Servlet to generate JPG/GIF image

Question

I've got sth like that:
response.setContentType("image/gif");
OutputStream out = response.getOutputStream();
Image messageImage = makeMessageImage(message, fontName, fontSize);What I should do next to send it to the browser and display it?

Answer 1

You can create a BufferedImage, draw messageImage onto it, and then send the BufferedImage through the OutputStream via
ImageIO.write(theBufferedImage, "gif", out); Or if messageImage is already a BufferedImage, then you can just send it directly after casting it.
There's a slight complication, however. The GIF format uses palette-based images. If you send an image that's not palette-based then it will use the default palette. It's the same as if I had created this
BufferedImage theBufferedImage = new BufferedImage(
        messageImage.getWidth(null),
        messageImage.getHeight(null),
        BufferedImage.TYPE_BYTE_INDEXED); drew messageImage onto it and then sent it. The default palette almost certainly isn't the 256 most representative colors in your message image. This may or may not be a problem. I don't know the kind of quality you want. If your image doesn't have any color, a viable alternative is TYPE_BYTE_GRAY.
Ideally, for a full-colored image you would create an IndexColorModel of what you feel is the 256 most representative colors in the image. Then you would create a BufferedImage using this palette, draw the original image onto it, and send it off.