DrawImage takes long time for images created with Photoshop

Question

Hello,
I created a simple program to resize images using the drawImage method and it works very well for images except images which have either been created or modified with Photoshop 8.
The main block of my code is
public static BufferedImage scale(  BufferedImage image,
                                      int targetWidth, int targetHeight) {
   int type = (image.getTransparency() == Transparency.OPAQUE) ?
                    BufferedImage.TYPE_INT_RGB :
                    BufferedImage.TYPE_INT_RGB;
   BufferedImage ret = (BufferedImage) image;
   BufferedImage temp = new BufferedImage(targetWidth, targetHeight, type);
   Graphics2D g2 = temp.createGraphics();
   g2.setRenderingHint
         RenderingHints.KEY_INTERPOLATION, 
         RenderingHints.VALUE_INTERPOLATION_BICUBIC
   g2.drawImage(ret, 0, 0, targetWidth, targetHeight, null);
   g2.dispose();
   ret = temp;
   return ret;
}The program is a little longer, but this is the gist of it.
When I run a jpg through this program (without Photoshop modifications) , I get the following trace results (when I trace each line of the code) telling me how long each step took in milliseconds:
Temp BufferedImage: 16
createGraphics: 78
drawimage: 31
dispose: 0
However, the same image saved in Photoshop (no modifications except saving in Photohop ) gave me the following results:
Temp BufferedImage: 16
createGraphics: 78
drawimage: 27250
dispose: 0
The difference is shocking. It took the drawImage process 27 seconds to resize the file in comparison to 0.78 seconds!
My questions:
1. Why does it take so much longer for the drawImage to process the file when the file is saved in Photoshop?
2. Are there any code improvements which will speed up the image drawing?
Thanks for your help,
-Rogier

Answer 1

You saved the file in PNG format. The default PNGImagReader in core java has a habit of occasionally returning TYPE_CUSTOM buffered images. Photoshop 8 probably saves the png file in such a way that TYPE_CUSTOM pops up more.
And when you draw a TYPE_CUSTOM buffered image onto a graphics context it almost always takes an unbearably long time.
So a quick fix would be to load the file with the Toolkit instead, and then scale that image.
Image img = Toolkit.getDefaultToolkit().createImage(/*the file*/);
new ImageIcon(img);
//send off image to be scaled A more elaborate fix involves specifying your own type of BufferedImage you want the PNGImageReader to use
ImageInputStream in = ImageIO.createImageInputStream(/*file*/);
ImageReader reader = ImageIO.getImageReaders(in).next();
reader.setInput(in,true,true);
ImageTypeSpecifier sourceImageType = reader.getImageTypes(0).next();
ImageReadParam readParam = reader.getDefaultReadParam();
//to implement
configureReadParam(sourceImageType, readParam);
BufferedImage img = reader.read(0,readParam);
//clean up
reader.dispose();
in.close(); The thing that needs to be implemented is the method I called configureReadParam. In this method you would check the color space, color model, and BufferedImage type of the supplied ImageTypeSpecifier and set a new ImageTypeSpecifier if need be. The method would essentially boil down to a series of if statements
1) If the image type specifier already uses a non-custom BufferedImage, then all is well and we don't need to do anything to the readParam
2) If the ColorSpace is gray then we create a new ImageTypeSpecifier based on a TYPE_BYTE_GRAY BufferedImage.
3) If the ColorSpace is gray, but the color model includes alpha, then we need to do the above and also call seSourceBands on the readParam to discard the alpha channel.
3) If the ColorSpace is RGB and the color model includes alpha, then we create a new ImageTypeSpecifier based on an ARGB BufferedImage.
4) If the ColorSpace if RGB and the color model doesn't include alpha, then we create a new ImageTypeSpecifier based on TYPE_3BYTE_BGR
5) If the ColorSpace is not Gray or RGB, then we do nothing to the readParam and ColorConvertOp the resulting image to an RGB image.
If this looks absolutely daunting to you, then go with the Toolkit approach mentioned first.