Undo reversible jpeg2000 compression

[userdude]

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:

Code: Select all

convert filename.jp2 filename.tif 

... 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.

[magick]

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

[userdude]

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.

[anthony]

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