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SDL_SetAlpha(3)
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SDL_!SetAlpha !!!SDL_!SetAlpha NAME SYNOPSIS DESCRIPTION SEE ALSO ---- !!NAME SDL_!SetAlpha- Adjust the alpha properties of a surface !!SYNOPSIS __#include __ __int SDL_!SetAlpha__(__SDL_Surface *surface, Uint32 flag, Uint8 alpha__); !!DESCRIPTION __Note:__ This function and the semantics of SDL alpha blending have changed since version 1.1.4. Up until version 1.1.5, an alpha value of 0 was considered opaque and a value of 255 was considered transparent. This has now been inverted: 0 (__SDL_ALPHA_TRANSPARENT__) is now considered transparent and 255 (__SDL_ALPHA_OPAQUE__) is now considered opaque. __SDL_!SetAlpha__ is used for setting the per-surface alpha and/or enabling and disabling per-pixel alpha blending. The __surface__ parameter specifies which surface whose alpha attributes you wish to adjust. __flags__ is used to specify whether alpha blending should be used (__SDL_SRCALPHA__) and whether the surface should use RLE acceleration for blitting (__SDL_RLEACCEL__). __flags__ can be an OR'd combination of these two options, one of these options or 0. If __SDL_SRCALPHA__ is not passed as a flag then all alpha information is ignored when blitting the surface. The __alpha__ parameter is the per-surface alpha value, a surface need not have an alpha channel to use per-surface alpha and blitting can still be accelerated with __SDL_RLEACCEL__. Setting the per-surface alpha value to 0 disables per-surface alpha blending. __Note:__ The per-surface alpha value of 128 is considered a special case and is optimised, so it's much faster than other per-surface values. Alpha effects surface blitting in the following ways: RGBA-SDL_SRCALPHA__ The source is alpha-blended with the destination, using the alpha channel. __SDL_SRCCOLORKEY__ and the per-surface alpha are ignored. RGBA-SDL_SRCALPHA__ The RGB data is copied from the source. The source alpha channel and the per-surface alpha value are ignored. RGB-SDL_SRCALPHA__ The source is alpha-blended with the destination using the per-surface alpha value. If __SDL_SRCCOLORKEY__literal __ RGB-SDL_SRCALPHA__ The RGB data is copied from the source and the destination alpha is zero to opaque. If __SDL_SRCCOLORKEY__ is set, only the pixels not matching the colorkey value are copied. RGBA-SDL_SRCALPHA__ The source is alpha-blended with the destination using the source alpha channel. The alpha channel in the destination surface is left untouched. __SDL_SRCCOLORKEY__ is ignored. RGBA-SDL_SRCALPHA__ The RGBA data is copied to the destination surface. If __SDL_SRCCOLORKEY__ is set, only the pixels not matching the colorkey value are copied. RGB-SDL_SRCALPHA__ The source is alpha-blended with the destination using the per-surface alpha value. If __SDL_SRCCOLORKEY__ is set, only the pixels not matching the colorkey value are copied. RGB-SDL_SRCALPHA__ The RGB data is copied from the source. If __SDL_SRCCOLORKEY__ is set, only the pixels not matching the colorkey value are copied. !!SEE ALSO __SDL_MapRGBA__, __SDL_GetRGBA__, __SDL_!DisplayFormatAlpha__, __SDL_!BlitSurface__ ----
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