Example Remove Perspective Distortion

• 

  Input file where the billboard is experiencing heavy perspective distortion.

• 

  Output image after a homography is used to remap the billboard and remove perspective distortion.

It is often easier to process an image after perspective distortion is removed. The billboard in this example is at an acute angle relative to the camera, making its text hard to read. A homography can be created, using the for cornerns of the billboard, and used to remove this distortion.

Example Code:

• ExampleRemovePerspectiveDistortion.java

Concepts:

• Homography
• Perspective
• Distortion

Relevant Examples:

• Example Overhead View

Example Code

/**
 * Certain image processing techniques, such as Optical Character Recognition (OCR), can be performed better if
 * perspective distortion is remove from an image.  In this example a homography is computed from the four corners
 * of a bulletin board and the image is projected into a square image without perspective distortion.  The
 * {@link RemovePerspectiveDistortion} class is used to perform the distortion.  The class is easy to understand
 * if you know what a homography is, you should look at it!
 *
 * @author Peter Abeles
 */
public class ExampleRemovePerspectiveDistortion {
	public static void main( String[] args ) {
		// load a color image
		BufferedImage buffered = UtilImageIO.loadImage(UtilIO.pathExample("goals_and_stuff.jpg"));
		Planar<GrayF32> input = ConvertBufferedImage.convertFromPlanar(buffered, null, true, GrayF32.class);

		RemovePerspectiveDistortion<Planar<GrayF32>> removePerspective =
				new RemovePerspectiveDistortion<>(400, 500, ImageType.pl(3, GrayF32.class));

		// Specify the corners in the input image of the region.
		// Order matters! top-left, top-right, bottom-right, bottom-left
		if (!removePerspective.apply(input,
				new Point2D_F64(267, 182), new Point2D_F64(542, 68),
				new Point2D_F64(519, 736), new Point2D_F64(276, 570))) {
			throw new RuntimeException("Failed!?!?");
		}

		Planar<GrayF32> output = removePerspective.getOutput();

		BufferedImage flat = ConvertBufferedImage.convertTo_F32(output, null, true);
		ShowImages.showWindow(buffered, "Original Image", true);
		ShowImages.showWindow(flat, "Without Perspective Distortion", true);
	}
}