Mercurial > sdl-ios-xcode
view test/testalpha.c @ 94:ae6e6b73333f
Cleaned up the OpenBSD port, thanks to Peter Valchev
author | Sam Lantinga <slouken@lokigames.com> |
---|---|
date | Sun, 08 Jul 2001 09:00:06 +0000 |
parents | 74212992fb08 |
children | 609543e2b3a1 |
line wrap: on
line source
/* 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, done; SDL_Event event; SDL_Surface *light; int mouse_pressed; Uint32 ticks, lastticks; /* 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; } videoflags = SDL_SWSURFACE; while ( argc > 1 ) { --argc; if ( strcmp(argv[argc-1], "-bpp") == 0 ) { video_bpp = atoi(argv[argc]); --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; for ( i=0; i<screen->h; ++i ) { memset(buffer,(i*255)/screen->h, screen->pitch); 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); }