Add uniform-nearest shader

Features:
-produces nearest neighbor look with fractional scales.
-uses texture AA shader code.
-uses hotizontal subpixel scaling.
-due to different pixel sizes, moving sprites change dimension if nearest neighbor is used with fractional scaling. This looks unsteady. This shader uniforms pixel dimensions. Output looks much quieter.

https://forums.libretro.com/t/uniform-nearest-interpolation-shader/41492

interpolation/shaders/uniform-nearest.glsl

@@ -0,0 +1,168 @@
+/* 
+ * gizmo98 uniform-nearest shader
+ * Copyright (C) 2023 gizmo98
+ *
+ *   This program is free software; you can redistribute it and/or modify it
+ *   under the terms of the GNU General Public License as published by the Free
+ *   Software Foundation; either version 2 of the License, or (at your option)
+ *   any later version.
+ *
+ * version 0.1, 28.04.2023
+ * ---------------------------------------------------------------------------------------
+ * - initial commit
+ * 
+ * https://github.com/gizmo98/gizmo-crt-shader
+ *
+ * This shader texture AA shader code and subpixel scaling to produce a nearest neighbor
+ * look with even placed pixels. If nearest neighbor is applied to fractional scaled output 
+ * pixels look uneven and moving sprites change dimension which looks ugly.
+ *
+ * BGR_LCD_PATTERN most LCDs have a RGB pixel pattern. Enable BGR pattern with this switch
+ *
+ * uses parts of texture anti-aliasing shader from Ikaros https://www.shadertoy.com/view/ldsSRX
+ */
+
+#pragma parameter BGR_LCD_PATTERN "BGR output pattern"         0.0 0.0 1.0 1.0
+
+#if defined(VERTEX)
+
+#if __VERSION__ >= 130
+#define COMPAT_VARYING out
+#define COMPAT_ATTRIBUTE in
+#define COMPAT_TEXTURE texture
+#else
+#define COMPAT_VARYING varying 
+#define COMPAT_ATTRIBUTE attribute 
+#define COMPAT_TEXTURE texture2D
+#endif
+
+#ifdef GL_ES
+#define COMPAT_PRECISION mediump
+#else
+#define COMPAT_PRECISION
+#endif
+
+COMPAT_ATTRIBUTE vec4 VertexCoord;
+COMPAT_ATTRIBUTE vec4 COLOR;
+COMPAT_ATTRIBUTE vec4 TexCoord;
+COMPAT_VARYING vec4 COL0;
+COMPAT_VARYING vec4 TEX0;
+
+uniform mat4 MVPMatrix;
+uniform COMPAT_PRECISION int FrameDirection;
+uniform COMPAT_PRECISION int FrameCount;
+uniform COMPAT_PRECISION vec2 OutputSize;
+uniform COMPAT_PRECISION vec2 TextureSize;
+uniform COMPAT_PRECISION vec2 InputSize;
+
+#ifdef PARAMETER_UNIFORM
+uniform COMPAT_PRECISION float BGR_LCD_PATTERN;
+#else
+#define BGR_LCD_PATTERN 0.0
+#endif
+
+void main()
+{
+    gl_Position = VertexCoord.x * MVPMatrix[0] + VertexCoord.y * MVPMatrix[1] + VertexCoord.z * MVPMatrix[2] + VertexCoord.w * MVPMatrix[3];
+    TEX0.xy = TexCoord.xy;
+}
+
+#elif defined(FRAGMENT)
+
+#if __VERSION__ >= 130
+#define COMPAT_VARYING in
+#define COMPAT_TEXTURE texture
+out vec4 FragColor;
+#else
+#define COMPAT_VARYING varying
+#define FragColor gl_FragColor
+#define COMPAT_TEXTURE texture2D
+#endif
+
+#ifdef GL_ES
+#ifdef GL_FRAGMENT_PRECISION_HIGH
+precision highp float;
+#else
+precision mediump float;
+#endif
+#define COMPAT_PRECISION mediump
+#else
+#define COMPAT_PRECISION
+#endif
+
+uniform COMPAT_PRECISION int FrameDirection;
+uniform COMPAT_PRECISION int FrameCount;
+uniform COMPAT_PRECISION vec2 OutputSize;
+uniform COMPAT_PRECISION vec2 TextureSize;
+uniform COMPAT_PRECISION vec2 InputSize;
+uniform sampler2D Texture;
+COMPAT_VARYING vec4 TEX0;
+
+#ifdef PARAMETER_UNIFORM
+uniform COMPAT_PRECISION float BGR_LCD_PATTERN;
+#endif
+
+float Y(in float X)
+{
+    return 4.0 * (-X * X + X);
+}
+
+
+vec2 saturateA(in vec2 x)
+{
+    return clamp(x, 0.0, 1.0);
+}
+
+vec2 magnify(in vec2 uv, in vec2 res)
+{
+    uv *= res; 
+    return (saturateA(fract(uv) / saturateA(fwidth(uv))) + floor(uv) - 0.5) / res.xy;
+}
+vec4 textureAA(in vec2 uv){
+    uv = magnify(uv,TextureSize.xy);
+    uv = uv*TextureSize.xy + 0.5;
+
+    COMPAT_PRECISION vec2 iuv = floor(uv);
+    COMPAT_PRECISION vec2 fuv = uv - iuv;  
+      
+    uv = vec2(uv + vec2(-0.5,-0.5)) / TextureSize.xy;
+    return COMPAT_TEXTURE( Texture, uv );
+}
+
+vec4 textureSubSample(in vec2 uvr, in vec2 uvg, in vec2 uvb ){
+    return vec4(textureAA(uvr).r,textureAA(uvg).g, textureAA(uvb).b, 255);
+}
+
+vec3 XCoords(in float coord, in float factor){
+    COMPAT_PRECISION float iGlobalTime = float(FrameCount)*0.025;
+    COMPAT_PRECISION float spread = 0.333;
+    COMPAT_PRECISION vec3 coords = vec3(coord);
+    if(BGR_LCD_PATTERN == 1.0)
+        coords.r += spread * 2.0;
+    else
+        coords.b += spread * 2.0;
+    coords.g += spread;
+    coords *= factor;
+    return coords;
+}
+
+float YCoord(in float coord, in float factor){
+    return coord * factor;
+}
+
+void main()
+{
+    vec2 texcoord = TEX0.xy;
+    
+    COMPAT_PRECISION vec2 fragCoord = texcoord.xy * OutputSize.xy;
+    COMPAT_PRECISION vec2 factor = TextureSize.xy / OutputSize.xy ;
+    COMPAT_PRECISION float yCoord = YCoord(fragCoord.y, factor.y) ;
+    COMPAT_PRECISION vec3  xCoords = XCoords(fragCoord.x, factor.x);
+
+    COMPAT_PRECISION vec2 coord_r = vec2(xCoords.r, yCoord) / TextureSize.xy;
+    COMPAT_PRECISION vec2 coord_g = vec2(xCoords.g, yCoord) / TextureSize.xy;
+    COMPAT_PRECISION vec2 coord_b = vec2(xCoords.b, yCoord) / TextureSize.xy;
+
+    FragColor = textureSubSample(coord_r,coord_g,coord_b);
+}
+#endif

interpolation/uniform-nearest.glslp

@@ -0,0 +1,8 @@
+shaders = "1"
+shader0 = "shaders/uniform-nearest.glsl"
+filter_linear0 = "true"
+scale_type0 = viewport
+
+parameters = "BGR_LCD_PATTERN"
+BGR_LCD_PATTERN = "0.0"
+