/*
   Merge Dithering and Pseudo Transparency Shader v2.8 - Pass 3
   by Sp00kyFox, 2014

   Backpropagation and checkerboard smoothing.

*/

#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 OrigTexture;
#define Original OrigTexture
COMPAT_VARYING vec4 TEX0;

// compatibility #defines
#define Source Texture
#define vTexCoord TEX0.xy
#define texture(c, d) COMPAT_TEXTURE(c, d)
#define SourceSize vec4(TextureSize, 1.0 / TextureSize) //either TextureSize or InputSize
#define OutSize vec4(OutputSize, 1.0 / OutputSize)

#define TEX(dx,dy)   texture(Source, vTexCoord+vec2((dx),(dy))*SourceSize.zw)
#define TEXt0(dx,dy) texture(Original, vTexCoord+vec2((dx),(dy))*SourceSize.zw)

bool eq(vec3 A, vec3 B){
	return (A == B);
}

float and(float a, float b){
	return min(a,b);
}

float or(float a, float b, float c, float d, float e, float f, float g, float h, float i){
	return max(a, max(b, max(c, max(d, max(e, max(f, max(g, max(h,i))))))));
}

vec2 and(vec2 a, vec2 b){
	return min(a,b);
}

vec2 or(vec2 a, vec2 b){
	return max(a,b);
}

vec2 or(vec2 a, vec2 b, vec2 c, vec2 d){
	return max(a, max(b, max(c,d)));
}

void main()
{
	/*
		UL U UR
		L  C R
		DL D DR
	*/

	vec4 C  = TEX( 0., 0.);		vec3 c  = TEXt0( 0., 0.).xyz;
	vec2 L  = TEX(-1., 0.).xy;	vec3 l  = TEXt0(-1., 0.).xyz;
	vec2 R  = TEX( 1., 0.).xy;	vec3 r  = TEXt0( 1., 0.).xyz;
	vec2 U  = TEX( 0.,-1.).xy;	vec3 u  = TEXt0( 0.,-1.).xyz;
	vec2 D  = TEX( 0., 1.).xy;	vec3 d  = TEXt0( 0., 1.).xyz;
	float UL = TEX(-1.,-1.).y;	vec3 ul = TEXt0(-1.,-1.).xyz;
	float UR = TEX( 1.,-1.).y;	vec3 ur = TEXt0( 1.,-1.).xyz;
	float DL = TEX(-1., 1.).y;	vec3 dl = TEXt0(-1., 1.).xyz;
	float DR = TEX( 1., 1.).y;	vec3 dr = TEXt0( 1., 1.).xyz;

	// Backpropagation
	C.xy = or(C.xy, and(C.zw, or(L, R, U, D)));

	// Checkerboard Smoothing
	C.y = or(C.y, min(U.y, float(eq(c,u))), min(D.y, float(eq(c,d))), min(L.y, float(eq(c,l))), min(R.y, float(eq(c,r))), min(UL, float(eq(c,ul))), min(UR, float(eq(c,ur))), min(DL, float(eq(c,dl))), min(DR, float(eq(c,dr))));

   FragColor = vec4(C);
}
#endif
