// =========================================================
// Module:      OR_GATE
//
// Description: Apply Boolean OR Gate for 2 images' channel(s)
//              1) parameter: threshold 
//                  set threshold function to convert data to binary for boolean logic. 
//                      Truth table
//                      1 1 = 1
//                      1 0 = 1
//                      0 1 = 1
//                      0 0 = 0
//              2) parameter: channel 
//                  set channel to apply OR gate logic.
//                      4: RGB mean
//                      3: Alpha channel
//                      0: Red channel
//                      1: Green channel
//                      2: Blue channel
//
// Author(s):   CT Yeung (cty)
//
// History:
// 26Nov09      1st implementation                      cty
// =========================================================
<languageVersion : 1.0;>

kernel OR_GATE
<   namespace : "CT Yeung";
    vendor : "";
    version : 1;
    description : "OR Gate for 2 images' channel(s)";
>
{
    // grayscale threshold value
    parameter float threshold
    <
        minValue: 0.0;
        maxValue: 1.0;
        defaultValue: .5;
    >;
     
    // channel to use
    parameter int channel
    <
        minValue: 0;
        maxValue: 4;
        defaultValue: 0;
    >;
     
    input image4 src1;
    input image4 src2;
    output pixel4 dst;

    void
    evaluatePixel() {
        float4 inClr1 = sampleNearest(src1, outCoord());
        float4 inClr2 = sampleNearest(src2, outCoord());
        
        if(channel == 4) {                  // 4: RGB mean
            float src1Mean = (inClr1.r + inClr1.g + inClr1.b)/3.0;
            float src2Mean = (inClr2.r + inClr2.g + inClr2.b)/3.0;
            if((src1Mean >= threshold ) || (src2Mean >= threshold)) {
                inClr1 = inClr2;
            }
        }
        else {                              // 3: Alpha channel
                                            // 0: Red channel
                                            // 1: Green channel
                                            // 2: Blue channel
            if(channel == 0) {
                if( (inClr1[0] >= threshold)||
                    (inClr2[0] >= threshold)) {
                
                    inClr1[0] = inClr2[0];
                }
            }
            else if(channel == 1) {
                if( (inClr1[1] >= threshold)||
                    (inClr2[1] >= threshold)) {
                
                    inClr1[1] = inClr2[1];
                }
            }
            else if(channel == 2) {
                if( (inClr1[2] >= threshold)||
                    (inClr2[2] >= threshold)) {
                
                    inClr1[2] = inClr2[2];
                }
            }
            else if(channel == 3) {
                if( (inClr1[3] >= threshold)||
                    (inClr2[3] >= threshold)) {
                
                    inClr1[3] = inClr2[3];
                }
            }
        }
        dst = inClr1;
    }
}