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484 lines
15 KiB
GLSL
484 lines
15 KiB
GLSL
#[versions]
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standard = "";
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dithered = "#define BC1_DITHER";
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#[compute]
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#version 450
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#include "CrossPlatformSettings_piece_all.glsl"
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#include "UavCrossPlatform_piece_all.glsl"
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#define FLT_MAX 340282346638528859811704183484516925440.0f
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layout(binding = 0) uniform sampler2D srcTex;
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layout(binding = 1, rg32ui) uniform restrict writeonly uimage2D dstTexture;
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layout(std430, binding = 2) readonly restrict buffer globalBuffer {
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float2 c_oMatch5[256];
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float2 c_oMatch6[256];
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};
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layout(push_constant, std430) uniform Params {
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uint p_numRefinements;
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uint p_padding[3];
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}
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params;
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layout(local_size_x = 8, //
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local_size_y = 8, //
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local_size_z = 1) in;
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float3 rgb565to888(float rgb565) {
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float3 retVal;
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retVal.x = floor(rgb565 / 2048.0f);
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retVal.y = floor(mod(rgb565, 2048.0f) / 32.0f);
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retVal.z = floor(mod(rgb565, 32.0f));
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// This is the correct 565 to 888 conversion:
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// rgb = floor( rgb * ( 255.0f / float3( 31.0f, 63.0f, 31.0f ) ) + 0.5f )
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//
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// However stb_dxt follows a different one:
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// rb = floor( rb * ( 256 / 32 + 8 / 32 ) );
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// g = floor( g * ( 256 / 64 + 4 / 64 ) );
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//
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// I'm not sure exactly why but it's possible this is how the S3TC specifies it should be decoded
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// It's quite possible this is the reason:
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// http://www.ludicon.com/castano/blog/2009/03/gpu-dxt-decompression/
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//
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// Or maybe it's just because it's cheap to do with integer shifts.
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// Anyway, we follow stb_dxt's conversion just in case
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// (gives almost the same result, with 1 or -1 of difference for a very few values)
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//
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// Perhaps when we make 888 -> 565 -> 888 it doesn't matter
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// because they end up mapping to the original number
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return floor(retVal * float3(8.25f, 4.0625f, 8.25f));
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}
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float rgb888to565(float3 rgbValue) {
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rgbValue.rb = floor(rgbValue.rb * 31.0f / 255.0f + 0.5f);
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rgbValue.g = floor(rgbValue.g * 63.0f / 255.0f + 0.5f);
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return rgbValue.r * 2048.0f + rgbValue.g * 32.0f + rgbValue.b;
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}
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// linear interpolation at 1/3 point between a and b, using desired rounding type
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float3 lerp13(float3 a, float3 b) {
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#ifdef STB_DXT_USE_ROUNDING_BIAS
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// with rounding bias
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return a + floor((b - a) * (1.0f / 3.0f) + 0.5f);
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#else
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// without rounding bias
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return floor((2.0f * a + b) / 3.0f);
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#endif
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}
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/// Unpacks a block of 4 colors from two 16-bit endpoints
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void EvalColors(out float3 colors[4], float c0, float c1) {
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colors[0] = rgb565to888(c0);
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colors[1] = rgb565to888(c1);
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colors[2] = lerp13(colors[0], colors[1]);
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colors[3] = lerp13(colors[1], colors[0]);
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}
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/** The color optimization function. (Clever code, part 1)
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@param outMinEndp16 [out]
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Minimum endpoint, in RGB565
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@param outMaxEndp16 [out]
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Maximum endpoint, in RGB565
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*/
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void OptimizeColorsBlock(const uint srcPixelsBlock[16], out float outMinEndp16, out float outMaxEndp16) {
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// determine color distribution
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float3 avgColor;
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float3 minColor;
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float3 maxColor;
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avgColor = minColor = maxColor = unpackUnorm4x8(srcPixelsBlock[0]).xyz;
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for (int i = 1; i < 16; ++i) {
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const float3 currColorUnorm = unpackUnorm4x8(srcPixelsBlock[i]).xyz;
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avgColor += currColorUnorm;
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minColor = min(minColor, currColorUnorm);
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maxColor = max(maxColor, currColorUnorm);
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}
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avgColor = round(avgColor * 255.0f / 16.0f);
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maxColor *= 255.0f;
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minColor *= 255.0f;
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// determine covariance matrix
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float cov[6];
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for (int i = 0; i < 6; ++i)
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cov[i] = 0;
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for (int i = 0; i < 16; ++i) {
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const float3 currColor = unpackUnorm4x8(srcPixelsBlock[i]).xyz * 255.0f;
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float3 rgbDiff = currColor - avgColor;
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cov[0] += rgbDiff.r * rgbDiff.r;
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cov[1] += rgbDiff.r * rgbDiff.g;
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cov[2] += rgbDiff.r * rgbDiff.b;
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cov[3] += rgbDiff.g * rgbDiff.g;
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cov[4] += rgbDiff.g * rgbDiff.b;
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cov[5] += rgbDiff.b * rgbDiff.b;
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}
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// convert covariance matrix to float, find principal axis via power iter
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for (int i = 0; i < 6; ++i)
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cov[i] /= 255.0f;
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float3 vF = maxColor - minColor;
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const int nIterPower = 4;
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for (int iter = 0; iter < nIterPower; ++iter) {
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const float r = vF.r * cov[0] + vF.g * cov[1] + vF.b * cov[2];
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const float g = vF.r * cov[1] + vF.g * cov[3] + vF.b * cov[4];
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const float b = vF.r * cov[2] + vF.g * cov[4] + vF.b * cov[5];
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vF.r = r;
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vF.g = g;
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vF.b = b;
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}
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float magn = max3(abs(vF.r), abs(vF.g), abs(vF.b));
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float3 v;
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if (magn < 4.0f) { // too small, default to luminance
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v.r = 299.0f; // JPEG YCbCr luma coefs, scaled by 1000.
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v.g = 587.0f;
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v.b = 114.0f;
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} else {
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v = trunc(vF * (512.0f / magn));
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}
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// Pick colors at extreme points
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float3 minEndpoint, maxEndpoint;
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float minDot = FLT_MAX;
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float maxDot = -FLT_MAX;
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for (int i = 0; i < 16; ++i) {
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const float3 currColor = unpackUnorm4x8(srcPixelsBlock[i]).xyz * 255.0f;
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const float dotValue = dot(currColor, v);
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if (dotValue < minDot) {
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minDot = dotValue;
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minEndpoint = currColor;
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}
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if (dotValue > maxDot) {
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maxDot = dotValue;
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maxEndpoint = currColor;
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}
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}
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outMinEndp16 = rgb888to565(minEndpoint);
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outMaxEndp16 = rgb888to565(maxEndpoint);
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}
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// The color matching function
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uint MatchColorsBlock(const uint srcPixelsBlock[16], float3 color[4]) {
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uint mask = 0u;
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float3 dir = color[0] - color[1];
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float stops[4];
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for (int i = 0; i < 4; ++i)
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stops[i] = dot(color[i], dir);
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// think of the colors as arranged on a line; project point onto that line, then choose
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// next color out of available ones. we compute the crossover points for "best color in top
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// half"/"best in bottom half" and then the same inside that subinterval.
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//
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// relying on this 1d approximation isn't always optimal in terms of euclidean distance,
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// but it's very close and a lot faster.
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// http://cbloomrants.blogspot.com/2008/12/12-08-08-dxtc-summary.html
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float c0Point = trunc((stops[1] + stops[3]) * 0.5f);
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float halfPoint = trunc((stops[3] + stops[2]) * 0.5f);
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float c3Point = trunc((stops[2] + stops[0]) * 0.5f);
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#ifndef BC1_DITHER
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// the version without dithering is straightforward
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for (uint i = 16u; i-- > 0u;) {
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const float3 currColor = unpackUnorm4x8(srcPixelsBlock[i]).xyz * 255.0f;
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const float dotValue = dot(currColor, dir);
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mask <<= 2u;
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if (dotValue < halfPoint)
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mask |= ((dotValue < c0Point) ? 1u : 3u);
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else
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mask |= ((dotValue < c3Point) ? 2u : 0u);
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}
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#else
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// with floyd-steinberg dithering
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float4 ep1 = float4(0, 0, 0, 0);
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float4 ep2 = float4(0, 0, 0, 0);
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c0Point *= 16.0f;
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halfPoint *= 16.0f;
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c3Point *= 16.0f;
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for (uint y = 0u; y < 4u; ++y) {
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float ditherDot;
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uint lmask, step;
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float3 currColor;
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float dotValue;
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currColor = unpackUnorm4x8(srcPixelsBlock[y * 4 + 0]).xyz * 255.0f;
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dotValue = dot(currColor, dir);
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ditherDot = (dotValue * 16.0f) + (3 * ep2[1] + 5 * ep2[0]);
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if (ditherDot < halfPoint)
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step = (ditherDot < c0Point) ? 1u : 3u;
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else
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step = (ditherDot < c3Point) ? 2u : 0u;
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ep1[0] = dotValue - stops[step];
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lmask = step;
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currColor = unpackUnorm4x8(srcPixelsBlock[y * 4 + 1]).xyz * 255.0f;
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dotValue = dot(currColor, dir);
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ditherDot = (dotValue * 16.0f) + (7 * ep1[0] + 3 * ep2[2] + 5 * ep2[1] + ep2[0]);
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if (ditherDot < halfPoint)
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step = (ditherDot < c0Point) ? 1u : 3u;
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else
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step = (ditherDot < c3Point) ? 2u : 0u;
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ep1[1] = dotValue - stops[step];
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lmask |= step << 2u;
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currColor = unpackUnorm4x8(srcPixelsBlock[y * 4 + 2]).xyz * 255.0f;
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dotValue = dot(currColor, dir);
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ditherDot = (dotValue * 16.0f) + (7 * ep1[1] + 3 * ep2[3] + 5 * ep2[2] + ep2[1]);
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if (ditherDot < halfPoint)
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step = (ditherDot < c0Point) ? 1u : 3u;
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else
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step = (ditherDot < c3Point) ? 2u : 0u;
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ep1[2] = dotValue - stops[step];
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lmask |= step << 4u;
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currColor = unpackUnorm4x8(srcPixelsBlock[y * 4 + 2]).xyz * 255.0f;
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dotValue = dot(currColor, dir);
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ditherDot = (dotValue * 16.0f) + (7 * ep1[2] + 5 * ep2[3] + ep2[2]);
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if (ditherDot < halfPoint)
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step = (ditherDot < c0Point) ? 1u : 3u;
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else
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step = (ditherDot < c3Point) ? 2u : 0u;
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ep1[3] = dotValue - stops[step];
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lmask |= step << 6u;
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mask |= lmask << (y * 8u);
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{
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float4 tmp = ep1;
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ep1 = ep2;
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ep2 = tmp;
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} // swap
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}
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#endif
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return mask;
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}
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// The refinement function. (Clever code, part 2)
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// Tries to optimize colors to suit block contents better.
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// (By solving a least squares system via normal equations+Cramer's rule)
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bool RefineBlock(const uint srcPixelsBlock[16], uint mask, inout float inOutMinEndp16,
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inout float inOutMaxEndp16) {
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float newMin16, newMax16;
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const float oldMin = inOutMinEndp16;
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const float oldMax = inOutMaxEndp16;
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if ((mask ^ (mask << 2u)) < 4u) // all pixels have the same index?
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{
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// yes, linear system would be singular; solve using optimal
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// single-color match on average color
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float3 rgbVal = float3(8.0f / 255.0f, 8.0f / 255.0f, 8.0f / 255.0f);
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for (int i = 0; i < 16; ++i)
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rgbVal += unpackUnorm4x8(srcPixelsBlock[i]).xyz;
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rgbVal = floor(rgbVal * (255.0f / 16.0f));
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newMax16 = c_oMatch5[uint(rgbVal.r)][0] * 2048.0f + //
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c_oMatch6[uint(rgbVal.g)][0] * 32.0f + //
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c_oMatch5[uint(rgbVal.b)][0];
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newMin16 = c_oMatch5[uint(rgbVal.r)][1] * 2048.0f + //
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c_oMatch6[uint(rgbVal.g)][1] * 32.0f + //
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c_oMatch5[uint(rgbVal.b)][1];
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} else {
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const float w1Tab[4] = { 3, 0, 2, 1 };
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const float prods[4] = { 589824.0f, 2304.0f, 262402.0f, 66562.0f };
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// ^some magic to save a lot of multiplies in the accumulating loop...
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// (precomputed products of weights for least squares system, accumulated inside one 32-bit
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// register)
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float akku = 0.0f;
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uint cm = mask;
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float3 at1 = float3(0, 0, 0);
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float3 at2 = float3(0, 0, 0);
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for (int i = 0; i < 16; ++i, cm >>= 2u) {
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const float3 currColor = unpackUnorm4x8(srcPixelsBlock[i]).xyz * 255.0f;
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const uint step = cm & 3u;
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const float w1 = w1Tab[step];
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akku += prods[step];
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at1 += currColor * w1;
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at2 += currColor;
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}
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at2 = 3.0f * at2 - at1;
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// extract solutions and decide solvability
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const float xx = floor(akku / 65535.0f);
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const float yy = floor(mod(akku, 65535.0f) / 256.0f);
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const float xy = mod(akku, 256.0f);
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float2 f_rb_g;
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f_rb_g.x = 3.0f * 31.0f / 255.0f / (xx * yy - xy * xy);
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f_rb_g.y = f_rb_g.x * 63.0f / 31.0f;
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// solve.
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const float3 newMaxVal = clamp(floor((at1 * yy - at2 * xy) * f_rb_g.xyx + 0.5f),
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float3(0.0f, 0.0f, 0.0f), float3(31, 63, 31));
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newMax16 = newMaxVal.x * 2048.0f + newMaxVal.y * 32.0f + newMaxVal.z;
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const float3 newMinVal = clamp(floor((at2 * xx - at1 * xy) * f_rb_g.xyx + 0.5f),
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float3(0.0f, 0.0f, 0.0f), float3(31, 63, 31));
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newMin16 = newMinVal.x * 2048.0f + newMinVal.y * 32.0f + newMinVal.z;
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}
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inOutMinEndp16 = newMin16;
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inOutMaxEndp16 = newMax16;
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return oldMin != newMin16 || oldMax != newMax16;
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}
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#ifdef BC1_DITHER
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/// Quantizes 'srcValue' which is originally in 888 (full range),
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/// converting it to 565 and then back to 888 (quantized)
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float3 quant(float3 srcValue) {
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srcValue = clamp(srcValue, 0.0f, 255.0f);
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// Convert 888 -> 565
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srcValue = floor(srcValue * float3(31.0f / 255.0f, 63.0f / 255.0f, 31.0f / 255.0f) + 0.5f);
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// Convert 565 -> 888 back
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srcValue = floor(srcValue * float3(8.25f, 4.0625f, 8.25f));
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return srcValue;
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}
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void DitherBlock(const uint srcPixBlck[16], out uint dthPixBlck[16]) {
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float3 ep1[4] = { float3(0, 0, 0), float3(0, 0, 0), float3(0, 0, 0), float3(0, 0, 0) };
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float3 ep2[4] = { float3(0, 0, 0), float3(0, 0, 0), float3(0, 0, 0), float3(0, 0, 0) };
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for (uint y = 0u; y < 16u; y += 4u) {
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float3 srcPixel, dithPixel;
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srcPixel = unpackUnorm4x8(srcPixBlck[y + 0u]).xyz * 255.0f;
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dithPixel = quant(srcPixel + trunc((3 * ep2[1] + 5 * ep2[0]) * (1.0f / 16.0f)));
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ep1[0] = srcPixel - dithPixel;
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dthPixBlck[y + 0u] = packUnorm4x8(float4(dithPixel * (1.0f / 255.0f), 1.0f));
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srcPixel = unpackUnorm4x8(srcPixBlck[y + 1u]).xyz * 255.0f;
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dithPixel = quant(
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srcPixel + trunc((7 * ep1[0] + 3 * ep2[2] + 5 * ep2[1] + ep2[0]) * (1.0f / 16.0f)));
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ep1[1] = srcPixel - dithPixel;
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dthPixBlck[y + 1u] = packUnorm4x8(float4(dithPixel * (1.0f / 255.0f), 1.0f));
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srcPixel = unpackUnorm4x8(srcPixBlck[y + 2u]).xyz * 255.0f;
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dithPixel = quant(
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srcPixel + trunc((7 * ep1[1] + 3 * ep2[3] + 5 * ep2[2] + ep2[1]) * (1.0f / 16.0f)));
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ep1[2] = srcPixel - dithPixel;
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dthPixBlck[y + 2u] = packUnorm4x8(float4(dithPixel * (1.0f / 255.0f), 1.0f));
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srcPixel = unpackUnorm4x8(srcPixBlck[y + 3u]).xyz * 255.0f;
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dithPixel = quant(srcPixel + trunc((7 * ep1[2] + 5 * ep2[3] + ep2[2]) * (1.0f / 16.0f)));
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ep1[3] = srcPixel - dithPixel;
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dthPixBlck[y + 3u] = packUnorm4x8(float4(dithPixel * (1.0f / 255.0f), 1.0f));
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// swap( ep1, ep2 )
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for (uint i = 0u; i < 4u; ++i) {
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float3 tmp = ep1[i];
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ep1[i] = ep2[i];
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ep2[i] = tmp;
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}
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}
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}
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#endif
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void main() {
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uint srcPixelsBlock[16];
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bool bAllColorsEqual = true;
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// Load the whole 4x4 block
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const uint2 pixelsToLoadBase = gl_GlobalInvocationID.xy << 2u;
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for (uint i = 0u; i < 16u; ++i) {
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const uint2 pixelsToLoad = pixelsToLoadBase + uint2(i & 0x03u, i >> 2u);
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const float3 srcPixels0 = OGRE_Load2D(srcTex, int2(pixelsToLoad), 0).xyz;
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srcPixelsBlock[i] = packUnorm4x8(float4(srcPixels0, 1.0f));
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bAllColorsEqual = bAllColorsEqual && srcPixelsBlock[0] == srcPixelsBlock[i];
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}
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float maxEndp16, minEndp16;
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uint mask = 0u;
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|
|
|
if (bAllColorsEqual) {
|
|
const uint3 rgbVal = uint3(unpackUnorm4x8(srcPixelsBlock[0]).xyz * 255.0f);
|
|
mask = 0xAAAAAAAAu;
|
|
maxEndp16 =
|
|
c_oMatch5[rgbVal.r][0] * 2048.0f + c_oMatch6[rgbVal.g][0] * 32.0f + c_oMatch5[rgbVal.b][0];
|
|
minEndp16 =
|
|
c_oMatch5[rgbVal.r][1] * 2048.0f + c_oMatch6[rgbVal.g][1] * 32.0f + c_oMatch5[rgbVal.b][1];
|
|
} else {
|
|
#ifdef BC1_DITHER
|
|
uint ditherPixelsBlock[16];
|
|
// first step: compute dithered version for PCA if desired
|
|
DitherBlock(srcPixelsBlock, ditherPixelsBlock);
|
|
#else
|
|
#define ditherPixelsBlock srcPixelsBlock
|
|
#endif
|
|
|
|
// second step: pca+map along principal axis
|
|
OptimizeColorsBlock(ditherPixelsBlock, minEndp16, maxEndp16);
|
|
if (minEndp16 != maxEndp16) {
|
|
float3 colors[4];
|
|
EvalColors(colors, maxEndp16, minEndp16); // Note min/max are inverted
|
|
mask = MatchColorsBlock(srcPixelsBlock, colors);
|
|
}
|
|
|
|
// third step: refine (multiple times if requested)
|
|
bool bStopRefinement = false;
|
|
for (uint i = 0u; i < params.p_numRefinements && !bStopRefinement; ++i) {
|
|
const uint lastMask = mask;
|
|
|
|
if (RefineBlock(ditherPixelsBlock, mask, minEndp16, maxEndp16)) {
|
|
if (minEndp16 != maxEndp16) {
|
|
float3 colors[4];
|
|
EvalColors(colors, maxEndp16, minEndp16); // Note min/max are inverted
|
|
mask = MatchColorsBlock(srcPixelsBlock, colors);
|
|
} else {
|
|
mask = 0u;
|
|
bStopRefinement = true;
|
|
}
|
|
}
|
|
|
|
bStopRefinement = mask == lastMask || bStopRefinement;
|
|
}
|
|
}
|
|
|
|
// write the color block
|
|
if (maxEndp16 < minEndp16) {
|
|
const float tmpValue = minEndp16;
|
|
minEndp16 = maxEndp16;
|
|
maxEndp16 = tmpValue;
|
|
mask ^= 0x55555555u;
|
|
}
|
|
|
|
uint2 outputBytes;
|
|
outputBytes.x = uint(maxEndp16) | (uint(minEndp16) << 16u);
|
|
outputBytes.y = mask;
|
|
|
|
uint2 dstUV = gl_GlobalInvocationID.xy;
|
|
imageStore(dstTexture, int2(dstUV), uint4(outputBytes.xy, 0u, 0u));
|
|
}
|