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