SameBoy | Accurate GB/GBC emulator |
| download: https://git.y1.nz/archives/sameboy.tar.gz | |
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Shaders/HQ2x.fsh
1 /* Based on this (really good) article: http://blog.pkh.me/p/19-butchering-hqx-scaling-filters.html */
2
3 /* The colorspace used by the HQnx filters is not really YUV, despite the algorithm description claims it is. It is
4 also not normalized. Therefore, we shall call the colorspace used by HQnx "HQ Colorspace" to avoid confusion. */
5 STATIC vec3 rgb_to_hq_colospace(vec4 rgb)
6 {
7 return vec3( 0.250 * rgb.r + 0.250 * rgb.g + 0.250 * rgb.b,
8 0.250 * rgb.r - 0.000 * rgb.g - 0.250 * rgb.b,
9 -0.125 * rgb.r + 0.250 * rgb.g - 0.125 * rgb.b);
10 }
11
12 STATIC bool is_different(vec4 a, vec4 b)
13 {
14 vec3 diff = abs(rgb_to_hq_colospace(a) - rgb_to_hq_colospace(b));
15 return diff.x > 0.018 || diff.y > 0.002 || diff.z > 0.005;
16 }
17
18 #define P(m, r) ((pattern & (m)) == (r))
19
20 STATIC vec4 interp_2px(vec4 c1, float w1, vec4 c2, float w2)
21 {
22 return (c1 * w1 + c2 * w2) / (w1 + w2);
23 }
24
25 STATIC vec4 interp_3px(vec4 c1, float w1, vec4 c2, float w2, vec4 c3, float w3)
26 {
27 return (c1 * w1 + c2 * w2 + c3 * w3) / (w1 + w2 + w3);
28 }
29
30 STATIC vec4 scale(sampler2D image, vec2 position, vec2 input_resolution, vec2 output_resolution)
31 {
32 // o = offset, the width of a pixel
33 vec2 o = vec2(1, 1);
34
35 /* We always calculate the top left pixel. If we need a different pixel, we flip the image */
36
37 // p = the position within a pixel [0...1]
38 vec2 p = fract(position * input_resolution);
39
40 if (p.x > 0.5) o.x = -o.x;
41 if (p.y > 0.5) o.y = -o.y;
42
43 vec4 w0 = texture_relative(image, position, vec2( -o.x, -o.y));
44 vec4 w1 = texture_relative(image, position, vec2( 0, -o.y));
45 vec4 w2 = texture_relative(image, position, vec2( o.x, -o.y));
46 vec4 w3 = texture_relative(image, position, vec2( -o.x, 0));
47 vec4 w4 = texture_relative(image, position, vec2( 0, 0));
48 vec4 w5 = texture_relative(image, position, vec2( o.x, 0));
49 vec4 w6 = texture_relative(image, position, vec2( -o.x, o.y));
50 vec4 w7 = texture_relative(image, position, vec2( 0, o.y));
51 vec4 w8 = texture_relative(image, position, vec2( o.x, o.y));
52
53 int pattern = 0;
54 if (is_different(w0, w4)) pattern |= 1;
55 if (is_different(w1, w4)) pattern |= 2;
56 if (is_different(w2, w4)) pattern |= 4;
57 if (is_different(w3, w4)) pattern |= 8;
58 if (is_different(w5, w4)) pattern |= 16;
59 if (is_different(w6, w4)) pattern |= 32;
60 if (is_different(w7, w4)) pattern |= 64;
61 if (is_different(w8, w4)) pattern |= 128;
62
63 if ((P(0xBF,0x37) || P(0xDB,0x13)) && is_different(w1, w5)) {
64 return interp_2px(w4, 3.0, w3, 1.0);
65 }
66 if ((P(0xDB,0x49) || P(0xEF,0x6D)) && is_different(w7, w3)) {
67 return interp_2px(w4, 3.0, w1, 1.0);
68 }
69 if ((P(0x0B,0x0B) || P(0xFE,0x4A) || P(0xFE,0x1A)) && is_different(w3, w1)) {
70 return w4;
71 }
72 if ((P(0x6F,0x2A) || P(0x5B,0x0A) || P(0xBF,0x3A) || P(0xDF,0x5A) ||
73 P(0x9F,0x8A) || P(0xCF,0x8A) || P(0xEF,0x4E) || P(0x3F,0x0E) ||
74 P(0xFB,0x5A) || P(0xBB,0x8A) || P(0x7F,0x5A) || P(0xAF,0x8A) ||
75 P(0xEB,0x8A)) && is_different(w3, w1)) {
76 return interp_2px(w4, 3.0, w0, 1.0);
77 }
78 if (P(0x0B,0x08)) {
79 return interp_3px(w4, 2.0, w0, 1.0, w1, 1.0);
80 }
81 if (P(0x0B,0x02)) {
82 return interp_3px(w4, 2.0, w0, 1.0, w3, 1.0);
83 }
84 if (P(0x2F,0x2F)) {
85 return interp_3px(w4, 4.0, w3, 1.0, w1, 1.0);
86 }
87 if (P(0xBF,0x37) || P(0xDB,0x13)) {
88 return interp_3px(w4, 5.0, w1, 2.0, w3, 1.0);
89 }
90 if (P(0xDB,0x49) || P(0xEF,0x6D)) {
91 return interp_3px(w4, 5.0, w3, 2.0, w1, 1.0);
92 }
93 if (P(0x1B,0x03) || P(0x4F,0x43) || P(0x8B,0x83) || P(0x6B,0x43)) {
94 return interp_2px(w4, 3.0, w3, 1.0);
95 }
96 if (P(0x4B,0x09) || P(0x8B,0x89) || P(0x1F,0x19) || P(0x3B,0x19)) {
97 return interp_2px(w4, 3.0, w1, 1.0);
98 }
99 if (P(0x7E,0x2A) || P(0xEF,0xAB) || P(0xBF,0x8F) || P(0x7E,0x0E)) {
100 return interp_3px(w4, 2.0, w3, 3.0, w1, 3.0);
101 }
102 if (P(0xFB,0x6A) || P(0x6F,0x6E) || P(0x3F,0x3E) || P(0xFB,0xFA) ||
103 P(0xDF,0xDE) || P(0xDF,0x1E)) {
104 return interp_2px(w4, 3.0, w0, 1.0);
105 }
106 if (P(0x0A,0x00) || P(0x4F,0x4B) || P(0x9F,0x1B) || P(0x2F,0x0B) ||
107 P(0xBE,0x0A) || P(0xEE,0x0A) || P(0x7E,0x0A) || P(0xEB,0x4B) ||
108 P(0x3B,0x1B)) {
109 return interp_3px(w4, 2.0, w3, 1.0, w1, 1.0);
110 }
111
112 return interp_3px(w4, 6.0, w3, 1.0, w1, 1.0);
113 }
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