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// Copyright 2015 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef CC_RASTER_TEXTURE_COMPRESSOR_ETC1_H_
#define CC_RASTER_TEXTURE_COMPRESSOR_ETC1_H_
#include "cc/raster/texture_compressor.h"
#include "base/compiler_specific.h"
#include "base/logging.h"
namespace cc {
template <typename T>
inline T clamp(T val, T min, T max) {
return val < min ? min : (val > max ? max : val);
}
inline uint8_t round_to_5_bits(float val) {
return clamp<uint8_t>(val * 31.0f / 255.0f + 0.5f, 0, 31);
}
inline uint8_t round_to_4_bits(float val) {
return clamp<uint8_t>(val * 15.0f / 255.0f + 0.5f, 0, 15);
}
union Color {
struct BgraColorType {
uint8_t b;
uint8_t g;
uint8_t r;
uint8_t a;
} channels;
uint8_t components[4];
uint32_t bits;
};
// Codeword tables.
// See: Table 3.17.2
ALIGNAS(16) static const int16_t g_codeword_tables[8][4] = {
{-8, -2, 2, 8},
{-17, -5, 5, 17},
{-29, -9, 9, 29},
{-42, -13, 13, 42},
{-60, -18, 18, 60},
{-80, -24, 24, 80},
{-106, -33, 33, 106},
{-183, -47, 47, 183}};
// Maps modifier indices to pixel index values.
// See: Table 3.17.3
static const uint8_t g_mod_to_pix[4] = {3, 2, 0, 1};
// The ETC1 specification index texels as follows:
// [a][e][i][m] [ 0][ 4][ 8][12]
// [b][f][j][n] <-> [ 1][ 5][ 9][13]
// [c][g][k][o] [ 2][ 6][10][14]
// [d][h][l][p] [ 3][ 7][11][15]
// [ 0][ 1][ 2][ 3] [ 0][ 1][ 4][ 5]
// [ 4][ 5][ 6][ 7] <-> [ 8][ 9][12][13]
// [ 8][ 9][10][11] [ 2][ 3][ 6][ 7]
// [12][13][14][15] [10][11][14][15]
// However, when extracting sub blocks from BGRA data the natural array
// indexing order ends up different:
// vertical0: [a][e][b][f] horizontal0: [a][e][i][m]
// [c][g][d][h] [b][f][j][n]
// vertical1: [i][m][j][n] horizontal1: [c][g][k][o]
// [k][o][l][p] [d][h][l][p]
// In order to translate from the natural array indices in a sub block to the
// indices (number) used by specification and hardware we use this table.
static const uint8_t g_idx_to_num[4][8] = {
{0, 4, 1, 5, 2, 6, 3, 7}, // Vertical block 0.
{8, 12, 9, 13, 10, 14, 11, 15}, // Vertical block 1.
{0, 4, 8, 12, 1, 5, 9, 13}, // Horizontal block 0.
{2, 6, 10, 14, 3, 7, 11, 15} // Horizontal block 1.
};
inline void WriteColors444(uint8_t* block,
const Color& color0,
const Color& color1) {
// Write output color for BGRA textures.
block[0] = (color0.channels.r & 0xf0) | (color1.channels.r >> 4);
block[1] = (color0.channels.g & 0xf0) | (color1.channels.g >> 4);
block[2] = (color0.channels.b & 0xf0) | (color1.channels.b >> 4);
}
inline void WriteColors555(uint8_t* block,
const Color& color0,
const Color& color1) {
// Table for conversion to 3-bit two complement format.
static const uint8_t two_compl_trans_table[8] = {
4, // -4 (100b)
5, // -3 (101b)
6, // -2 (110b)
7, // -1 (111b)
0, // 0 (000b)
1, // 1 (001b)
2, // 2 (010b)
3, // 3 (011b)
};
int16_t delta_r =
static_cast<int16_t>(color1.channels.r >> 3) - (color0.channels.r >> 3);
int16_t delta_g =
static_cast<int16_t>(color1.channels.g >> 3) - (color0.channels.g >> 3);
int16_t delta_b =
static_cast<int16_t>(color1.channels.b >> 3) - (color0.channels.b >> 3);
DCHECK_GE(delta_r, -4);
DCHECK_LE(delta_r, 3);
DCHECK_GE(delta_g, -4);
DCHECK_LE(delta_g, 3);
DCHECK_GE(delta_b, -4);
DCHECK_LE(delta_b, 3);
// Write output color for BGRA textures.
block[0] = (color0.channels.r & 0xf8) | two_compl_trans_table[delta_r + 4];
block[1] = (color0.channels.g & 0xf8) | two_compl_trans_table[delta_g + 4];
block[2] = (color0.channels.b & 0xf8) | two_compl_trans_table[delta_b + 4];
}
inline void WriteCodewordTable(uint8_t* block,
uint8_t sub_block_id,
uint8_t table) {
DCHECK_LT(sub_block_id, 2);
DCHECK_LT(table, 8);
uint8_t shift = (2 + (3 - sub_block_id * 3));
block[3] &= ~(0x07 << shift);
block[3] |= table << shift;
}
inline void WritePixelData(uint8_t* block, uint32_t pixel_data) {
block[4] |= pixel_data >> 24;
block[5] |= (pixel_data >> 16) & 0xff;
block[6] |= (pixel_data >> 8) & 0xff;
block[7] |= pixel_data & 0xff;
}
inline void WriteFlip(uint8_t* block, bool flip) {
block[3] &= ~0x01;
block[3] |= static_cast<uint8_t>(flip);
}
inline void WriteDiff(uint8_t* block, bool diff) {
block[3] &= ~0x02;
block[3] |= static_cast<uint8_t>(diff) << 1;
}
// Compress and rounds BGR888 into BGR444. The resulting BGR444 color is
// expanded to BGR888 as it would be in hardware after decompression. The
// actual 444-bit data is available in the four most significant bits of each
// channel.
inline Color MakeColor444(const float* bgr) {
uint8_t b4 = round_to_4_bits(bgr[0]);
uint8_t g4 = round_to_4_bits(bgr[1]);
uint8_t r4 = round_to_4_bits(bgr[2]);
Color bgr444;
bgr444.channels.b = (b4 << 4) | b4;
bgr444.channels.g = (g4 << 4) | g4;
bgr444.channels.r = (r4 << 4) | r4;
// Added to distinguish between expanded 555 and 444 colors.
bgr444.channels.a = 0x44;
return bgr444;
}
// Compress and rounds BGR888 into BGR555. The resulting BGR555 color is
// expanded to BGR888 as it would be in hardware after decompression. The
// actual 555-bit data is available in the five most significant bits of each
// channel.
inline Color MakeColor555(const float* bgr) {
uint8_t b5 = round_to_5_bits(bgr[0]);
uint8_t g5 = round_to_5_bits(bgr[1]);
uint8_t r5 = round_to_5_bits(bgr[2]);
Color bgr555;
bgr555.channels.b = (b5 << 3) | (b5 >> 2);
bgr555.channels.g = (g5 << 3) | (g5 >> 2);
bgr555.channels.r = (r5 << 3) | (r5 >> 2);
// Added to distinguish between expanded 555 and 444 colors.
bgr555.channels.a = 0x55;
return bgr555;
}
class CC_EXPORT TextureCompressorETC1 : public TextureCompressor {
public:
TextureCompressorETC1() {}
// Compress a texture using ETC1. Note that the |quality| parameter is
// ignored. The current implementation does not support different quality
// settings.
void Compress(const uint8_t* src,
uint8_t* dst,
int width,
int height,
Quality quality) override;
private:
DISALLOW_COPY_AND_ASSIGN(TextureCompressorETC1);
};
} // namespace cc
#endif // CC_RASTER_TEXTURE_COMPRESSOR_ETC1_H_
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