Mercurial > sdl-ios-xcode
annotate docs/html/sdlpixelformat.html @ 320:66f815c147ed
Date: Thu, 28 Mar 2002 09:20:03 +0200
From: "Mike Gorchak" <mike@malva.ua>
Subject: New QNX patch.
Hi !
1. Removed warning (possible bug) with invalid type, passing to the function
in ph_WarpedMotion.
2. Rewritten handler of Ph_WM_RESIZE message, now works, but buggy (old
handler doesn't work at all).
3. Added stub handler for Ph_WM_MAX (maximize) message.
4. Added more #ifdef HAVE_OPENGL to disable OpenGL stuff when it not needed.
5. Added support for SDL_NOFRAME and SDL_RESIZABLE flags (in OpenGL windows
too).
6. Added cosmetic changes, if no SDL_RESIZABLE flag defined, disable resize
handlers in window border and maximize button at caption.
7. Fixed my bug with invalid arguments count passed to PtCreateWidget call.
8. Fixed some palette problems.
9. Updated README.QNX file.
And I changed testgl.c test application:
10. Added in testgl.c application support for SDL_NOFRAME flag and
option -noframe.
| author | Sam Lantinga <slouken@libsdl.org> |
|---|---|
| date | Thu, 28 Mar 2002 16:20:10 +0000 |
| parents | e5bc29de3f0a |
| children | 355632dca928 |
| rev | line source |
|---|---|
| 0 | 1 <HTML |
| 2 ><HEAD | |
| 3 ><TITLE | |
| 4 >SDL_PixelFormat</TITLE | |
| 5 ><META | |
| 6 NAME="GENERATOR" | |
|
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7 CONTENT="Modular DocBook HTML Stylesheet Version 1.64 |
| 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_Palette" | |
| 17 HREF="sdlpalette.html"><LINK | |
| 18 REL="NEXT" | |
| 19 TITLE="SDL_Surface" | |
| 20 HREF="sdlsurface.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 | |
| 31 WIDTH="100%" | |
| 32 BORDER="0" | |
| 33 CELLPADDING="0" | |
| 34 CELLSPACING="0" | |
| 35 ><TR | |
| 36 ><TH | |
| 37 COLSPAN="3" | |
| 38 ALIGN="center" | |
| 39 >SDL Library Documentation</TH | |
| 40 ></TR | |
| 41 ><TR | |
| 42 ><TD | |
| 43 WIDTH="10%" | |
| 44 ALIGN="left" | |
| 45 VALIGN="bottom" | |
| 46 ><A | |
| 47 HREF="sdlpalette.html" | |
| 48 >Prev</A | |
| 49 ></TD | |
| 50 ><TD | |
| 51 WIDTH="80%" | |
| 52 ALIGN="center" | |
| 53 VALIGN="bottom" | |
| 54 ></TD | |
| 55 ><TD | |
| 56 WIDTH="10%" | |
| 57 ALIGN="right" | |
| 58 VALIGN="bottom" | |
| 59 ><A | |
| 60 HREF="sdlsurface.html" | |
| 61 >Next</A | |
| 62 ></TD | |
| 63 ></TR | |
| 64 ></TABLE | |
| 65 ><HR | |
| 66 ALIGN="LEFT" | |
| 67 WIDTH="100%"></DIV | |
| 68 ><H1 | |
| 69 ><A | |
| 70 NAME="SDLPIXELFORMAT" | |
| 71 >SDL_PixelFormat</A | |
| 72 ></H1 | |
| 73 ><DIV | |
| 74 CLASS="REFNAMEDIV" | |
| 75 ><A | |
|
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76 NAME="AEN2794" |
| 0 | 77 ></A |
| 78 ><H2 | |
| 79 >Name</H2 | |
| 80 >SDL_PixelFormat -- Stores surface format information</DIV | |
| 81 ><DIV | |
| 82 CLASS="REFSECT1" | |
| 83 ><A | |
|
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84 NAME="AEN2797" |
| 0 | 85 ></A |
| 86 ><H2 | |
| 87 >Structure Definition</H2 | |
| 88 ><PRE | |
| 89 CLASS="PROGRAMLISTING" | |
| 90 >typedef struct{ | |
| 91 SDL_Palette *palette; | |
| 92 Uint8 BitsPerPixel; | |
| 93 Uint8 BytesPerPixel; | |
| 94 Uint32 Rmask, Gmask, Bmask, Amask; | |
| 95 Uint8 Rshift, Gshift, Bshift, Ashift; | |
| 96 Uint8 Rloss, Gloss, Bloss, Aloss; | |
| 97 Uint32 colorkey; | |
| 98 Uint8 alpha; | |
| 99 } SDL_PixelFormat;</PRE | |
| 100 ></DIV | |
| 101 ><DIV | |
| 102 CLASS="REFSECT1" | |
| 103 ><A | |
|
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104 NAME="AEN2800" |
| 0 | 105 ></A |
| 106 ><H2 | |
| 107 >Structure Data</H2 | |
| 108 ><DIV | |
| 109 CLASS="INFORMALTABLE" | |
| 110 ><A | |
|
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111 NAME="AEN2802" |
| 0 | 112 ></A |
| 113 ><P | |
| 114 ></P | |
| 115 ><TABLE | |
| 116 BORDER="0" | |
| 117 CLASS="CALSTABLE" | |
| 118 ><TBODY | |
| 119 ><TR | |
| 120 ><TD | |
| 121 ALIGN="LEFT" | |
| 122 VALIGN="TOP" | |
| 123 ><TT | |
| 124 CLASS="STRUCTFIELD" | |
| 125 ><I | |
| 126 >palette</I | |
| 127 ></TT | |
| 128 ></TD | |
| 129 ><TD | |
| 130 ALIGN="LEFT" | |
| 131 VALIGN="TOP" | |
| 132 >Pointer to the <A | |
| 133 HREF="sdlpalette.html" | |
| 134 >palette</A | |
| 135 >, or <TT | |
| 136 CLASS="LITERAL" | |
| 137 >NULL</TT | |
| 138 > if the <TT | |
| 139 CLASS="STRUCTFIELD" | |
| 140 ><I | |
| 141 >BitsPerPixel</I | |
| 142 ></TT | |
| 143 >>8</TD | |
| 144 ></TR | |
| 145 ><TR | |
| 146 ><TD | |
| 147 ALIGN="LEFT" | |
| 148 VALIGN="TOP" | |
| 149 ><TT | |
| 150 CLASS="STRUCTFIELD" | |
| 151 ><I | |
| 152 >BitsPerPixel</I | |
| 153 ></TT | |
| 154 ></TD | |
| 155 ><TD | |
| 156 ALIGN="LEFT" | |
| 157 VALIGN="TOP" | |
| 158 >The number of bits used to represent each pixel in a surface. Usually 8, 16, 24 or 32.</TD | |
| 159 ></TR | |
| 160 ><TR | |
| 161 ><TD | |
| 162 ALIGN="LEFT" | |
| 163 VALIGN="TOP" | |
| 164 ><TT | |
| 165 CLASS="STRUCTFIELD" | |
| 166 ><I | |
| 167 >BytesPerPixel</I | |
| 168 ></TT | |
| 169 ></TD | |
| 170 ><TD | |
| 171 ALIGN="LEFT" | |
| 172 VALIGN="TOP" | |
| 173 >The number of bytes used to represent each pixel in a surface. Usually one to four.</TD | |
| 174 ></TR | |
| 175 ><TR | |
| 176 ><TD | |
| 177 ALIGN="LEFT" | |
| 178 VALIGN="TOP" | |
| 179 ><TT | |
| 180 CLASS="STRUCTFIELD" | |
| 181 ><I | |
| 182 >[RGBA]mask</I | |
| 183 ></TT | |
| 184 ></TD | |
| 185 ><TD | |
| 186 ALIGN="LEFT" | |
| 187 VALIGN="TOP" | |
| 188 >Binary mask used to retrieve individual color values</TD | |
| 189 ></TR | |
| 190 ><TR | |
| 191 ><TD | |
| 192 ALIGN="LEFT" | |
| 193 VALIGN="TOP" | |
| 194 ><TT | |
| 195 CLASS="STRUCTFIELD" | |
| 196 ><I | |
| 197 >[RGBA]loss</I | |
| 198 ></TT | |
| 199 ></TD | |
| 200 ><TD | |
| 201 ALIGN="LEFT" | |
| 202 VALIGN="TOP" | |
| 203 >Precision loss of each color component (2<SUP | |
| 204 >[RGBA]loss</SUP | |
| 205 >)</TD | |
| 206 ></TR | |
| 207 ><TR | |
| 208 ><TD | |
| 209 ALIGN="LEFT" | |
| 210 VALIGN="TOP" | |
| 211 ><TT | |
| 212 CLASS="STRUCTFIELD" | |
| 213 ><I | |
| 214 >[RGBA]shift</I | |
| 215 ></TT | |
| 216 ></TD | |
| 217 ><TD | |
| 218 ALIGN="LEFT" | |
| 219 VALIGN="TOP" | |
| 220 >Binary left shift of each color component in the pixel value</TD | |
| 221 ></TR | |
| 222 ><TR | |
| 223 ><TD | |
| 224 ALIGN="LEFT" | |
| 225 VALIGN="TOP" | |
| 226 ><TT | |
| 227 CLASS="STRUCTFIELD" | |
| 228 ><I | |
| 229 >colorkey</I | |
| 230 ></TT | |
| 231 ></TD | |
| 232 ><TD | |
| 233 ALIGN="LEFT" | |
| 234 VALIGN="TOP" | |
| 235 >Pixel value of transparent pixels</TD | |
| 236 ></TR | |
| 237 ><TR | |
| 238 ><TD | |
| 239 ALIGN="LEFT" | |
| 240 VALIGN="TOP" | |
| 241 ><TT | |
| 242 CLASS="STRUCTFIELD" | |
| 243 ><I | |
| 244 >alpha</I | |
| 245 ></TT | |
| 246 ></TD | |
| 247 ><TD | |
| 248 ALIGN="LEFT" | |
| 249 VALIGN="TOP" | |
| 250 >Overall surface alpha value</TD | |
| 251 ></TR | |
| 252 ></TBODY | |
| 253 ></TABLE | |
| 254 ><P | |
| 255 ></P | |
| 256 ></DIV | |
| 257 ></DIV | |
| 258 ><DIV | |
| 259 CLASS="REFSECT1" | |
| 260 ><A | |
|
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261 NAME="AEN2841" |
| 0 | 262 ></A |
| 263 ><H2 | |
| 264 >Description</H2 | |
| 265 ><P | |
| 266 >A <SPAN | |
| 267 CLASS="STRUCTNAME" | |
| 268 >SDL_PixelFormat</SPAN | |
| 269 > describes the format of the pixel data stored at the <TT | |
| 270 CLASS="STRUCTFIELD" | |
| 271 ><I | |
| 272 >pixels</I | |
| 273 ></TT | |
| 274 > field of a <A | |
| 275 HREF="sdlsurface.html" | |
| 276 ><SPAN | |
| 277 CLASS="STRUCTNAME" | |
| 278 >SDL_Surface</SPAN | |
| 279 ></A | |
| 280 >. Every surface stores a <SPAN | |
| 281 CLASS="STRUCTNAME" | |
| 282 >SDL_PixelFormat</SPAN | |
| 283 > in the <TT | |
| 284 CLASS="STRUCTFIELD" | |
| 285 ><I | |
| 286 >format</I | |
| 287 ></TT | |
| 288 > field.</P | |
| 289 ><P | |
| 290 >If you wish to do pixel level modifications on a surface, then understanding how SDL stores its color information is essential.</P | |
| 291 ><P | |
| 292 >8-bit pixel formats are the easiest to understand. Since its an 8-bit format, we have 8 <TT | |
| 293 CLASS="STRUCTFIELD" | |
| 294 ><I | |
| 295 >BitsPerPixel</I | |
| 296 ></TT | |
| 297 > and 1 <TT | |
| 298 CLASS="STRUCTFIELD" | |
| 299 ><I | |
| 300 >BytesPerPixel</I | |
| 301 ></TT | |
| 302 >. Since <TT | |
| 303 CLASS="STRUCTFIELD" | |
| 304 ><I | |
| 305 >BytesPerPixel</I | |
| 306 ></TT | |
| 307 > is 1, all pixels are represented by a Uint8 which contains an index into <TT | |
| 308 CLASS="STRUCTFIELD" | |
| 309 ><I | |
| 310 >palette</I | |
| 311 ></TT | |
| 312 >-><TT | |
| 313 CLASS="STRUCTFIELD" | |
| 314 ><I | |
| 315 >colors</I | |
| 316 ></TT | |
| 317 >. So, to determine the color of a pixel in a 8-bit surface: we read the color index from <SPAN | |
| 318 CLASS="STRUCTNAME" | |
| 319 >surface</SPAN | |
| 320 >-><TT | |
| 321 CLASS="STRUCTFIELD" | |
| 322 ><I | |
| 323 >pixels</I | |
| 324 ></TT | |
| 325 > and we use that index to read the <A | |
| 326 HREF="sdlcolor.html" | |
| 327 ><SPAN | |
| 328 CLASS="STRUCTNAME" | |
| 329 >SDL_Color</SPAN | |
| 330 ></A | |
| 331 > structure from <SPAN | |
| 332 CLASS="STRUCTNAME" | |
| 333 >surface</SPAN | |
| 334 >-><TT | |
| 335 CLASS="STRUCTFIELD" | |
| 336 ><I | |
| 337 >format</I | |
| 338 ></TT | |
| 339 >-><TT | |
| 340 CLASS="STRUCTFIELD" | |
| 341 ><I | |
| 342 >palette</I | |
| 343 ></TT | |
| 344 >-><TT | |
| 345 CLASS="STRUCTFIELD" | |
| 346 ><I | |
| 347 >colors</I | |
| 348 ></TT | |
| 349 >. Like so: | |
| 350 <PRE | |
| 351 CLASS="PROGRAMLISTING" | |
| 352 >SDL_Surface *surface; | |
| 353 SDL_PixelFormat *fmt; | |
| 354 SDL_Color *color; | |
| 355 Uint8 index; | |
| 356 | |
| 357 . | |
| 358 . | |
| 359 | |
| 360 /* Create surface */ | |
| 361 . | |
| 362 . | |
| 363 fmt=surface->format; | |
| 364 | |
| 365 /* Check the bitdepth of the surface */ | |
| 366 if(fmt->BitsPerPixel!=8){ | |
| 367 fprintf(stderr, "Not an 8-bit surface.\n"); | |
| 368 return(-1); | |
| 369 } | |
| 370 | |
| 371 /* Lock the surface */ | |
| 372 SDL_LockSurface(surface); | |
| 373 | |
| 374 /* Get the topleft pixel */ | |
| 375 index=*(Uint8 *)surface->pixels; | |
| 376 color=fmt->palette->colors[index]; | |
| 377 | |
| 378 /* Unlock the surface */ | |
| 379 SDL_UnlockSurface(surface); | |
| 380 printf("Pixel Color-> Red: %d, Green: %d, Blue: %d. Index: %d\n", | |
| 381 color->r, color->g, color->b, index); | |
| 382 . | |
| 383 .</PRE | |
| 384 ></P | |
| 385 ><P | |
|
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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. |
| 0 | 393 <PRE |
| 394 CLASS="PROGRAMLISTING" | |
| 395 >/* Extracting color components from a 32-bit color value */ | |
| 396 SDL_PixelFormat *fmt; | |
| 397 SDL_Surface *surface; | |
| 398 Uint32 temp, pixel; | |
| 399 Uint8 red, green, blue, alpha; | |
| 400 . | |
| 401 . | |
| 402 . | |
| 403 fmt=surface->format; | |
| 404 SDL_LockSurface(surface); | |
|
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405 pixel=*((Uint32*)surface->pixels); |
| 0 | 406 SDL_UnlockSurface(surface); |
| 407 | |
| 408 /* Get Red component */ | |
| 409 temp=pixel&fmt->Rmask; /* Isolate red component */ | |
| 410 temp=temp>>fmt->Rshift;/* Shift it down to 8-bit */ | |
| 411 temp=temp<<fmt->Rloss; /* Expand to a full 8-bit number */ | |
| 412 red=(Uint8)temp; | |
| 413 | |
| 414 /* Get Green component */ | |
| 415 temp=pixel&fmt->Gmask; /* Isolate green component */ | |
| 416 temp=temp>>fmt->Gshift;/* Shift it down to 8-bit */ | |
| 417 temp=temp<<fmt->Gloss; /* Expand to a full 8-bit number */ | |
| 418 green=(Uint8)temp; | |
| 419 | |
| 420 /* Get Blue component */ | |
| 421 temp=pixel&fmt->Bmask; /* Isolate blue component */ | |
| 422 temp=temp>>fmt->Bshift;/* Shift it down to 8-bit */ | |
| 423 temp=temp<<fmt->Bloss; /* Expand to a full 8-bit number */ | |
| 424 blue=(Uint8)temp; | |
| 425 | |
| 426 /* Get Alpha component */ | |
| 427 temp=pixel&fmt->Amask; /* Isolate alpha component */ | |
| 428 temp=temp>>fmt->Ashift;/* Shift it down to 8-bit */ | |
| 429 temp=temp<<fmt->Aloss; /* Expand to a full 8-bit number */ | |
| 430 alpha=(Uint8)temp; | |
| 431 | |
| 432 printf("Pixel Color -> R: %d, G: %d, B: %d, A: %d\n", red, green, blue, alpha); | |
| 433 . | |
| 434 . | |
| 435 .</PRE | |
| 436 ></P | |
| 437 ></DIV | |
| 438 ><DIV | |
| 439 CLASS="REFSECT1" | |
| 440 ><A | |
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441 NAME="AEN2868" |
| 0 | 442 ></A |
| 443 ><H2 | |
| 444 >See Also</H2 | |
| 445 ><P | |
| 446 ><A | |
| 447 HREF="sdlsurface.html" | |
| 448 ><SPAN | |
| 449 CLASS="STRUCTNAME" | |
| 450 >SDL_Surface</SPAN | |
| 451 ></A | |
| 452 >, | |
| 453 <A | |
| 454 HREF="sdlmaprgb.html" | |
| 455 ><TT | |
| 456 CLASS="FUNCTION" | |
| 457 >SDL_MapRGB</TT | |
| 458 ></A | |
| 459 ></P | |
| 460 ></DIV | |
| 461 ><DIV | |
| 462 CLASS="NAVFOOTER" | |
| 463 ><HR | |
| 464 ALIGN="LEFT" | |
| 465 WIDTH="100%"><TABLE | |
| 466 WIDTH="100%" | |
| 467 BORDER="0" | |
| 468 CELLPADDING="0" | |
| 469 CELLSPACING="0" | |
| 470 ><TR | |
| 471 ><TD | |
| 472 WIDTH="33%" | |
| 473 ALIGN="left" | |
| 474 VALIGN="top" | |
| 475 ><A | |
| 476 HREF="sdlpalette.html" | |
| 477 >Prev</A | |
| 478 ></TD | |
| 479 ><TD | |
| 480 WIDTH="34%" | |
| 481 ALIGN="center" | |
| 482 VALIGN="top" | |
| 483 ><A | |
| 484 HREF="index.html" | |
| 485 >Home</A | |
| 486 ></TD | |
| 487 ><TD | |
| 488 WIDTH="33%" | |
| 489 ALIGN="right" | |
| 490 VALIGN="top" | |
| 491 ><A | |
| 492 HREF="sdlsurface.html" | |
| 493 >Next</A | |
| 494 ></TD | |
| 495 ></TR | |
| 496 ><TR | |
| 497 ><TD | |
| 498 WIDTH="33%" | |
| 499 ALIGN="left" | |
| 500 VALIGN="top" | |
| 501 >SDL_Palette</TD | |
| 502 ><TD | |
| 503 WIDTH="34%" | |
| 504 ALIGN="center" | |
| 505 VALIGN="top" | |
| 506 ><A | |
| 507 HREF="video.html" | |
| 508 >Up</A | |
| 509 ></TD | |
| 510 ><TD | |
| 511 WIDTH="33%" | |
| 512 ALIGN="right" | |
| 513 VALIGN="top" | |
| 514 >SDL_Surface</TD | |
| 515 ></TR | |
| 516 ></TABLE | |
| 517 ></DIV | |
| 518 ></BODY | |
| 519 ></HTML | |
| 520 > |