[sdl_omap.git] / docs / html / guidevideo.html

<HTML
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>Graphics and Video</TITLE
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><DIV
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><H1
><A
NAME="GUIDEVIDEO"
></A
>Chapter 2. Graphics and Video</H1
><DIV
CLASS="TOC"
><DL
><DT
><B
>Table of Contents</B
></DT
><DT
><A
HREF="guidevideo.html#GUIDEVIDEOINTRO"
>Introduction to SDL Video</A
></DT
><DT
><A
HREF="guidevideoopengl.html"
>Using OpenGL With SDL</A
></DT
></DL
></DIV
><DIV
CLASS="SECT1"
><H1
CLASS="SECT1"
><A
NAME="GUIDEVIDEOINTRO"
></A
>Introduction to SDL Video</H1
><P
>Video is probably the most common thing that SDL is used for, and
so it has the most complete subsystem. Here are a few
examples to demonstrate the basics.</P
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN68"
></A
>Initializing the Video Display</H2
><P
>This is what almost all SDL programs have to do in one way or
another.</P
><DIV
CLASS="EXAMPLE"
><A
NAME="AEN71"
></A
><P
><B
>Example 2-1. Initializing the Video Display</B
></P
><PRE
CLASS="PROGRAMLISTING"
>    SDL_Surface *screen;

    /* Initialize the SDL library */
    if( SDL_Init(SDL_INIT_VIDEO) &#60; 0 ) {
        fprintf(stderr,
                "Couldn't initialize SDL: %s\n", SDL_GetError());
        exit(1);
    }

    /* Clean up on exit */
    atexit(SDL_Quit);
    
    /*
     * Initialize the display in a 640x480 8-bit palettized mode,
     * requesting a software surface
     */
    screen = SDL_SetVideoMode(640, 480, 8, SDL_SWSURFACE);
    if ( screen == NULL ) {
        fprintf(stderr, "Couldn't set 640x480x8 video mode: %s\n",
                        SDL_GetError());
        exit(1);
    }</PRE
></DIV
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN74"
></A
>Initializing the Best Video Mode</H2
><P
>If you have a preference for a certain pixel depth but will accept any
other, use SDL_SetVideoMode with SDL_ANYFORMAT as below. You can also
use SDL_VideoModeOK() to find the native video mode that is closest to
the mode you request.</P
><DIV
CLASS="EXAMPLE"
><A
NAME="AEN77"
></A
><P
><B
>Example 2-2. Initializing the Best Video Mode</B
></P
><PRE
CLASS="PROGRAMLISTING"
>    /* Have a preference for 8-bit, but accept any depth */
    screen = SDL_SetVideoMode(640, 480, 8, SDL_SWSURFACE|SDL_ANYFORMAT);
    if ( screen == NULL ) {
        fprintf(stderr, "Couldn't set 640x480x8 video mode: %s\n",
                        SDL_GetError());
        exit(1);
    }
    printf("Set 640x480 at %d bits-per-pixel mode\n",
           screen-&#62;format-&#62;BitsPerPixel);</PRE
></DIV
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN80"
></A
>Loading and Displaying a BMP File</H2
><P
>The following function loads and displays a BMP file given as
argument, once SDL is initialised and a video mode has been set.</P
><DIV
CLASS="EXAMPLE"
><A
NAME="AEN83"
></A
><P
><B
>Example 2-3. Loading and Displaying a BMP File</B
></P
><PRE
CLASS="PROGRAMLISTING"
>void display_bmp(char *file_name)
{
    SDL_Surface *image;

    /* Load the BMP file into a surface */
    image = SDL_LoadBMP(file_name);
    if (image == NULL) {
        fprintf(stderr, "Couldn't load %s: %s\n", file_name, SDL_GetError());
        return;
    }

    /*
     * Palettized screen modes will have a default palette (a standard
     * 8*8*4 colour cube), but if the image is palettized as well we can
     * use that palette for a nicer colour matching
     */
    if (image-&#62;format-&#62;palette &#38;&#38; screen-&#62;format-&#62;palette) {
    SDL_SetColors(screen, image-&#62;format-&#62;palette-&#62;colors, 0,
                  image-&#62;format-&#62;palette-&#62;ncolors);
    }

    /* Blit onto the screen surface */
    if(SDL_BlitSurface(image, NULL, screen, NULL) &#60; 0)
        fprintf(stderr, "BlitSurface error: %s\n", SDL_GetError());

    SDL_UpdateRect(screen, 0, 0, image-&#62;w, image-&#62;h);

    /* Free the allocated BMP surface */
    SDL_FreeSurface(image);
}</PRE
></DIV
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN86"
></A
>Drawing Directly to the Display</H2
><P
>The following two functions can be used to get and set single
pixels of a surface. They are carefully written to work with any depth
currently supported by SDL. Remember to lock the surface before
calling them, and to unlock it before calling any other SDL
functions.</P
><P
>To convert between pixel values and their red, green, blue
components, use SDL_GetRGB() and SDL_MapRGB().</P
><DIV
CLASS="EXAMPLE"
><A
NAME="AEN90"
></A
><P
><B
>Example 2-4. getpixel()</B
></P
><PRE
CLASS="PROGRAMLISTING"
>/*
 * Return the pixel value at (x, y)
 * NOTE: The surface must be locked before calling this!
 */
Uint32 getpixel(SDL_Surface *surface, int x, int y)
{
    int bpp = surface-&#62;format-&#62;BytesPerPixel;
    /* Here p is the address to the pixel we want to retrieve */
    Uint8 *p = (Uint8 *)surface-&#62;pixels + y * surface-&#62;pitch + x * bpp;

    switch(bpp) {
    case 1:
        return *p;

    case 2:
        return *(Uint16 *)p;

    case 3:
        if(SDL_BYTEORDER == SDL_BIG_ENDIAN)
            return p[0] &#60;&#60; 16 | p[1] &#60;&#60; 8 | p[2];
        else
            return p[0] | p[1] &#60;&#60; 8 | p[2] &#60;&#60; 16;

    case 4:
        return *(Uint32 *)p;

    default:
        return 0;       /* shouldn't happen, but avoids warnings */
    }
}</PRE
></DIV
><DIV
CLASS="EXAMPLE"
><A
NAME="AEN93"
></A
><P
><B
>Example 2-5. putpixel()</B
></P
><PRE
CLASS="PROGRAMLISTING"
>/*
 * Set the pixel at (x, y) to the given value
 * NOTE: The surface must be locked before calling this!
 */
void putpixel(SDL_Surface *surface, int x, int y, Uint32 pixel)
{
    int bpp = surface-&#62;format-&#62;BytesPerPixel;
    /* Here p is the address to the pixel we want to set */
    Uint8 *p = (Uint8 *)surface-&#62;pixels + y * surface-&#62;pitch + x * bpp;

    switch(bpp) {
    case 1:
        *p = pixel;
        break;

    case 2:
        *(Uint16 *)p = pixel;
        break;

    case 3:
        if(SDL_BYTEORDER == SDL_BIG_ENDIAN) {
            p[0] = (pixel &#62;&#62; 16) &#38; 0xff;
            p[1] = (pixel &#62;&#62; 8) &#38; 0xff;
            p[2] = pixel &#38; 0xff;
        } else {
            p[0] = pixel &#38; 0xff;
            p[1] = (pixel &#62;&#62; 8) &#38; 0xff;
            p[2] = (pixel &#62;&#62; 16) &#38; 0xff;
        }
        break;

    case 4:
        *(Uint32 *)p = pixel;
        break;
    }
}</PRE
></DIV
><P
>The following code uses the putpixel() function above to set a
yellow pixel in the middle of the screen.</P
><DIV
CLASS="EXAMPLE"
><A
NAME="AEN97"
></A
><P
><B
>Example 2-6. Using putpixel()</B
></P
><PRE
CLASS="PROGRAMLISTING"
>&#13;    /* Code to set a yellow pixel at the center of the screen */

    int x, y;
    Uint32 yellow;

    /* Map the color yellow to this display (R=0xff, G=0xFF, B=0x00)
       Note:  If the display is palettized, you must set the palette first.
    */
    yellow = SDL_MapRGB(screen-&#62;format, 0xff, 0xff, 0x00);

    x = screen-&#62;w / 2;
    y = screen-&#62;h / 2;

    /* Lock the screen for direct access to the pixels */
    if ( SDL_MUSTLOCK(screen) ) {
        if ( SDL_LockSurface(screen) &#60; 0 ) {
            fprintf(stderr, "Can't lock screen: %s\n", SDL_GetError());
            return;
        }
    }

    putpixel(screen, x, y, yellow);

    if ( SDL_MUSTLOCK(screen) ) {
        SDL_UnlockSurface(screen);
    }
    /* Update just the part of the display that we've changed */
    SDL_UpdateRect(screen, x, y, 1, 1);

    return;&#13;</PRE
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Commit	Line	Data
e14743d1	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
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	22	CLASS="CHAPTER"
	23	BGCOLOR="#FFF8DC"
	24	TEXT="#000000"
	25	LINK="#0000ee"
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	29	CLASS="NAVHEADER"
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	31	SUMMARY="Header navigation table"
	32	WIDTH="100%"
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	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
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	53	WIDTH="80%"
	54	ALIGN="center"
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	59	ALIGN="right"
	60	VALIGN="bottom"
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	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) < 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->format->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	* 884 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->format->palette && screen->format->palette) {
229	SDL_SetColors(screen, image->format->palette->colors, 0,
230	image->format->palette->ncolors);
231	}
232
233	/* Blit onto the screen surface */
234	if(SDL_BlitSurface(image, NULL, screen, NULL) < 0)
235	fprintf(stderr, "BlitSurface error: %s\n", SDL_GetError());
236
237	SDL_UpdateRect(screen, 0, 0, image->w, image->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->format->BytesPerPixel;
279	/* Here p is the address to the pixel we want to retrieve */
280	Uint8 p = (Uint8 )surface->pixels + y * surface->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] << 16 \| p[1] << 8 \| p[2];
292	else
293	return p[0] \| p[1] << 8 \| p[2] << 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->format->BytesPerPixel;
321	/* Here p is the address to the pixel we want to set */
322	Uint8 p = (Uint8 )surface->pixels + y * surface->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 >> 16) & 0xff;
336	p[1] = (pixel >> 8) & 0xff;
337	p[2] = pixel & 0xff;
338	} else {
339	p[0] = pixel & 0xff;
340	p[1] = (pixel >> 8) & 0xff;
341	p[2] = (pixel >> 16) & 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	> /* 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->format, 0xff, 0xff, 0x00);
374
375	x = screen->w / 2;
376	y = screen->h / 2;
377
378	/* Lock the screen for direct access to the pixels */
379	if ( SDL_MUSTLOCK(screen) ) {
380	if ( SDL_LockSurface(screen) < 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; </PRE
395	></DIV
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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	>