Add Game Boy palette shader

handheld/gb-palette-dmg.glslp

@@ -0,0 +1,9 @@
+shaders = 1
+shader0 = shaders/gb-palette/gb-palette.glsl	//colorize image
+
+scale_type0 = source
+filter_linear0 = false
+
+textures = COLOR_PALETTE
+COLOR_PALETTE = shaders/gb-palette/resources/palette-dmg.png
+COLOR_PALETTE_linear = false

handheld/gb-palette-light.glslp

@@ -0,0 +1,9 @@
+shaders = 1
+shader0 = shaders/gb-palette/gb-palette.glsl	//colorize image
+
+scale_type0 = source
+filter_linear0 = false
+
+textures = COLOR_PALETTE
+COLOR_PALETTE = shaders/gb-palette/resources/palette-light.png
+COLOR_PALETTE_linear = false

handheld/gb-palette-pocket.glslp

@@ -0,0 +1,9 @@
+shaders = 1
+shader0 = shaders/gb-palette/gb-palette.glsl	//colorize image
+
+scale_type0 = source
+filter_linear0 = false
+
+textures = COLOR_PALETTE
+COLOR_PALETTE = shaders/gb-palette/resources/palette-pocket.png
+COLOR_PALETTE_linear = false

handheld/shaders/gb-palette/gb-palette.glsl

@@ -0,0 +1,98 @@
+#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;
+
+vec4 _oPosition1; 
+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;
+
+// compatibility #defines
+#define vTexCoord TEX0.xy
+#define SourceSize vec4(TextureSize, 1.0 / TextureSize) //either TextureSize or InputSize
+#define OutSize vec4(OutputSize, 1.0 / OutputSize)
+
+void main()
+{
+    gl_Position = MVPMatrix * VertexCoord;
+    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;
+uniform sampler2D COLOR_PALETTE;
+COMPAT_VARYING vec4 TEX0;
+
+// compatibility #defines
+#define Source Texture
+#define vTexCoord TEX0.xy
+
+#define SourceSize vec4(TextureSize, 1.0 / TextureSize) //either TextureSize or InputSize
+#define OutSize vec4(OutputSize, 1.0 / OutputSize)
+
+void main()
+{
+     //sample the input textures
+
+     vec4 out_color = COMPAT_TEXTURE(Source, vTexCoord.xy);
+
+     //input grayscale values:
+     //0.000 black - 0.333 medium gray - 0.667 light gray - 1.000 white
+     //multiply grayscale value by 3 to obtain int value in range [0, 3], acts as index for arrays storing custom palette UV coordinates and alpha value
+
+     vec2 palette_coordinate = vec2(0.5, (abs(1 - out_color.r) * 0.75) + 0.125);	//directly map input grayscale value to color palette y coordinate
+     out_color = vec4(COMPAT_TEXTURE(COLOR_PALETTE, palette_coordinate).rgb, ceil(abs(1.0 - out_color.r)));	//sample color from palette, alpha = 1 if color is not transparent
+
+     FragColor = out_color;
+} 
+#endif