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comparison test/testalpha.c @ 0:74212992fb08

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Initial revision
author Sam Lantinga <slouken@lokigames.com>
date Thu, 26 Apr 2001 16:45:43 +0000
parents
children 609543e2b3a1
comparison
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-1:000000000000 0:74212992fb08
1
2 /* Simple program: Fill a colormap with gray and stripe it down the screen,
3 Then move an alpha valued sprite around the screen.
4 */
5
6 #include <stdio.h>
7 #include <stdlib.h>
8 #include <string.h>
9 #include <math.h>
10
11 #include "SDL.h"
12
13 #define FRAME_TICKS (1000/30) /* 30 frames/second */
14
15 /* Create a "light" -- a yellowish surface with variable alpha */
16 SDL_Surface *CreateLight(SDL_Surface *screen, int radius)
17 {
18 Uint8 trans, alphamask;
19 int range, addition;
20 int xdist, ydist;
21 Uint16 x, y;
22 Uint16 skip;
23 Uint32 pixel;
24 SDL_Surface *light;
25
26 #ifdef LIGHT_16BIT
27 Uint16 *buf;
28
29 /* Create a 16 (4/4/4/4) bpp square with a full 4-bit alpha channel */
30 /* Note: this isn't any faster than a 32 bit alpha surface */
31 alphamask = 0x0000000F;
32 light = SDL_CreateRGBSurface(SDL_SWSURFACE, 2*radius, 2*radius, 16,
33 0x0000F000, 0x00000F00, 0x000000F0, alphamask);
34 #else
35 Uint32 *buf;
36
37 /* Create a 32 (8/8/8/8) bpp square with a full 8-bit alpha channel */
38 alphamask = 0x000000FF;
39 light = SDL_CreateRGBSurface(SDL_SWSURFACE, 2*radius, 2*radius, 32,
40 0xFF000000, 0x00FF0000, 0x0000FF00, alphamask);
41 if ( light == NULL ) {
42 fprintf(stderr, "Couldn't create light: %s\n", SDL_GetError());
43 return(NULL);
44 }
45 #endif
46
47 /* Fill with a light yellow-orange color */
48 skip = light->pitch-(light->w*light->format->BytesPerPixel);
49 #ifdef LIGHT_16BIT
50 buf = (Uint16 *)light->pixels;
51 #else
52 buf = (Uint32 *)light->pixels;
53 #endif
54 /* Get a tranparent pixel value - we'll add alpha later */
55 pixel = SDL_MapRGBA(light->format, 0xFF, 0xDD, 0x88, 0);
56 for ( y=0; y<light->h; ++y ) {
57 for ( x=0; x<light->w; ++x ) {
58 *buf++ = pixel;
59 }
60 buf += skip; /* Almost always 0, but just in case... */
61 }
62
63 /* Calculate alpha values for the surface. */
64 #ifdef LIGHT_16BIT
65 buf = (Uint16 *)light->pixels;
66 #else
67 buf = (Uint32 *)light->pixels;
68 #endif
69 for ( y=0; y<light->h; ++y ) {
70 for ( x=0; x<light->w; ++x ) {
71 /* Slow distance formula (from center of light) */
72 xdist = x-(light->w/2);
73 ydist = y-(light->h/2);
74 range = (int)sqrt(xdist*xdist+ydist*ydist);
75
76 /* Scale distance to range of transparency (0-255) */
77 if ( range > radius ) {
78 trans = alphamask;
79 } else {
80 /* Increasing transparency with distance */
81 trans = (Uint8)((range*alphamask)/radius);
82
83 /* Lights are very transparent */
84 addition = (alphamask+1)/8;
85 if ( (int)trans+addition > alphamask ) {
86 trans = alphamask;
87 } else {
88 trans += addition;
89 }
90 }
91 /* We set the alpha component as the right N bits */
92 *buf++ |= (255-trans);
93 }
94 buf += skip; /* Almost always 0, but just in case... */
95 }
96 /* Enable RLE acceleration of this alpha surface */
97 SDL_SetAlpha(light, SDL_SRCALPHA|SDL_RLEACCEL, 0);
98
99 /* We're done! */
100 return(light);
101 }
102
103 static Uint32 flashes = 0;
104 static Uint32 flashtime = 0;
105
106 void FlashLight(SDL_Surface *screen, SDL_Surface *light, int x, int y)
107 {
108 SDL_Rect position;
109 Uint32 ticks1;
110 Uint32 ticks2;
111
112 /* Easy, center light */
113 position.x = x-(light->w/2);
114 position.y = y-(light->h/2);
115 position.w = light->w;
116 position.h = light->h;
117 ticks1 = SDL_GetTicks();
118 SDL_BlitSurface(light, NULL, screen, &position);
119 ticks2 = SDL_GetTicks();
120 SDL_UpdateRects(screen, 1, &position);
121 ++flashes;
122
123 /* Update time spend doing alpha blitting */
124 flashtime += (ticks2-ticks1);
125 }
126
127 static int sprite_visible = 0;
128 static SDL_Surface *sprite;
129 static SDL_Surface *backing;
130 static SDL_Rect position;
131 static int x_vel, y_vel;
132 static int alpha_vel;
133
134 int LoadSprite(SDL_Surface *screen, char *file)
135 {
136 SDL_Surface *converted;
137
138 /* Load the sprite image */
139 sprite = SDL_LoadBMP(file);
140 if ( sprite == NULL ) {
141 fprintf(stderr, "Couldn't load %s: %s", file, SDL_GetError());
142 return(-1);
143 }
144
145 /* Set transparent pixel as the pixel at (0,0) */
146 if ( sprite->format->palette ) {
147 SDL_SetColorKey(sprite, SDL_SRCCOLORKEY,
148 *(Uint8 *)sprite->pixels);
149 }
150
151 /* Convert sprite to video format */
152 converted = SDL_DisplayFormat(sprite);
153 SDL_FreeSurface(sprite);
154 if ( converted == NULL ) {
155 fprintf(stderr, "Couldn't convert background: %s\n",
156 SDL_GetError());
157 return(-1);
158 }
159 sprite = converted;
160
161 /* Create the background */
162 backing = SDL_CreateRGBSurface(SDL_SWSURFACE, sprite->w, sprite->h, 8,
163 0, 0, 0, 0);
164 if ( backing == NULL ) {
165 fprintf(stderr, "Couldn't create background: %s\n",
166 SDL_GetError());
167 SDL_FreeSurface(sprite);
168 return(-1);
169 }
170
171 /* Convert background to video format */
172 converted = SDL_DisplayFormat(backing);
173 SDL_FreeSurface(backing);
174 if ( converted == NULL ) {
175 fprintf(stderr, "Couldn't convert background: %s\n",
176 SDL_GetError());
177 SDL_FreeSurface(sprite);
178 return(-1);
179 }
180 backing = converted;
181
182 /* Set the initial position of the sprite */
183 position.x = (screen->w-sprite->w)/2;
184 position.y = (screen->h-sprite->h)/2;
185 position.w = sprite->w;
186 position.h = sprite->h;
187 x_vel = 0; y_vel = 0;
188 alpha_vel = 1;
189
190 /* We're ready to roll. :) */
191 return(0);
192 }
193
194 void AttractSprite(Uint16 x, Uint16 y)
195 {
196 x_vel = ((int)x-position.x)/10;
197 y_vel = ((int)y-position.y)/10;
198 }
199
200 void MoveSprite(SDL_Surface *screen, SDL_Surface *light)
201 {
202 SDL_Rect updates[2];
203 int alpha;
204
205 /* Erase the sprite if it was visible */
206 if ( sprite_visible ) {
207 updates[0] = position;
208 SDL_BlitSurface(backing, NULL, screen, &updates[0]);
209 } else {
210 updates[0].x = 0; updates[0].y = 0;
211 updates[0].w = 0; updates[0].h = 0;
212 sprite_visible = 1;
213 }
214
215 /* Since the sprite is off the screen, we can do other drawing
216 without being overwritten by the saved area behind the sprite.
217 */
218 if ( light != NULL ) {
219 int x, y;
220
221 SDL_GetMouseState(&x, &y);
222 FlashLight(screen, light, x, y);
223 }
224
225 /* Move the sprite, bounce at the wall */
226 position.x += x_vel;
227 if ( (position.x < 0) || (position.x >= screen->w) ) {
228 x_vel = -x_vel;
229 position.x += x_vel;
230 }
231 position.y += y_vel;
232 if ( (position.y < 0) || (position.y >= screen->h) ) {
233 y_vel = -y_vel;
234 position.y += y_vel;
235 }
236
237 /* Update transparency (fade in and out) */
238 alpha = sprite->format->alpha;
239 if ( (alpha+alpha_vel) < 0 ) {
240 alpha_vel = -alpha_vel;
241 } else
242 if ( (alpha+alpha_vel) > 255 ) {
243 alpha_vel = -alpha_vel;
244 }
245 SDL_SetAlpha(sprite, SDL_SRCALPHA, (Uint8)(alpha+alpha_vel));
246
247 /* Save the area behind the sprite */
248 updates[1] = position;
249 SDL_BlitSurface(screen, &updates[1], backing, NULL);
250
251 /* Blit the sprite onto the screen */
252 updates[1] = position;
253 SDL_BlitSurface(sprite, NULL, screen, &updates[1]);
254
255 /* Make it so! */
256 SDL_UpdateRects(screen, 2, updates);
257 }
258
259 void WarpSprite(SDL_Surface *screen, int x, int y)
260 {
261 SDL_Rect updates[2];
262
263 /* Erase, move, Draw, update */
264 updates[0] = position;
265 SDL_BlitSurface(backing, NULL, screen, &updates[0]);
266 position.x = x-sprite->w/2; /* Center about X */
267 position.y = y-sprite->h/2; /* Center about Y */
268 updates[1] = position;
269 SDL_BlitSurface(screen, &updates[1], backing, NULL);
270 updates[1] = position;
271 SDL_BlitSurface(sprite, NULL, screen, &updates[1]);
272 SDL_UpdateRects(screen, 2, updates);
273 }
274
275 int main(int argc, char *argv[])
276 {
277 const SDL_VideoInfo *info;
278 SDL_Surface *screen;
279 Uint8 video_bpp;
280 Uint32 videoflags;
281 Uint8 *buffer;
282 int i, done;
283 SDL_Event event;
284 SDL_Surface *light;
285 int mouse_pressed;
286 Uint32 ticks, lastticks;
287
288 /* Initialize SDL */
289 if ( SDL_Init(SDL_INIT_VIDEO) < 0 ) {
290 fprintf(stderr, "Couldn't initialize SDL: %s\n",SDL_GetError());
291 exit(1);
292 }
293 atexit(SDL_Quit);
294
295 /* Alpha blending doesn't work well at 8-bit color */
296 info = SDL_GetVideoInfo();
297 if ( info->vfmt->BitsPerPixel > 8 ) {
298 video_bpp = info->vfmt->BitsPerPixel;
299 } else {
300 video_bpp = 16;
301 }
302 videoflags = SDL_SWSURFACE;
303 while ( argc > 1 ) {
304 --argc;
305 if ( strcmp(argv[argc-1], "-bpp") == 0 ) {
306 video_bpp = atoi(argv[argc]);
307 --argc;
308 } else
309 if ( strcmp(argv[argc], "-hw") == 0 ) {
310 videoflags |= SDL_HWSURFACE;
311 } else
312 if ( strcmp(argv[argc], "-warp") == 0 ) {
313 videoflags |= SDL_HWPALETTE;
314 } else
315 if ( strcmp(argv[argc], "-fullscreen") == 0 ) {
316 videoflags |= SDL_FULLSCREEN;
317 } else {
318 fprintf(stderr,
319 "Usage: %s [-bpp N] [-warp] [-hw] [-fullscreen]\n",
320 argv[0]);
321 exit(1);
322 }
323 }
324
325 /* Set 640x480 video mode */
326 if ( (screen=SDL_SetVideoMode(640,480,video_bpp,videoflags)) == NULL ) {
327 fprintf(stderr, "Couldn't set 640x480x%d video mode: %s\n",
328 video_bpp, SDL_GetError());
329 exit(2);
330 }
331
332 /* Set the surface pixels and refresh! */
333 if ( SDL_LockSurface(screen) < 0 ) {
334 fprintf(stderr, "Couldn't lock the display surface: %s\n",
335 SDL_GetError());
336 exit(2);
337 }
338 buffer=(Uint8 *)screen->pixels;
339 for ( i=0; i<screen->h; ++i ) {
340 memset(buffer,(i*255)/screen->h, screen->pitch);
341 buffer += screen->pitch;
342 }
343 SDL_UnlockSurface(screen);
344 SDL_UpdateRect(screen, 0, 0, 0, 0);
345
346 /* Create the light */
347 light = CreateLight(screen, 82);
348 if ( light == NULL ) {
349 exit(1);
350 }
351
352 /* Load the sprite */
353 if ( LoadSprite(screen, "icon.bmp") < 0 ) {
354 SDL_FreeSurface(light);
355 exit(1);
356 }
357
358 /* Set a clipping rectangle to clip the outside edge of the screen */
359 { SDL_Rect clip;
360 clip.x = 32;
361 clip.y = 32;
362 clip.w = screen->w-(2*32);
363 clip.h = screen->h-(2*32);
364 SDL_SetClipRect(screen, &clip);
365 }
366
367 /* Wait for a keystroke */
368 lastticks = SDL_GetTicks();
369 done = 0;
370 mouse_pressed = 0;
371 while ( !done ) {
372 /* Update the frame -- move the sprite */
373 if ( mouse_pressed ) {
374 MoveSprite(screen, light);
375 mouse_pressed = 0;
376 } else {
377 MoveSprite(screen, NULL);
378 }
379
380 /* Slow down the loop to 30 frames/second */
381 ticks = SDL_GetTicks();
382 if ( (ticks-lastticks) < FRAME_TICKS ) {
383 #ifdef CHECK_SLEEP_GRANULARITY
384 fprintf(stderr, "Sleeping %d ticks\n", FRAME_TICKS-(ticks-lastticks));
385 #endif
386 SDL_Delay(FRAME_TICKS-(ticks-lastticks));
387 #ifdef CHECK_SLEEP_GRANULARITY
388 fprintf(stderr, "Slept %d ticks\n", (SDL_GetTicks()-ticks));
389 #endif
390 }
391 lastticks = ticks;
392
393 /* Check for events */
394 while ( SDL_PollEvent(&event) ) {
395 switch (event.type) {
396 /* Attract sprite while mouse is held down */
397 case SDL_MOUSEMOTION:
398 if (event.motion.state != 0) {
399 AttractSprite(event.motion.x,
400 event.motion.y);
401 mouse_pressed = 1;
402 }
403 break;
404 case SDL_MOUSEBUTTONDOWN:
405 if ( event.button.button == 1 ) {
406 AttractSprite(event.button.x,
407 event.button.y);
408 mouse_pressed = 1;
409 } else {
410 SDL_Rect area;
411
412 area.x = event.button.x-16;
413 area.y = event.button.y-16;
414 area.w = 32;
415 area.h = 32;
416 SDL_FillRect(screen, &area, 0);
417 SDL_UpdateRects(screen,1,&area);
418 }
419 break;
420 case SDL_KEYDOWN:
421 /* Any keypress quits the app... */
422 case SDL_QUIT:
423 done = 1;
424 break;
425 default:
426 break;
427 }
428 }
429 }
430 SDL_FreeSurface(light);
431 SDL_FreeSurface(sprite);
432 SDL_FreeSurface(backing);
433
434 /* Print out some timing information */
435 if ( flashes > 0 ) {
436 printf("%d alpha blits, ~%4.4f ms per blit\n",
437 flashes, (float)flashtime/flashes);
438 }
439 return(0);
440 }