Problem with .png files?

Great! Glad to know I wasn't going crazy :wink:

Cheers,
Mike

Wayne E. Harlan wrote:

路路路

By the time I did the update it was at 3931 but it works just fine. I inserted the 6"x8" picture into swriter and it shows up at 6"x8". Thank you very much !

Wayne

Michael Droettboom wrote:

Wayne E. Harlan wrote:

Michael:

Both r3927 and r3929 resulted in the smaller png file that's just transparent background.

The point of interest is r3926, before this change. r3927 and r3929 are identical on the trunk.

It turns out there was a peculiarity with how image files are saved in the GtkAgg backend that was triggering this bug. That should now be fixed in r3930. Please try that and let me know how that works for you.

It's roughly 20% of the size of the file I get with the latest release, 0.90.1, which opens fine (but has the wrong dpi). That tells me that on my system, some stuff just isn't getting written to the file. I have attached my matplotlibrc and will read the docs to see how to save a raw image and attach that, too. I don't have ImageMagick, but can download and compile it later today. I tried a 300 dpi jpg with r3929 and the image saves OK but has the wrong dpi (72). The .raw image is also attached. It was over 17 MB so I bzipped it. I'm surprised it ended up at 700 bytes !

That raw file is fully white and transparent also.

Hope that helps,
Mike

Wayne

Michael Droettboom wrote:

Unfortunately, I'm not able to reproduce this here with the .py you attached. Both SVN r3926 (before the PNG resolution change) and SVN r3927 (after the PNG resolution change) work for me. Are you comparing those two SVN revisions, or SVN vs. 0.90.1?

I can confirm that the PNG you attached is all white and fully transparent.

Just for information, my machine (RHEL4) has libpng 1.2.7.

Can you send a copy of your matplotlibrc? Also, can you save out a .raw image? (If you rename it to foo.rgba, you can display these images with the ImageMagick command "display -size 1800x1200 -depth 8 foo.rgba") That would help determine whether the problem is in the PNG-writing code or something higher up.

Cheers,
Mike

Wayne E. Harlan wrote:

Michael:

I tried a complete checkout for comparison (3929). In the meantime, my libpng is 1.2.18 (installed from source as is everything - this is an LFS/BLFS system.) Yes, the plot was working before the change and I can send you some png's from that if you need to see them, or I can backtrack to 0.90.1 and repeat this. Please bear in mind that the plot displays (and always has) quite correctly on screen - it's just the saved file that consists of just background. I have attached the script, the resulting png and a saved screenshot from the Gimp. Attachments are gzipped.

Wayne

Michael Droettboom wrote:

Hmmm. I'm very surprised that this change could cause that. All it does is add an additional metadata chunk to the PNG file, which shouldn't have any affect on the image data itself. simple_plot.py works fine for me in GIMP 2.0.5 both before and after this change. Can you verify that this plot was working before the change to save the resolution in the PNG file? If so, can you send me the source for your plot and the PNG file? Also, what version of libpng are you using? (pkg-config --version libpng should display this on most recent Linux distros).
  
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Michael Droettboom
Science Software Branch
Operations and Engineering Division
Space Telescope Science Institute
Operated by AURA for NASA