inkspread.frag

#version 150

uniform sampler2DRect tex0;
uniform float T;
const float diag = 1.414213562373095;

in vec2 fragCoord;
out vec4 outputColor;

vec4 F(vec4 x0,vec4 x1,float dist)
{
    return (x1-x0)/(T*dist);  //Swap out T here for hardcoded float, such as 0.5
}

void main()
{
    ivec2 ix = ivec2(fragCoord.xy);

    vec4 x11 = texelFetch(tex0, ix);
    vec4 x01 = texelFetchOffset(tex0, ix, ivec2(-1, 0));
    vec4 x21 = texelFetchOffset(tex0, ix, ivec2( 1, 0));
    vec4 x10 = texelFetchOffset(tex0, ix, ivec2( 0,-1));
    vec4 x12 = texelFetchOffset(tex0, ix, ivec2( 0, 1));
    vec4 x00 = texelFetchOffset(tex0, ix, ivec2(-1,-1));
    vec4 x02 = texelFetchOffset(tex0, ix, ivec2(-1, 1));
    vec4 x20 = texelFetchOffset(tex0, ix, ivec2( 1,-1));
    vec4 x22 = texelFetchOffset(tex0, ix, ivec2( 1, 1));
    vec4 d01 = F(x11,x01,1.0);
    vec4 d21 = F(x11,x21,1.0);
    vec4 d10 = F(x11,x10,1.0);
    vec4 d12 = F(x11,x12,1.0);
    vec4 d00 = F(x11,x00,diag);
    vec4 d02 = F(x11,x02,diag);
    vec4 d20 = F(x11,x20,diag);
    vec4 d22 = F(x11,x22,diag);
    vec4 res = x11+d01+d21+d10+d12+d00+d02+d20+d22;

    vec4 color = texture(tex0,fragCoord);
    //outputColor = vec4(color.rgb,1.0);
    outputColor = vec4(res);
}