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Date: Tue, 12 Aug 2003 14:26:19 +0200 (MEST) From: "Mattias Engdeg?rd" Subject: bug in SDL_GetRGB/GetRGBA There's an embarrassing bug in GetRGB/GetRGBA which apparently has been there for years. It incorrectly converts colours with < 8 bits/channel. It came to my attention today in #sdl. What it does now is (for each channel): rv = (pixel & fmt->Rmask) >> fmt->Rshift; *r = (rv << fmt->Rloss) + (rv >> (8 - fmt->Rloss)); which is wrong; the last line should be *r = (rv << fmt->Rloss) + (rv >> (8 - (fmt->Rloss << 1)));
author Sam Lantinga <slouken@libsdl.org>
date Tue, 12 Aug 2003 15:17:20 +0000
parents e5bc29de3f0a
children 355632dca928
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<HTML
><HEAD
><TITLE
>SDL_Color</TITLE
><META
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><H1
><A
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>SDL_Color</A
></H1
><DIV
CLASS="REFNAMEDIV"
><A
NAME="AEN2698"
></A
><H2
>Name</H2
>SDL_Color&nbsp;--&nbsp;Format independent color description</DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN2701"
></A
><H2
>Structure Definition</H2
><PRE
CLASS="PROGRAMLISTING"
>typedef struct{
  Uint8 r;
  Uint8 g;
  Uint8 b;
  Uint8 unused;
} SDL_Color;</PRE
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN2704"
></A
><H2
>Structure Data</H2
><DIV
CLASS="INFORMALTABLE"
><A
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></A
><P
></P
><TABLE
BORDER="0"
CLASS="CALSTABLE"
><TBODY
><TR
><TD
ALIGN="LEFT"
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><TT
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><I
>r</I
></TT
></TD
><TD
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>Red intensity</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="STRUCTFIELD"
><I
>g</I
></TT
></TD
><TD
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>Green intensity</TD
></TR
><TR
><TD
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><TT
CLASS="STRUCTFIELD"
><I
>b</I
></TT
></TD
><TD
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>Blue intensity</TD
></TR
><TR
><TD
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><TT
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><I
>unused</I
></TT
></TD
><TD
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>Unused</TD
></TR
></TBODY
></TABLE
><P
></P
></DIV
></DIV
><DIV
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><A
NAME="AEN2725"
></A
><H2
>Description</H2
><P
><SPAN
CLASS="STRUCTNAME"
>SDL_Color</SPAN
> describes a color in a format independent way. You can convert a <SPAN
CLASS="STRUCTNAME"
>SDL_Color</SPAN
> to a pixel value for a certain pixel format using <A
HREF="sdlmaprgb.html"
><TT
CLASS="FUNCTION"
>SDL_MapRGB</TT
></A
>.</P
></DIV
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><A
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></A
><H2
>See Also</H2
><P
><A
HREF="sdlpixelformat.html"
><SPAN
CLASS="STRUCTNAME"
>SDL_PixelFormat</SPAN
></A
>,
<A
HREF="sdlsetcolors.html"
><TT
CLASS="FUNCTION"
>SDL_SetColors</TT
></A
>,
<A
HREF="sdlpalette.html"
><TT
CLASS="FUNCTION"
>SDL_Palette</TT
></A
></P
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