Java convert image format with low memory footprint

Question

I'm writing a Web application that let user upload images in several formats (e.g. png,jpg,bmp). After the image has been uploaded the system should convert it to "png" and scale it to a predefined resolution.

To convert the image I use the handy method:

javax.imageio.ImageIO.write(im, type, baos);

Here's where the problem start. The first argument of Image javax.imageio.ImageIO.write is a RenderedImage. The Java Doc states that the only known implementation is BufferedImage.

I try to find a way to convert a java.awt.Image to a BufferedImage, but it doesn't seems possible. However, it is possible to draw an image on a BufferedImage.

The problem is that creating a new BufferedImage each time is very memory expensive. I can start creating a pool of BufferedImage but I'm looking for clever/news ideas.

Answer 1

You could look at the implementation of BufferedImage and implement your own (A file-based implementation perhaps?). These classes are generally pretty straight-forward to read, often 50-70% comments and clearly written.

They give out the sources, why not make use of 'em?

Answer 2

There's a bunch of Java libraries and SO posts about this. Did you check them out?

• http://www.fightingquaker.com/sanselan/
• http://sourceforge.net/projects/jiu/
• http://rsbweb.nih.gov/ij/
• http://stackoverflow.com/questions/603283/what-is-the-best-java-image-processing-library-approach

Answer 3

You could reuse one buffered image over and over again, using subimage to size appropriately when it's time to use the ImageIO.write method

Answer 4

Launch a native converter like netpbm or imagemagick.