[SDL] Re: Displaying transparent images

[Juan Ignacio Carniglia]

I am using BMP, and setting the transparent color to RGB =
(255,255,254).
By using the SDL_SetColorKey alone, I have had no problems displaying
Transparent sprites. Perhaps, you should try either using a BMP, or
checking
the actual RGB values of your transparent color.

Juan Ignacio Carniglia - Programmer - Buenos Aires, Argentina.


> 
> --- Thomas Harte <T.Harte at btinternet.com> wrote:
> 
> > > I had a lot of problems loading(and displaying) a gif image that 
> > > contains some transparent areas..
> 
> > Presumably whatever method you are using to load GIFs is telling you
> > which colour is the transparent one, or else you are just assuming
> > it is colour 0 or something?
> > 
> > What you want to do is to use SDL_SetColorKey to establish the
> > transparent colour for the surface with the sprite in it, use 
> > SDL_SetAlpha to enable SDL_SRCALPHA but leave the alpha flag at 128.
> > 
> > Following this, blit should work with transparent pixels removed.
> 
>  I'm curious.  To set transparency for the chosen 
> transparency color in my work, I have just the following line 
> of code....
> 
> SDL_SetColorKey(spriteImages_p, SDL_SRCCOLORKEY, 
> SDL_MapRGB(spriteImages_p->format, 0, 255, 255));
> 
> with no call to SDL_SetAlpha().
> 
>  It appears to work fine in my application.  Why do you feel 
> the call to SDL_SetAlpha() is important?  What are the 
> consequences of not having it?
> 
>  I'm not using .GIFs to load my images, I'm using .BMPs.
> 
>                                                             NBarnes
> 
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