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| 5131 | clevermous | 1 | |
| 2 | > |
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| 3 | > |
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| 4 | >SDL_PixelFormat |
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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_Palette" |
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| 17 | HREF="sdlpalette.html"> |
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| 18 | REL="NEXT" |
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| 19 | TITLE="SDL_Surface" |
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| 20 | HREF="sdlsurface.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="sdlpalette.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="sdlsurface.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="SDLPIXELFORMAT" |
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| 71 | >SDL_PixelFormat |
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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="AEN2756" |
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| 77 | > |
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| 78 | > |
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| 79 | >Name |
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| 80 | >SDL_PixelFormat -- Stores surface format information |
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| 81 | > |
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| 82 | CLASS="REFSECT1" |
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| 83 | > |
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| 84 | NAME="AEN2759" |
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| 85 | > |
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| 86 | > |
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| 87 | >Structure Definition |
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| 88 | > |
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| 89 | CLASS="PROGRAMLISTING" |
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| 90 | >typedef struct{ |
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| 91 | SDL_Palette *palette; |
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| 92 | Uint8 BitsPerPixel; |
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| 93 | Uint8 BytesPerPixel; |
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| 94 | Uint32 Rmask, Gmask, Bmask, Amask; |
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| 95 | Uint8 Rshift, Gshift, Bshift, Ashift; |
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| 96 | Uint8 Rloss, Gloss, Bloss, Aloss; |
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| 97 | Uint32 colorkey; |
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| 98 | Uint8 alpha; |
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| 99 | } SDL_PixelFormat; |
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| 100 | > |
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| 101 | > |
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| 102 | CLASS="REFSECT1" |
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| 103 | > |
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| 104 | NAME="AEN2762" |
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| 105 | > |
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| 106 | > |
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| 107 | >Structure Data |
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| 108 | > |
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| 109 | CLASS="INFORMALTABLE" |
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| 110 | > |
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| 111 | NAME="AEN2764" |
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| 112 | > |
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| 113 | > |
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| 114 | > |
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| 115 | > |
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| 116 | BORDER="0" |
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| 117 | CLASS="CALSTABLE" |
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| 118 | > |
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| 119 | > |
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| 120 | > |
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| 121 | ALIGN="LEFT" |
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| 122 | VALIGN="TOP" |
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| 123 | > |
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| 124 | CLASS="STRUCTFIELD" |
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| 125 | > |
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| 126 | >palette |
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| 127 | > |
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| 128 | > |
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| 129 | > |
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| 130 | ALIGN="LEFT" |
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| 131 | VALIGN="TOP" |
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| 132 | >Pointer to the |
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| 133 | HREF="sdlpalette.html" |
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| 134 | >palette |
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| 135 | >, or |
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| 136 | CLASS="LITERAL" |
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| 137 | >NULL |
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| 138 | > if the |
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| 139 | CLASS="STRUCTFIELD" |
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| 140 | > |
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| 141 | >BitsPerPixel |
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| 142 | > |
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| 143 | >>8 |
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| 144 | > |
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| 145 | > |
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| 146 | > |
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| 147 | ALIGN="LEFT" |
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| 148 | VALIGN="TOP" |
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| 149 | > |
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| 150 | CLASS="STRUCTFIELD" |
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| 151 | > |
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| 152 | >BitsPerPixel |
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| 153 | > |
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| 154 | > |
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| 155 | > |
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| 156 | ALIGN="LEFT" |
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| 157 | VALIGN="TOP" |
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| 158 | >The number of bits used to represent each pixel in a surface. Usually 8, 16, 24 or 32. |
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| 159 | > |
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| 160 | > |
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| 161 | > |
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| 162 | ALIGN="LEFT" |
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| 163 | VALIGN="TOP" |
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| 164 | > |
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| 165 | CLASS="STRUCTFIELD" |
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| 166 | > |
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| 167 | >BytesPerPixel |
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| 168 | > |
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| 169 | > |
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| 170 | > |
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| 171 | ALIGN="LEFT" |
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| 172 | VALIGN="TOP" |
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| 173 | >The number of bytes used to represent each pixel in a surface. Usually one to four. |
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| 174 | > |
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| 175 | > |
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| 176 | > |
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| 177 | ALIGN="LEFT" |
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| 178 | VALIGN="TOP" |
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| 179 | > |
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| 180 | CLASS="STRUCTFIELD" |
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| 181 | > |
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| 182 | >[RGBA]mask |
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| 183 | > |
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| 184 | > |
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| 185 | > |
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| 186 | ALIGN="LEFT" |
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| 187 | VALIGN="TOP" |
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| 188 | >Binary mask used to retrieve individual color values |
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| 189 | > |
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| 190 | > |
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| 191 | > |
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| 192 | ALIGN="LEFT" |
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| 193 | VALIGN="TOP" |
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| 194 | > |
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| 195 | CLASS="STRUCTFIELD" |
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| 196 | > |
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| 197 | >[RGBA]loss |
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| 198 | > |
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| 199 | > |
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| 200 | > |
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| 201 | ALIGN="LEFT" |
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| 202 | VALIGN="TOP" |
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| 203 | >Precision loss of each color component (2 |
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| 204 | >[RGBA]loss |
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| 205 | >) |
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| 206 | > |
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| 207 | > |
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| 208 | > |
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| 209 | ALIGN="LEFT" |
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| 210 | VALIGN="TOP" |
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| 211 | > |
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| 212 | CLASS="STRUCTFIELD" |
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| 213 | > |
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| 214 | >[RGBA]shift |
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| 215 | > |
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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 | >Binary left shift of each color component in the pixel value |
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| 221 | > |
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| 222 | > |
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| 223 | > |
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| 224 | ALIGN="LEFT" |
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| 225 | VALIGN="TOP" |
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| 226 | > |
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| 227 | CLASS="STRUCTFIELD" |
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| 228 | > |
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| 229 | >colorkey |
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| 230 | > |
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| 231 | > |
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| 232 | > |
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| 233 | ALIGN="LEFT" |
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| 234 | VALIGN="TOP" |
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| 235 | >Pixel value of transparent pixels |
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| 236 | > |
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| 237 | > |
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| 238 | > |
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| 239 | ALIGN="LEFT" |
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| 240 | VALIGN="TOP" |
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| 241 | > |
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| 242 | CLASS="STRUCTFIELD" |
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| 243 | > |
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| 244 | >alpha |
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| 245 | > |
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| 246 | > |
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| 247 | > |
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| 248 | ALIGN="LEFT" |
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| 249 | VALIGN="TOP" |
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| 250 | >Overall surface alpha value |
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| 251 | > |
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| 252 | > |
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| 253 | > |
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| 254 | > |
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| 255 | > |
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| 256 | > |
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| 257 | > |
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| 258 | > |
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| 259 | CLASS="REFSECT1" |
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| 260 | > |
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| 261 | NAME="AEN2803" |
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| 262 | > |
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| 263 | > |
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| 264 | >Description |
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| 265 | > |
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| 266 | >A |
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| 267 | CLASS="STRUCTNAME" |
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| 268 | >SDL_PixelFormat |
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| 269 | > describes the format of the pixel data stored at the |
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| 270 | CLASS="STRUCTFIELD" |
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| 271 | > |
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| 272 | >pixels |
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| 273 | > |
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| 274 | > field of a |
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| 275 | HREF="sdlsurface.html" |
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| 276 | > |
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| 277 | CLASS="STRUCTNAME" |
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| 278 | >SDL_Surface |
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| 279 | > |
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| 280 | >. Every surface stores a |
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| 281 | CLASS="STRUCTNAME" |
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| 282 | >SDL_PixelFormat |
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| 283 | > in the |
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| 284 | CLASS="STRUCTFIELD" |
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| 285 | > |
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| 286 | >format |
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| 287 | > |
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| 288 | > field. |
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| 289 | > |
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| 290 | >If you wish to do pixel level modifications on a surface, then understanding how SDL stores its color information is essential. |
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| 291 | > |
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| 292 | >8-bit pixel formats are the easiest to understand. Since its an 8-bit format, we have 8 |
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| 293 | CLASS="STRUCTFIELD" |
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| 294 | > |
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| 295 | >BitsPerPixel |
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| 296 | > |
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| 297 | > and 1 |
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| 298 | CLASS="STRUCTFIELD" |
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| 299 | > |
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| 300 | >BytesPerPixel |
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| 301 | > |
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| 302 | >. Since |
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| 303 | CLASS="STRUCTFIELD" |
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| 304 | > |
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| 305 | >BytesPerPixel |
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| 306 | > |
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| 307 | > is 1, all pixels are represented by a Uint8 which contains an index into |
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| 308 | CLASS="STRUCTFIELD" |
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| 309 | > |
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| 310 | >palette |
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| 311 | > |
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| 312 | >-> |
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| 313 | CLASS="STRUCTFIELD" |
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| 314 | > |
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| 315 | >colors |
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| 316 | > |
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| 317 | >. So, to determine the color of a pixel in a 8-bit surface: we read the color index from |
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| 318 | CLASS="STRUCTNAME" |
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| 319 | >surface |
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| 320 | >-> |
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| 321 | CLASS="STRUCTFIELD" |
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| 322 | > |
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| 323 | >pixels |
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| 324 | > |
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| 325 | > and we use that index to read the |
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| 326 | HREF="sdlcolor.html" |
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| 327 | > |
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| 328 | CLASS="STRUCTNAME" |
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| 329 | >SDL_Color |
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| 330 | > |
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| 331 | > structure from |
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| 332 | CLASS="STRUCTNAME" |
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| 333 | >surface |
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| 334 | >-> |
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| 335 | CLASS="STRUCTFIELD" |
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| 336 | > |
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| 337 | >format |
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| 338 | > |
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| 339 | >-> |
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| 340 | CLASS="STRUCTFIELD" |
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| 341 | > |
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| 342 | >palette |
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| 343 | > |
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| 344 | >-> |
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| 345 | CLASS="STRUCTFIELD" |
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| 346 | > |
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| 347 | >colors |
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| 348 | > |
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| 349 | >. Like so: |
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| 350 | |||
| 351 | CLASS="PROGRAMLISTING" |
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| 352 | >SDL_Surface *surface; |
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| 353 | SDL_PixelFormat *fmt; |
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| 354 | SDL_Color *color; |
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| 355 | Uint8 index; |
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| 356 | |||
| 357 | . |
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| 358 | . |
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| 359 | |||
| 360 | /* Create surface */ |
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| 361 | . |
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| 362 | . |
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| 363 | fmt=surface->format; |
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| 364 | |||
| 365 | /* Check the bitdepth of the surface */ |
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| 366 | if(fmt->BitsPerPixel!=8){ |
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| 367 | fprintf(stderr, "Not an 8-bit surface.\n"); |
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| 368 | return(-1); |
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| 369 | } |
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| 370 | |||
| 371 | /* Lock the surface */ |
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| 372 | SDL_LockSurface(surface); |
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| 373 | |||
| 374 | /* Get the topleft pixel */ |
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| 375 | index=*(Uint8 *)surface->pixels; |
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| 376 | color=fmt->palette->colors[index]; |
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| 377 | |||
| 378 | /* Unlock the surface */ |
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| 379 | SDL_UnlockSurface(surface); |
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| 380 | printf("Pixel Color-> Red: %d, Green: %d, Blue: %d. Index: %d\n", |
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| 381 | color->r, color->g, color->b, index); |
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| 382 | . |
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| 383 | . |
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| 384 | > |
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| 385 | > |
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| 386 | >Pixel formats above 8-bit are an entirely different experience. They are |
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| 387 | considered to be "TrueColor" formats and the color information is stored in the |
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| 388 | pixels themselves, not in a palette. The mask, shift and loss fields tell us |
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| 389 | how the color information is encoded. The mask fields allow us to isolate each |
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| 390 | color component, the shift fields tell us the number of bits to the right of |
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| 391 | each component in the pixel value and the loss fields tell us the number of |
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| 392 | bits lost from each component when packing 8-bit color component in a pixel. |
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| 393 | |||
| 394 | CLASS="PROGRAMLISTING" |
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| 395 | >/* Extracting color components from a 32-bit color value */ |
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| 396 | SDL_PixelFormat *fmt; |
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| 397 | SDL_Surface *surface; |
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| 398 | Uint32 temp, pixel; |
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| 399 | Uint8 red, green, blue, alpha; |
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| 400 | . |
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| 401 | . |
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| 402 | . |
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| 403 | fmt=surface->format; |
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| 404 | SDL_LockSurface(surface); |
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| 405 | pixel=*((Uint32*)surface->pixels); |
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| 406 | SDL_UnlockSurface(surface); |
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| 407 | |||
| 408 | /* Get Red component */ |
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| 409 | temp=pixel&fmt->Rmask; /* Isolate red component */ |
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| 410 | temp=temp>>fmt->Rshift;/* Shift it down to 8-bit */ |
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| 411 | temp=temp<<fmt->Rloss; /* Expand to a full 8-bit number */ |
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| 412 | red=(Uint8)temp; |
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| 413 | |||
| 414 | /* Get Green component */ |
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| 415 | temp=pixel&fmt->Gmask; /* Isolate green component */ |
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| 416 | temp=temp>>fmt->Gshift;/* Shift it down to 8-bit */ |
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| 417 | temp=temp<<fmt->Gloss; /* Expand to a full 8-bit number */ |
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| 418 | green=(Uint8)temp; |
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| 419 | |||
| 420 | /* Get Blue component */ |
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| 421 | temp=pixel&fmt->Bmask; /* Isolate blue component */ |
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| 422 | temp=temp>>fmt->Bshift;/* Shift it down to 8-bit */ |
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| 423 | temp=temp<<fmt->Bloss; /* Expand to a full 8-bit number */ |
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| 424 | blue=(Uint8)temp; |
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| 425 | |||
| 426 | /* Get Alpha component */ |
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| 427 | temp=pixel&fmt->Amask; /* Isolate alpha component */ |
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| 428 | temp=temp>>fmt->Ashift;/* Shift it down to 8-bit */ |
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| 429 | temp=temp<<fmt->Aloss; /* Expand to a full 8-bit number */ |
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| 430 | alpha=(Uint8)temp; |
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| 431 | |||
| 432 | printf("Pixel Color -> R: %d, G: %d, B: %d, A: %d\n", red, green, blue, alpha); |
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| 433 | . |
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| 434 | . |
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| 435 | . |
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| 436 | > |
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| 437 | > |
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| 438 | > |
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| 439 | CLASS="REFSECT1" |
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| 440 | > |
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| 441 | NAME="AEN2830" |
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| 442 | > |
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| 443 | > |
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| 444 | >See Also |
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| 445 | > |
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| 446 | > |
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| 447 | HREF="sdlsurface.html" |
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| 448 | > |
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| 449 | CLASS="STRUCTNAME" |
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| 450 | >SDL_Surface |
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| 451 | > |
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| 452 | >, |
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| 453 | |||
| 454 | HREF="sdlmaprgb.html" |
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| 455 | > |
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| 456 | CLASS="FUNCTION" |
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| 457 | >SDL_MapRGB |
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| 458 | > |
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| 459 | > |
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| 460 | > |
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| 461 | > |
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| 462 | CLASS="NAVFOOTER" |
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| 463 | > |
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| 464 | ALIGN="LEFT" |
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| 465 | WIDTH="100%"> |
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| 466 | WIDTH="100%" |
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| 467 | BORDER="0" |
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| 468 | CELLPADDING="0" |
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| 469 | CELLSPACING="0" |
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| 470 | > |
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| 471 | > |
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| 472 | WIDTH="33%" |
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| 473 | ALIGN="left" |
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| 474 | VALIGN="top" |
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| 475 | > |
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| 476 | HREF="sdlpalette.html" |
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| 477 | >Prev |
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| 478 | > |
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| 479 | > |
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| 480 | WIDTH="34%" |
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| 481 | ALIGN="center" |
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| 482 | VALIGN="top" |
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| 483 | > |
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| 484 | HREF="index.html" |
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| 485 | >Home |
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| 486 | > |
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| 487 | > |
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| 488 | WIDTH="33%" |
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| 489 | ALIGN="right" |
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| 490 | VALIGN="top" |
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| 491 | > |
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| 492 | HREF="sdlsurface.html" |
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| 493 | >Next |
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| 494 | > |
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| 495 | > |
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| 496 | > |
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| 497 | > |
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| 498 | WIDTH="33%" |
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| 499 | ALIGN="left" |
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| 500 | VALIGN="top" |
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| 501 | >SDL_Palette |
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| 502 | > |
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| 503 | WIDTH="34%" |
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| 504 | ALIGN="center" |
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| 505 | VALIGN="top" |
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| 506 | > |
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| 507 | HREF="video.html" |
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| 508 | >Up |
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| 509 | > |
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| 510 | > |
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| 511 | WIDTH="33%" |
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| 512 | ALIGN="right" |
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| 513 | VALIGN="top" |
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| 514 | >SDL_Surface |
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| 515 | > |
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| 516 | > |
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| 517 | > |
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| 518 | > |
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| 519 | > |
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| 520 | > |