When JPEG becomes lossless

A useful benefit of the JPEG format is that the degree of lossiness can be varied by adjusting compression parameters. This means that the image maker can trade off the file size against the output image quality. But isn’t there a lossless JPEG? ImageConverter Plus lets the users choose from 4 compression parameters – baseline, progressive, sequential and lossless, and you might be wondering if lossless is something really new. In fact, lossless JPEG is not really popular. It doesn’t compress images nearly as well as baseline JPEG. It does not provide useful compression of palette-color images or low-bit images. Lossless JPEG works on images with 2 to 16 bits per channel, but performs best on images with 6 or more bits per channel. For such images, the typical compression ratio achieved is 2:1. For image data with fewer bits per pixels, other compression schemes perform better. With ImageConverter Plus the baseline compression parameter is set by default, but we try to follow and adjust to the needs and desires of our users that may vary a lot.