Mail Archives: djgpp/2000/01/02/09:53:36
On 2 Jan 00, at 12:03, Matej wrote:
> > Just pick a color that you want to be transparent, most people
> > choose 255 or just 0, and make a BMP displayer that skips the pixels
> > with that value.
>
>
> Yes, but how to do it? Can you give me an example?
> Thanks
Hi!,
I am not quite sure whether you are asking about how to create
transparent images or how to write a blitting routine that handles
transparent pixels. If you want to create transparent images like
the ones you see on the web pages then then I hope the following
helps you.
GIF files support transparency. This is how you do it, If you load a
GIF file to your paint program there should be a menu option which
would allow you to select a single colour from your image which
would be marked as transparent.
So if your 256 colour image had a background of purple and if
purple was palette entry 15 (of the total 256 palette entries) you
would select purple from the palette and you've got a transparent
GIF. All the pixels in the GIF which are drawn with entry 15 (purple
in this case) would not be drawn by the program which draws the
GIF (like Netscape etc if your thinking of a web page). So since
this pixels are not drawn your background will show through these
areas and you've got your transparency.
Actually some paint programs allow you to just simply select the
transparent colour using a color picker from the image.
I use Gif Constructionset Professional from alchemy mindworks to
create my GIF's. It's Never expiring shareware so you might try
getting it. (I've forgotten the URL, Please do a search).
Hope This Help's
Kalum
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