Simple Edge Detection

Let’s make a picture that looks like a pencil sketch.
Here is a simple technique that can help you to achieve the above said results.

  • Find an area of high contrast between a pixel and the pixel below it
  • if contrast is high we can make pixel black otherwise white

Question here is how to find high or low contrast pixels? Follow the steps below :

  • Average the RGB of current pixel and the pixel below it
  • Find the difference between both average values
  • If the resultant value is higher than a given amount, set current pixel to black, otherwise white

Here is an example program. Have a look on it and add it in to your MyPicture class used in our tutorial.

public void edgeDetection(double amount) {
	Pixel currPixel = null;
	Pixel belowPixel = null;

	int endY = this.getHeight() - 1;

	// loop through y values from 0 to height - 1
	for (int y = 0; y < endY; y++) {

		// loop through the x values from 0 to width
		for (int x = 0; x < this.getWidth(); x++) {

			// get the top and bottom pixels
			currPixel = this.getPixel(x, y);
			belowPixel = this.getPixel(x, y + 1);

			 * get the color averages for the two pixels, check if the
			 * absolute value of the difference is less than the amount
			if (Math.abs(currPixel.getAverage() - belowPixel.getAverage()) < amount)

			// else set the color to black

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