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| 5131 | clevermous | 1 | |
| 2 | > |
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| 3 | > |
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| 4 | >SDL_SetAlpha |
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| 5 | > |
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| 6 | NAME="GENERATOR" |
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| 7 | CONTENT="Modular DocBook HTML Stylesheet Version 1.64 |
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| 8 | "> |
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| 9 | REL="HOME" |
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| 10 | TITLE="SDL Library Documentation" |
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| 11 | HREF="index.html"> |
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| 12 | REL="UP" |
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| 13 | TITLE="Video" |
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| 14 | HREF="video.html"> |
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| 15 | REL="PREVIOUS" |
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| 16 | TITLE="SDL_SetColorKey" |
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| 17 | HREF="sdlsetcolorkey.html"> |
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| 18 | REL="NEXT" |
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| 19 | TITLE="SDL_SetClipRect" |
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| 20 | HREF="sdlsetcliprect.html"> |
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| 21 | > |
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| 22 | CLASS="REFENTRY" |
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| 23 | BGCOLOR="#FFF8DC" |
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| 24 | TEXT="#000000" |
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| 25 | LINK="#0000ee" |
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| 26 | VLINK="#551a8b" |
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| 27 | ALINK="#ff0000" |
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| 28 | > |
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| 29 | CLASS="NAVHEADER" |
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| 30 | > |
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| 31 | WIDTH="100%" |
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| 32 | BORDER="0" |
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| 33 | CELLPADDING="0" |
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| 34 | CELLSPACING="0" |
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| 35 | > |
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| 36 | > |
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| 37 | COLSPAN="3" |
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| 38 | ALIGN="center" |
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| 39 | >SDL Library Documentation |
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| 40 | > |
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| 41 | > |
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| 42 | > |
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| 43 | WIDTH="10%" |
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| 44 | ALIGN="left" |
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| 45 | VALIGN="bottom" |
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| 46 | > |
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| 47 | HREF="sdlsetcolorkey.html" |
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| 48 | >Prev |
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| 49 | > |
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| 50 | > |
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| 51 | WIDTH="80%" |
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| 52 | ALIGN="center" |
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| 53 | VALIGN="bottom" |
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| 54 | > |
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| 55 | > |
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| 56 | WIDTH="10%" |
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| 57 | ALIGN="right" |
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| 58 | VALIGN="bottom" |
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| 59 | > |
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| 60 | HREF="sdlsetcliprect.html" |
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| 61 | >Next |
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| 62 | > |
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| 63 | > |
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| 64 | > |
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| 65 | > |
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| 66 | ALIGN="LEFT" |
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| 67 | WIDTH="100%"> |
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| 68 | > |
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| 69 | > |
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| 70 | NAME="SDLSETALPHA" |
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| 71 | >SDL_SetAlpha |
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| 72 | > |
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| 73 | > |
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| 74 | CLASS="REFNAMEDIV" |
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| 75 | > |
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| 76 | NAME="AEN1681" |
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| 77 | > |
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| 78 | > |
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| 79 | >Name |
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| 80 | >SDL_SetAlpha -- Adjust the alpha properties of a surface |
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| 81 | > |
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| 82 | CLASS="REFSYNOPSISDIV" |
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| 83 | > |
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| 84 | NAME="AEN1684" |
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| 85 | > |
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| 86 | > |
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| 87 | >Synopsis |
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| 88 | > |
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| 89 | CLASS="FUNCSYNOPSIS" |
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| 90 | > |
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| 91 | NAME="AEN1685" |
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| 92 | > |
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| 93 | > |
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| 94 | > |
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| 95 | > |
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| 96 | CLASS="FUNCSYNOPSISINFO" |
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| 97 | >#include "SDL.h" |
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| 98 | > |
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| 99 | > |
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| 100 | > |
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| 101 | CLASS="FUNCDEF" |
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| 102 | >int |
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| 103 | CLASS="FSFUNC" |
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| 104 | >SDL_SetAlpha |
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| 105 | > |
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| 106 | >(SDL_Surface *surface, Uint32 flag, Uint8 alpha); |
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| 107 | > |
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| 108 | > |
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| 109 | > |
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| 110 | > |
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| 111 | > |
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| 112 | > |
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| 113 | CLASS="REFSECT1" |
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| 114 | > |
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| 115 | NAME="AEN1691" |
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| 116 | > |
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| 117 | > |
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| 118 | >Description |
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| 119 | > |
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| 120 | CLASS="NOTE" |
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| 121 | > |
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| 122 | CLASS="NOTE" |
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| 123 | > |
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| 124 | > |
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| 125 | >Note: |
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| 126 | >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 ( |
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| 127 | CLASS="LITERAL" |
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| 128 | >SDL_ALPHA_TRANSPARENT |
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| 129 | >) is now considered transparent and 255 ( |
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| 130 | CLASS="LITERAL" |
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| 131 | >SDL_ALPHA_OPAQUE |
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| 132 | >) is now considered opaque. |
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| 133 | > |
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| 134 | > |
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| 135 | > |
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| 136 | > |
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| 137 | CLASS="FUNCTION" |
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| 138 | >SDL_SetAlpha |
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| 139 | > is used for setting the per-surface alpha |
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| 140 | value and/or enabling and disabling alpha blending. |
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| 141 | > |
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| 142 | >The |
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| 143 | CLASS="PARAMETER" |
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| 144 | > |
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| 145 | >surface |
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| 146 | > |
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| 147 | > parameter specifies which surface whose alpha |
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| 148 | attributes you wish to adjust. |
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| 149 | CLASS="PARAMETER" |
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| 150 | > |
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| 151 | >flags |
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| 152 | > |
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| 153 | > is used to specify |
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| 154 | whether alpha blending should be used ( |
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| 155 | CLASS="LITERAL" |
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| 156 | >SDL_SRCALPHA |
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| 157 | >) and |
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| 158 | whether the surface should use RLE acceleration for blitting |
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| 159 | ( |
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| 160 | CLASS="LITERAL" |
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| 161 | >SDL_RLEACCEL |
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| 162 | >). |
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| 163 | CLASS="PARAMETER" |
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| 164 | > |
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| 165 | >flags |
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| 166 | > |
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| 167 | > can be an OR'd |
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| 168 | combination of these two options, one of these options or 0. If |
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| 169 | |||
| 170 | CLASS="LITERAL" |
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| 171 | >SDL_SRCALPHA |
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| 172 | > is not passed as a flag then all alpha |
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| 173 | information is ignored when blitting the surface. The |
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| 174 | |||
| 175 | CLASS="PARAMETER" |
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| 176 | > |
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| 177 | >alpha |
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| 178 | > |
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| 179 | > parameter is the per-surface alpha value; a |
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| 180 | surface need not have an alpha channel to use per-surface alpha and blitting |
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| 181 | can still be accelerated with |
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| 182 | CLASS="LITERAL" |
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| 183 | >SDL_RLEACCEL |
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| 184 | >. |
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| 185 | > |
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| 186 | CLASS="NOTE" |
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| 187 | > |
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| 188 | CLASS="NOTE" |
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| 189 | > |
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| 190 | > |
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| 191 | >Note: |
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| 192 | >The per-surface alpha value of 128 is considered a special case and |
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| 193 | is optimised, so it's much faster than other per-surface values. |
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| 194 | > |
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| 195 | > |
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| 196 | > |
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| 197 | >Alpha effects surface blitting in the following ways: |
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| 198 | > |
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| 199 | CLASS="INFORMALTABLE" |
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| 200 | > |
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| 201 | NAME="AEN1711" |
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| 202 | > |
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| 203 | > |
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| 204 | > |
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| 205 | > |
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| 206 | BORDER="0" |
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| 207 | CLASS="CALSTABLE" |
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| 208 | > |
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| 209 | > |
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| 210 | > |
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| 211 | ALIGN="LEFT" |
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| 212 | VALIGN="TOP" |
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| 213 | >RGBA->RGB with |
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| 214 | CLASS="LITERAL" |
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| 215 | >SDL_SRCALPHA |
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| 216 | > |
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| 217 | > |
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| 218 | ALIGN="LEFT" |
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| 219 | VALIGN="TOP" |
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| 220 | > |
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| 221 | >The source is alpha-blended with the destination, using the alpha channel. |
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| 222 | CLASS="LITERAL" |
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| 223 | >SDL_SRCCOLORKEY |
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| 224 | > and the per-surface alpha are ignored. |
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| 225 | > |
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| 226 | > |
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| 227 | > |
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| 228 | > |
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| 229 | ALIGN="LEFT" |
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| 230 | VALIGN="TOP" |
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| 231 | >RGBA->RGB without |
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| 232 | CLASS="LITERAL" |
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| 233 | >SDL_SRCALPHA |
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| 234 | > |
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| 235 | > |
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| 236 | ALIGN="LEFT" |
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| 237 | VALIGN="TOP" |
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| 238 | > |
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| 239 | >The RGB data is copied from the source. The source alpha channel and the per-surface alpha value are ignored. |
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| 240 | > |
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| 241 | > |
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| 242 | > |
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| 243 | > |
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| 244 | ALIGN="LEFT" |
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| 245 | VALIGN="TOP" |
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| 246 | >RGB->RGBA with |
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| 247 | CLASS="LITERAL" |
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| 248 | >SDL_SRCALPHA |
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| 249 | > |
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| 250 | > |
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| 251 | ALIGN="LEFT" |
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| 252 | VALIGN="TOP" |
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| 253 | > |
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| 254 | >The source is alpha-blended with the destination using the per-surface alpha |
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| 255 | value. If |
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| 256 | CLASS="LITERAL" |
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| 257 | >SDL_SRCCOLORKEY |
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| 258 | > is set, only the pixels not |
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| 259 | matching the colorkey value are copied. The alpha channel of the copied pixels |
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| 260 | is set to opaque. |
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| 261 | > |
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| 262 | > |
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| 263 | > |
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| 264 | > |
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| 265 | ALIGN="LEFT" |
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| 266 | VALIGN="TOP" |
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| 267 | >RGB->RGBA without |
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| 268 | CLASS="LITERAL" |
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| 269 | >SDL_SRCALPHA |
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| 270 | > |
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| 271 | > |
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| 272 | ALIGN="LEFT" |
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| 273 | VALIGN="TOP" |
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| 274 | > |
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| 275 | >The RGB data is copied from the source and the alpha value of the copied pixels |
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| 276 | is set to opaque. If |
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| 277 | CLASS="LITERAL" |
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| 278 | >SDL_SRCCOLORKEY |
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| 279 | > is set, only the pixels |
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| 280 | not matching the colorkey value are copied. |
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| 281 | > |
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| 282 | > |
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| 283 | > |
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| 284 | > |
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| 285 | ALIGN="LEFT" |
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| 286 | VALIGN="TOP" |
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| 287 | >RGBA->RGBA with |
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| 288 | CLASS="LITERAL" |
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| 289 | >SDL_SRCALPHA |
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| 290 | > |
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| 291 | > |
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| 292 | ALIGN="LEFT" |
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| 293 | VALIGN="TOP" |
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| 294 | > |
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| 295 | >The source is alpha-blended with the destination using the source alpha |
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| 296 | channel. The alpha channel in the destination surface is left untouched. |
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| 297 | |||
| 298 | CLASS="LITERAL" |
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| 299 | >SDL_SRCCOLORKEY |
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| 300 | > is ignored. |
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| 301 | > |
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| 302 | > |
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| 303 | > |
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| 304 | > |
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| 305 | ALIGN="LEFT" |
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| 306 | VALIGN="TOP" |
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| 307 | >RGBA->RGBA without |
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| 308 | CLASS="LITERAL" |
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| 309 | >SDL_SRCALPHA |
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| 310 | > |
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| 311 | > |
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| 312 | ALIGN="LEFT" |
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| 313 | VALIGN="TOP" |
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| 314 | > |
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| 315 | >The RGBA data is copied to the destination surface. If |
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| 316 | CLASS="LITERAL" |
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| 317 | >SDL_SRCCOLORKEY |
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| 318 | > is set, only the pixels not matching the colorkey value are copied. |
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| 319 | > |
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| 320 | > |
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| 321 | > |
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| 322 | > |
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| 323 | ALIGN="LEFT" |
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| 324 | VALIGN="TOP" |
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| 325 | >RGB->RGB with |
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| 326 | CLASS="LITERAL" |
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| 327 | >SDL_SRCALPHA |
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| 328 | > |
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| 329 | > |
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| 330 | ALIGN="LEFT" |
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| 331 | VALIGN="TOP" |
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| 332 | > |
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| 333 | >The source is alpha-blended with the destination using the per-surface alpha value. If |
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| 334 | CLASS="LITERAL" |
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| 335 | >SDL_SRCCOLORKEY |
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| 336 | > is set, only the pixels not matching the colorkey value are copied. |
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| 337 | > |
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| 338 | > |
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| 339 | > |
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| 340 | > |
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| 341 | ALIGN="LEFT" |
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| 342 | VALIGN="TOP" |
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| 343 | >RGB->RGB without |
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| 344 | CLASS="LITERAL" |
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| 345 | >SDL_SRCALPHA |
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| 346 | > |
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| 347 | > |
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| 348 | ALIGN="LEFT" |
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| 349 | VALIGN="TOP" |
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| 350 | > |
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| 351 | >The RGB data is copied from the source. If |
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| 352 | CLASS="LITERAL" |
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| 353 | >SDL_SRCCOLORKEY |
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| 354 | > is set, only the pixels not matching the colorkey value are copied. |
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| 355 | > |
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| 356 | > |
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| 357 | > |
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| 358 | > |
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| 359 | > |
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| 360 | > |
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| 361 | > |
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| 362 | > |
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| 363 | CLASS="NOTE" |
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| 364 | > |
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| 365 | CLASS="NOTE" |
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| 366 | > |
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| 367 | > |
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| 368 | >Note: |
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| 369 | > Note that RGBA->RGBA blits (with SDL_SRCALPHA set) keep the alpha |
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| 370 | of the destination surface. This means that you cannot compose two arbitrary |
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| 371 | RGBA surfaces this way and get the result you would expect from "overlaying" |
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| 372 | them; the destination alpha will work as a mask. |
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| 373 | > |
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| 374 | >Also note that per-pixel and per-surface alpha cannot be combined; |
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| 375 | the per-pixel alpha is always used if available |
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| 376 | > |
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| 377 | > |
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| 378 | > |
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| 379 | > |
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| 380 | CLASS="REFSECT1" |
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| 381 | > |
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| 382 | NAME="AEN1764" |
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| 383 | > |
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| 384 | > |
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| 385 | >Return Value |
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| 386 | > |
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| 387 | >This function returns |
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| 388 | CLASS="RETURNVALUE" |
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| 389 | >0 |
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| 390 | >, or |
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| 391 | |||
| 392 | CLASS="RETURNVALUE" |
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| 393 | >-1 |
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| 394 | > if there was an error. |
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| 395 | > |
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| 396 | > |
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| 397 | CLASS="REFSECT1" |
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| 398 | > |
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| 399 | NAME="AEN1769" |
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| 400 | > |
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| 401 | > |
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| 402 | >See Also |
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| 403 | > |
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| 404 | > |
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| 405 | HREF="sdlmaprgba.html" |
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| 406 | > |
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| 407 | CLASS="FUNCTION" |
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| 408 | >SDL_MapRGBA |
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| 409 | > |
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| 410 | >, |
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| 411 | |||
| 412 | HREF="sdlgetrgba.html" |
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| 413 | > |
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| 414 | CLASS="FUNCTION" |
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| 415 | >SDL_GetRGBA |
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| 416 | > |
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| 417 | >, |
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| 418 | |||
| 419 | HREF="sdldisplayformatalpha.html" |
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| 420 | > |
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| 421 | CLASS="FUNCTION" |
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| 422 | >SDL_DisplayFormatAlpha |
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| 423 | > |
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| 424 | >, |
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| 425 | |||
| 426 | HREF="sdlblitsurface.html" |
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| 427 | > |
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| 428 | CLASS="FUNCTION" |
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| 429 | >SDL_BlitSurface |
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| 430 | > |
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| 431 | > |
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| 432 | > |
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| 433 | > |
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| 434 | CLASS="NAVFOOTER" |
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| 435 | > |
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| 436 | ALIGN="LEFT" |
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| 437 | WIDTH="100%"> |
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| 438 | WIDTH="100%" |
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| 439 | BORDER="0" |
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| 440 | CELLPADDING="0" |
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| 441 | CELLSPACING="0" |
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| 442 | > |
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| 443 | > |
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| 444 | WIDTH="33%" |
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| 445 | ALIGN="left" |
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| 446 | VALIGN="top" |
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| 447 | > |
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| 448 | HREF="sdlsetcolorkey.html" |
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| 449 | >Prev |
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| 450 | > |
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| 451 | > |
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| 452 | WIDTH="34%" |
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| 453 | ALIGN="center" |
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| 454 | VALIGN="top" |
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| 455 | > |
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| 456 | HREF="index.html" |
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| 457 | >Home |
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| 458 | > |
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| 459 | > |
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| 460 | WIDTH="33%" |
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| 461 | ALIGN="right" |
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| 462 | VALIGN="top" |
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| 463 | > |
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| 464 | HREF="sdlsetcliprect.html" |
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| 465 | >Next |
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| 466 | > |
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| 467 | > |
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| 468 | > |
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| 469 | > |
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| 470 | WIDTH="33%" |
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| 471 | ALIGN="left" |
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| 472 | VALIGN="top" |
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| 473 | >SDL_SetColorKey |
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| 474 | > |
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| 475 | WIDTH="34%" |
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| 476 | ALIGN="center" |
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| 477 | VALIGN="top" |
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| 478 | > |
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| 479 | HREF="video.html" |
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| 480 | >Up |
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| 482 | > |
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| 483 | WIDTH="33%" |
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| 484 | ALIGN="right" |
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| 485 | VALIGN="top" |
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| 486 | >SDL_SetClipRect |
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| 487 | > |
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| 488 | > |
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| 489 | > |
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| 490 | > |
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| 491 | > |
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| 492 | > |