Example Image Enhancement

• 

  Dark image before histogram adjustment

• 

  Image after its histogram has been globally adjusted

• 

  Image after its edges are enhanced

Demonstration of different image enhancement operations. If an image is excessively dark or light the visibility of features can be improved by adjusting its histogram. Another technique makes the edges in an image more pronounced by.

Example Code:

• ExampleImageEnhancement.java

Concepts:

• Visibility

Relevant Applets:

• Image Enhancement

Example Code

/**
 * Demonstration of various ways an image can be "enhanced".  Image enhancement typically refers to making it easier
 * for people to view the image and pick out its details.
 *
 * @author Peter Abeles
 */
public class ExampleImageEnhancement {

	static String imagePath = "enhance/dark.jpg";
//	static String imagePath = "enhance/dull.jpg";

	static ListDisplayPanel mainPanel = new ListDisplayPanel();

	/**
	 * Histogram adjustment algorithms aim to spread out pixel intensity values uniformly across the allowed range.
	 * This if an image is dark, it will have greater contrast and be brighter.
	 */
	public static void histogram() {
		BufferedImage buffered = UtilImageIO.loadImage(UtilIO.pathExample(imagePath));
		GrayU8 gray = ConvertBufferedImage.convertFrom(buffered,(GrayU8)null);
		GrayU8 adjusted = gray.createSameShape();

		int histogram[] = new int[256];
		int transform[] = new int[256];

		ListDisplayPanel panel = new ListDisplayPanel();

		ImageStatistics.histogram(gray, histogram);
		EnhanceImageOps.equalize(histogram, transform);
		EnhanceImageOps.applyTransform(gray, transform, adjusted);
		panel.addImage(ConvertBufferedImage.convertTo(adjusted, null), "Global");

		EnhanceImageOps.equalizeLocal(gray, 50, adjusted, histogram, transform);
		panel.addImage(ConvertBufferedImage.convertTo(adjusted,null),"Local");

		panel.addImage(ConvertBufferedImage.convertTo(gray, null), "Original");

		panel.setPreferredSize(new Dimension(gray.width, gray.height));
		mainPanel.addItem(panel, "Histogram");
	}

	/**
	 * When an image is sharpened the intensity of edges are made more extreme while flat regions remain unchanged.
	 */
	public static void sharpen() {
		BufferedImage buffered = UtilImageIO.loadImage(UtilIO.pathExample(imagePath));
		GrayU8 gray = ConvertBufferedImage.convertFrom(buffered,(GrayU8)null);
		GrayU8 adjusted = gray.createSameShape();


		ListDisplayPanel panel = new ListDisplayPanel();

		EnhanceImageOps.sharpen4(gray, adjusted);
		panel.addImage(ConvertBufferedImage.convertTo(adjusted,null),"Sharpen-4");

		EnhanceImageOps.sharpen8(gray, adjusted);
		panel.addImage(ConvertBufferedImage.convertTo(adjusted,null),"Sharpen-8");

		panel.addImage(ConvertBufferedImage.convertTo(gray,null),"Original");

		panel.setPreferredSize(new Dimension(gray.width,gray.height));
		mainPanel.addItem(panel, "Sharpen");
	}

	public static void main( String args[] )
	{
		histogram();
		sharpen();
		ShowImages.showWindow(mainPanel,"Enhancement",true);
	}

}