Reads an image in a file and creates a thumbnail in another file. : Image « 2D Graphics GUI « Java

Reads an image in a file and creates a thumbnail in another file.

//package net.gqu.utils;

import java.awt.Color;
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.RenderingHints;
import java.awt.Toolkit;
import java.awt.geom.AffineTransform;
import java.awt.image.BufferedImage;

import javax.swing.ImageIcon;

import com.sun.image.codec.jpeg.JPEGCodec;
import com.sun.image.codec.jpeg.JPEGImageEncoder;

public class Thumbnail {
  * Reads an image in a file and creates a thumbnail in another file.
  * largestDimension is the largest dimension of the thumbnail, the other dimension is scaled accordingly.
  * Utilises weighted stepping method to gradually reduce the image size for better results,
  * i.e. larger steps to start with then smaller steps to finish with.
  * Note: always writes a JPEG because GIF is protected or something - so always make your outFilename end in 'jpg'.
  * PNG's with transparency are given white backgrounds
  public String createThumbnail(String inFilename, String outFilename, int largestDimension)
      double scale;
      int sizeDifference, originalImageLargestDim;
      if(!inFilename.endsWith(".jpg") && !inFilename.endsWith(".jpeg") && !inFilename.endsWith(".gif") && !inFilename.endsWith(".png"))
        return "Error: Unsupported image type, please only either JPG, GIF or PNG";
        Image inImage = Toolkit.getDefaultToolkit().getImage(inFilename);
        if(inImage.getWidth(null) == -1 || inImage.getHeight(null) == -1)
          return "Error loading file: \"" + inFilename + "\"";
          //find biggest dimension      
          if(inImage.getWidth(null) > inImage.getHeight(null))
            scale = (double)largestDimension/(double)inImage.getWidth(null);
            sizeDifference = inImage.getWidth(null) - largestDimension;
            originalImageLargestDim = inImage.getWidth(null);
            scale = (double)largestDimension/(double)inImage.getHeight(null);
            sizeDifference = inImage.getHeight(null) - largestDimension;
            originalImageLargestDim = inImage.getHeight(null);
          //create an image buffer to draw to
          BufferedImage outImage = new BufferedImage(100, 100, BufferedImage.TYPE_INT_RGB); //arbitrary init so code compiles
          Graphics2D g2d;
          AffineTransform tx;
          if(scale < 1.0d) //only scale if desired size is smaller than original
            int numSteps = sizeDifference / 100;
            int stepSize = sizeDifference / numSteps;
            int stepWeight = stepSize/2;
            int heavierStepSize = stepSize + stepWeight;
            int lighterStepSize = stepSize - stepWeight;
            int currentStepSize, centerStep;
            double scaledW = inImage.getWidth(null);
            double scaledH = inImage.getHeight(null);
            if(numSteps % 2 == 1) //if there's an odd number of steps
              centerStep = (int)Math.ceil((double)numSteps / 2d); //find the center step
              centerStep = -1; //set it to -1 so it's ignored later
            Integer intermediateSize = originalImageLargestDim, previousIntermediateSize = originalImageLargestDim;
            Integer calculatedDim;
            for(Integer i=0; i<numSteps; i++)
              if(i+1 != centerStep) //if this isn't the center step
                if(i == numSteps-1) //if this is the last step
                  //fix the stepsize to account for decimal place errors previously
                  currentStepSize = previousIntermediateSize - largestDimension;
                  if(numSteps - i > numSteps/2) //if we're in the first half of the reductions
                    currentStepSize = heavierStepSize;
                    currentStepSize = lighterStepSize;
              else //center step, use natural step size
                currentStepSize = stepSize;
              intermediateSize = previousIntermediateSize - currentStepSize;
              scale = (double)intermediateSize/(double)previousIntermediateSize;
              scaledW = (int)scaledW*scale;
              scaledH = (int)scaledH*scale;
              outImage = new BufferedImage((int)scaledW, (int)scaledH, BufferedImage.TYPE_INT_RGB);
              g2d = outImage.createGraphics();
              g2d.clearRect(0, 0, outImage.getWidth(), outImage.getHeight());
              g2d.setRenderingHint(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY);
              tx = new AffineTransform();
              tx.scale(scale, scale);
              g2d.drawImage(inImage, tx, null);
              inImage = new ImageIcon(outImage).getImage();
              previousIntermediateSize = intermediateSize;
          //just copy the original
          outImage = new BufferedImage(inImage.getWidth(null), inImage.getHeight(null), BufferedImage.TYPE_INT_RGB);
          g2d = outImage.createGraphics();
          g2d.clearRect(0, 0, outImage.getWidth(), outImage.getHeight());
          tx = new AffineTransform();
          tx.setToIdentity(); //use identity matrix so image is copied exactly
          g2d.drawImage(inImage, tx, null);
          //JPEG-encode the image and write to file.
          OutputStream os = new FileOutputStream(outFilename);
          JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(os);
    catch(Exception ex)
      String errorMsg = "";
      errorMsg += "<br>Exception: " + ex.toString();
      errorMsg += "<br>Cause = " + ex.getCause();
      errorMsg += "<br>Stack Trace = ";
      StackTraceElement stackTrace[] = ex.getStackTrace();
      for(int traceLine=0; traceLine<stackTrace.length; traceLine++)
        errorMsg += "<br>" + stackTrace[traceLine];
      return errorMsg;
    return ""; //success


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