Java Image compression

Question

From our application we fetch images (jpeg/png) from a third party service, after download we want to save these images as compressed.

Can any one please guide how to compress images in Java ?

Answer 1

JPG and PNG images already are compressed, so it's not entirely clear what your intention is. However, in general, you can write images with ImageIO:

ImageIO.write(image, "jpg", outputStream);

(or "png", analogously). By default, this does not allow you to select the compression level (that is, the trade-off between file size and image quality). In order to write a JPG file with a different than the default compression, you can use a utility method like this:

public static void writeJPG(
    BufferedImage bufferedImage,
    OutputStream outputStream,
    float quality) throws IOException
{
    Iterator<ImageWriter> iterator =
        ImageIO.getImageWritersByFormatName("jpg");
    ImageWriter imageWriter = iterator.next();
    ImageWriteParam imageWriteParam = imageWriter.getDefaultWriteParam();
    imageWriteParam.setCompressionMode(ImageWriteParam.MODE_EXPLICIT);
    imageWriteParam.setCompressionQuality(quality);
    ImageOutputStream imageOutputStream =
        new MemoryCacheImageOutputStream(outputStream);
    imageWriter.setOutput(imageOutputStream);
    IIOImage iioimage = new IIOImage(bufferedImage, null, null);
    imageWriter.write(null, iioimage, imageWriteParam);
    imageOutputStream.flush();
}