PNG Encoder Type—Provides a selection of the PNG encoder between the Java own encoder, the JAI ImageIO native one, and a PNGJ based one:
The Java own encoder is always set to maximum compression. It provides the smallest output images, balanced by a high performance cost (up to six times slower than the other two alternatives).
The ImageIO native encoder, available only when the ImageIO native extensions are installed, provided higher performance, but also generated significantly larger PNG images
The PNGJ based encoder provides the best performance and generated PNG images that are just slighly larged than the Java own encoder. It is the recommended choice, but it’s also newer than the other two, so in case of misbehavior the other two encoders are left as an option for the administrator.