Re: LOSSLESS JPEG usage
Ross Presser <[email protected]>
| Newsgroups | gmane.comp.video.image-magick.user |
|---|---|
| Message-ID | <[email protected]> |
On Sun, Feb 7, 2010 at 5:43 AM, KKH <[email protected]> wrote: > > hi > i want to compress lossless jpeg > > regarding to : http://www.imagemagick.org/Usage/formats/#jpg_lossless > This URL you cite describes lossless *processing* of existing JPEG images: | These command include "rdjpgcom", "wrjpgcom", and the most important one "jpegtran" | which allows you to flip, crop and insert image data rounded into 8x8 pixel blocks, without | loosing image quality. JPEG is inherently lossy; every image you write will use lossy compression. The lossless processing is so that when you have a JPEG image that starts lossy, you don't lose any MORE information when you rotate, flip, crop, etc. Even -quality 100 for JPEG is still lossy. Not much, but you do NOT get the same pixels out that you put in. As Fred said, JPEG2000 includes lossless compression. But PNG is a much better choice because it is more widely supported.