Mercurial > sdl-ios-xcode
annotate docs/html/sdldisplayformatalpha.html @ 2787:93764fe8601a
It turns out both the software and the OpenGL renderer had the same problem.
According to the spec, when SDL_SRCALPHA is set, the colorkey is ignored, so
we just need to convert the colorkey into the alpha channel.
| author | Sam Lantinga <slouken@libsdl.org> |
|---|---|
| date | Tue, 25 Nov 2008 05:29:14 +0000 |
| parents | 355632dca928 |
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| rev | line source |
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| 0 | 1 <HTML |
| 2 ><HEAD | |
| 3 ><TITLE | |
| 4 >SDL_DisplayFormatAlpha</TITLE | |
| 5 ><META | |
| 6 NAME="GENERATOR" | |
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7 CONTENT="Modular DocBook HTML Stylesheet Version 1.76b+ |
| 0 | 8 "><LINK |
| 9 REL="HOME" | |
| 10 TITLE="SDL Library Documentation" | |
| 11 HREF="index.html"><LINK | |
| 12 REL="UP" | |
| 13 TITLE="Video" | |
| 14 HREF="video.html"><LINK | |
| 15 REL="PREVIOUS" | |
| 16 TITLE="SDL_DisplayFormat" | |
| 17 HREF="sdldisplayformat.html"><LINK | |
| 18 REL="NEXT" | |
| 19 TITLE="SDL_WarpMouse" | |
| 20 HREF="sdlwarpmouse.html"></HEAD | |
| 21 ><BODY | |
| 22 CLASS="REFENTRY" | |
| 23 BGCOLOR="#FFF8DC" | |
| 24 TEXT="#000000" | |
| 25 LINK="#0000ee" | |
| 26 VLINK="#551a8b" | |
| 27 ALINK="#ff0000" | |
| 28 ><DIV | |
| 29 CLASS="NAVHEADER" | |
| 30 ><TABLE | |
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31 SUMMARY="Header navigation table" |
| 0 | 32 WIDTH="100%" |
| 33 BORDER="0" | |
| 34 CELLPADDING="0" | |
| 35 CELLSPACING="0" | |
| 36 ><TR | |
| 37 ><TH | |
| 38 COLSPAN="3" | |
| 39 ALIGN="center" | |
| 40 >SDL Library Documentation</TH | |
| 41 ></TR | |
| 42 ><TR | |
| 43 ><TD | |
| 44 WIDTH="10%" | |
| 45 ALIGN="left" | |
| 46 VALIGN="bottom" | |
| 47 ><A | |
| 48 HREF="sdldisplayformat.html" | |
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49 ACCESSKEY="P" |
| 0 | 50 >Prev</A |
| 51 ></TD | |
| 52 ><TD | |
| 53 WIDTH="80%" | |
| 54 ALIGN="center" | |
| 55 VALIGN="bottom" | |
| 56 ></TD | |
| 57 ><TD | |
| 58 WIDTH="10%" | |
| 59 ALIGN="right" | |
| 60 VALIGN="bottom" | |
| 61 ><A | |
| 62 HREF="sdlwarpmouse.html" | |
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63 ACCESSKEY="N" |
| 0 | 64 >Next</A |
| 65 ></TD | |
| 66 ></TR | |
| 67 ></TABLE | |
| 68 ><HR | |
| 69 ALIGN="LEFT" | |
| 70 WIDTH="100%"></DIV | |
| 71 ><H1 | |
| 72 ><A | |
| 73 NAME="SDLDISPLAYFORMATALPHA" | |
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74 ></A |
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75 >SDL_DisplayFormatAlpha</H1 |
| 0 | 76 ><DIV |
| 77 CLASS="REFNAMEDIV" | |
| 78 ><A | |
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79 NAME="AEN2432" |
| 0 | 80 ></A |
| 81 ><H2 | |
| 82 >Name</H2 | |
| 83 >SDL_DisplayFormatAlpha -- Convert a surface to the display format</DIV | |
| 84 ><DIV | |
| 85 CLASS="REFSYNOPSISDIV" | |
| 86 ><A | |
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87 NAME="AEN2435" |
| 0 | 88 ></A |
| 89 ><H2 | |
| 90 >Synopsis</H2 | |
| 91 ><DIV | |
| 92 CLASS="FUNCSYNOPSIS" | |
| 93 ><A | |
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94 NAME="AEN2436" |
| 0 | 95 ></A |
| 96 ><P | |
| 97 ></P | |
| 98 ><PRE | |
| 99 CLASS="FUNCSYNOPSISINFO" | |
| 100 >#include "SDL.h"</PRE | |
| 101 ><P | |
| 102 ><CODE | |
| 103 ><CODE | |
| 104 CLASS="FUNCDEF" | |
| 105 >SDL_Surface *<B | |
| 106 CLASS="FSFUNC" | |
| 107 >SDL_DisplayFormatAlpha</B | |
| 108 ></CODE | |
| 109 >(SDL_Surface *surface);</CODE | |
| 110 ></P | |
| 111 ><P | |
| 112 ></P | |
| 113 ></DIV | |
| 114 ></DIV | |
| 115 ><DIV | |
| 116 CLASS="REFSECT1" | |
| 117 ><A | |
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118 NAME="AEN2442" |
| 0 | 119 ></A |
| 120 ><H2 | |
| 121 >Description</H2 | |
| 122 ><P | |
| 123 >This function takes a surface and copies it to a new surface of the | |
| 124 pixel format and colors of the video framebuffer plus an alpha channel, | |
| 125 suitable for fast blitting onto the display surface. It calls | |
| 126 <A | |
| 127 HREF="sdlconvertsurface.html" | |
| 128 >SDL_ConvertSurface</A | |
| 129 ></P | |
| 130 ><P | |
| 131 >If you want to take advantage of hardware colorkey or alpha blit | |
| 132 acceleration, you should set the colorkey and alpha value before | |
| 133 calling this function.</P | |
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134 ><P |
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135 >This function can be used to convert a colourkey to an alpha channel, |
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136 if the <TT |
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137 CLASS="LITERAL" |
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138 >SDL_SRCCOLORKEY</TT |
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139 > flag is set on the surface. |
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140 The generated surface will then be transparent (alpha=0) where the |
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141 pixels match the colourkey, and opaque (alpha=255) elsewhere.</P |
| 0 | 142 ></DIV |
| 143 ><DIV | |
| 144 CLASS="REFSECT1" | |
| 145 ><A | |
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146 NAME="AEN2449" |
| 0 | 147 ></A |
| 148 ><H2 | |
| 149 >Return Value</H2 | |
| 150 ><P | |
| 151 >If the conversion fails or runs out of memory, it returns | |
| 152 <SPAN | |
| 153 CLASS="RETURNVALUE" | |
| 154 >NULL</SPAN | |
| 155 ></P | |
| 156 ></DIV | |
| 157 ><DIV | |
| 158 CLASS="REFSECT1" | |
| 159 ><A | |
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160 NAME="AEN2453" |
| 0 | 161 ></A |
| 162 ><H2 | |
| 163 >See Also</H2 | |
| 164 ><P | |
| 165 ><A | |
| 166 HREF="sdlconvertsurface.html" | |
| 167 >SDL_ConvertSurface</A | |
| 168 >, | |
| 169 <A | |
| 170 HREF="sdlsetalpha.html" | |
| 171 >SDL_SetAlpha</A | |
| 172 >, | |
| 173 <A | |
| 174 HREF="sdlsetcolorkey.html" | |
| 175 >SDL_SetColorKey</A | |
| 176 >, | |
| 177 <A | |
| 178 HREF="sdldisplayformat.html" | |
| 179 >SDL_DisplayFormat</A | |
| 180 >, | |
| 181 <A | |
| 182 HREF="sdlsurface.html" | |
| 183 >SDL_Surface</A | |
| 184 ></P | |
| 185 ></DIV | |
| 186 ><DIV | |
| 187 CLASS="NAVFOOTER" | |
| 188 ><HR | |
| 189 ALIGN="LEFT" | |
| 190 WIDTH="100%"><TABLE | |
|
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191 SUMMARY="Footer navigation table" |
| 0 | 192 WIDTH="100%" |
| 193 BORDER="0" | |
| 194 CELLPADDING="0" | |
| 195 CELLSPACING="0" | |
| 196 ><TR | |
| 197 ><TD | |
| 198 WIDTH="33%" | |
| 199 ALIGN="left" | |
| 200 VALIGN="top" | |
| 201 ><A | |
| 202 HREF="sdldisplayformat.html" | |
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203 ACCESSKEY="P" |
| 0 | 204 >Prev</A |
| 205 ></TD | |
| 206 ><TD | |
| 207 WIDTH="34%" | |
| 208 ALIGN="center" | |
| 209 VALIGN="top" | |
| 210 ><A | |
| 211 HREF="index.html" | |
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212 ACCESSKEY="H" |
| 0 | 213 >Home</A |
| 214 ></TD | |
| 215 ><TD | |
| 216 WIDTH="33%" | |
| 217 ALIGN="right" | |
| 218 VALIGN="top" | |
| 219 ><A | |
| 220 HREF="sdlwarpmouse.html" | |
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221 ACCESSKEY="N" |
| 0 | 222 >Next</A |
| 223 ></TD | |
| 224 ></TR | |
| 225 ><TR | |
| 226 ><TD | |
| 227 WIDTH="33%" | |
| 228 ALIGN="left" | |
| 229 VALIGN="top" | |
| 230 >SDL_DisplayFormat</TD | |
| 231 ><TD | |
| 232 WIDTH="34%" | |
| 233 ALIGN="center" | |
| 234 VALIGN="top" | |
| 235 ><A | |
| 236 HREF="video.html" | |
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237 ACCESSKEY="U" |
| 0 | 238 >Up</A |
| 239 ></TD | |
| 240 ><TD | |
| 241 WIDTH="33%" | |
| 242 ALIGN="right" | |
| 243 VALIGN="top" | |
| 244 >SDL_WarpMouse</TD | |
| 245 ></TR | |
| 246 ></TABLE | |
| 247 ></DIV | |
| 248 ></BODY | |
| 249 ></HTML | |
| 250 > |