Mercurial > sdl-ios-xcode
diff docs/html/sdlsetalpha.html @ 0:74212992fb08
Initial revision
| author | Sam Lantinga <slouken@lokigames.com> |
|---|---|
| date | Thu, 26 Apr 2001 16:45:43 +0000 |
| parents | |
| children | 55f1f1b3e27d |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/docs/html/sdlsetalpha.html Thu Apr 26 16:45:43 2001 +0000 @@ -0,0 +1,440 @@ +<HTML +><HEAD +><TITLE +>SDL_SetAlpha</TITLE +><META +NAME="GENERATOR" +CONTENT="Modular DocBook HTML Stylesheet Version 1.61 +"><LINK +REL="HOME" +TITLE="SDL Library Documentation" +HREF="index.html"><LINK +REL="UP" +TITLE="Video" +HREF="video.html"><LINK +REL="PREVIOUS" +TITLE="SDL_SetColorKey" +HREF="sdlsetcolorkey.html"><LINK +REL="NEXT" +TITLE="SDL_SetClipRect" +HREF="sdlsetcliprect.html"></HEAD +><BODY +CLASS="REFENTRY" +BGCOLOR="#FFF8DC" +TEXT="#000000" +LINK="#0000ee" +VLINK="#551a8b" +ALINK="#ff0000" +><DIV +CLASS="NAVHEADER" +><TABLE +WIDTH="100%" +BORDER="0" +CELLPADDING="0" +CELLSPACING="0" +><TR +><TH +COLSPAN="3" +ALIGN="center" +>SDL Library Documentation</TH +></TR +><TR +><TD +WIDTH="10%" +ALIGN="left" +VALIGN="bottom" +><A +HREF="sdlsetcolorkey.html" +>Prev</A +></TD +><TD +WIDTH="80%" +ALIGN="center" +VALIGN="bottom" +></TD +><TD +WIDTH="10%" +ALIGN="right" +VALIGN="bottom" +><A +HREF="sdlsetcliprect.html" +>Next</A +></TD +></TR +></TABLE +><HR +ALIGN="LEFT" +WIDTH="100%"></DIV +><H1 +><A +NAME="SDLSETALPHA" +>SDL_SetAlpha</A +></H1 +><DIV +CLASS="REFNAMEDIV" +><A +NAME="AEN1612" +></A +><H2 +>Name</H2 +>SDL_SetAlpha -- Adjust the alpha properties of a surface</DIV +><DIV +CLASS="REFSYNOPSISDIV" +><A +NAME="AEN1615" +></A +><H2 +>Synopsis</H2 +><DIV +CLASS="FUNCSYNOPSIS" +><A +NAME="AEN1616" +></A +><P +></P +><PRE +CLASS="FUNCSYNOPSISINFO" +>#include "SDL.h"</PRE +><P +><CODE +><CODE +CLASS="FUNCDEF" +>int <B +CLASS="FSFUNC" +>SDL_SetAlpha</B +></CODE +>(SDL_Surface *surface, Uint32 flag, Uint8 alpha);</CODE +></P +><P +></P +></DIV +></DIV +><DIV +CLASS="REFSECT1" +><A +NAME="AEN1622" +></A +><H2 +>Description</H2 +><DIV +CLASS="NOTE" +><BLOCKQUOTE +CLASS="NOTE" +><P +><B +>Note: </B +>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 (<TT +CLASS="LITERAL" +>SDL_ALPHA_TRANSPARENT</TT +>) is now considered transparent and 255 (<TT +CLASS="LITERAL" +>SDL_ALPHA_OPAQUE</TT +>) is now considered opaque.</P +></BLOCKQUOTE +></DIV +><P +><TT +CLASS="FUNCTION" +>SDL_SetAlpha</TT +> is used for setting the per-surface alpha and/or enabling and disabling per-pixel alpha blending.</P +><P +>The <TT +CLASS="PARAMETER" +><I +>surface</I +></TT +> parameter specifies which surface whose alpha attributes you wish to adjust. <TT +CLASS="PARAMETER" +><I +>flags</I +></TT +> is used to specify whether alpha blending should be used (<TT +CLASS="LITERAL" +>SDL_SRCALPHA</TT +>) and whether the surface should use RLE acceleration for blitting (<TT +CLASS="LITERAL" +>SDL_RLEACCEL</TT +>). <TT +CLASS="PARAMETER" +><I +>flags</I +></TT +> can be an OR'd combination of these two options, one of these options or 0. If <TT +CLASS="LITERAL" +>SDL_SRCALPHA</TT +> is not passed as a flag then all alpha information is ignored when blitting the surface. The <TT +CLASS="PARAMETER" +><I +>alpha</I +></TT +> 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 <TT +CLASS="LITERAL" +>SDL_RLEACCEL</TT +>. Setting the per-surface alpha value to 0 disables per-surface alpha blending.</P +><DIV +CLASS="NOTE" +><BLOCKQUOTE +CLASS="NOTE" +><P +><B +>Note: </B +>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.</P +></BLOCKQUOTE +></DIV +><P +>Alpha effects surface blitting in the following ways:</P +><DIV +CLASS="INFORMALTABLE" +><A +NAME="AEN1642" +></A +><P +></P +><TABLE +BORDER="0" +CLASS="CALSTABLE" +><TBODY +><TR +><TD +ALIGN="LEFT" +VALIGN="TOP" +>RGBA->RGB with <TT +CLASS="LITERAL" +>SDL_SRCALPHA</TT +></TD +><TD +ALIGN="LEFT" +VALIGN="TOP" +><P +>The source is alpha-blended with the destination, using the alpha channel. <TT +CLASS="LITERAL" +>SDL_SRCCOLORKEY</TT +> and the per-surface alpha are ignored.</P +></TD +></TR +><TR +><TD +ALIGN="LEFT" +VALIGN="TOP" +>RGBA->RGB without <TT +CLASS="LITERAL" +>SDL_SRCALPHA</TT +></TD +><TD +ALIGN="LEFT" +VALIGN="TOP" +><P +>The RGB data is copied from the source. The source alpha channel and the per-surface alpha value are ignored.</P +></TD +></TR +><TR +><TD +ALIGN="LEFT" +VALIGN="TOP" +>RGB->RGBA with <TT +CLASS="LITERAL" +>SDL_SRCALPHA</TT +></TD +><TD +ALIGN="LEFT" +VALIGN="TOP" +><P +>The source is alpha-blended with the destination using the per-surface alpha value. If <TT +CLASS="LITERAL" +>SDL_SRCCOLORKEY</TT +>literal> is set, only the pixels not matching the colorkey value are copied.</P +></TD +></TR +><TR +><TD +ALIGN="LEFT" +VALIGN="TOP" +>RGB->RGBA without <TT +CLASS="LITERAL" +>SDL_SRCALPHA</TT +></TD +><TD +ALIGN="LEFT" +VALIGN="TOP" +><P +>The RGB data is copied from the source and the destination alpha is zero to opaque. If <TT +CLASS="LITERAL" +>SDL_SRCCOLORKEY</TT +> is set, only the pixels not matching the colorkey value are copied.</P +></TD +></TR +><TR +><TD +ALIGN="LEFT" +VALIGN="TOP" +>RGBA->RGBA with <TT +CLASS="LITERAL" +>SDL_SRCALPHA</TT +></TD +><TD +ALIGN="LEFT" +VALIGN="TOP" +><P +>The source is alpha-blended with the destination using the source alpha channel. The alpha channel in the destination surface is left untouched. <TT +CLASS="LITERAL" +>SDL_SRCCOLORKEY</TT +> is ignored.</P +></TD +></TR +><TR +><TD +ALIGN="LEFT" +VALIGN="TOP" +>RGBA->RGBA without <TT +CLASS="LITERAL" +>SDL_SRCALPHA</TT +></TD +><TD +ALIGN="LEFT" +VALIGN="TOP" +><P +>The RGBA data is copied to the destination surface. If <TT +CLASS="LITERAL" +>SDL_SRCCOLORKEY</TT +> is set, only the pixels not matching the colorkey value are copied.</P +></TD +></TR +><TR +><TD +ALIGN="LEFT" +VALIGN="TOP" +>RGB->RGB with <TT +CLASS="LITERAL" +>SDL_SRCALPHA</TT +></TD +><TD +ALIGN="LEFT" +VALIGN="TOP" +><P +>The source is alpha-blended with the destination using the per-surface alpha value. If <TT +CLASS="LITERAL" +>SDL_SRCCOLORKEY</TT +> is set, only the pixels not matching the colorkey value are copied.</P +></TD +></TR +><TR +><TD +ALIGN="LEFT" +VALIGN="TOP" +>RGB->RGB without <TT +CLASS="LITERAL" +>SDL_SRCALPHA</TT +></TD +><TD +ALIGN="LEFT" +VALIGN="TOP" +><P +>The RGB data is copied from the source. If <TT +CLASS="LITERAL" +>SDL_SRCCOLORKEY</TT +> is set, only the pixels not matching the colorkey value are copied.</P +></TD +></TR +></TBODY +></TABLE +><P +></P +></DIV +></DIV +><DIV +CLASS="REFSECT1" +><A +NAME="AEN1692" +></A +><H2 +>See Also</H2 +><P +><A +HREF="sdlmaprgba.html" +><TT +CLASS="FUNCTION" +>SDL_MapRGBA</TT +></A +>, +<A +HREF="sdlgetrgba.html" +><TT +CLASS="FUNCTION" +>SDL_GetRGBA</TT +></A +>, +<A +HREF="sdldisplayformatalpha.html" +><TT +CLASS="FUNCTION" +>SDL_DisplayFormatAlpha</TT +></A +>, +<A +HREF="sdlblitsurface.html" +><TT +CLASS="FUNCTION" +>SDL_BlitSurface</TT +></A +></P +></DIV +><DIV +CLASS="NAVFOOTER" +><HR +ALIGN="LEFT" +WIDTH="100%"><TABLE +WIDTH="100%" +BORDER="0" +CELLPADDING="0" +CELLSPACING="0" +><TR +><TD +WIDTH="33%" +ALIGN="left" +VALIGN="top" +><A +HREF="sdlsetcolorkey.html" +>Prev</A +></TD +><TD +WIDTH="34%" +ALIGN="center" +VALIGN="top" +><A +HREF="index.html" +>Home</A +></TD +><TD +WIDTH="33%" +ALIGN="right" +VALIGN="top" +><A +HREF="sdlsetcliprect.html" +>Next</A +></TD +></TR +><TR +><TD +WIDTH="33%" +ALIGN="left" +VALIGN="top" +>SDL_SetColorKey</TD +><TD +WIDTH="34%" +ALIGN="center" +VALIGN="top" +><A +HREF="video.html" +>Up</A +></TD +><TD +WIDTH="33%" +ALIGN="right" +VALIGN="top" +>SDL_SetClipRect</TD +></TR +></TABLE +></DIV +></BODY +></HTML +> \ No newline at end of file