add sharp-bilinear-simple, -scanlines and -2x-prescale shaders

For more information, see
https://github.com/rsn8887/Sharp-Bilinear-Shaders

retro/shaders/sharp-bilinear-scanlines.slang

@@ -0,0 +1,87 @@
+#version 450
+
+layout(push_constant) uniform Push
+{
+  vec4 OutputSize;
+  vec4 OriginalSize;
+  vec4 SourceSize;
+  float SCANLINE_BASE_BRIGHTNESS;
+  float SCANLINE_HORIZONTAL_MODULATION;
+  float SCANLINE_VERTICAL_MODULATION;
+} params;
+
+layout(std140, set = 0, binding = 0) uniform UBO
+{
+   mat4 MVP;
+} global;
+
+/*
+   Author: rsn8887 (based on TheMaister)
+   License: Public domain
+
+   This is an integer prescale filter that should be combined
+   with a bilinear hardware filtering (GL_BILINEAR filter or some such) to achieve
+   a smooth scaling result with minimum blur. This is good for pixelgraphics
+   that are scaled by non-integer factors.
+   
+   The prescale factor and texel coordinates are precalculated
+   in the vertex shader for speed.
+*/
+
+// Parameter lines go here:
+#pragma parameter SCANLINE_BASE_BRIGHTNESS "Scanline Base Brightness" 0.60 0.0 1.0 0.01
+#pragma parameter SCANLINE_HORIZONTAL_MODULATION "Scanline Horizontal Modulation" 0.0 0.0 2.00 0.01
+#pragma parameter SCANLINE_VERTICAL_MODULATION "Scanline Vertical Modulation" 0.75 0.0 2.0 0.01
+
+#define pi 3.141592654
+
+#pragma stage vertex
+layout(location = 0) in vec4 Position;
+layout(location = 1) in vec2 TexCoord;
+layout(location = 0) out vec2 vTexCoord;
+layout(location = 1) out vec2 precalc_texel;
+layout(location = 2) out vec2 precalc_scale;
+layout(location = 3) out vec2 omega;
+
+void main()
+{
+   gl_Position = global.MVP * Position;
+   vTexCoord = TexCoord;
+   omega = vec2(2.0 * pi * params.SourceSize.x, 2.0 * pi * params.SourceSize.y);
+   precalc_scale = max(floor(params.OutputSize.xy / params.SourceSize.xy), vec2(1.0, 1.0));
+   precalc_texel = vTexCoord * params.SourceSize.xy;
+}
+
+#pragma stage fragment
+layout(location = 0) in vec2 vTexCoord;
+layout(location = 1) in vec2 precalc_texel;
+layout(location = 2) in vec2 precalc_scale;
+layout(location = 3) in vec2 omega;
+layout(location = 0) out vec4 FragColor;
+layout(set = 0, binding = 2) uniform sampler2D Source;
+
+void main()
+{
+   vec2 texel = precalc_texel;
+   vec2 scale = precalc_scale;
+   vec2 texel_floored = floor(texel);
+   vec2 s = fract(texel);
+   vec2 region_range = 0.5 - 0.5 / scale;
+
+   // Figure out where in the texel to sample to get correct pre-scaled bilinear.
+   // Uses the hardware bilinear interpolator to avoid having to sample 4 times manually.
+
+   vec2 center_dist = s - 0.5;
+   vec2 f = (center_dist - clamp(center_dist, -region_range, region_range)) * scale + 0.5;
+
+   vec2 mod_texel = texel_floored + f;
+
+   vec3 res = texture(Source, mod_texel / params.SourceSize.xy).xyz;
+
+   // thick scanlines (thickness pre-calculated in vertex shader based on source resolution)
+   vec2 sine_comp = vec2(params.SCANLINE_HORIZONTAL_MODULATION, params.SCANLINE_VERTICAL_MODULATION);
+
+   vec3 scanline = res * (params.SCANLINE_BASE_BRIGHTNESS + dot(sine_comp * sin(vTexCoord * omega), vec2(1.0, 1.0)));
+
+   FragColor = vec4(scanline.rgb, 1.0);
+}

retro/shaders/sharp-bilinear-simple.slang

@@ -0,0 +1,67 @@
+#version 450
+
+layout(push_constant) uniform Push
+{
+  vec4 OutputSize;
+  vec4 OriginalSize;
+  vec4 SourceSize;
+} params;
+
+layout(std140, set = 0, binding = 0) uniform UBO
+{
+   mat4 MVP;
+} global;
+
+/*
+   Author: rsn8887 (based on TheMaister)
+   License: Public domain
+
+   This is an integer prescale filter that should be combined
+   with a bilinear hardware filtering (GL_BILINEAR filter or some such) to achieve
+   a smooth scaling result with minimum blur. This is good for pixelgraphics
+   that are scaled by non-integer factors.
+   
+   The prescale factor and texel coordinates are precalculated
+   in the vertex shader for speed.
+*/
+
+#pragma stage vertex
+layout(location = 0) in vec4 Position;
+layout(location = 1) in vec2 TexCoord;
+layout(location = 0) out vec2 vTexCoord;
+layout(location = 1) out vec2 precalc_texel;
+layout(location = 2) out vec2 precalc_scale;
+
+void main()
+{
+   gl_Position = global.MVP * Position;
+   vTexCoord = TexCoord;
+   precalc_scale = max(floor(params.OutputSize.xy / params.SourceSize.xy), vec2(1.0, 1.0));
+   precalc_texel = vTexCoord * params.SourceSize.xy;
+}
+
+#pragma stage fragment
+layout(location = 0) in vec2 vTexCoord;
+layout(location = 1) in vec2 precalc_texel;
+layout(location = 2) in vec2 precalc_scale;
+layout(location = 0) out vec4 FragColor;
+layout(set = 0, binding = 2) uniform sampler2D Source;
+
+void main()
+{
+   vec2 texel = precalc_texel;
+   vec2 scale = precalc_scale;
+   vec2 texel_floored = floor(texel);
+   vec2 s = fract(texel);
+   vec2 region_range = 0.5 - 0.5 / scale;
+
+   // Figure out where in the texel to sample to get correct pre-scaled bilinear.
+   // Uses the hardware bilinear interpolator to avoid having to sample 4 times manually.
+
+   vec2 center_dist = s - 0.5;
+   vec2 f = (center_dist - clamp(center_dist, -region_range, region_range)) * scale + 0.5;
+
+   vec2 mod_texel = texel_floored + f;
+
+   FragColor = vec4(texture(Source, mod_texel / params.SourceSize.xy).rgb, 1.0);
+}

retro/sharp-bilinear-2x-prescale.slangp

@@ -0,0 +1,7 @@
+shaders = 2
+shader0 = "../stock.slang"
+filter_linear0 = false
+scale_type0 = source
+scale0 = 2.0
+shader1 = "../stock.slang"
+filter_linear1 = true

retro/sharp-bilinear-scanlines.slangp

@@ -0,0 +1,4 @@
+shaders = 1
+
+shader0 = "shaders/sharp-bilinear-scanlines.slang"
+filter_linear0 = true

retro/sharp-bilinear-simple.slangp

@@ -0,0 +1,4 @@
+shaders = 1
+
+shader0 = "shaders/sharp-bilinear-simple.slang"
+filter_linear0 = true