image: jp2 pow2 reduction fails for some images

[mangtronix]

JP2 pow2 reduction will fail if insufficient levels are available.

[mangtronix (mang)]

E.g. http://ia331403.us.archive.org:80/BookReader/BookReaderImages.php?zip=/1/items/cu31924004007625/cu31924004007625_jp2.zip&file=cu31924004007625_jp2/cu31924004007625_0016.jp2&scale=16&rotate=0

$ unzip -p '/1/items/cu31924004007625/cu31924004007625_jp2.zip' 'cu31924004007625_jp2/cu31924004007625_0016.jp2' | /petabox/sw/bin/kdu_expand -no_seek -quiet -reduce 4 -rotate 0 -i /dev/stdin -o /tmp/stdout.bmp | bmptopnm | pnmtojpeg -quality 75 > hmm.jpg
Kakadu Core Error:
Attempting to access a non-existent resolution level within some
tile-component. Problem almost certainly caused by trying to discard more
resolution levels than the number of DWT levels used to compress a
tile-component.
bmptopnm: Windows BMP, 106x163x8
bmptopnm: -: couldn't read row 162
pnmtojpeg: EOF / read error reading magic number

[mangtronix (mang)]

The number of DWT levels is present in the jp2 codestream.

For example it can be read using the openjpeg command line tool:

http://www.openjpeg.org/index.php?menu=doc

Index file *.Idx : -x index_name.Idx
This option offers the possibility to create an index file.

Number of decompositions (=(number of resolutions - 1)):
NumDWT

Kakadu can also get this information. Not sure if it surfaces in one of their command line tools.

It may be more efficient to catch the case where the requested level is not available instead of reading the codestream first.

[mangtronix (mang)]

Can pull it out with kdu_expand:

$ kdu_expand -i cu31924004007625_0016.jp2 -record record.txt | grep levels record.txt
Clevels=3

[mangtronix (mang)]

I have code implemented that detects image processing failure and retries at less aggressive reduction level.

[mangtronix (mang)]

The thumbnail images should always display (they may take some time to load) even if zoomed out and they will be displayed very small.