git.infertux.com SDL-1.2.7 / master test / testalpha.c
master

Tree @master (Download .tar.gz)

testalpha.c @masterraw · history · blame

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
/* Simple program:  Fill a colormap with gray and stripe it down the screen,
		    Then move an alpha valued sprite around the screen.
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>

#include "SDL.h"

#define FRAME_TICKS	(1000/30)		/* 30 frames/second */

/* Create a "light" -- a yellowish surface with variable alpha */
SDL_Surface *CreateLight(SDL_Surface *screen, int radius)
{
	Uint8  trans, alphamask;
	int    range, addition;
	int    xdist, ydist;
	Uint16 x, y;
	Uint16 skip;
	Uint32 pixel;
	SDL_Surface *light;

#ifdef LIGHT_16BIT
	Uint16 *buf;

	/* Create a 16 (4/4/4/4) bpp square with a full 4-bit alpha channel */
	/* Note: this isn't any faster than a 32 bit alpha surface */
	alphamask = 0x0000000F;
	light = SDL_CreateRGBSurface(SDL_SWSURFACE, 2*radius, 2*radius, 16,
			0x0000F000, 0x00000F00, 0x000000F0, alphamask);
#else
	Uint32 *buf;

	/* Create a 32 (8/8/8/8) bpp square with a full 8-bit alpha channel */
	alphamask = 0x000000FF;
	light = SDL_CreateRGBSurface(SDL_SWSURFACE, 2*radius, 2*radius, 32,
			0xFF000000, 0x00FF0000, 0x0000FF00, alphamask);
	if ( light == NULL ) {
		fprintf(stderr, "Couldn't create light: %s\n", SDL_GetError());
		return(NULL);
	}
#endif

	/* Fill with a light yellow-orange color */
	skip = light->pitch-(light->w*light->format->BytesPerPixel);
#ifdef LIGHT_16BIT
	buf = (Uint16 *)light->pixels;
#else
	buf = (Uint32 *)light->pixels;
#endif
        /* Get a tranparent pixel value - we'll add alpha later */
	pixel = SDL_MapRGBA(light->format, 0xFF, 0xDD, 0x88, 0);
	for ( y=0; y<light->h; ++y ) {
		for ( x=0; x<light->w; ++x ) {
			*buf++ = pixel;
		}
		buf += skip;	/* Almost always 0, but just in case... */
	}

	/* Calculate alpha values for the surface. */
#ifdef LIGHT_16BIT
	buf = (Uint16 *)light->pixels;
#else
	buf = (Uint32 *)light->pixels;
#endif
	for ( y=0; y<light->h; ++y ) {
		for ( x=0; x<light->w; ++x ) {
			/* Slow distance formula (from center of light) */
			xdist = x-(light->w/2);
			ydist = y-(light->h/2);
			range = (int)sqrt(xdist*xdist+ydist*ydist);

			/* Scale distance to range of transparency (0-255) */
			if ( range > radius ) {
				trans = alphamask;
			} else {
				/* Increasing transparency with distance */
				trans = (Uint8)((range*alphamask)/radius);

				/* Lights are very transparent */
				addition = (alphamask+1)/8;
				if ( (int)trans+addition > alphamask ) {
					trans = alphamask;
				} else {
					trans += addition;
				}
			}
			/* We set the alpha component as the right N bits */
			*buf++ |= (255-trans);
		}
		buf += skip;	/* Almost always 0, but just in case... */
	}
	/* Enable RLE acceleration of this alpha surface */
	SDL_SetAlpha(light, SDL_SRCALPHA|SDL_RLEACCEL, 0);

	/* We're done! */
	return(light);
}

static Uint32 flashes = 0;
static Uint32 flashtime = 0;

void FlashLight(SDL_Surface *screen, SDL_Surface *light, int x, int y)
{
	SDL_Rect position;
	Uint32   ticks1;
	Uint32   ticks2;

	/* Easy, center light */
	position.x = x-(light->w/2);
	position.y = y-(light->h/2);
	position.w = light->w;
	position.h = light->h;
	ticks1 = SDL_GetTicks();
	SDL_BlitSurface(light, NULL, screen, &position);
	ticks2 = SDL_GetTicks();
	SDL_UpdateRects(screen, 1, &position);
	++flashes;

	/* Update time spend doing alpha blitting */
	flashtime += (ticks2-ticks1);
}

static int sprite_visible = 0;
static SDL_Surface *sprite;
static SDL_Surface *backing;
static SDL_Rect    position;
static int         x_vel, y_vel;
static int	   alpha_vel;

int LoadSprite(SDL_Surface *screen, char *file)
{
	SDL_Surface *converted;

	/* Load the sprite image */
	sprite = SDL_LoadBMP(file);
	if ( sprite == NULL ) {
		fprintf(stderr, "Couldn't load %s: %s", file, SDL_GetError());
		return(-1);
	}

	/* Set transparent pixel as the pixel at (0,0) */
	if ( sprite->format->palette ) {
		SDL_SetColorKey(sprite, SDL_SRCCOLORKEY,
						*(Uint8 *)sprite->pixels);
	}

	/* Convert sprite to video format */
	converted = SDL_DisplayFormat(sprite);
	SDL_FreeSurface(sprite);
	if ( converted == NULL ) {
		fprintf(stderr, "Couldn't convert background: %s\n",
							SDL_GetError());
		return(-1);
	}
	sprite = converted;

	/* Create the background */
	backing = SDL_CreateRGBSurface(SDL_SWSURFACE, sprite->w, sprite->h, 8,
								0, 0, 0, 0);
	if ( backing == NULL ) {
		fprintf(stderr, "Couldn't create background: %s\n",
							SDL_GetError());
		SDL_FreeSurface(sprite);
		return(-1);
	}

	/* Convert background to video format */
	converted = SDL_DisplayFormat(backing);
	SDL_FreeSurface(backing);
	if ( converted == NULL ) {
		fprintf(stderr, "Couldn't convert background: %s\n",
							SDL_GetError());
		SDL_FreeSurface(sprite);
		return(-1);
	}
	backing = converted;

	/* Set the initial position of the sprite */
	position.x = (screen->w-sprite->w)/2;
	position.y = (screen->h-sprite->h)/2;
	position.w = sprite->w;
	position.h = sprite->h;
	x_vel = 0; y_vel = 0;
	alpha_vel = 1;

	/* We're ready to roll. :) */
	return(0);
}

void AttractSprite(Uint16 x, Uint16 y)
{
	x_vel = ((int)x-position.x)/10;
	y_vel = ((int)y-position.y)/10;
}

void MoveSprite(SDL_Surface *screen, SDL_Surface *light)
{
	SDL_Rect updates[2];
	int alpha;

	/* Erase the sprite if it was visible */
	if ( sprite_visible ) {
		updates[0] = position;
		SDL_BlitSurface(backing, NULL, screen, &updates[0]);
	} else {
		updates[0].x = 0; updates[0].y = 0;
		updates[0].w = 0; updates[0].h = 0;
		sprite_visible = 1;
	}

	/* Since the sprite is off the screen, we can do other drawing
	   without being overwritten by the saved area behind the sprite.
	 */
	if ( light != NULL ) {
		int x, y;

		SDL_GetMouseState(&x, &y);
		FlashLight(screen, light, x, y);
	}
	   
	/* Move the sprite, bounce at the wall */
	position.x += x_vel;
	if ( (position.x < 0) || (position.x >= screen->w) ) {
		x_vel = -x_vel;
		position.x += x_vel;
	}
	position.y += y_vel;
	if ( (position.y < 0) || (position.y >= screen->h) ) {
		y_vel = -y_vel;
		position.y += y_vel;
	}

	/* Update transparency (fade in and out) */
	alpha = sprite->format->alpha;
	if ( (alpha+alpha_vel) < 0 ) {
		alpha_vel = -alpha_vel;
	} else
	if ( (alpha+alpha_vel) > 255 ) {
		alpha_vel = -alpha_vel;
	}
	SDL_SetAlpha(sprite, SDL_SRCALPHA, (Uint8)(alpha+alpha_vel));

	/* Save the area behind the sprite */
	updates[1] = position;
	SDL_BlitSurface(screen, &updates[1], backing, NULL);
	
	/* Blit the sprite onto the screen */
	updates[1] = position;
	SDL_BlitSurface(sprite, NULL, screen, &updates[1]);

	/* Make it so! */
	SDL_UpdateRects(screen, 2, updates);
}

void WarpSprite(SDL_Surface *screen, int x, int y)
{
	SDL_Rect updates[2];

	/* Erase, move, Draw, update */
	updates[0] = position;
	SDL_BlitSurface(backing, NULL, screen, &updates[0]);
	position.x = x-sprite->w/2;	/* Center about X */
	position.y = y-sprite->h/2;	/* Center about Y */
	updates[1] = position;
	SDL_BlitSurface(screen, &updates[1], backing, NULL);
	updates[1] = position;
	SDL_BlitSurface(sprite, NULL, screen, &updates[1]);
	SDL_UpdateRects(screen, 2, updates);
}

int main(int argc, char *argv[])
{
	const SDL_VideoInfo *info;
	SDL_Surface *screen;
	Uint8  video_bpp;
	Uint32 videoflags;
	Uint8 *buffer;
	int    i, k, done;
	SDL_Event event;
	SDL_Surface *light;
	int mouse_pressed;
	Uint32 ticks, lastticks;
	Uint16 *buffer16;
        Uint16 color;
        Uint8  gradient;


	/* Initialize SDL */
	if ( SDL_Init(SDL_INIT_VIDEO) < 0 ) {
		fprintf(stderr, "Couldn't initialize SDL: %s\n",SDL_GetError());
		exit(1);
	}
	atexit(SDL_Quit);

	/* Alpha blending doesn't work well at 8-bit color */
	info = SDL_GetVideoInfo();
	if ( info->vfmt->BitsPerPixel > 8 ) {
		video_bpp = info->vfmt->BitsPerPixel;
	} else {
		video_bpp = 16;
                fprintf(stderr, "forced 16 bpp mode\n");
	}
	videoflags = SDL_SWSURFACE;
	while ( argc > 1 ) {
		--argc;
		if ( strcmp(argv[argc-1], "-bpp") == 0 ) {
			video_bpp = atoi(argv[argc]);
                        if (video_bpp<=8) {
                            video_bpp=16;
                            fprintf(stderr, "forced 16 bpp mode\n");
                        }
			--argc;
		} else
		if ( strcmp(argv[argc], "-hw") == 0 ) {
			videoflags |= SDL_HWSURFACE;
		} else
		if ( strcmp(argv[argc], "-warp") == 0 ) {
			videoflags |= SDL_HWPALETTE;
		} else
		if ( strcmp(argv[argc], "-fullscreen") == 0 ) {
			videoflags |= SDL_FULLSCREEN;
		} else {
			fprintf(stderr, 
			"Usage: %s [-bpp N] [-warp] [-hw] [-fullscreen]\n",
								argv[0]);
			exit(1);
		}
	}

	/* Set 640x480 video mode */
	if ( (screen=SDL_SetVideoMode(640,480,video_bpp,videoflags)) == NULL ) {
		fprintf(stderr, "Couldn't set 640x480x%d video mode: %s\n",
						video_bpp, SDL_GetError());
		exit(2);
	}

	/* Set the surface pixels and refresh! */
	if ( SDL_LockSurface(screen) < 0 ) {
		fprintf(stderr, "Couldn't lock the display surface: %s\n",
							SDL_GetError());
		exit(2);
	}
	buffer=(Uint8 *)screen->pixels;
	if (screen->format->BytesPerPixel!=2) {
		for ( i=0; i<screen->h; ++i ) {
			memset(buffer,(i*255)/screen->h, screen->pitch);
			buffer += screen->pitch;
		}
	}
        else
        {
		for ( i=0; i<screen->h; ++i ) {
			gradient=((i*255)/screen->h);
                        color = SDL_MapRGB(screen->format, gradient, gradient, gradient);
                        buffer16=(Uint16*)buffer;
                        for (k=0; k<screen->w; k++)
                        {
                            *(buffer16+k)=color;
                        }
			buffer += screen->pitch;
		}
        }

	SDL_UnlockSurface(screen);
	SDL_UpdateRect(screen, 0, 0, 0, 0);

	/* Create the light */
	light = CreateLight(screen, 82);
	if ( light == NULL ) {
		exit(1);
	}

	/* Load the sprite */
	if ( LoadSprite(screen, "icon.bmp") < 0 ) {
		SDL_FreeSurface(light);
		exit(1);
	}

	/* Set a clipping rectangle to clip the outside edge of the screen */
	{ SDL_Rect clip;
		clip.x = 32;
		clip.y = 32;
		clip.w = screen->w-(2*32);
		clip.h = screen->h-(2*32);
		SDL_SetClipRect(screen, &clip);
	}

	/* Wait for a keystroke */
	lastticks = SDL_GetTicks();
	done = 0;
	mouse_pressed = 0;
	while ( !done ) {
		/* Update the frame -- move the sprite */
		if ( mouse_pressed ) {
			MoveSprite(screen, light);
			mouse_pressed = 0;
		} else {
			MoveSprite(screen, NULL);
		}

		/* Slow down the loop to 30 frames/second */
		ticks = SDL_GetTicks();
		if ( (ticks-lastticks) < FRAME_TICKS ) {
#ifdef CHECK_SLEEP_GRANULARITY
fprintf(stderr, "Sleeping %d ticks\n", FRAME_TICKS-(ticks-lastticks));
#endif
			SDL_Delay(FRAME_TICKS-(ticks-lastticks));
#ifdef CHECK_SLEEP_GRANULARITY
fprintf(stderr, "Slept %d ticks\n", (SDL_GetTicks()-ticks));
#endif
		}
		lastticks = ticks;

		/* Check for events */
		while ( SDL_PollEvent(&event) ) {
			switch (event.type) {
				/* Attract sprite while mouse is held down */
				case SDL_MOUSEMOTION:
					if (event.motion.state != 0) {
						AttractSprite(event.motion.x,
								event.motion.y);
						mouse_pressed = 1;
					}
					break;
				case SDL_MOUSEBUTTONDOWN:
					if ( event.button.button == 1 ) {
						AttractSprite(event.button.x,
						              event.button.y);
						mouse_pressed = 1;
					} else {
						SDL_Rect area;

						area.x = event.button.x-16;
						area.y = event.button.y-16;
						area.w = 32;
						area.h = 32;
						SDL_FillRect(screen, &area, 0);
						SDL_UpdateRects(screen,1,&area);
					}
					break;
				case SDL_KEYDOWN:
					/* Any keypress quits the app... */
				case SDL_QUIT:
					done = 1;
					break;
				default:
					break;
			}
		}
	}
	SDL_FreeSurface(light);
	SDL_FreeSurface(sprite);
	SDL_FreeSurface(backing);

	/* Print out some timing information */
	if ( flashes > 0 ) {
		printf("%d alpha blits, ~%4.4f ms per blit\n", 
			flashes, (float)flashtime/flashes);
	}
	return(0);
}