About two and a half years ago (january 2005) I had chosen Photoshop's jpeg 2000 implementation to be the format to use for backing up all my flattened photoshop files. I did a little test that reveiled it to have the best lossless compression. Also it has the advantage of inlcuding EXIF info and color profiles (which other jpeg 2000 implementations don't have). However, after converting maybe a few hundred psd and tiff files I found that a few resulting jpeg 2000 files were corrupted (maybe 2 or 3 I found, there could be more). I will share one.
Here's the original image in tiff format (9.6 Mb). It's a flattened photoshop file I want to keep as master file.
Now here's the tiff file converted to jpeg 2000 in Photoshop (7.4 Mb). (I renamed the extension from .jpf to .jpx so ACDSee recognizes it.) I used the following jpeg 2000 setting:
Lossless On Fast Mode Off Quality 50 (Grayed out) Include Metadata On Include Color Settings On Include Transparancy Off (Grayed out) JP2 Compatible On (Grayed out) Compliance General Device Wavelet Filter Integer Tile Size 1024 x 1024 JPEG 2000 XML Off (Grayed out) XMP On EXIF On ICC Profile On Restricted ICC Profile On Order Growing Thumbnail Region of Interest None (Grayed out) Enhance 50% (Grayed out) Download Preview 14.4 Kbps (Cell Phone)
However ACDSee does not display this file properly, nor does Irfan View. If I re-open it in Photoshop I find that the lower left corner (exactly 1024x1024 pixels) is corrupted. Here's the corrupted jpeg 2000 file converted to jpeg (1.3 Mb) for easier viewing for those that don't have a jpeg 2000 viewer/plugin installed. Here's a 100% crop of part of the problem area.
I performed this test several times, on both my PC and my laptop, with both CS1 and CS2. I always get the same result (more specifically, it's always the lower left corner that's corrupted, I have not actually checked that the corruption is always bit for bit equal, though I suspect it is).
If I either set Fast Mode to On, or change the Tile Size to 512 x 512 the corruption is gone and the file seems OK. But my trust in the stability of the plugin is gone. I don't trust it enough to use it as a main format for backing up all my master files. I'm sticking with tiff with lzw compression untill I'm convinced the plugin is reliable (or another implementation with exif & color profiles or another format comes along).
Eppe Tot, august 2007.
