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import QtQuick 2.0

Effect {
    parameters: ListModel {
        ListElement {
            name: "threshold"
            value: 0.5
        }
    }

    // Transform slider values, and bind result to shader uniforms
    property real threshold: parameters.get(0).value
    property real targetSize: 250 - (200 * threshold) // TODO: fix ...
    property real resS: targetSize
    property real resT: targetSize

    // TODO
    property real magTol: 0.3
    property real quantize: 8.0

    fragmentShaderSrc: "uniform float dividerValue;
                        uniform float threshold;
                        uniform float resS;
                        uniform float resT;
                        uniform float magTol;
                        uniform float quantize;

                        uniform sampler2D source;
                        uniform lowp float qt_Opacity;
                        varying vec2 qt_TexCoord0;

                        void main()
                        {
                            vec4 color = vec4(1.0, 0.0, 0.0, 1.1);
                            vec2 uv = qt_TexCoord0.xy;
                            if (uv.x < dividerValue) {
                                vec2 st = qt_TexCoord0.st;
                                vec3 rgb = texture2D(source, st).rgb;
                                vec2 stp0 = vec2(1.0/resS,  0.0);
                                vec2 st0p = vec2(0.0     ,  1.0/resT);
                                vec2 stpp = vec2(1.0/resS,  1.0/resT);
                                vec2 stpm = vec2(1.0/resS, -1.0/resT);
                                float i00 =   dot( texture2D(source, st).rgb, vec3(0.2125,0.7154,0.0721));
                                float im1m1 = dot( texture2D(source, st-stpp).rgb, vec3(0.2125,0.7154,0.0721));
                                float ip1p1 = dot( texture2D(source, st+stpp).rgb, vec3(0.2125,0.7154,0.0721));
                                float im1p1 = dot( texture2D(source, st-stpm).rgb, vec3(0.2125,0.7154,0.0721));
                                float ip1m1 = dot( texture2D(source, st+stpm).rgb, vec3(0.2125,0.7154,0.0721));
                                float im10 =  dot( texture2D(source, st-stp0).rgb, vec3(0.2125,0.7154,0.0721));
                                float ip10 =  dot( texture2D(source, st+stp0).rgb, vec3(0.2125,0.7154,0.0721));
                                float i0m1 =  dot( texture2D(source, st-st0p).rgb, vec3(0.2125,0.7154,0.0721));
                                float i0p1 =  dot( texture2D(source, st+st0p).rgb, vec3(0.2125,0.7154,0.0721));
                                float h = -1.*im1p1 - 2.*i0p1 - 1.*ip1p1  +  1.*im1m1 + 2.*i0m1 + 1.*ip1m1;
                                float v = -1.*im1m1 - 2.*im10 - 1.*im1p1  +  1.*ip1m1 + 2.*ip10 + 1.*ip1p1;
                                float mag = sqrt(h*h + v*v);
                                if (mag > magTol) {
                                    color = vec4(0.0, 0.0, 0.0, 1.0);
                                }
                                else {
                                    rgb.rgb *= quantize;
                                    rgb.rgb += vec3(0.5, 0.5, 0.5);
                                    ivec3 irgb = ivec3(rgb.rgb);
                                    rgb.rgb = vec3(irgb) / quantize;
                                    color = vec4(rgb, 1.0);
                                }
                            } else {
                                color = texture2D(source, uv);
                            }
                            gl_FragColor = qt_Opacity * color;
                        }"
}