116 lines
4.3 KiB
GLSL
116 lines
4.3 KiB
GLSL
/* Based on this (really good) article: http://blog.pkh.me/p/19-butchering-hqx-scaling-filters.html */
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/* The colorspace used by the HQnx filters is not really YUV, despite the algorithm description claims it is. It is
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also not normalized. Therefore, we shall call the colorspace used by HQnx "HQ Colorspace" to avoid confusion. */
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STATIC vec3 rgb_to_hq_colospace(vec4 rgb)
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{
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return vec3( 0.250 * rgb.r + 0.250 * rgb.g + 0.250 * rgb.b,
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0.250 * rgb.r - 0.000 * rgb.g - 0.250 * rgb.b,
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-0.125 * rgb.r + 0.250 * rgb.g - 0.125 * rgb.b);
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}
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STATIC bool is_different(vec4 a, vec4 b)
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{
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vec3 diff = abs(rgb_to_hq_colospace(a) - rgb_to_hq_colospace(b));
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return diff.x > 0.018 || diff.y > 0.002 || diff.z > 0.005;
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}
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#define P(m, r) ((pattern & (m)) == (r))
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STATIC vec4 interp_2px(vec4 c1, float w1, vec4 c2, float w2)
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{
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return (c1 * w1 + c2 * w2) / (w1 + w2);
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}
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STATIC vec4 interp_3px(vec4 c1, float w1, vec4 c2, float w2, vec4 c3, float w3)
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{
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return (c1 * w1 + c2 * w2 + c3 * w3) / (w1 + w2 + w3);
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}
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STATIC vec4 scale(sampler2D image, vec2 position, vec2 input_resolution, vec2 output_resolution)
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{
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// o = offset, the width of a pixel
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vec2 o = 1.0 / input_resolution;
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/* We always calculate the top left pixel. If we need a different pixel, we flip the image */
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// p = the position within a pixel [0...1]
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vec2 p = fract(position * input_resolution);
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if (p.x > 0.5) o.x = -o.x;
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if (p.y > 0.5) o.y = -o.y;
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vec4 w0 = texture(image, position + vec2( -o.x, -o.y));
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vec4 w1 = texture(image, position + vec2( 0, -o.y));
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vec4 w2 = texture(image, position + vec2( o.x, -o.y));
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vec4 w3 = texture(image, position + vec2( -o.x, 0));
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vec4 w4 = texture(image, position + vec2( 0, 0));
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vec4 w5 = texture(image, position + vec2( o.x, 0));
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vec4 w6 = texture(image, position + vec2( -o.x, o.y));
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vec4 w7 = texture(image, position + vec2( 0, o.y));
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vec4 w8 = texture(image, position + vec2( o.x, o.y));
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int pattern = 0;
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if (is_different(w0, w4)) pattern |= 1;
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if (is_different(w1, w4)) pattern |= 2;
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if (is_different(w2, w4)) pattern |= 4;
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if (is_different(w3, w4)) pattern |= 8;
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if (is_different(w5, w4)) pattern |= 16;
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if (is_different(w6, w4)) pattern |= 32;
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if (is_different(w7, w4)) pattern |= 64;
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if (is_different(w8, w4)) pattern |= 128;
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if ((P(0xBF,0x37) || P(0xDB,0x13)) && is_different(w1, w5)) {
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return interp_2px(w4, 3.0, w3, 1.0);
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}
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if ((P(0xDB,0x49) || P(0xEF,0x6D)) && is_different(w7, w3)) {
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return interp_2px(w4, 3.0, w1, 1.0);
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}
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if ((P(0x0B,0x0B) || P(0xFE,0x4A) || P(0xFE,0x1A)) && is_different(w3, w1)) {
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return w4;
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}
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if ((P(0x6F,0x2A) || P(0x5B,0x0A) || P(0xBF,0x3A) || P(0xDF,0x5A) ||
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P(0x9F,0x8A) || P(0xCF,0x8A) || P(0xEF,0x4E) || P(0x3F,0x0E) ||
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P(0xFB,0x5A) || P(0xBB,0x8A) || P(0x7F,0x5A) || P(0xAF,0x8A) ||
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P(0xEB,0x8A)) && is_different(w3, w1)) {
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return interp_2px(w4, 3.0, w0, 1.0);
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}
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if (P(0x0B,0x08)) {
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return interp_3px(w4, 2.0, w0, 1.0, w1, 1.0);
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}
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if (P(0x0B,0x02)) {
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return interp_3px(w4, 2.0, w0, 1.0, w3, 1.0);
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}
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if (P(0x2F,0x2F)) {
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return interp_3px(w4, 4.0, w3, 1.0, w1, 1.0);
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}
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if (P(0xBF,0x37) || P(0xDB,0x13)) {
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return interp_3px(w4, 5.0, w1, 2.0, w3, 1.0);
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}
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if (P(0xDB,0x49) || P(0xEF,0x6D)) {
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return interp_3px(w4, 5.0, w3, 2.0, w1, 1.0);
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}
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if (P(0x1B,0x03) || P(0x4F,0x43) || P(0x8B,0x83) || P(0x6B,0x43)) {
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return interp_2px(w4, 3.0, w3, 1.0);
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}
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if (P(0x4B,0x09) || P(0x8B,0x89) || P(0x1F,0x19) || P(0x3B,0x19)) {
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return interp_2px(w4, 3.0, w1, 1.0);
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}
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if (P(0x7E,0x2A) || P(0xEF,0xAB) || P(0xBF,0x8F) || P(0x7E,0x0E)) {
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return interp_3px(w4, 2.0, w3, 3.0, w1, 3.0);
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}
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if (P(0xFB,0x6A) || P(0x6F,0x6E) || P(0x3F,0x3E) || P(0xFB,0xFA) ||
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P(0xDF,0xDE) || P(0xDF,0x1E)) {
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return interp_2px(w4, 3.0, w0, 1.0);
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}
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if (P(0x0A,0x00) || P(0x4F,0x4B) || P(0x9F,0x1B) || P(0x2F,0x0B) ||
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P(0xBE,0x0A) || P(0xEE,0x0A) || P(0x7E,0x0A) || P(0xEB,0x4B) ||
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P(0x3B,0x1B)) {
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return interp_3px(w4, 2.0, w3, 1.0, w1, 1.0);
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}
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return interp_3px(w4, 6.0, w3, 1.0, w1, 1.0);
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}
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