Alpha channel

How to obtain it

I downloaded SpinApp 4 and tested it with a generic graphic. It did what I wanted but it left behind all the previous rotations in each new rotation. Since I don't want this in-game I need to add a mask except I don't know how to get the alpha channel. Does anyone out there know how to get the alpha channel from images on a PC?

The picture you're trying to use must be 32 bit. 32 bit color means that 8 bits go to each of the three primary colors, red green and blue, for a total of 24 bits and the last 8 bits go to the alpha channel. So if you're using 16 bit or 24 bit images it Spinapp won't ask if it can make a alpha mask because it can't.

This post has been edited by JacaByte : 11 October 2006 - 12:07 PM

Is the image your using a gif? Then that could help explain the problem. GIF uses a transperency layer instead of an Alpha channel, and SpinApp is unable to make a mask from that, and also, it keeps the transperency so that's how you see the previous rotations further on. Anyway, I'd suggest using PNG instead of GIF, as GIF is pretty lossy.

So I must save the base image as a 32 bit image before using Spinapp? Hmmm... That would be nice except I don't think I have a program that has 32 bit saving capabilities. I used MSPaint (blech!) to make a 16 bit .bmp into a JPG in just a few seconds. MSPaint however has no 32 bit option when you go to save an image. Is their a program elswhere that allows 32 bit image saving (prefferably as a PNG)?

(NOTE) I just downloaded a program that looks promising, however, I can't test it until I go home (I'm at college).

Usually a rendering program has the option to export into RGBA. (Red, Green, Blue, Alpha) Does whatever program you're using to make ships have that option?

You can't magically create an alpha channel from an image which doesn't have one (well you can create one but it will be empty and pointless). The problem you're having with spinning the sprite occurs if part of your sprite will end up outside the frame when rotated to a certain angle. You can avoid this by padding your image by a few extra pixels on all sides (recommended, else your sprite will be clipped anyway) or ask EVWeb to fix SpinApp so this doesn't happen (probably a good idea too, I can offer one solution to this ;)). Once you have your sprite you can just let EVNEW create the mask for you.

This post has been edited by Guy : 11 October 2006 - 05:41 PM

Guy, I think you're misunderstanding his problem, it sounds like his image is fine in size, it just happens to leave part of itself behind each time it rotates.

Like the attached image:

Attached File(s)

  • Attached File Spin.png (86.95K)
    Number of downloads: 43

You said that happens with GIFs with transparency, right? I highly doubt he's using GIFs (I highly doubt anyone ever has, does or will use GIFs during their sprite creation). The problem also happens if a point in the sprite is on or close to the edge of the frame such that as soon as it's rotated a couple of degrees the locus of that point will drag it outside of the frame (imagine your sprite is just a big square - what happens when you rotate that square?). So in the first frame it will look fine but in the second frame those points will be clipped and the same points from the first frame will not get "covered up" because the rotated square frame leaves gaps in the corners. Er, hope that made sense.

(edit) Although, choosing not to handle this situation would be a good way to indicate to the user that their sprite will be clipped and they should do something about it 😉

This post has been edited by Guy : 02 August 2007 - 05:12 AM

Yeah, but that would mean uncluding a Read Me or something, and I don't want to bother. I figure that the person should be smart enough... nevermind, most people are complete morons, so I'll just leave it at that I'm too lazy.

@evweb, on Oct 12 2006, 06:24 PM, said in Alpha channel:

nevermind, most people are complete morons

Ain't that the truth 😄
Though you really should be including a read me regardless, with contact info and instructions and stuff (so you wouldn't need that first dialog).

This post has been edited by Guy : 12 October 2006 - 02:41 AM

@evweb, on Oct 11 2006, 09:19 PM, said in Alpha channel:


Say, that's kinda cool. Any way to do it on purpose? 😄

This post has been edited by JacaByte : 12 October 2006 - 12:42 PM

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