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    please explain how exactly this program is working, i unable to understand the logic of the matrix( kernel) ,
    secondly how can i know the location of the edge...thank you 








    /**
    * Edge Detection.
    *
    * Exposing areas of contrast within an image
    * by processing it through a high-pass filter.
    */

    float[][] kernel = { { -1, -1, -1 },
    { -1, 9, -1 },
    { -1, -1, -1 } };

    size(200, 200);
    PImage img = loadImage("house.jpg"); // Load the original image
    image(img, 0, 0); // Displays the image from point (0,0)
    img.loadPixels();
    // Create an opaque image of the same size as the original
    PImage edgeImg = createImage(img.width, img.height, RGB);
    // Loop through every pixel in the image.
    for (int y = 1; y < img.height-1; y++) { // Skip top and bottom edges
    for (int x = 1; x < img.width-1; x++) { // Skip left and right edges
    float sum = 0; // Kernel sum for this pixel
    for (int ky = -1; ky <= 1; ky++) {
    for (int kx = -1; kx <= 1; kx++) {
    // Calculate the adjacent pixel for this kernel point
    int pos = (y + ky)*img.width + (x + kx);
    // Image is grayscale, red/green/blue are identical
    float val = red(img.pixels[pos]);
    // Multiply adjacent pixels based on the kernel values
    sum += kernel[ky+1][kx+1] * val;
    }
    }
    // For this pixel in the new image, set the gray value
    // based on the sum from the kernel
    edgeImg.pixels[y*img.width + x] = color(sum);
    }
    }
    // State that there are changes to edgeImg.pixels[]
    edgeImg.updatePixels();
    image(edgeImg, 100, 0); // Draw the new image