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Added new docs for SDL 1.2.1

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Sam Lantinga 2001-06-10 19:31:57 +00:00
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docs/html/sdlsetalpha.html
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@ -4,7 +4,7 @@
>SDL_SetAlpha</TITLE
><META
NAME="GENERATOR"
CONTENT="Modular DocBook HTML Stylesheet Version 1.61
CONTENT="Modular DocBook HTML Stylesheet Version 1.64
"><LINK
REL="HOME"
TITLE="SDL Library Documentation"
@ -73,7 +73,7 @@ NAME="SDLSETALPHA"
><DIV
CLASS="REFNAMEDIV"
><A
NAME="AEN1612"
NAME="AEN1681"
></A
><H2
>Name</H2
@ -81,14 +81,14 @@ NAME="AEN1612"
><DIV
CLASS="REFSYNOPSISDIV"
><A
NAME="AEN1615"
NAME="AEN1684"
></A
><H2
>Synopsis</H2
><DIV
CLASS="FUNCSYNOPSIS"
><A
NAME="AEN1616"
NAME="AEN1685"
></A
><P
></P
@ -112,7 +112,7 @@ CLASS="FSFUNC"
><DIV
CLASS="REFSECT1"
><A
NAME="AEN1622"
NAME="AEN1691"
></A
><H2
>Description</H2
@ -136,22 +136,27 @@ CLASS="LITERAL"
><TT
CLASS="FUNCTION"
>SDL_SetAlpha</TT
> is used for setting the per-surface alpha and/or enabling and disabling per-pixel alpha blending.</P
> is used for setting the per-surface alpha
value and/or enabling and disabling alpha blending.</P
><P
>The <TT
>The<TT
CLASS="PARAMETER"
><I
>surface</I
></TT
> parameter specifies which surface whose alpha attributes you wish to adjust. <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
> 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
>) and
whether the surface should use RLE acceleration for blitting
(<TT
CLASS="LITERAL"
>SDL_RLEACCEL</TT
>). <TT
@ -159,18 +164,24 @@ CLASS="PARAMETER"
><I
>flags</I
></TT
> can be an OR'd combination of these two options, one of these options or 0. If <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
> 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
> 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
>.</P
><DIV
CLASS="NOTE"
><BLOCKQUOTE
@ -178,7 +189,8 @@ 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
>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
@ -186,7 +198,7 @@ CLASS="NOTE"
><DIV
CLASS="INFORMALTABLE"
><A
NAME="AEN1642"
NAME="AEN1711"
></A
><P
></P
@ -239,10 +251,13 @@ CLASS="LITERAL"
ALIGN="LEFT"
VALIGN="TOP"
><P
>The source is alpha-blended with the destination using the per-surface alpha value. If <TT
>The source is alpha-blended with the destination using the per-surface alpha
value. If <TT
CLASS="LITERAL"
>SDL_SRCCOLORKEY</TT
>literal&#62; is set, only the pixels not matching the colorkey value are copied.</P
> is set, only the pixels not
matching the colorkey value are copied. The alpha channel of the copied pixels
is set to opaque.</P
></TD
></TR
><TR
@ -257,10 +272,12 @@ CLASS="LITERAL"
ALIGN="LEFT"
VALIGN="TOP"
><P
>The RGB data is copied from the source and the destination alpha is zero to opaque. If <TT
>The RGB data is copied from the source and the alpha value of the copied pixels
is set to opaque. If <TT
CLASS="LITERAL"
>SDL_SRCCOLORKEY</TT
> is set, only the pixels not matching the colorkey value are copied.</P
> is set, only the pixels
not matching the colorkey value are copied. </P
></TD
></TR
><TR
@ -275,7 +292,9 @@ CLASS="LITERAL"
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
>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
@ -340,11 +359,44 @@ CLASS="LITERAL"
><P
></P
></DIV
><DIV
CLASS="NOTE"
><BLOCKQUOTE
CLASS="NOTE"
><P
><B
>Note: </B
> Note that RGBA-&#62;RGBA blits (with SDL_SRCALPHA set) keep the alpha
of the destination surface. This means that you cannot compose two arbitrary
RGBA surfaces this way and get the result you would expect from "overlaying"
them; the destination alpha will work as a mask.</P
><P
>Also note that per-pixel and per-surface alpha cannot be combined;
the per-pixel alpha is always used if available</P
></BLOCKQUOTE
></DIV
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN1692"
NAME="AEN1764"
></A
><H2
>Return Value</H2
><P
>This function returns <SPAN
CLASS="RETURNVALUE"
>0</SPAN
>, or
<SPAN
CLASS="RETURNVALUE"
>-1</SPAN
> if there was an error.</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN1769"
></A
><H2
>See Also</H2