; ++i) {
-        if (!is_extremal(uniquePixels[i])) {
-            ++nonExtremalPixels;
-        }
-    }
-
-    // If all the pixels are nonmaximal then compute the palette using
-    // the bounding box of all the pixels.
-    if (nonExtremalPixels == nUniquePixels) {
-        // This is really just for correctness, in all of my tests we
-        // never take this step. We don't lose too much perf here because
-        // most of the processing in this function is worth it for the 
-        // 1 == nUniquePixels optimization.
-        return compress_latc_block_bb(pixels);
-    } else {
-        return compress_latc_block_bb_ignore_extremal(pixels);
-    }
-}
-
-static inline bool compress_a8_to_latc(uint8_t* dst, const uint8_t* src,
-                                       int width, int height, int rowBytes) {
-    return compress_4x4_a8_to_64bit(dst, src, width, height, rowBytes, compress_latc_block);
-}
-
-////////////////////////////////////////////////////////////////////////////////
-//
-// R11 EAC Compressor
-//
-////////////////////////////////////////////////////////////////////////////////
-
-// #define COMPRESS_R11_EAC_SLOW 1
-// #define COMPRESS_R11_EAC_FAST 1
-#define COMPRESS_R11_EAC_FASTEST 1
-
-// Blocks compressed into R11 EAC are represented as follows:
-// 0000000000000000000000000000000000000000000000000000000000000000
-// |base_cw|mod|mul|  ----------------- indices -------------------
-//
-// To reconstruct the value of a given pixel, we use the formula:
-// clamp[0, 2047](base_cw * 8 + 4 + mod_val*mul*8)
-//
-// mod_val is chosen from a palette of values based on the index of the
-// given pixel. The palette is chosen by the value stored in mod.
-// This formula returns a value between 0 and 2047, which is converted
-// to a float from 0 to 1 in OpenGL.
-//
-// If mul is zero, then we set mul = 1/8, so that the formula becomes
-// clamp[0, 2047](base_cw * 8 + 4 + mod_val)
-
-#if COMPRESS_R11_EAC_SLOW
-
-static const int kNumR11EACPalettes = 16;
-static const int kR11EACPaletteSize = 8;
-static const int kR11EACModifierPalettes[kNumR11EACPalettes][kR11EACPaletteSize] = {
-    {-3, -6, -9, -15, 2, 5, 8, 14},
-    {-3, -7, -10, -13, 2, 6, 9, 12},
-    {-2, -5, -8, -13, 1, 4, 7, 12},
-    {-2, -4, -6, -13, 1, 3, 5, 12},
-    {-3, -6, -8, -12, 2, 5, 7, 11},
-    {-3, -7, -9, -11, 2, 6, 8, 10},
-    {-4, -7, -8, -11, 3, 6, 7, 10},
-    {-3, -5, -8, -11, 2, 4, 7, 10},
-    {-2, -6, -8, -10, 1, 5, 7, 9},
-    {-2, -5, -8, -10, 1, 4, 7, 9},
-    {-2, -4, -8, -10, 1, 3, 7, 9},
-    {-2, -5, -7, -10, 1, 4, 6, 9},
-    {-3, -4, -7, -10, 2, 3, 6, 9},
-    {-1, -2, -3, -10, 0, 1, 2, 9},
-    {-4, -6, -8, -9, 3, 5, 7, 8},
-    {-3, -5, -7, -9, 2, 4, 6, 8}
-};
-
-// Pack the base codeword, palette, and multiplier into the 64 bits necessary
-// to decode it.
-static uint64_t pack_r11eac_block(uint16_t base_cw, uint16_t palette, uint16_t multiplier,
-                                  uint64_t indices) {
-    SkASSERT(palette < 16);
-    SkASSERT(multiplier < 16);
-    SkASSERT(indices < (static_cast<uint64_t>(1) << 48));
-
-    const uint64_t b = static_cast<uint64_t>(base_cw) << 56;
-    const uint64_t m = static_cast<uint64_t>(multiplier) << 52;
-    const uint64_t p = static_cast<uint64_t>(palette) << 48;
-    return SkEndian_SwapBE64(b | m | p | indices);
-}
-
-// Given a base codeword, a modifier, and a multiplier, compute the proper
-// pixel value in the range [0, 2047].
-static uint16_t compute_r11eac_pixel(int base_cw, int modifier, int multiplier) {
-    int ret = (base_cw * 8 + 4) + (modifier * multiplier * 8);
-    return (ret > 2047)? 2047 : ((ret < 0)? 0 : ret);
-}
-
-// Compress a block into R11 EAC format.
-// The compression works as follows:
-// 1. Find the center of the span of the block's values. Use this as the base codeword.
-// 2. Choose a multiplier based roughly on the size of the span of block values
-// 3. Iterate through each palette and choose the one with the most accurate
-// modifiers.
-static inline uint64_t compress_heterogeneous_r11eac_block(const uint8_t block[16]) {
-    // Find the center of the data...
-    uint16_t bmin = block[0];
-    uint16_t bmax = block[0];
-    for (int i = 1; i < 16; ++i) {
-        bmin = SkTMin<uint16_t>(bmin, block[i]);
-        bmax = SkTMax<uint16_t>(bmax, block[i]);
-    }
-
-    uint16_t center = (bmax + bmin) >> 1;
-    SkASSERT(center <= 255);
-
-    // Based on the min and max, we can guesstimate a proper multiplier
-    // This is kind of a magic choice to start with.
-    uint16_t multiplier = (bmax - center) / 10;
-
-    // Now convert the block to 11 bits and transpose it to match
-    // the proper layout
-    uint16_t cblock[16];
-    for (int i = 0; i < 4; ++i) {
-        for (int j = 0; j < 4; ++j) {
-            int srcIdx = i*4+j;
-            int dstIdx = j*4+i;
-            cblock[dstIdx] = (block[srcIdx] << 3) | (block[srcIdx] >> 5);
-        }
-    }
-
-    // Finally, choose the proper palette and indices
-    uint32_t bestError = 0xFFFFFFFF;
-    uint64_t bestIndices = 0;
-    uint16_t bestPalette = 0;
-    for (uint16_t paletteIdx = 0; paletteIdx < kNumR11EACPalettes; ++paletteIdx) {
-        const int *palette = kR11EACModifierPalettes[paletteIdx];
-
-        // Iterate through each pixel to find the best palette index
-        // and update the indices with the choice. Also store the error
-        // for this palette to be compared against the best error...
-        uint32_t error = 0;
-        uint64_t indices = 0;
-        for (int pixelIdx = 0; pixelIdx < 16; ++pixelIdx) {
-            const uint16_t pixel = cblock[pixelIdx];
-
-            // Iterate through each palette value to find the best index
-            // for this particular pixel for this particular palette.
-            uint16_t bestPixelError =
-                abs_diff(pixel, compute_r11eac_pixel(center, palette[0], multiplier));
-            int bestIndex = 0;
-            for (int i = 1; i < kR11EACPaletteSize; ++i) {
-                const uint16_t p = compute_r11eac_pixel(center, palette[i], multiplier);
-                const uint16_t perror = abs_diff(pixel, p);
-
-                // Is this index better?
-                if (perror < bestPixelError) {
-                    bestIndex = i;
-                    bestPixelError = perror;
-                }
-            }
-
-            SkASSERT(bestIndex < 8);
-
-            error += bestPixelError;
-            indices <<= 3;
-            indices |= bestIndex;
-        }
-
-        SkASSERT(indices < (static_cast<uint64_t>(1) << 48));
-
-        // Is this palette better?
-        if (error < bestError) {
-            bestPalette = paletteIdx;
-            bestIndices = indices;
-            bestError = error;
-        }
-    }
-
-    // Finally, pack everything together...
-    return pack_r11eac_block(center, bestPalette, multiplier, bestIndices);
-}
-#endif // COMPRESS_R11_EAC_SLOW
-
-#if COMPRESS_R11_EAC_FAST
-// This function takes into account that most blocks that we compress have a gradation from
-// fully opaque to fully transparent. The compression scheme works by selecting the
-// palette and multiplier that has the tightest fit to the 0-255 range. This is encoded
-// as the block header (0x8490). The indices are then selected by considering the top
-// three bits of each alpha value. For alpha masks, this reduces the dynamic range from
-// 17 to 8, but the quality is still acceptable.
-//
-// There are a few caveats that need to be taken care of...
-//
-// 1. The block is read in as scanlines, so the indices are stored as:
-//     0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
-//    However, the decomrpession routine reads them in column-major order, so they
-//    need to be packed as:
-//     0 4 8 12 1 5 9 13 2 6 10 14 3 7 11 15
-//    So when reading, they must be transposed.
-//
-// 2. We cannot use the top three bits as an index directly, since the R11 EAC palettes
-//    above store the modulation values first decreasing and then increasing:
-//      e.g. {-3, -6, -9, -15, 2, 5, 8, 14}
-//    Hence, we need to convert the indices with the following mapping:
-//      From: 0 1 2 3 4 5 6 7
-//      To:   3 2 1 0 4 5 6 7
-static inline uint64_t compress_heterogeneous_r11eac_block(const uint8_t block[16]) {
-    uint64_t retVal = static_cast<uint64_t>(0x8490) << 48;
-    for(int i = 0; i < 4; ++i) {
-        for(int j = 0; j < 4; ++j) {
-            const int shift = 45-3*(j*4+i);
-            SkASSERT(shift <= 45);
-            const uint64_t idx = block[i*4+j] >> 5;
-            SkASSERT(idx < 8);
-
-            // !SPEED! This is slightly faster than having an if-statement.
-            switch(idx) {
-                case 0:
-                case 1:
-                case 2:
-                case 3:
-                    retVal |= (3-idx) << shift;
-                    break;
-                default:
-                    retVal |= idx << shift;
-                    break;
-            }
-        }
-    }
-
-    return SkEndian_SwapBE64(retVal);
-}
-#endif // COMPRESS_R11_EAC_FAST
-
-#if (COMPRESS_R11_EAC_SLOW) || (COMPRESS_R11_EAC_FAST)
-static uint64_t compress_r11eac_block(const uint8_t block[16]) {
-    // Are all blocks a solid color?
-    bool solid = true;
-    for (int i = 1; i < 16; ++i) {
-        if (block[i] != block[0]) {
-            solid = false;
-            break;
-        }
-    }
-
-    if (solid) {
-        switch(block[0]) {
-            // Fully transparent? We know the encoding...
-            case 0:
-                // (0x0020 << 48) produces the following:
-                // basw_cw: 0
-                // mod: 0, palette: {-3, -6, -9, -15, 2, 5, 8, 14}
-                // multiplier: 2
-                // mod_val: -3
-                //
-                // this gives the following formula:
-                // clamp[0, 2047](0*8+4+(-3)*2*8) = 0
-                // 
-                // Furthermore, it is impervious to endianness:
-                // 0x0020000000002000ULL
-                // Will produce one pixel with index 2, which gives:
-                // clamp[0, 2047](0*8+4+(-9)*2*8) = 0
-                return 0x0020000000002000ULL;
-
-            // Fully opaque? We know this encoding too...
-            case 255:
-            
-                // -1 produces the following:
-                // basw_cw: 255
-                // mod: 15, palette: {-3, -5, -7, -9, 2, 4, 6, 8}
-                // mod_val: 8
-                //
-                // this gives the following formula:
-                // clamp[0, 2047](255*8+4+8*8*8) = clamp[0, 2047](2556) = 2047
-                return 0xFFFFFFFFFFFFFFFFULL;
-
-            default:
-                // !TODO! krajcevski:
-                // This will probably never happen, since we're using this format
-                // primarily for compressing alpha maps. Usually the only
-                // non-fullly opaque or fully transparent blocks are not a solid
-                // intermediate color. If we notice that they are, then we can
-                // add another optimization...
-                break;
-        }
-    }
-
-    return compress_heterogeneous_r11eac_block(block);
-}
-#endif  // (COMPRESS_R11_EAC_SLOW) || (COMPRESS_R11_EAC_FAST)
-
-#if COMPRESS_R11_EAC_FASTEST
-static inline uint64_t interleave6(uint64_t topRows, uint64_t bottomRows) {
-    // If our 3-bit block indices are laid out as:
-    // a b c d
-    // e f g h
-    // i j k l
-    // m n o p
-    //
-    // This function expects topRows and bottomRows to contain the first two rows
-    // of indices interleaved in the least significant bits of a and b. In other words...
-    //
-    // If the architecture is big endian, then topRows and bottomRows will contain the following:
-    // Bits 31-0:
-    // a: 00 a e 00 b f 00 c g 00 d h
-    // b: 00 i m 00 j n 00 k o 00 l p
-    //
-    // If the architecture is little endian, then topRows and bottomRows will contain
-    // the following:
-    // Bits 31-0:
-    // a: 00 d h 00 c g 00 b f 00 a e
-    // b: 00 l p 00 k o 00 j n 00 i m
-    //
-    // This function returns a 48-bit packing of the form:
-    // a e i m b f j n c g k o d h l p
-    //
-    // !SPEED! this function might be even faster if certain SIMD intrinsics are
-    // used..
-
-    // For both architectures, we can figure out a packing of the bits by
-    // using a shuffle and a few shift-rotates...
-    uint64_t x = (static_cast<uint64_t>(topRows) << 32) | static_cast<uint64_t>(bottomRows);
-
-    // x: 00 a e 00 b f 00 c g 00 d h 00 i m 00 j n 00 k o 00 l p
-
-    uint64_t t = (x ^ (x >> 10)) & 0x3FC0003FC00000ULL;
-    x = x ^ t ^ (t << 10);
-
-    // x: b f 00 00 00 a e c g i m 00 00 00 d h j n 00 k o 00 l p
-
-    x = (x | ((x << 52) & (0x3FULL << 52)) | ((x << 20) & (0x3FULL << 28))) >> 16;
-
-    // x: 00 00 00 00 00 00 00 00 b f l p a e c g i m k o d h j n
-
-    t = (x ^ (x >> 6)) & 0xFC0000ULL;
-    x = x ^ t ^ (t << 6);
-
-#if defined (SK_CPU_BENDIAN)
-    // x: 00 00 00 00 00 00 00 00 b f l p a e i m c g k o d h j n
-
-    t = (x ^ (x >> 36)) & 0x3FULL;
-    x = x ^ t ^ (t << 36);
-
-    // x: 00 00 00 00 00 00 00 00 b f j n a e i m c g k o d h l p
-
-    t = (x ^ (x >> 12)) & 0xFFF000000ULL;
-    x = x ^ t ^ (t << 12);
-
-    // x: 00 00 00 00 00 00 00 00 a e i m b f j n c g k o d h l p
-    return x;
-#else
-    // If our CPU is little endian, then the above logic will
-    // produce the following indices:
-    // x: 00 00 00 00 00 00 00 00 c g i m d h l p b f j n a e k o
-
-    t = (x ^ (x >> 36)) & 0xFC0ULL;
-    x = x ^ t ^ (t << 36);
-
-    // x: 00 00 00 00 00 00 00 00 a e i m d h l p b f j n c g k o
-    
-    x = (x & (0xFFFULL << 36)) | ((x & 0xFFFFFFULL) << 12) | ((x >> 24) & 0xFFFULL);
-
-    // x: 00 00 00 00 00 00 00 00 a e i m b f j n c g k o d h l p
-    
-    return x;
-#endif
-}
-
-// This function converts an integer containing four bytes of alpha
-// values into an integer containing four bytes of indices into R11 EAC.
-// Note, there needs to be a mapping of indices:
-// 0 1 2 3 4 5 6 7
-// 3 2 1 0 4 5 6 7
-//
-// To compute this, we first negate each byte, and then add three, which
-// gives the mapping
-// 3 2 1 0 -1 -2 -3 -4
-//
-// Then we mask out the negative values, take their absolute value, and
-// add three.
-//
-// Most of the voodoo in this function comes from Hacker's Delight, section 2-18
-static inline uint32_t convert_indices(uint32_t x) {
-    // Take the top three bits...
-    x = (x & 0xE0E0E0E0) >> 5;
-
-    // Negate...
-    x = ~((0x80808080 - x) ^ 0x7F7F7F7F);
-
-    // Add three
-    const uint32_t s = (x & 0x7F7F7F7F) + 0x03030303;
-    x = ((x ^ 0x03030303) & 0x80808080) ^ s;
-
-    // Absolute value
-    const uint32_t a = x & 0x80808080;
-    const uint32_t b = a >> 7;
-
-    // Aside: mask negatives (m is three if the byte was negative)
-    const uint32_t m = (a >> 6) | b;
-
-    // .. continue absolute value
-    x = (x ^ ((a - b) | a)) + b;
-
-    // Add three
-    return x + m;
-}
-
-// This function follows the same basic procedure as compress_heterogeneous_r11eac_block
-// above when COMPRESS_R11_EAC_FAST is defined, but it avoids a few loads/stores and
-// tries to optimize where it can using SIMD.
-static uint64_t compress_r11eac_block_fast(const uint8_t* src, int rowBytes) {
-    // Store each row of alpha values in an integer
-    const uint32_t alphaRow1 = *(reinterpret_cast<const uint32_t*>(src));
-    const uint32_t alphaRow2 = *(reinterpret_cast<const uint32_t*>(src + rowBytes));
-    const uint32_t alphaRow3 = *(reinterpret_cast<const uint32_t*>(src + 2*rowBytes));
-    const uint32_t alphaRow4 = *(reinterpret_cast<const uint32_t*>(src + 3*rowBytes));
-
-    // Check for solid blocks. The explanations for these values
-    // can be found in the comments of compress_r11eac_block above
-    if (alphaRow1 == alphaRow2 && alphaRow1 == alphaRow3 && alphaRow1 == alphaRow4) {
-        if (0 == alphaRow1) {
-            // Fully transparent block
-            return 0x0020000000002000ULL;
-        } else if (0xFFFFFFFF == alphaRow1) {
-            // Fully opaque block
-            return 0xFFFFFFFFFFFFFFFFULL;
-        }
-    }
-
-    // Convert each integer of alpha values into an integer of indices
-    const uint32_t indexRow1 = convert_indices(alphaRow1);
-    const uint32_t indexRow2 = convert_indices(alphaRow2);
-    const uint32_t indexRow3 = convert_indices(alphaRow3);
-    const uint32_t indexRow4 = convert_indices(alphaRow4);
-
-    // Interleave the indices from the top two rows and bottom two rows
-    // prior to passing them to interleave6. Since each index is at most
-    // three bits, then each byte can hold two indices... The way that the
-    // compression scheme expects the packing allows us to efficiently pack
-    // the top two rows and bottom two rows. Interleaving each 6-bit sequence
-    // and tightly packing it into a uint64_t is a little trickier, which is
-    // taken care of in interleave6.
-    const uint32_t r1r2 = (indexRow1 << 3) | indexRow2;
-    const uint32_t r3r4 = (indexRow3 << 3) | indexRow4;
-    const uint64_t indices = interleave6(r1r2, r3r4);
-
-    // Return the packed incdices in the least significant bits with the magic header
-    return SkEndian_SwapBE64(0x8490000000000000ULL | indices);
-}
-
-static bool compress_a8_to_r11eac_fast(uint8_t* dst, const uint8_t* src,
-                                       int width, int height, int rowBytes) {
-    // Make sure that our data is well-formed enough to be considered for compression
-    if (0 == width || 0 == height || (width % 4) != 0 || (height % 4) != 0) {
-        return false;
-    }
-
-    const int blocksX = width >> 2;
-    const int blocksY = height >> 2;
-
-    uint64_t* encPtr = reinterpret_cast<uint64_t*>(dst);
-    for (int y = 0; y < blocksY; ++y) {
-        for (int x = 0; x < blocksX; ++x) {
-            // Compress it
-            *encPtr = compress_r11eac_block_fast(src + 4*x, rowBytes);
-            ++encPtr;
-        }
-        src += 4 * rowBytes;
-    }
-    return true;
-}
-#endif // COMPRESS_R11_EAC_FASTEST
-
-// The R11 EAC format expects that indices are given in column-major order. Since
-// we receive alpha values in raster order, this usually means that we have to use
-// pack6 above to properly pack our indices. However, if our indices come from the
-// blitter, then each integer will be a column of indices, and hence can be efficiently
-// packed. This function takes the bottom three bits of each byte and places them in
-// the least significant 12 bits of the resulting integer.
-static inline uint32_t pack_indices_vertical(uint32_t x) {
-#if defined (SK_CPU_BENDIAN)
-    return 
-        (x & 7) |
-        ((x >> 5) & (7 << 3)) |
-        ((x >> 10) & (7 << 6)) |
-        ((x >> 15) & (7 << 9));
-#else
-    return 
-        ((x >> 24) & 7) |
-        ((x >> 13) & (7 << 3)) |
-        ((x >> 2) & (7 << 6)) |
-        ((x << 9) & (7 << 9));
-#endif
-}
-
-// This function returns the compressed format of a block given as four columns of
-// alpha values. Each column is assumed to be loaded from top to bottom, and hence
-// must first be converted to indices and then packed into the resulting 64-bit
-// integer.
-static inline uint64_t compress_block_vertical(const uint32_t alphaColumn0,
-                                               const uint32_t alphaColumn1,
-                                               const uint32_t alphaColumn2,
-                                               const uint32_t alphaColumn3) {
-
-    if (alphaColumn0 == alphaColumn1 &&
-        alphaColumn2 == alphaColumn3 &&
-        alphaColumn0 == alphaColumn2) {
-
-        if (0 == alphaColumn0) {
-            // Transparent
-            return 0x0020000000002000ULL;
-        }
-        else if (0xFFFFFFFF == alphaColumn0) {
-            // Opaque
-            return 0xFFFFFFFFFFFFFFFFULL;
-        }
-    }
-
-    const uint32_t indexColumn0 = convert_indices(alphaColumn0);
-    const uint32_t indexColumn1 = convert_indices(alphaColumn1);
-    const uint32_t indexColumn2 = convert_indices(alphaColumn2);
-    const uint32_t indexColumn3 = convert_indices(alphaColumn3);
-
-    const uint32_t packedIndexColumn0 = pack_indices_vertical(indexColumn0);
-    const uint32_t packedIndexColumn1 = pack_indices_vertical(indexColumn1);
-    const uint32_t packedIndexColumn2 = pack_indices_vertical(indexColumn2);
-    const uint32_t packedIndexColumn3 = pack_indices_vertical(indexColumn3);
-
-    return SkEndian_SwapBE64(0x8490000000000000ULL |
-                             (static_cast<uint64_t>(packedIndexColumn0) << 36) |
-                             (static_cast<uint64_t>(packedIndexColumn1) << 24) |
-                             static_cast<uint64_t>(packedIndexColumn2 << 12) |
-                             static_cast<uint64_t>(packedIndexColumn3));
-        
-}
-
-static inline bool compress_a8_to_r11eac(uint8_t* dst, const uint8_t* src,
-                                         int width, int height, int rowBytes) {
-#if (COMPRESS_R11_EAC_SLOW) || (COMPRESS_R11_EAC_FAST)
-    return compress_4x4_a8_to_64bit(dst, src, width, height, rowBytes, compress_r11eac_block);
-#elif COMPRESS_R11_EAC_FASTEST
-    return compress_a8_to_r11eac_fast(dst, src, width, height, rowBytes);
-#else
-#error "Must choose R11 EAC algorithm"
-#endif
-}
-
-// Updates the block whose columns are stored in blockColN. curAlphai is expected
-// to store, as an integer, the four alpha values that will be placed within each
-// of the columns in the range [col, col+colsLeft).
-static inline void update_block_columns(
-    uint32_t* blockCol1, uint32_t* blockCol2, uint32_t* blockCol3, uint32_t* blockCol4,
-    const int col, const int colsLeft, const uint32_t curAlphai) {
-    SkASSERT(NULL != blockCol1);
-    SkASSERT(NULL != blockCol2);
-    SkASSERT(NULL != blockCol3);
-    SkASSERT(NULL != blockCol4);
-    SkASSERT(col + colsLeft <= 4);
-    for (int i = col; i < (col + colsLeft); ++i) {
-        switch(i) {
-        case 0:
-            *blockCol1 = curAlphai;
-            break;
-        case 1:
-            *blockCol2 = curAlphai;
-            break;
-        case 2:
-            *blockCol3 = curAlphai;
-            break;
-        case 3:
-            *blockCol4 = curAlphai;
-            break;
-        }
-    }
-}
-
-////////////////////////////////////////////////////////////////////////////////
 
 namespace SkTextureCompressor {
 
-static inline size_t get_compressed_data_size(Format fmt, int width, int height) {
+int GetCompressedDataSize(Format fmt, int width, int height) {
     switch (fmt) {
         // These formats are 64 bits per 4x4 block.
         case kR11_EAC_Format:
         case kLATC_Format:
         {
-            static const int kLATCEncodedBlockSize = 8;
+            static const int kBlockDimension = 4;
+            static const int kEncodedBlockSize = 8;
 
-            const int blocksX = width / kLATCBlockSize;
-            const int blocksY = height / kLATCBlockSize;
+            if(((width % kBlockDimension) == 0) && ((height % kBlockDimension) == 0)) {
 
-            return blocksX * blocksY * kLATCEncodedBlockSize;
+                const int blocksX = width / kBlockDimension;
+                const int blocksY = height / kBlockDimension;
+
+                return blocksX * blocksY * kEncodedBlockSize;
+            }
+
+            return -1;
         }
 
         default:
             SkFAIL("Unknown compressed format!");
-            return 0;
+            return -1;
     }
 }
 
 bool CompressBufferToFormat(uint8_t* dst, const uint8_t* src, SkColorType srcColorType,
                             int width, int height, int rowBytes, Format format, bool opt) {
     CompressionProc proc = NULL;
     if (opt) {
         proc = SkTextureCompressorGetPlatformProc(srcColorType, format);
     }
 
     if (NULL == proc) {
         switch (srcColorType) {
             case kAlpha_8_SkColorType:
             {
                 switch (format) {
                     case kLATC_Format:
-                        proc = compress_a8_to_latc;
+                        proc = CompressA8ToLATC;
                         break;
                     case kR11_EAC_Format:
-                        proc = compress_a8_to_r11eac;
+                        proc = CompressA8ToR11EAC;
                         break;
                     default:
                         // Do nothing...
                         break;
                 }
             }
             break;
 
             default:
                 // Do nothing...
                 break;
         }
     }
 
     if (NULL != proc) {
         return proc(dst, src, width, height, rowBytes);
     }
 
     return false;
 }
 
 SkData *CompressBitmapToFormat(const SkBitmap &bitmap, Format format) {
     SkAutoLockPixels alp(bitmap);
 
-    int compressedDataSize = get_compressed_data_size(format, bitmap.width(), bitmap.height());
+    int compressedDataSize = GetCompressedDataSize(format, bitmap.width(), bitmap.height());
+
     const uint8_t* src = reinterpret_cast<const uint8_t*>(bitmap.getPixels());
     uint8_t* dst = reinterpret_cast<uint8_t*>(sk_malloc_throw(compressedDataSize));
+
     if (CompressBufferToFormat(dst, src, bitmap.colorType(), bitmap.width(), bitmap.height(),
                                bitmap.rowBytes(), format)) {
         return SkData::NewFromMalloc(dst, compressedDataSize);
     }
 
     sk_free(dst);
     return NULL;
 }
 
-R11_EACBlitter::R11_EACBlitter(int width, int height, void *latcBuffer)
-    // 0x7FFE is one minus the largest positive 16-bit int. We use it for
-    // debugging to make sure that we're properly setting the nextX distance
-    // in flushRuns(). 
-    : kLongestRun(0x7FFE), kZeroAlpha(0)
-    , fNextRun(0)
-    , fWidth(width)
-    , fHeight(height)
-    , fBuffer(reinterpret_cast<uint64_t*const>(latcBuffer))
-{
-    SkASSERT((width % kR11_EACBlockSz) == 0);
-    SkASSERT((height % kR11_EACBlockSz) == 0);
-}
+SkBlitter* CreateBlitterForFormat(int width, int height, void* compressedBuffer, Format format) {
+    switch(format) {

[robertphillips, 2014/07/21 21:56:57]

default at bottom ?

[krajcevski, 2014/07/21 22:03:55]

Done.

+        default:
+            return NULL;
 
-void R11_EACBlitter::blitAntiH(int x, int y,
-                               const SkAlpha* antialias,
-                               const int16_t* runs) {
-    // Make sure that the new row to blit is either the first
-    // row that we're blitting, or it's exactly the next scan row
-    // since the last row that we blit. This is to ensure that when
-    // we go to flush the runs, that they are all the same four
-    // runs.
-    if (fNextRun > 0 &&
-        ((x != fBufferedRuns[fNextRun-1].fX) ||
-         (y-1 != fBufferedRuns[fNextRun-1].fY))) {
-        this->flushRuns();
+        case kLATC_Format:
+            return CreateLATCBlitter(width, height, compressedBuffer);
+
+        case kR11_EAC_Format:
+            return CreateR11EACBlitter(width, height, compressedBuffer);
     }
 
-    // Align the rows to a block boundary. If we receive rows that
-    // are not on a block boundary, then fill in the preceding runs
-    // with zeros. We do this by producing a single RLE that says
-    // that we have 0x7FFE pixels of zero (0x7FFE = 32766).
-    const int row = y & ~3;
-    while ((row + fNextRun) < y) {
-        fBufferedRuns[fNextRun].fAlphas = &kZeroAlpha;
-        fBufferedRuns[fNextRun].fRuns = &kLongestRun;
-        fBufferedRuns[fNextRun].fX = 0;
-        fBufferedRuns[fNextRun].fY = row + fNextRun;
-        ++fNextRun;
-    }
-
-    // Make sure that our assumptions aren't violated...
-    SkASSERT(fNextRun == (y & 3));
-    SkASSERT(fNextRun == 0 || fBufferedRuns[fNextRun - 1].fY < y);
-
-    // Set the values of the next run
-    fBufferedRuns[fNextRun].fAlphas = antialias;
-    fBufferedRuns[fNextRun].fRuns = runs;
-    fBufferedRuns[fNextRun].fX = x;
-    fBufferedRuns[fNextRun].fY = y;
-
-    // If we've output four scanlines in a row that don't violate our
-    // assumptions, then it's time to flush them...
-    if (4 == ++fNextRun) {
-        this->flushRuns();
-    }
-}
-
-void R11_EACBlitter::flushRuns() {
-
-    // If we don't have any runs, then just return.
-    if (0 == fNextRun) {
-        return;
-    }
-
-#ifndef NDEBUG
-    // Make sure that if we have any runs, they all match
-    for (int i = 1; i < fNextRun; ++i) {
-        SkASSERT(fBufferedRuns[i].fY == fBufferedRuns[i-1].fY + 1);
-        SkASSERT(fBufferedRuns[i].fX == fBufferedRuns[i-1].fX);
-    }
-#endif
-
-    // If we dont have as many runs as we have rows, fill in the remaining
-    // runs with constant zeros.
-    for (int i = fNextRun; i < kR11_EACBlockSz; ++i) {
-        fBufferedRuns[i].fY = fBufferedRuns[0].fY + i;
-        fBufferedRuns[i].fX = fBufferedRuns[0].fX;
-        fBufferedRuns[i].fAlphas = &kZeroAlpha;
-        fBufferedRuns[i].fRuns = &kLongestRun;
-    }
-
-    // Make sure that our assumptions aren't violated.
-    SkASSERT(fNextRun > 0 && fNextRun <= 4);
-    SkASSERT((fBufferedRuns[0].fY & 3) == 0);
-
-    // The following logic walks four rows at a time and outputs compressed
-    // blocks to the buffer passed into the constructor.
-    // We do the following:
-    //
-    //      c1 c2 c3 c4
-    // -----------------------------------------------------------------------
-    // ... |  |  |  |  |  ----> fBufferedRuns[0]
-    // -----------------------------------------------------------------------
-    // ... |  |  |  |  |  ----> fBufferedRuns[1]
-    // -----------------------------------------------------------------------
-    // ... |  |  |  |  |  ----> fBufferedRuns[2]
-    // -----------------------------------------------------------------------
-    // ... |  |  |  |  |  ----> fBufferedRuns[3]
-    // -----------------------------------------------------------------------
-    // 
-    // curX -- the macro X value that we've gotten to.
-    // c1, c2, c3, c4 -- the integers that represent the columns of the current block
-    //                   that we're operating on
-    // curAlphaColumn -- integer containing the column of alpha values from fBufferedRuns.
-    // nextX -- for each run, the next point at which we need to update curAlphaColumn
-    //          after the value of curX.
-    // finalX -- the minimum of all the nextX values.
-    //
-    // curX advances to finalX outputting any blocks that it passes along
-    // the way. Since finalX will not change when we reach the end of a
-    // run, the termination criteria will be whenever curX == finalX at the
-    // end of a loop.
-
-    // Setup:
-    uint32_t c1 = 0;
-    uint32_t c2 = 0;
-    uint32_t c3 = 0;
-    uint32_t c4 = 0;
-
-    uint32_t curAlphaColumn = 0;
-    SkAlpha *curAlpha = reinterpret_cast<SkAlpha*>(&curAlphaColumn);
-
-    int nextX[kR11_EACBlockSz];
-    for (int i = 0; i < kR11_EACBlockSz; ++i) {
-        nextX[i] = 0x7FFFFF;
-    }
-
-    uint64_t* outPtr = this->getBlock(fBufferedRuns[0].fX, fBufferedRuns[0].fY);
-
-    // Populate the first set of runs and figure out how far we need to
-    // advance on the first step
-    int curX = 0;
-    int finalX = 0xFFFFF;
-    for (int i = 0; i < kR11_EACBlockSz; ++i) {
-        nextX[i] = *(fBufferedRuns[i].fRuns);
-        curAlpha[i] = *(fBufferedRuns[i].fAlphas);
-
-        finalX = SkMin32(nextX[i], finalX);
-    }
-
-    // Make sure that we have a valid right-bound X value
-    SkASSERT(finalX < 0xFFFFF);
-
-    // Run the blitter...
-    while (curX != finalX) {
-        SkASSERT(finalX >= curX);
-
-        // Do we need to populate the rest of the block?
-        if ((finalX - (curX & ~3)) >= kR11_EACBlockSz) {
-            const int col = curX & 3;
-            const int colsLeft = 4 - col;
-            SkASSERT(curX + colsLeft <= finalX);
-
-            update_block_columns(&c1, &c2, &c3, &c4, col, colsLeft, curAlphaColumn);
-
-            // Write this block
-            *outPtr = compress_block_vertical(c1, c2, c3, c4);
-            ++outPtr;
-            curX += colsLeft;
-        }
-
-        // If we can advance even further, then just keep memsetting the block
-        if ((finalX - curX) >= kR11_EACBlockSz) {
-            SkASSERT((curX & 3) == 0);
-
-            const int col = 0;
-            const int colsLeft = kR11_EACBlockSz;
-
-            update_block_columns(&c1, &c2, &c3, &c4, col, colsLeft, curAlphaColumn);
-
-            // While we can keep advancing, just keep writing the block.
-            uint64_t lastBlock = compress_block_vertical(c1, c2, c3, c4);
-            while((finalX - curX) >= kR11_EACBlockSz) {
-                *outPtr = lastBlock;
-                ++outPtr;
-                curX += kR11_EACBlockSz;
-            }
-        }
-
-        // If we haven't advanced within the block then do so.
-        if (curX < finalX) {
-            const int col = curX & 3;
-            const int colsLeft = finalX - curX;
-
-            update_block_columns(&c1, &c2, &c3, &c4, col, colsLeft, curAlphaColumn);
-
-            curX += colsLeft;
-        }
-
-        SkASSERT(curX == finalX);
-
-        // Figure out what the next advancement is...
-        for (int i = 0; i < kR11_EACBlockSz; ++i) {
-            if (nextX[i] == finalX) {
-                const int16_t run = *(fBufferedRuns[i].fRuns);
-                fBufferedRuns[i].fRuns += run;
-                fBufferedRuns[i].fAlphas += run;
-                curAlpha[i] = *(fBufferedRuns[i].fAlphas);
-                nextX[i] += *(fBufferedRuns[i].fRuns);
-            }
-        }
-
-        finalX = 0xFFFFF;
-        for (int i = 0; i < kR11_EACBlockSz; ++i) {
-            finalX = SkMin32(nextX[i], finalX);
-        }
-    }
-
-    // If we didn't land on a block boundary, output the block...
-    if ((curX & 3) > 1) {
-        *outPtr = compress_block_vertical(c1, c2, c3, c4);
-    }
-
-    fNextRun = 0;
+    return NULL;
 }
 
 }  // namespace SkTextureCompressor