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 java.io.FileOutputStream;
import java.io.OutputStream;
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)
{
try
{
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";
}
else
{
Image inImage = Toolkit.getDefaultToolkit().getImage(inFilename);
if(inImage.getWidth(null) == -1 || inImage.getHeight(null) == -1)
{
return "Error loading file: \"" + inFilename + "\"";
}
else
{
//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);
}
else
{
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
else
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;
}
else
{
if(numSteps - i > numSteps/2) //if we're in the first half of the reductions
currentStepSize = heavierStepSize;
else
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.setBackground(Color.WHITE);
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);
g2d.dispose();
inImage = new ImageIcon(outImage).getImage();
previousIntermediateSize = intermediateSize;
}
}
else
{
//just copy the original
outImage = new BufferedImage(inImage.getWidth(null), inImage.getHeight(null), BufferedImage.TYPE_INT_RGB);
g2d = outImage.createGraphics();
g2d.setBackground(Color.WHITE);
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);
g2d.dispose();
}
//JPEG-encode the image and write to file.
OutputStream os = new FileOutputStream(outFilename);
JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(os);
encoder.encode(outImage);
os.close();
}
}
}
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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