Example Depot

// Reads the jpeg image in infile, compresses the image, // and writes it back out to outfile. // compressionQuality ranges between 0 and 1, // 0-lowest, 1-highest. public void compressJpegFile(File infile, File outfile, float compressionQuality) { try { // Retrieve jpg image to be compressed RenderedImage rendImage = ImageIO.read(infile); // Find a jpeg writer ImageWriter writer = null; Iterator iter = ImageIO.getImageWritersByFormatName("jpg"); if (iter.hasNext()) { writer = (ImageWriter)iter.next(); } // Prepare output file ImageOutputStream ios = ImageIO.createImageOutputStream(outfile); writer.setOutput(ios); // Set the compression quality ImageWriteParam iwparam = new MyImageWriteParam(); iwparam.setCompressionMode(ImageWriteParam.MODE_EXPLICIT) ; iwparam.setCompressionQuality(compressionQuality); // Write the image writer.write(null, new IIOImage(rendImage, null, null), iwparam); // Cleanup ios.flush(); writer.dispose(); ios.close(); } catch (IOException e) { } } // This class overrides the setCompressionQuality() method to workaround // a problem in compressing JPEG images using the javax.imageio package. public class MyImageWriteParam extends JPEGImageWriteParam { public MyImageWriteParam() { super(Locale.getDefault()); } // This method accepts quality levels between 0 (lowest) and 1 (highest) and simply converts // it to a range between 0 and 256; this is not a correct conversion algorithm. // However, a proper alternative is a lot more complicated. // This should do until the bug is fixed. public void setCompressionQuality(float quality) { if (quality < 0.0F || quality > 1.0F) { throw new IllegalArgumentException("Quality out-of-bounds!"); } this.compressionQuality = 256 - (quality * 256); } }