48 lines
1.4 KiB
GLSL
48 lines
1.4 KiB
GLSL
// Based on https://github.com/libretro/slang-shaders/blob/master/interpolation/shaders/sharp-bilinear.slang
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// by Themaister, Public Domain license
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// Does a bilinear stretch, with a preapplied Nx nearest-neighbor scale,
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// giving a sharper image than plain bilinear.
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/*
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[configuration]
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[OptionRangeFloat]
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GUIName = Prescale Factor (set to 0 for automatic)
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OptionName = PRESCALE_FACTOR
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MinValue = 0.0
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MaxValue = 16.0
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StepAmount = 1.0
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DefaultValue = 0.0
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[/configuration]
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*/
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float CalculatePrescale(float config_scale) {
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if (config_scale == 0.0) {
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float2 source_size = GetResolution();
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float2 window_size = GetWindowResolution();
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return ceil(max(window_size.x / source_size.x, window_size.y / source_size.y));
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} else {
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return config_scale;
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}
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}
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void main()
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{
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float2 source_size = GetResolution();
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float2 texel = GetCoordinates() * source_size;
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float2 texel_floored = floor(texel);
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float2 s = fract(texel);
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float config_scale = GetOption(PRESCALE_FACTOR);
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float scale = CalculatePrescale(config_scale);
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float region_range = 0.5 - 0.5 / scale;
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// Figure out where in the texel to sample to get correct pre-scaled bilinear.
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// Uses the hardware bilinear interpolator to avoid having to sample 4 times manually.
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float2 center_dist = s - 0.5;
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float2 f = (center_dist - clamp(center_dist, -region_range, region_range)) * scale + 0.5;
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float2 mod_texel = texel_floored + f;
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SetOutput(SampleLocation(mod_texel / source_size));
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}
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