Legacy ImageMagick Discussions Archive

Hi;

I'm wondering if it's possible to undo the reversible compression in a jpeg2000 file, and convert it to a lossless tiff file? I've tried the following command:
... but the above seems to result in a tiff file that shows compression artifacts.

Exifprobe reports that the jp2 file I'm working was reversibly compressed:

@0x0000c99=3225 : Start of JPEG2000 (5/3 reversible compression with explicit quantization) image [8221x5499] length 6831651

The file that I'm trying to convert can be downloaded here:

http://memory.loc.gov/gmd//gmd370m/g370 ... 000054.jp2

I realize there's a chance that the original image used to create the jp2 file had compression artifacts, although I'm hoping that's not the case. Any advice is very much appreciated! Thanks in advance.

JPEG-2000 is compressed with a lossless compression algorithm. The pixels are returned exactly as they were saved.

Thanks for the prompt reply. I guess I was originally misunderstanding things -- but if I'm understanding things correctly now, it sounds like reversible compression is one and the same as lossless compression.

I guess that means that the Library of Congress (at least in this case) compressed the image before saving it again using a lossless compression method. Kind of a silly way of archiving things.

More than likely they scanned the images before jpg2000 was commonly available.