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PNG's alpha channel in dim3 - ggadwa - Feb 16, 2003 04:25 PM

Probably somebody here has an answer to this.

I converted dim3 (in the current unreleased version) to use 32-bit PNGs. There is no more "blue screening" (old 24-bit dim3 art used pure blue as a alpha=0 color). Now you should be able to have any type of alpha.

My problem: I have NO idea how to edit the alpha! I'm this close to wasting time and making a program to convert blue -> alpha=0 and resave, but that doesn't gain me anything new.

Is there anything that handles this well? GIMP? I haven't d/l it (or X11) but I will if it works well for that.

[>] Brian


PNG's alpha channel in dim3 - OneSadCookie - Feb 16, 2003 05:25 PM

GraphicConverter lets you edit the alpha as a grayscale image.


PNG's alpha channel in dim3 - jamie - Feb 16, 2003 07:20 PM

photoshop lets you build/edit one as a 4th channel in an RGB image also I believe.


PNG's alpha channel in dim3 - ggadwa - Feb 16, 2003 09:47 PM

Quote:Originally posted by OneSadCookie
GraphicConverter lets you edit the alpha as a grayscale image.


I d/l GraphicConverter ... nice program.

I still don't get it, though Smile I'll check the online docs. I can "show alpha channel" but I'm not quite sure what's going on. If that's an actual gray-scale representation of the alpha channel, and can't seem to work with it.

I'll figure this out yet. If anybody would like to post a quick tutorial, I'd be happy to read it.

For instance, if I had an image that had pure blue in it (0x000000FF), and I wanted to make that the alpha channel (i.e., cut out things that are blue.) I could select it, copy it to the alpha mask? That doesn't seem to work, but then again, I'm out of my area when it comes to art ...

[>] Brian


PNG's alpha channel in dim3 - OneSadCookie - Feb 16, 2003 10:35 PM

I just remembered, GraphicConverter is buggy in 10.2.4. That probably makes it a not-so-good tool for trying to do this Smile


PNG's alpha channel in dim3 - acedia - Feb 17, 2003 03:05 PM

In Photoshop, this would be easy - in fact, I think you could probably batch-process all your files at once.

However, using Graphic Converter (4.2), I think I figured out a way as well.

Open bmp.

Select 'effect' menu => 'Add alpha/mask channel'

Then choose the magic wand tool (sorta looks like a little sparkler - on my palette, it's the second one down on the right.) and use it to select the blue pixels - whatever you want to be masked out (shift-select additional areas).

Once everything you want is selected, choose 'edit' menu => 'copy'

Select 'effect' menu => 'show alpha/mask channel'

Select 'edit' menu => 'paste at position' (0,0)

Now the only problem now is that the blue doesn't quite come out as true black in a greyscale channel, and only black is completely transparent, so:

Select 'picture' menu => 'levels,' to change the black and white levels, or it might be easier to select 'picture' menu => 'contrast' and increase the contrast as high as possible.

Then 'save as...' png.

This isn't a program I use much, so it might not be the most direct way to do it? Seems to work, though.