Transparent bitmaps

This is a discussion on Transparent bitmaps within the Game Programming forums, part of the General Programming Boards category; Alright thus far I have been using simple shapes as the character in my games but I want to do ...

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    Transparent bitmaps

    Alright thus far I have been using simple shapes as the character in my games but I want to do something more dynamic. I looked up sprite animation, but the only drawing program I have is microsoft paint and I cannot seem to find a way to make the background color transparent for my character animations. I want the character to not look like a giant square blocking out the background. Any shortcuts to this or do I need to buy a new drawing program? Thank you for your time.

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    Webhead Spidey's Avatar
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    Any shortcuts to this or do I need to buy a new drawing program?
    Most graphics libraries allow you to define a ColorKey which can be tested against if you are AlphaBlending.

    So for example if I have a sprite with a pink background and I set the ColorKey color to that color. Then all the pixels which are of that color will not be rendered.
    Last edited by Spidey; 07-14-2009 at 05:22 AM.

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    ok I am using Dev C++ what would be the proper syntax for setting ColorKey? Is it already predefined or do I have to define it first. Then I assume I must use the hexidecimal code for the color? Or R G B?

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    ok I am using Dev C++ what would be the proper syntax for setting ColorKey? Is it already predefined or do I have to define it first. Then I assume I must use the hexidecimal code for the color? Or R G B?
    Dev C++ is an IDE, not a graphics library. Those would be allegro,SDL, openGL, DirectX etc
    Each one has its own different way of handling color key's.

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    forgive my ignorance. I am currently learning SDL.

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    Super Moderator VirtualAce's Avatar
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    Direct3D does not have the idea of a color key. You use alpha blending to get transparency or alpha testing to get an all or nothing blend.
    In D3DX you can use D3DXCreateTextureFromFileEx() which allows you to specify a transparent color. Under the hood it is creating an alpha channel for you.

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    Do you know how to define the bitmap transparency color in SDL though? or have a link to a tutorial that does?

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    Take a look at SDL_SetColorKey. It should do it.

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    Dr Dipshi++ mike_g's Avatar
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    Take a look at SDL_SetColorKey. It should do it.
    Yep, that would be what you want.

    Alpha transparency is neat when you want to draw semi transparent things. PNGs would probably be a better image type to use than bitmaps in general; might be worth checking out the SDL_Image lib too.

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    Thank you guys continually for the help. I appreciate it. I finally got my first SDL game complete that continually generates new levels, or at least a mode of it. Whats in my mind now is way bigger than what I had set out to do lol, and I could't do it without this message board having alot of great minds. I appreciate it.

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