implemented downscale borrowed from BSL

shaders/composite.fsh

@@ -9,8 +9,11 @@
 #define rgbSteps 4 // the number of rgb values to use [2 4 8 16 32 64]
 
 //#define BLACKEN // Whether or not to blackent the background
+#define pixelSize 2 // the size of pixels [1 2 4 8 16]
 
 uniform sampler2D gcolor;
+uniform sampler2D colortex1;
+uniform float viewWidth, viewHeight;
 
 varying vec2 texcoord;
 
@@ -107,8 +110,18 @@ float dither(float color, float dithersteps) {
 }
 
 void main() {
+	vec2 newcoord = texcoord;
+	#if pixelSize > 1
+		vec2 view = vec2(viewWidth, viewHeight) / float(pixelSize);
+		float offset = (ceil(pixelSize * 0.5) - 0.5) / float(pixelSize);
+		newcoord = (floor(newcoord * view) + offset) / view;
+	#endif
+	vec3 color = texture2D(gcolor, newcoord).rgb;
+    //gl_FragData[0] = vec4(vec3(color), 1.0);
+
 	float mask;
-	vec3 ogRGB = texture2D(gcolor, texcoord).rgb;
+	//vec3 ogRGB = texture2D(gcolor, texcoord).rgb;
+	vec3 ogRGB = color;
 	vec3 ogHSV = rgb2hsv(ogRGB).xyz;
     float val = ogHSV.z;
     vec3 ditherhsv = hsv2rgb(vec3(dither(ogHSV.x, hueSteps), dither(ogHSV.y, satSteps), dither(ogHSV.z, valSteps))).rgb;
@@ -120,7 +133,6 @@ void main() {
     #else 
         vec3 final = ditherhsv;
     #endif
-/* DRAWBUFFERS:0 */
-	gl_FragData[0] = vec4(vec3(final), 1.0); //gcolor
+    gl_FragData[0] = vec4(vec3(final), 1.0); //gcolor
 }
 

shaders/lang/en_US.lang

@@ -0,0 +1,19 @@
+
+option.pixelSize=Downscaling
+value.pixelSize.1=Off
+value.pixelSize.2=Low (2x)
+value.pixelSize.4=Medium (4x)
+value.pixelSize.8=High (8x)
+value.pixelSize.16=Silly (16x)
+
+screen.COLOR=Color Depth
+option.RGB=Use RGB
+option.rgbSteps=RGB Depth
+option.hueSteps=Hue Depth
+option.satSteps=Saturation Depth
+option.valSteps=Value Depth
+
+screen.PSX=PSX
+option.vWarp=Vertex Warping
+option.tWarp=Texture Warping
+

shaders/shaders.properties

@@ -1 +1,7 @@
-sliders=hueSteps satSteps valSteps
+sliders=pixelSize hueSteps satSteps valSteps rgbSteps
+
+screen=pixelSize [COLOR] [PSX]
+
+screen.COLOR=RGB rgbSteps pixelSize hueSteps satSteps valSteps
+screen.PSX=<empty>
+