Legacy ImageMagick Discussions Archive

Hi,
I have a problem with compressing tifs.

I use the following code to compress my tif:

convert.exe input.tif -type TrueColorMatte -compress zip output.tif

the type flag destroys my alpha channel but if I use TrueColor i have no alpha channel. I simply want the input file compressed. I used the type flag because I dont want to have a grayscaled image when i had one.

Maybe someone can help.

try putting -type TrueColorMatte as the last operator

and perhaps

-channel rgba -alpha on

right after the input image

What version IM? What platform? Post the URL to a file that shows the problem.

Thanks for your help.

My version is: ImageMagick-6.5.4-8 16bit HDR

I have a 16bit TIF. With 8bit everything works. I hope I can upload a file after work.

Do you need to be in IM HDRI compile mode? Perhaps there is some issue in that mode? Have you tried the same with normal Q16 (not HDRI)?

Here is the link to the tif file: deleted

Look into the alpha channel. One sphere is alpha black. After compressing the "black alpha" sphere disappears.

I have not tried the non HDRI yet.

On my system (regular IM v6.6.3-0 Q16), I have no problem with the file. So, it seems to be limited to the HDRI version.
Can you upload your 'output.tif', too?

Here are the links. I had to redo the input file:

deleted

Well, the alpha channel itself is not touched in your older IM version - but the regular color channels get changed (so that the blue circle is lost completely). The handling of TIF files like yours is different now (in current IM packages) - but the older 'behaviour' is ok, too.
The two TIF files here have associated alpha - which means that the regular color channels are stored as if they were flattened over a black background (a bit like "-alpha Background"). The older IM versions keep it 'associated' in subsequent convert commands - and get rid of the fully transparent colors (which is the normal state of 'associated' alpha). The newer IM versions convert such images to 'unassociated' alpha - and the fully transparent colors can be kept. (But I wonder why these colors still exist in your 'associated' TIF files in the first place.)

Solution for you:
You have to either use "convert -define tiff:alpha=unassociated input.tif output.tif" once with your files (in your old IM).
Or update to a current ImageMagick.

Thanks for your help Drarakel.

I compiled the newest version 6.6.3. The problem is indeed the HRDI option. Without it worked.

Please post a short note about this in the Bugs forum stating the command that does not work in HDRI but works in non-HDRI and point back here to this topic. It would appear that you have uncovered a bug with HDRI.

It's not a bug - and despite the first guesses, it's not related to HDRI. (Or did you test your file in IM v6.6.3-0 HDRI and IM v6.6.3-0 non-HDRI and got different results? @jho)
I had tested jho's file in my old IM v6.5.8-5 (Q16 without HDRI) and got the same result as in 'untitled_zip.tif'. The handling of 'associated alpha' TIFFs is different in older versions - compared to the current version. But as I tried to explain, both approaches seem valid to me.

Drarakel has a good point. I assumed you tested in HDRI and non-HDRI in the same version of IM. Sorry for the false alarm.

Sorry guys. I dont know why, but the image was only in 8bit. Here is a picture in 32bit with values over 1.

http://ul.to/3xt2av

I compiled the newest version as Q32, x64 and HDRI enabled. When I simply convert the picture without flags the sphere with black alpha disappears. Identify now shows me that the image has unaccociated alpha.

I tried to download, but it tells me it is not an image but an application (and tries to append .html). When downloaded and I try to open it, I get an html page that says file not found.

Perhaps I am doing something wrong.