Bug with Linux png Image Sequences and Alpha?


The top 4 are individual images - as you can see, they do have alpha on them. Load these images as a sequence however and Blender loses the alpha channel.

I’m only getting this bug with images rendered in Linux.

The mysterious PNG alpha problem. I have had problems with blender losing alpha information as well on PNGs. You may want to try and convert them to TGA just to see what happens.
I have reported alpha problems with PNGs a couple of times and others can not reproduce my results so the problem remains unfixed.

I have had problems with blender losing alpha information as well on PNGs.

Have you tried turning on the RGBA button underneath the output selection menu?

Obviously he did because the individual frames are showing alpha.

I haven’t seen that problem on Linux (I haven’t tried 2.45 on Linux) but I strongly recommend that you do not render .png sequences from Blender because Blender only renders .png at 8 bits per channel. Rendering to OpenExr then converting to .png in another imaging program like Photoshop (with batch processing), After Effects, etc… will allow you to maintain maximum image quality. OpenExr should maintain the alpha since it’s Blender’s native format.

O.K., I’ll give these tips a try. It’s good to know other people are having this problem and I’m not crazy.

.tga format doesn’t work any better than .png. The alpha channels are there, I can see them in Photoshop, but Blender throws them away. The strange thing is, Blender has no problem seeing the alpha channels of png’s rendered in Windows. It’s the ones created in Linux it’s balking at.

I’ll try re-rendering in Open EXR format and hope that works.

Some lot of the image formats that Blender is capable of reading and writing are accessed via the QuickTime api or something along those lines. For
instance blender can read Photoshop’s .psd files if you have QT installed but it can’t access layers, it imports them as flattened or merged layers.

I’m going to guess “no,” but can Blender use and write .psd files with layers? I’ve never seen anything to make me think it can, except what you just wrote, but I would so much love to have texture layers in Blender I will ask a stupid question anyway.

Have you got an opinion on this problem (link) I’ve been having?


Now I am having the same bug appear in .png files rendered in Windows, and OpenEXR files rendered in Windows.

Is there no bug-free way to load an image sequence with alpha in this program?

I can upload a short OpenEXR image sequence if it helps. I zipped up five frames and they were still 40 megs, which is a lot to send over dial-up. But if it helps I will start uploading and maybe I can get it done in a couple days.

If you are applying them to a plane, you need to click Ztransp button or the alpha will only reveal the difuse color of the material and not let it shine through to the background. Also try setting the Alpha (A slider) to 0.

I posted my nodes solution here…

It’s not on a plane. I’m compositing rendered image sequences (or I would be).


It’s not just the alpha channel being lost, but the regular image as well?

I eventually found a way to recover the image and alpha data - by loading the image sequences into the Vidoe Sequencer and rendering to avi. Maybe they could be rendered as new image sequences.

Does anyone think this bug is worth reporting? It’s driving me crazy because I see it so often - but if I’m seeing it that often, the dev’s have got to know about it.