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8708900eca8ec609d279270e72936258f81ddfb7
unity/crnlib/crn_dxt.cpp
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Alexander Suvorov 660322d3a6 Add compression support for ETC1S/ETC2AS encodings 
Explanation:

ETC1S encoding is a subset of ETC1, which is using only one color endpoint per 4x4 block. The base color is therefore is always encoded as RGB555 and there is no need to encode block flips. ETC2AS encoding is a subset of ETC2A encoding which is using ETC1S encoding for color and default ETC2A encoding for alpha.

ETC1S/ETC2AS Crunch compression and decompression is based on ETC and DXT Crunch compression and decompression algorithms:
- ETC1S/ETC2AS tiling is performed within the area of 8x8 pixels using DXT1/DXT5 tiling scheme
- ETC1S color endpoints are generated using standard ETC1 optimization
- ETC1S color codebook encoding is equivalent to ETC1 codebook encoding
- ETC1S level encoding is equivalent to DXT1 level encoding
- ETC2AS alpha codebook encoding is equivalent to ETC2A alpha codebook encoding
- ETC2AS level encoding is equivalent to DXT5 level encoding

Testing results suggest that ETC1S/ETC2AS encodings can be used to achieve lower bitrates than ETC1/ETC2A on the Kodak test set while providing equivalent image quality (estimated using PSNR).

DXT Testing:

The modified algorithm has been tested on the Kodak test set using 64-bit build with default settings (running on Windows 10, i7-4790, 3.6GHz). All the decompressed test images are identical to the images being compressed and decompressed using original version of Crunch (revision ea9b8d8).

[Compressing Kodak set without mipmaps using DXT1 encoding]
Original: 1582222 bytes / 28.854 sec
Modified: 1468204 bytes / 5.473 sec
Improvement: 7.21% (compression ratio) / 81.03% (compression time)

[Compressing Kodak set with mipmaps using DXT1 encoding]
Original: 2065243 bytes / 36.925 sec
Modified: 1914805 bytes / 7.297 sec
Improvement: 7.28% (compression ratio) / 80.24% (compression time)

ETC Testing:

The modified algorithm has been tested on the Kodak test set using 64-bit build with default settings (running on Windows 10, i7-4790, 3.6GHz). The ETC1 quantization parameters have been selected in such a way, so that ETC1 compression gives approximately the same average Luma PSNR as the corresponding DXT1 compression (which is equal to 34.044 dB for the Kodak test set compressed without mipmaps using DXT1 encoding and default quality settings).

[Compressing Kodak set without mipmaps using ETC1 encoding]
Total size: 1607858 bytes
Total time: 12.842 sec
Average bitrate: 1.363 bpp
Average Luma PSNR: 34.050 dB

ETCS Testing:

The modified algorithm has been tested on the Kodak test set using 64-bit build with default settings (running on Windows 10, i7-4790, 3.6GHz). The ETC1S quantization parameters have been selected in such a way, so that ETC1S compression gives approximately the same average Luma PSNR as the corresponding DXT1 compression (which is equal to 34.044 dB for the Kodak test set compressed without mipmaps using DXT1 encoding and default quality settings).

[Compressing Kodak set without mipmaps using ETC1S encoding]
Total size: 1363676 bytes
Total time: 15.586 sec
Average bitrate: 1.156 bpp
Average Luma PSNR: 34.047 dB
2018-06-07 19:20:30 +02:00

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// File: crn_dxt.cpp
// See Copyright Notice and license at the end of inc/crnlib.h
#include "crn_core.h"
#include "crn_dxt.h"
#include "crn_dxt1.h"
#include "crn_ryg_dxt.hpp"
#include "crn_dxt_fast.h"
#include "crn_intersect.h"
namespace crnlib {
const uint8 g_dxt5_from_linear[cDXT5SelectorValues] = {0U, 2U, 3U, 4U, 5U, 6U, 7U, 1U};
const uint8 g_dxt5_to_linear[cDXT5SelectorValues] = {0U, 7U, 1U, 2U, 3U, 4U, 5U, 6U};
const uint8 g_dxt5_alpha6_to_linear[cDXT5SelectorValues] = {0U, 5U, 1U, 2U, 3U, 4U, 0U, 0U};
const uint8 g_dxt1_from_linear[cDXT1SelectorValues] = {0U, 2U, 3U, 1U};
const uint8 g_dxt1_to_linear[cDXT1SelectorValues] = {0U, 3U, 1U, 2U};
const uint8 g_six_alpha_invert_table[cDXT5SelectorValues] = {1, 0, 5, 4, 3, 2, 6, 7};
const uint8 g_eight_alpha_invert_table[cDXT5SelectorValues] = {1, 0, 7, 6, 5, 4, 3, 2};
const char* get_dxt_format_string(dxt_format fmt) {
switch (fmt) {
case cDXT1:
return "DXT1";
case cDXT1A:
return "DXT1A";
case cDXT3:
return "DXT3";
case cDXT5:
return "DXT5";
case cDXT5A:
return "DXT5A";
case cDXN_XY:
return "DXN_XY";
case cDXN_YX:
return "DXN_YX";
case cETC1:
return "ETC1";
case cETC2:
return "ETC2";
case cETC2A:
return "ETC2A";
case cETC1S:
return "ETC1S";
case cETC2AS:
return "ETC2AS";
default:
break;
}
CRNLIB_ASSERT(false);
return "?";
}
const char* get_dxt_compressor_name(crn_dxt_compressor_type c) {
switch (c) {
case cCRNDXTCompressorCRN:
return "CRN";
case cCRNDXTCompressorCRNF:
return "CRNF";
case cCRNDXTCompressorRYG:
return "RYG";
#if CRNLIB_SUPPORT_ATI_COMPRESS
case cCRNDXTCompressorATI:
return "ATI";
#endif
default:
break;
}
CRNLIB_ASSERT(false);
return "?";
}
uint get_dxt_format_bits_per_pixel(dxt_format fmt) {
switch (fmt) {
case cDXT1:
case cDXT1A:
case cDXT5A:
case cETC1:
case cETC2:
case cETC1S:
return 4;
case cDXT3:
case cDXT5:
case cDXN_XY:
case cDXN_YX:
case cETC2A:
case cETC2AS:
return 8;
default:
break;
}
CRNLIB_ASSERT(false);
return 0;
}
bool get_dxt_format_has_alpha(dxt_format fmt) {
switch (fmt) {
case cDXT1A:
case cDXT3:
case cDXT5:
case cDXT5A:
case cETC2A:
case cETC2AS:
return true;
default:
break;
}
return false;
}
uint16 dxt1_block::pack_color(const color_quad_u8& color, bool scaled, uint bias) {
uint r = color.r;
uint g = color.g;
uint b = color.b;
if (scaled) {
r = (r * 31U + bias) / 255U;
g = (g * 63U + bias) / 255U;
b = (b * 31U + bias) / 255U;
}
r = math::minimum(r, 31U);
g = math::minimum(g, 63U);
b = math::minimum(b, 31U);
return static_cast<uint16>(b | (g << 5U) | (r << 11U));
}
uint16 dxt1_block::pack_color(uint r, uint g, uint b, bool scaled, uint bias) {
return pack_color(color_quad_u8(r, g, b, 0), scaled, bias);
}
color_quad_u8 dxt1_block::unpack_color(uint16 packed_color, bool scaled, uint alpha) {
uint b = packed_color & 31U;
uint g = (packed_color >> 5U) & 63U;
uint r = (packed_color >> 11U) & 31U;
if (scaled) {
b = (b << 3U) | (b >> 2U);
g = (g << 2U) | (g >> 4U);
r = (r << 3U) | (r >> 2U);
}
return color_quad_u8(cNoClamp, r, g, b, math::minimum(alpha, 255U));
}
void dxt1_block::unpack_color(uint& r, uint& g, uint& b, uint16 packed_color, bool scaled) {
color_quad_u8 c(unpack_color(packed_color, scaled, 0));
r = c.r;
g = c.g;
b = c.b;
}
void dxt1_block::get_block_colors_NV5x(color_quad_u8* pDst, uint16 packed_col0, uint16 packed_col1, bool color4) {
color_quad_u8 col0(unpack_color(packed_col0, false));
color_quad_u8 col1(unpack_color(packed_col1, false));
pDst[0].r = (3 * col0.r * 22) / 8;
pDst[0].b = (3 * col0.b * 22) / 8;
pDst[0].g = (col0.g << 2) | (col0.g >> 4);
pDst[0].a = 0xFF;
pDst[1].r = (3 * col1.r * 22) / 8;
pDst[1].g = (col1.g << 2) | (col1.g >> 4);
pDst[1].b = (3 * col1.b * 22) / 8;
pDst[1].a = 0xFF;
int gdiff = pDst[1].g - pDst[0].g;
if (color4) //(packed_col0 > packed_col1)
{
pDst[2].r = static_cast<uint8>(((2 * col0.r + col1.r) * 22) / 8);
pDst[2].g = static_cast<uint8>((256 * pDst[0].g + gdiff / 4 + 128 + gdiff * 80) / 256);
pDst[2].b = static_cast<uint8>(((2 * col0.b + col1.b) * 22) / 8);
pDst[2].a = 0xFF;
pDst[3].r = static_cast<uint8>(((2 * col1.r + col0.r) * 22) / 8);
pDst[3].g = static_cast<uint8>((256 * pDst[1].g - gdiff / 4 + 128 - gdiff * 80) / 256);
pDst[3].b = static_cast<uint8>(((2 * col1.b + col0.b) * 22) / 8);
pDst[3].a = 0xFF;
} else {
pDst[2].r = static_cast<uint8>(((col0.r + col1.r) * 33) / 8);
pDst[2].g = static_cast<uint8>((256 * pDst[0].g + gdiff / 4 + 128 + gdiff * 128) / 256);
pDst[2].b = static_cast<uint8>(((col0.b + col1.b) * 33) / 8);
pDst[2].a = 0xFF;
pDst[3].r = 0x00;
pDst[3].g = 0x00;
pDst[3].b = 0x00;
pDst[3].a = 0x00;
}
}
uint dxt1_block::get_block_colors3(color_quad_u8* pDst, uint16 color0, uint16 color1) {
color_quad_u8 c0(unpack_color(color0, true));
color_quad_u8 c1(unpack_color(color1, true));
pDst[0] = c0;
pDst[1] = c1;
pDst[2].set_noclamp_rgba((c0.r + c1.r) >> 1U, (c0.g + c1.g) >> 1U, (c0.b + c1.b) >> 1U, 255U);
pDst[3].set_noclamp_rgba(0, 0, 0, 0);
return 3;
}
uint dxt1_block::get_block_colors4(color_quad_u8* pDst, uint16 color0, uint16 color1) {
color_quad_u8 c0(unpack_color(color0, true));
color_quad_u8 c1(unpack_color(color1, true));
pDst[0] = c0;
pDst[1] = c1;
// The compiler changes the div3 into a mul by recip+shift.
pDst[2].set_noclamp_rgba((c0.r * 2 + c1.r) / 3, (c0.g * 2 + c1.g) / 3, (c0.b * 2 + c1.b) / 3, 255U);
pDst[3].set_noclamp_rgba((c1.r * 2 + c0.r) / 3, (c1.g * 2 + c0.g) / 3, (c1.b * 2 + c0.b) / 3, 255U);
return 4;
}
uint dxt1_block::get_block_colors3_round(color_quad_u8* pDst, uint16 color0, uint16 color1) {
color_quad_u8 c0(unpack_color(color0, true));
color_quad_u8 c1(unpack_color(color1, true));
pDst[0] = c0;
pDst[1] = c1;
pDst[2].set_noclamp_rgba((c0.r + c1.r + 1) >> 1U, (c0.g + c1.g + 1) >> 1U, (c0.b + c1.b + 1) >> 1U, 255U);
pDst[3].set_noclamp_rgba(0, 0, 0, 0);
return 3;
}
uint dxt1_block::get_block_colors4_round(color_quad_u8* pDst, uint16 color0, uint16 color1) {
color_quad_u8 c0(unpack_color(color0, true));
color_quad_u8 c1(unpack_color(color1, true));
pDst[0] = c0;
pDst[1] = c1;
// 12/14/08 - Supposed to round according to DX docs, but this conflicts with the OpenGL S3TC spec. ?
// The compiler changes the div3 into a mul by recip+shift.
pDst[2].set_noclamp_rgba((c0.r * 2 + c1.r + 1) / 3, (c0.g * 2 + c1.g + 1) / 3, (c0.b * 2 + c1.b + 1) / 3, 255U);
pDst[3].set_noclamp_rgba((c1.r * 2 + c0.r + 1) / 3, (c1.g * 2 + c0.g + 1) / 3, (c1.b * 2 + c0.b + 1) / 3, 255U);
return 4;
}
uint dxt1_block::get_block_colors(color_quad_u8* pDst, uint16 color0, uint16 color1) {
if (color0 > color1)
return get_block_colors4(pDst, color0, color1);
else
return get_block_colors3(pDst, color0, color1);
}
uint dxt1_block::get_block_colors_round(color_quad_u8* pDst, uint16 color0, uint16 color1) {
if (color0 > color1)
return get_block_colors4_round(pDst, color0, color1);
else
return get_block_colors3_round(pDst, color0, color1);
}
color_quad_u8 dxt1_block::unpack_endpoint(uint32 endpoints, uint index, bool scaled, uint alpha) {
CRNLIB_ASSERT(index < 2);
return unpack_color(static_cast<uint16>((endpoints >> (index * 16U)) & 0xFFFFU), scaled, alpha);
}
uint dxt1_block::pack_endpoints(uint lo, uint hi) {
CRNLIB_ASSERT((lo <= 0xFFFFU) && (hi <= 0xFFFFU));
return lo | (hi << 16U);
}
void dxt3_block::set_alpha(uint x, uint y, uint value, bool scaled) {
CRNLIB_ASSERT((x < cDXTBlockSize) && (y < cDXTBlockSize));
if (scaled) {
CRNLIB_ASSERT(value <= 0xFF);
value = (value * 15U + 128U) / 255U;
} else {
CRNLIB_ASSERT(value <= 0xF);
}
uint ofs = (y << 1U) + (x >> 1U);
uint c = m_alpha[ofs];
c &= ~(0xF << ((x & 1U) << 2U));
c |= (value << ((x & 1U) << 2U));
m_alpha[ofs] = static_cast<uint8>(c);
}
uint dxt3_block::get_alpha(uint x, uint y, bool scaled) const {
CRNLIB_ASSERT((x < cDXTBlockSize) && (y < cDXTBlockSize));
uint value = m_alpha[(y << 1U) + (x >> 1U)];
if (x & 1)
value >>= 4;
value &= 0xF;
if (scaled)
value = (value << 4U) | value;
return value;
}
uint dxt5_block::get_block_values6(color_quad_u8* pDst, uint l, uint h) {
pDst[0].a = static_cast<uint8>(l);
pDst[1].a = static_cast<uint8>(h);
pDst[2].a = static_cast<uint8>((l * 4 + h) / 5);
pDst[3].a = static_cast<uint8>((l * 3 + h * 2) / 5);
pDst[4].a = static_cast<uint8>((l * 2 + h * 3) / 5);
pDst[5].a = static_cast<uint8>((l + h * 4) / 5);
pDst[6].a = 0;
pDst[7].a = 255;
return 6;
}
uint dxt5_block::get_block_values8(color_quad_u8* pDst, uint l, uint h) {
pDst[0].a = static_cast<uint8>(l);
pDst[1].a = static_cast<uint8>(h);
pDst[2].a = static_cast<uint8>((l * 6 + h) / 7);
pDst[3].a = static_cast<uint8>((l * 5 + h * 2) / 7);
pDst[4].a = static_cast<uint8>((l * 4 + h * 3) / 7);
pDst[5].a = static_cast<uint8>((l * 3 + h * 4) / 7);
pDst[6].a = static_cast<uint8>((l * 2 + h * 5) / 7);
pDst[7].a = static_cast<uint8>((l + h * 6) / 7);
return 8;
}
uint dxt5_block::get_block_values(color_quad_u8* pDst, uint l, uint h) {
if (l > h)
return get_block_values8(pDst, l, h);
else
return get_block_values6(pDst, l, h);
}
uint dxt5_block::get_block_values6(uint* pDst, uint l, uint h) {
pDst[0] = l;
pDst[1] = h;
pDst[2] = (l * 4 + h) / 5;
pDst[3] = (l * 3 + h * 2) / 5;
pDst[4] = (l * 2 + h * 3) / 5;
pDst[5] = (l + h * 4) / 5;
pDst[6] = 0;
pDst[7] = 255;
return 6;
}
uint dxt5_block::get_block_values8(uint* pDst, uint l, uint h) {
pDst[0] = l;
pDst[1] = h;
pDst[2] = (l * 6 + h) / 7;
pDst[3] = (l * 5 + h * 2) / 7;
pDst[4] = (l * 4 + h * 3) / 7;
pDst[5] = (l * 3 + h * 4) / 7;
pDst[6] = (l * 2 + h * 5) / 7;
pDst[7] = (l + h * 6) / 7;
return 8;
}
uint dxt5_block::unpack_endpoint(uint packed, uint index) {
CRNLIB_ASSERT(index < 2);
return (packed >> (8 * index)) & 0xFF;
}
uint dxt5_block::pack_endpoints(uint lo, uint hi) {
CRNLIB_ASSERT((lo <= 0xFF) && (hi <= 0xFF));
return lo | (hi << 8U);
}
uint dxt5_block::get_block_values(uint* pDst, uint l, uint h) {
if (l > h)
return get_block_values8(pDst, l, h);
else
return get_block_values6(pDst, l, h);
}
} // namespace crnlib
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