Saving Image with Alpha Channel in blender 2.5

I am trying to save an image with an alpha channel.

I set Render>Output> RGB To >RGBA
That doesn’t seem to affect the Image saved Via the image editor.

I’ve tried many different formats. Png,Bmp,Tga
Blender does not export the image with RGBA channels, only RGB.

Is it a bug? Or am I missing something.

I am using Blender 2.57 RC 2

there is a big gotcha in this - and i’m still working with it myself

you need to check the application you are using because

an alpha channel is not the same as ‘transparency’

you need to keep this in mind as you use your image in different applications



Workingsketches is right - I think you need to decide if you are saving an alpha channel or are intending on seeing transparency as well - if you do, then you will need to choose ‘premultiply’ instead of ‘sky’ in your render.

You’re missing something. If you are rendering an object and wish the background be transparent selecting RGBA is only half of the equation. You have to select straight alpha under the shading section of the render tab. The sky will then be transparent. Refer to the image below.


(Don’t know why that didn’t remain an image)

Example of what will be in your image editor

Not sure if this is what you are looking for.

you also have to save it in a format that can use alpha
like PNG or other formt

Yes, thanks Ricky. I forgot to add that.

Thanks everybody that helped.
ok, here is an example.

In blender, I create a new image.
I choose to create the image with an Alpha Channel.
With a size of 1024x1024.

Save Image as PNG.
Reload the Image.
It now only has RGB

I was using blender the whole time so it is not the application.
Also, I know how to tell if the image has RGBA or not.

Anyways, Today, using the same build that had problems saving the image with the alpha channel yesterday.
Is now saving the image with the image RGBA info

Edit: I forgot to mention I am going to Image>Invert>Invert Apha Channel
To force the creation of an alpha channel (This is the only way I know how to get blender to add the channel)
And then Saving the image

when you add the new image you can also specify the alpha value and color in uv editor at least

you can see example for this in snow making from blenderguru tut i think!

ok and now the tough one, how do u save alpha (or transparent sky) in yafaray integrated? :slight_smile:

this is wrong if you want to save with alpha-channel.
In the uv-editor with the created image with alpha
select for the save-action:
“Save a Copy”
choose png or tif (i did not test other, that are the formats i use)
and the saved file has the alpha-channel like in the uv-editor.

If you do a simple “Save Image” (i dont know why, the alpha-channel gets lost).
The “save image” will only save the alpha-channel, if it was loaded from a file with this image-format.

One may call it a bug, that the function “save image” does not take in account the alpha-channel (execpt from a loaded image with alpha). Same for the rendered image, in uv-editor switch on the display of alpha/transparency and use “Save a Copy” and the alpha is saved too.

ok I managed to save it, but I suppose I had to turn on RGBA in render settings, now the save image and save a copy worked both if i tested, thanx for help!