a port of the Processing Visualization Language

EdgeDetection

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

Original Processing.org Example: EdgeDetection

// All Examples Written by Casey Reas and Ben Fry

// unless otherwise stated.

/* @pjs preload="data/house.jpg"; */



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

                     { -1,  9, -1 },

                     { -1, -1, -1 } };

  

size(200, 200);

PImage img = loadImage("data/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)*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
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