Example Remove Perspective Distortion

From BoofCV

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:

Concepts:

  • Homography
  • Perspective
  • Distortion

Relevant Examples:

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);
	}
}