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><H1
><A
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>SDL_DisplayFormatAlpha</A
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><DIV
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><A
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><H2
>Name</H2
>SDL_DisplayFormatAlpha&nbsp;--&nbsp;Convert a surface to the display format</DIV
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>Synopsis</H2
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><PRE
CLASS="FUNCSYNOPSISINFO"
>#include "SDL.h"</PRE
><P
><CODE
><CODE
CLASS="FUNCDEF"
>SDL_Surface *<B
CLASS="FSFUNC"
>SDL_DisplayFormatAlpha</B
></CODE
>(SDL_Surface *surface);</CODE
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><H2
>Description</H2
><P
>This function takes a surface and copies it to a new surface of the
pixel format and colors of the video framebuffer plus an alpha channel,
suitable for fast blitting onto the display surface.  It calls
<A
HREF="sdlconvertsurface.html"
>SDL_ConvertSurface</A
></P
><P
>If you want to take advantage of hardware colorkey or alpha blit
acceleration, you should set the colorkey and alpha value before
calling this function.</P
><P
>This function can be used to convert a colourkey to an alpha channel,
if the <TT
CLASS="LITERAL"
>SDL_SRCCOLORKEY</TT
> flag is set on the surface.
The generated surface will then be transparent (alpha=0) where the
pixels match the colourkey, and opaque (alpha=255) elsewhere.</P
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><H2
>Return Value</H2
><P
>If the conversion fails or runs out of memory, it returns
<SPAN
CLASS="RETURNVALUE"
>NULL</SPAN
></P
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>See Also</H2
><P
><A
HREF="sdlconvertsurface.html"
>SDL_ConvertSurface</A
>,
<A
HREF="sdlsetalpha.html"
>SDL_SetAlpha</A
>,
<A
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>SDL_SetColorKey</A
>,
<A
HREF="sdldisplayformat.html"
>SDL_DisplayFormat</A
>,
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>SDL_Surface</A
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author	Sam Lantinga <slouken@libsdl.org>
date	Tue, 22 Jan 2002 18:28:35 +0000
parents	e5bc29de3f0a
children	355632dca928