Number of resolutions is too high

[Romasz]

Hello, I've stumbled into a bug (probably) either in ImageMagick or OpenJpeg2000 - while trying to convert small image like for example https://1drv.ms/u/s!AkG2rWqeWpmHhZI6tB-_C4anEJZAng I'm getting an error (tried with newest ImageMagick under W10). Some output:

PS C:\Bugs\PDFTest> magick convert .\problematic.png prob.jp2
convert: Number of resolutions is too high in comparison to the size of tiles
`OpenJP2' @ error/jp2.c/JP2ErrorHandler/194.
convert: unable to encode image file `prob.jp2' @ error/jp2.c/WriteJP2Image/1089.
PS C:\Bugs\PDFTest> magick -version
Version: ImageMagick 7.0.8-11 Q8 x64 2018-08-29 http://www.imagemagick.org

[fmw42]

First, if using IM 7, use magick, not magick convert and not convert. However, I get your same message for that input PNG using IM 7.0.8.11 Q16 and IM 6.9.10.11. But I can convert many other PNG files to JPG2 with no errors. So perhaps your PNG file is corrupt in some way. I have also tried several older version of ImageMagick and get the same issue.

P.S. You need OpenJPEG v2.1 or higher

[Romasz]

@fmw42 Good to hear that you were able to reproduce the issue. The provided png is fine, not corrupted in any way I know, you can view it in any image browser, edit it or anything. The problem is probably related with image size somehow. The problematic image is just a cropped bitmap, if I choose less crop (bigger image) it gets converted fine to JP2, however with bigger crop (smaller image) you get the error.

[snibgo]

The problem isn't specific to that particular file. For example:

Code: Select all

f:\web\im>%IMG7%magick -size 99x8 xc: x.jp2

magick: Number of resolutions is too high in comparison to the size of tiles
 `OpenJP2' @ error/jp2.c/JP2ErrorHandler/193.
magick: unable to encode image file `x.jp2' @ error/jp2.c/WriteJP2Image/1072.

Tested with v7.0.7-28 on Windows 8.1.

[fmw42]

I confirm snibgo's command error using IM 7.0.8.11 Q16 Mac OSX Sierra

Code: Select all

magick -size 99x8 xc: x.jp2

magick: Number of resolutions is too high in comparison to the size of tiles
`OpenJP2' @ error/jp2.c/JP2ErrorHandler/194.
magick: unable to encode image file `x.jp2' @ error/jp2.c/WriteJP2Image/1089

But this works fine:

Code: Select all

magick logo: logo.jp2

as does

Code: Select all

magick lena.png lena.jp2

[snibgo]

The problem seems to be high aspect ratios. For example, 99x16 and 16x99 are okay, but 99x15 and 15x99 fail.

[fmw42]

That does seem to be the case, at least this fails

Code: Select all

magick logo:[640x20+0+0] tmp.jp2

magick: Number of resolutions is too high in comparison to the size of tiles
`OpenJP2' @ error/jp2.c/JP2ErrorHandler/194.
magick: unable to encode image file `tmp.jp2' @ error/jp2.c/WriteJP2Image/1089.

[fmw42]

The issue is that jp2 has size limitations

code blocks are 64 samples in width and 32 samples in height

So if your height is less than 32, you need to specify only one resolution.

This works:

Code: Select all

convert logo:[640x32+0+0] tmp.jp2

But this fails:

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convert logo:[640x20+0+0] tmp.jp2

But specifying one resolution works again

Code: Select all

convert logo:[640x20+0+0] -define jp2:number-resolutions=1 tmp.jpg2

See https://www.imagemagick.org/script/jp2.php

[Romasz]

JP2 hasn't got any size limitation. It's just the problem of setting the number of resolutions (or the default value). If you take a look at openjpeg2000 code at: https://github.com/uclouvain/openjpeg/b ... 2k.c#L7847 you will see that it compares the size of the tiles to 2^(n-1) if size in x or y is lower then exception is thrown. It means that any image can fail if appropriate number of resolutions is set -> for n = 32 you would probably have to have image with height/width bigger than 2^31.

Unfortunately I haven't got much time to find out how number of resolutions is calculated or what is the default value. The same is for size of a tile, however it seems that for small images it's just a with/height of the image.

Setting number of resolutions to 1 is not a solution, as it result in much bigger file due to lower compression. The fact that IM can work for some images and for others not - dependent only on image size, makes it little useless in case of conversion to that particular format.

[fmw42]

I will have to defer to the ImageMagick developers to comment further.