Java Code House

To day in this article I will tell you how to resize or scale an image in Java. Many times while developing an application you maya need this. Most often you may require to create a thumbnail of an image in most web applications. This tutorial will guide you describing each steps in detail.

• First read an image from file or URL using ImageIO
• Now create a BufferedImage with specified width, height and image type
• Obtain a Graphics2D object from the destination object create in earlier step
• Draw the original image using the Graphics object
• Dispose the Graphics object
• Return or save the final image

import java.awt.AlphaComposite;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.geom.AffineTransform;
import java.awt.image.BufferedImage;
import java.io.File;

import javax.imageio.ImageIO;

public class ImageResizer {
 
 /**
  * Resizes an image without rendering hints depending on input width, height
  * @param src source image to be resized
  * @param width width of destination image
  * @param height height of destination image
  * @return resized image
  */
 public BufferedImage resizeImage(BufferedImage src,int width,int height){
  BufferedImage dest = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
  Graphics2D g2d = dest.createGraphics();
  g2d.drawImage(src, 0, 0, width, height, null);
  g2d.dispose();
  
  return dest;
 }
 
 /**
  * Resizes an image with rendering hints depending on input width, height
  * @param src source image to be resized
  * @param width width of destination image
  * @param height height of destination image
  * @return resized image
  */
 public BufferedImage resizeImageWithHints(BufferedImage src,int width,int height){
  BufferedImage dest = new BufferedImage(width, height, src.getType());
  Graphics2D g2d = dest.createGraphics();
  
  g2d.setComposite(AlphaComposite.Src);
  g2d.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);
  g2d.setRenderingHint(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY);
  g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
  
  g2d.drawImage(src, 0, 0, width, height, null);
  g2d.dispose();
  
  return dest;
 }
 
 /**
  * Scales an image depending on sclae factor and maintains
  * the aspect ratio of original image
  * @param src source image to be scaled
  * @param scale scale factor xscale = yscale
  * @return scaled image
  */
 public BufferedImage scaleImage(BufferedImage src, double scale){
  int w = (int)(src.getWidth()*scale);
  int h = (int)(src.getHeight()*scale);
  BufferedImage dest = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB);
  Graphics2D g2d = dest.createGraphics();
  AffineTransform at = AffineTransform.getScaleInstance(scale, scale);
  g2d.drawRenderedImage(src, at);
  
  return dest;
 }
 
 public static void main(String... args) throws Exception {
  ImageResizer resizer = new ImageResizer();
  BufferedImage src = ImageIO.read(new File("original.jpg"));

  BufferedImage dest = resizer.resizeImage(src, 100, 100);
  ImageIO.write(dest, "jpeg", new File("dest-resize.jpg"));
  
  dest = resizer.resizeImageWithHints(src, 100, 100);
  ImageIO.write(dest, "jpeg", new File("dest-resize-hints.jpg"));
  
  dest = resizer.scaleImage(src, 0.3);
  ImageIO.write(dest, "jpeg", new File("dest-scale.jpg"));
 }
}

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