Re: [csjava-developer] TheMatrix & Alpha values

[Toby D. <tj...@sf...>]

Daryl,

Yes it, would be good to fix this. If I recall correctly, the status of
alpha values for basic graphic file formats are:

  JPEG: no alpha information stored
  GIF: 1 bit per pixel of alpha information
  PNG: 8 bits per pixel of alpha information

So storing 8-bit alpha values will use up a little more memory in the case
of JPEG and GIF images, but it's probably not a big deal. It might be best
to make the default TYPE_INT_ARGB, and then provide a constructor option
that lets you set it to TYPE_INT_RGB in case someone wants to conserve
memory.

If you do want add these alpha values, then you should start with a demo
program that shows how different alpha values will be displayed in
TheMatrix. Indeed, a set of carefully created examples will probably help
explain and clarify these tricky alpha value issues.

I'll add the alpha values issue as a feature for you ...

Toby


On 5/14/05 9:55 AM, "Daryl Van Humbeck" <dva...@sf...> wrote:

> I just realized that TheMatrix isn't saving Alpha values that it's given.
> 
> When the BufferedImage is created in utils.Utilities.java, it's created
> with type TYPE_INT_RGB, which doesn't save Alpha values, instead of
> TYPE_INT_ARGB, which does.
> 
> Also, to create a Color object from an RGBA packed integer, using new
> Color(int) ignores the Alpha value, when you use new Color(int, boolean
> true) it actually copies it.
> 
> Another thing is when you're drawing an image with transparent pixels
> onto another image (see utils.Utilites.java, method BufferedImage
> makeBufferedImage(Image image, int image_type)) it doesn't copy the
> Alpha values, it just blends the pixels with alpha values with the color
> that's already there (usually black), which probably isn't what we want,
> is it?
> 
> I found this out by reading the JavaDocs, looking for information for
> another project I'm working on (if you want to know, NQL, Not Quite Liero).
> 
> If you want these problems fixed, I think I'd like to volunteer (unless
> you think I'm working on too much already).
> 
> Daryl.
> 

-- 
Dr. Toby Donaldson
School of Computing Science
Simon Fraser University