docs/html/guidevideo.html

   1 <HTML
   2 ><HEAD
   3 ><TITLE
   4 >Graphics and Video</TITLE
   5 ><META
   6 NAME="GENERATOR"
   7 CONTENT="Modular DocBook HTML Stylesheet Version 1.76b+
   8 "><LINK
   9 REL="HOME"
  10 TITLE="SDL Library Documentation"
  11 HREF="index.html"><LINK
  12 REL="UP"
  13 TITLE="SDL Guide"
  14 HREF="guide.html"><LINK
  15 REL="PREVIOUS"
  16 TITLE="Initializing SDL"
  17 HREF="guidebasicsinit.html"><LINK
  18 REL="NEXT"
  19 TITLE="Using OpenGL With SDL"
  20 HREF="guidevideoopengl.html"></HEAD
  21 ><BODY
  22 CLASS="CHAPTER"
  23 BGCOLOR="#FFF8DC"
  24 TEXT="#000000"
  25 LINK="#0000ee"
  26 VLINK="#551a8b"
  27 ALINK="#ff0000"
  28 ><DIV
  29 CLASS="NAVHEADER"
  30 ><TABLE
  31 SUMMARY="Header navigation table"
  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="guidebasicsinit.html"
  49 ACCESSKEY="P"
  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="guidevideoopengl.html"
  63 ACCESSKEY="N"
  64 >Next</A
  65 ></TD
  66 ></TR
  67 ></TABLE
  68 ><HR
  69 ALIGN="LEFT"
  70 WIDTH="100%"></DIV
  71 ><DIV
  72 CLASS="CHAPTER"
  73 ><H1
  74 ><A
  75 NAME="GUIDEVIDEO"
  76 ></A
  77 >Chapter 2. Graphics and Video</H1
  78 ><DIV
  79 CLASS="TOC"
  80 ><DL
  81 ><DT
  82 ><B
  83 >Table of Contents</B
  84 ></DT
  85 ><DT
  86 ><A
  87 HREF="guidevideo.html#GUIDEVIDEOINTRO"
  88 >Introduction to SDL Video</A
  89 ></DT
  90 ><DT
  91 ><A
  92 HREF="guidevideoopengl.html"
  93 >Using OpenGL With SDL</A
  94 ></DT
  95 ></DL
  96 ></DIV
  97 ><DIV
  98 CLASS="SECT1"
  99 ><H1
 100 CLASS="SECT1"
 101 ><A
 102 NAME="GUIDEVIDEOINTRO"
 103 ></A
 104 >Introduction to SDL Video</H1
 105 ><P
 106 >Video is probably the most common thing that SDL is used for, and
 107 so it has the most complete subsystem. Here are a few
 108 examples to demonstrate the basics.</P
 109 ><DIV
 110 CLASS="SECT2"
 111 ><H2
 112 CLASS="SECT2"
 113 ><A
 114 NAME="AEN68"
 115 ></A
 116 >Initializing the Video Display</H2
 117 ><P
 118 >This is what almost all SDL programs have to do in one way or
 119 another.</P
 120 ><DIV
 121 CLASS="EXAMPLE"
 122 ><A
 123 NAME="AEN71"
 124 ></A
 125 ><P
 126 ><B
 127 >Example 2-1. Initializing the Video Display</B
 128 ></P
 129 ><PRE
 130 CLASS="PROGRAMLISTING"
 131 >    SDL_Surface *screen;
 132
 133     /* Initialize the SDL library */
 134     if( SDL_Init(SDL_INIT_VIDEO) &#60; 0 ) {
 135         fprintf(stderr,
 136                 "Couldn't initialize SDL: %s\n", SDL_GetError());
 137         exit(1);
 138     }
 139
 140     /* Clean up on exit */
 141     atexit(SDL_Quit);
 142
 143     /*
 144      * Initialize the display in a 640x480 8-bit palettized mode,
 145      * requesting a software surface
 146      */
 147     screen = SDL_SetVideoMode(640, 480, 8, SDL_SWSURFACE);
 148     if ( screen == NULL ) {
 149         fprintf(stderr, "Couldn't set 640x480x8 video mode: %s\n",
 150                         SDL_GetError());
 151         exit(1);
 152     }</PRE
 153 ></DIV
 154 ></DIV
 155 ><DIV
 156 CLASS="SECT2"
 157 ><H2
 158 CLASS="SECT2"
 159 ><A
 160 NAME="AEN74"
 161 ></A
 162 >Initializing the Best Video Mode</H2
 163 ><P
 164 >If you have a preference for a certain pixel depth but will accept any
 165 other, use SDL_SetVideoMode with SDL_ANYFORMAT as below. You can also
 166 use SDL_VideoModeOK() to find the native video mode that is closest to
 167 the mode you request.</P
 168 ><DIV
 169 CLASS="EXAMPLE"
 170 ><A
 171 NAME="AEN77"
 172 ></A
 173 ><P
 174 ><B
 175 >Example 2-2. Initializing the Best Video Mode</B
 176 ></P
 177 ><PRE
 178 CLASS="PROGRAMLISTING"
 179 >    /* Have a preference for 8-bit, but accept any depth */
 180     screen = SDL_SetVideoMode(640, 480, 8, SDL_SWSURFACE|SDL_ANYFORMAT);
 181     if ( screen == NULL ) {
 182         fprintf(stderr, "Couldn't set 640x480x8 video mode: %s\n",
 183                         SDL_GetError());
 184         exit(1);
 185     }
 186     printf("Set 640x480 at %d bits-per-pixel mode\n",
 187            screen-&#62;format-&#62;BitsPerPixel);</PRE
 188 ></DIV
 189 ></DIV
 190 ><DIV
 191 CLASS="SECT2"
 192 ><H2
 193 CLASS="SECT2"
 194 ><A
 195 NAME="AEN80"
 196 ></A
 197 >Loading and Displaying a BMP File</H2
 198 ><P
 199 >The following function loads and displays a BMP file given as
 200 argument, once SDL is initialised and a video mode has been set.</P
 201 ><DIV
 202 CLASS="EXAMPLE"
 203 ><A
 204 NAME="AEN83"
 205 ></A
 206 ><P
 207 ><B
 208 >Example 2-3. Loading and Displaying a BMP File</B
 209 ></P
 210 ><PRE
 211 CLASS="PROGRAMLISTING"
 212 >void display_bmp(char *file_name)
 213 {
 214     SDL_Surface *image;
 215
 216     /* Load the BMP file into a surface */
 217     image = SDL_LoadBMP(file_name);
 218     if (image == NULL) {
 219         fprintf(stderr, "Couldn't load %s: %s\n", file_name, SDL_GetError());
 220         return;
 221     }
 222
 223     /*
 224      * Palettized screen modes will have a default palette (a standard
 225      * 8*8*4 colour cube), but if the image is palettized as well we can
 226      * use that palette for a nicer colour matching
 227      */
 228     if (image-&#62;format-&#62;palette &#38;&#38; screen-&#62;format-&#62;palette) {
 229     SDL_SetColors(screen, image-&#62;format-&#62;palette-&#62;colors, 0,
 230                   image-&#62;format-&#62;palette-&#62;ncolors);
 231     }
 232
 233     /* Blit onto the screen surface */
 234     if(SDL_BlitSurface(image, NULL, screen, NULL) &#60; 0)
 235         fprintf(stderr, "BlitSurface error: %s\n", SDL_GetError());
 236
 237     SDL_UpdateRect(screen, 0, 0, image-&#62;w, image-&#62;h);
 238
 239     /* Free the allocated BMP surface */
 240     SDL_FreeSurface(image);
 241 }</PRE
 242 ></DIV
 243 ></DIV
 244 ><DIV
 245 CLASS="SECT2"
 246 ><H2
 247 CLASS="SECT2"
 248 ><A
 249 NAME="AEN86"
 250 ></A
 251 >Drawing Directly to the Display</H2
 252 ><P
 253 >The following two functions can be used to get and set single
 254 pixels of a surface. They are carefully written to work with any depth
 255 currently supported by SDL. Remember to lock the surface before
 256 calling them, and to unlock it before calling any other SDL
 257 functions.</P
 258 ><P
 259 >To convert between pixel values and their red, green, blue
 260 components, use SDL_GetRGB() and SDL_MapRGB().</P
 261 ><DIV
 262 CLASS="EXAMPLE"
 263 ><A
 264 NAME="AEN90"
 265 ></A
 266 ><P
 267 ><B
 268 >Example 2-4. getpixel()</B
 269 ></P
 270 ><PRE
 271 CLASS="PROGRAMLISTING"
 272 >/*
 273  * Return the pixel value at (x, y)
 274  * NOTE: The surface must be locked before calling this!
 275  */
 276 Uint32 getpixel(SDL_Surface *surface, int x, int y)
 277 {
 278     int bpp = surface-&#62;format-&#62;BytesPerPixel;
 279     /* Here p is the address to the pixel we want to retrieve */
 280     Uint8 *p = (Uint8 *)surface-&#62;pixels + y * surface-&#62;pitch + x * bpp;
 281
 282     switch(bpp) {
 283     case 1:
 284         return *p;
 285
 286     case 2:
 287         return *(Uint16 *)p;
 288
 289     case 3:
 290         if(SDL_BYTEORDER == SDL_BIG_ENDIAN)
 291             return p[0] &#60;&#60; 16 | p[1] &#60;&#60; 8 | p[2];
 292         else
 293             return p[0] | p[1] &#60;&#60; 8 | p[2] &#60;&#60; 16;
 294
 295     case 4:
 296         return *(Uint32 *)p;
 297
 298     default:
 299         return 0;       /* shouldn't happen, but avoids warnings */
 300     }
 301 }</PRE
 302 ></DIV
 303 ><DIV
 304 CLASS="EXAMPLE"
 305 ><A
 306 NAME="AEN93"
 307 ></A
 308 ><P
 309 ><B
 310 >Example 2-5. putpixel()</B
 311 ></P
 312 ><PRE
 313 CLASS="PROGRAMLISTING"
 314 >/*
 315  * Set the pixel at (x, y) to the given value
 316  * NOTE: The surface must be locked before calling this!
 317  */
 318 void putpixel(SDL_Surface *surface, int x, int y, Uint32 pixel)
 319 {
 320     int bpp = surface-&#62;format-&#62;BytesPerPixel;
 321     /* Here p is the address to the pixel we want to set */
 322     Uint8 *p = (Uint8 *)surface-&#62;pixels + y * surface-&#62;pitch + x * bpp;
 323
 324     switch(bpp) {
 325     case 1:
 326         *p = pixel;
 327         break;
 328
 329     case 2:
 330         *(Uint16 *)p = pixel;
 331         break;
 332
 333     case 3:
 334         if(SDL_BYTEORDER == SDL_BIG_ENDIAN) {
 335             p[0] = (pixel &#62;&#62; 16) &#38; 0xff;
 336             p[1] = (pixel &#62;&#62; 8) &#38; 0xff;
 337             p[2] = pixel &#38; 0xff;
 338         } else {
 339             p[0] = pixel &#38; 0xff;
 340             p[1] = (pixel &#62;&#62; 8) &#38; 0xff;
 341             p[2] = (pixel &#62;&#62; 16) &#38; 0xff;
 342         }
 343         break;
 344
 345     case 4:
 346         *(Uint32 *)p = pixel;
 347         break;
 348     }
 349 }</PRE
 350 ></DIV
 351 ><P
 352 >The following code uses the putpixel() function above to set a
 353 yellow pixel in the middle of the screen.</P
 354 ><DIV
 355 CLASS="EXAMPLE"
 356 ><A
 357 NAME="AEN97"
 358 ></A
 359 ><P
 360 ><B
 361 >Example 2-6. Using putpixel()</B
 362 ></P
 363 ><PRE
 364 CLASS="PROGRAMLISTING"
 365 >&#13;    /* Code to set a yellow pixel at the center of the screen */
 366
 367     int x, y;
 368     Uint32 yellow;
 369
 370     /* Map the color yellow to this display (R=0xff, G=0xFF, B=0x00)
 371        Note:  If the display is palettized, you must set the palette first.
 372     */
 373     yellow = SDL_MapRGB(screen-&#62;format, 0xff, 0xff, 0x00);
 374
 375     x = screen-&#62;w / 2;
 376     y = screen-&#62;h / 2;
 377
 378     /* Lock the screen for direct access to the pixels */
 379     if ( SDL_MUSTLOCK(screen) ) {
 380         if ( SDL_LockSurface(screen) &#60; 0 ) {
 381             fprintf(stderr, "Can't lock screen: %s\n", SDL_GetError());
 382             return;
 383         }
 384     }
 385
 386     putpixel(screen, x, y, yellow);
 387
 388     if ( SDL_MUSTLOCK(screen) ) {
 389         SDL_UnlockSurface(screen);
 390     }
 391     /* Update just the part of the display that we've changed */
 392     SDL_UpdateRect(screen, x, y, 1, 1);
 393
 394     return;&#13;</PRE
 395 ></DIV
 396 ></DIV
 397 ></DIV
 398 ></DIV
 399 ><DIV
 400 CLASS="NAVFOOTER"
 401 ><HR
 402 ALIGN="LEFT"
 403 WIDTH="100%"><TABLE
 404 SUMMARY="Footer navigation table"
 405 WIDTH="100%"
 406 BORDER="0"
 407 CELLPADDING="0"
 408 CELLSPACING="0"
 409 ><TR
 410 ><TD
 411 WIDTH="33%"
 412 ALIGN="left"
 413 VALIGN="top"
 414 ><A
 415 HREF="guidebasicsinit.html"
 416 ACCESSKEY="P"
 417 >Prev</A
 418 ></TD
 419 ><TD
 420 WIDTH="34%"
 421 ALIGN="center"
 422 VALIGN="top"
 423 ><A
 424 HREF="index.html"
 425 ACCESSKEY="H"
 426 >Home</A
 427 ></TD
 428 ><TD
 429 WIDTH="33%"
 430 ALIGN="right"
 431 VALIGN="top"
 432 ><A
 433 HREF="guidevideoopengl.html"
 434 ACCESSKEY="N"
 435 >Next</A
 436 ></TD
 437 ></TR
 438 ><TR
 439 ><TD
 440 WIDTH="33%"
 441 ALIGN="left"
 442 VALIGN="top"
 443 >Initializing SDL</TD
 444 ><TD
 445 WIDTH="34%"
 446 ALIGN="center"
 447 VALIGN="top"
 448 ><A
 449 HREF="guide.html"
 450 ACCESSKEY="U"
 451 >Up</A
 452 ></TD
 453 ><TD
 454 WIDTH="33%"
 455 ALIGN="right"
 456 VALIGN="top"
 457 >Using OpenGL With SDL</TD
 458 ></TR
 459 ></TABLE
 460 ></DIV
 461 ></BODY
 462 ></HTML
 463 >