convert from pcx to pcx turns every pixel to black

[Dondon]

Running `convert in.pcx out.pcx` causes a valid out.pcx file with the same dimensions to be generated, but every pixel has been changed to black. This only happens on certain pcx files, though I'm not certain what might be unique about them.

Version: ImageMagick 6.7.5-6 2012-08-11 Q16

Here's a base64 encoding of in.pcx.bz2 which exhibits this bug:

Code: Select all

QlpoOTFBWSZTWVzJrD4AADfr//6QgACFAMIAAACAg8AAgACAEMAI///IgeqI6v/gB58AAAAAAAAA
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xw7JdwUYFTYJJwogoCG0im0mBKTGCiYNjhAggiaTBKsBibTAj92g/xdyRThQkFzJrD4=

To recreate the original pcx file on disk, run the following command `base64 -d | bzip2 -d > in.pcx` then paste the base64 text blob, then hit CTRL-D twice. (By the way, don't use the "SELECT ALL" link that this bulletin board webpage put on my post. That link causes bogus space characters to be inserted that will screw up the decoding. Just copy/paste it manually.)

[Dondon]

Note that this can be verified merely be running `identify -verbose in.pcx out.pcx` and looking at the "Histogram:" lines. The latter one will have only black. It can also be seen in an image viewer, which will show an all black image as well.

[Dondon]

(I haven't tried every other conversion, but just now for that same file I tried converting to png and that appears to be accurate.) Also, this was using the yum binaries on "Fedora release 17 (Beefy Miracle)".

[snibgo]

PCX conversion seem to works for me, on IM v6.8.8-7 on Windows 8.1.

Your version is very old. Do you have problems with current versions? Please put a PCX file that shows the problem somewhere like dropbox.com and paste the URL here.

[Dondon]

That version is the latest available on the OS. I didn't try compiling a custom one. See the original post for a PCX file that reproduces the problem.

[snibgo]

Sorry, I don't know how to turn "a base64 encoding of in.pcx.bz2" into in.pcx.

[fmw42]

convert in.pcx out.pcx

How did you run this, if you only have a base 64 encoding of in.pcx.bz2?

Surely you have in.pcx, if you were able to run the above command!

[Dondon]

Sorry, I accidentally assumed a certain type of unix command knowledge there. To recreate the original pcx file on disk, run the following command `base64 -d | bzip2 -d > in.pcx` then paste the base64 text blob, then hit CTRL-D twice. (By the way, don't use the "Select all" link that this bulletin board webpage put on my post. That link causes bogus space characters to be inserted that will screw up the decoding. Just copy/paste it manually.)

(I just edited the original post to mention those instructions.)

[snibgo]

Thanks. If I ran unix I could probably follow your instructions.

[fmw42]

To recreate the original pcx file on disk, run the following command `base64 -d | bzip2 -d > in.pcx` then paste the base64 text blob, then hit CTRL-D twice.

Why don't you follow those instructions and prepare an example pcx image and upload to dropbox.com (public folder) so that others can then download your image and test it.

Perhaps I am confused, but, with respect, how can you complain about a bug in Imagemagick, if you have not run the previously mentioned command, because you only have the base 64 encoded version. If you have run it, then you must have the image in.pcx that you can upload somewhere and post a link to it here.

The best way for us to verify a bug is to run the exact IM command that fails for you. We need to be sure that the problem is with IM and not with your base 64 data that may not be properly formed or converted to .pcx image format.

[Dondon]

I did run the original command. The whole point of the base64 thing was just to workaround the fact that this bug-hosting bulletin board website doesn't allow for file uploads. I have no convenient place to freely host it, so I just attached it as a base64 file. Any platform that can run ImageMagick can also run the base64 decode command.

[snibgo]

I don't have a base64 command.

If you provide the PCX, I can test it on various version of IM to see if it processes properly.

If, instead, you provide the PCX after processing through two filters, and I attempt the opposite, and IM doesn't process the result properly, we are not much further forward.

[fmw42]

The usual way to provide a proper image for this forum is to upload it to a free image hosting service such as dropbox.com (public folder) and then put a link here to your upload. Then we can download the .pcx file and test with it.

[Dondon]

The bug still occurs on "ImageMagick 6.8.6-3 2013-08-02 Q16" - behavior appears identical.

[dlemstra]

I can reproduce the error in IM 6.8.8-10. I will look into it.

Edit: A patch has been committed and this will be fixed in ImageMagick 6.9.0-0.