git.sesse.net Git - movit/blob - test.cpp

   1 #define GL_GLEXT_PROTOTYPES 1
   2 #define NO_SDL_GLEXT 1
   3
   4 #define WIDTH 1280
   5 #define HEIGHT 720
   6 #define BUFFER_OFFSET(i) ((char *)NULL + (i))
   7
   8 #define HSV_WHEEL_SIZE 128
   9
  10 #include <math.h>
  11 #include <time.h>
  12
  13 #include <SDL/SDL.h>
  14 #include <SDL/SDL_opengl.h>
  15 #include <SDL/SDL_image.h>
  16
  17 #include <GL/gl.h>
  18 #include <GL/glext.h>
  19
  20 #ifdef NDEBUG
  21 #define check_error()
  22 #else
  23 #define check_error() { int err = glGetError(); if (err != GL_NO_ERROR) { printf("GL error 0x%x at line %d\n", err, __LINE__); exit(1); } }
  24 #endif
  25
  26 unsigned char result[WIDTH * HEIGHT * 4];
  27
  28 float lift_theta = 0.0f, lift_rad = 0.0f, lift_v = 0.0f;
  29 float gamma_theta = 0.0f, gamma_rad = 0.0f, gamma_v = 0.5f;
  30 float gain_theta = 0.0f, gain_rad = 0.0f, gain_v = 0.25f;
  31 float saturation = 1.0f;
  32
  33 float lift_r = 0.0f, lift_g = 0.0f, lift_b = 0.0f;
  34 float gamma_r = 1.0f, gamma_g = 1.0f, gamma_b = 1.0f;
  35 float gain_r = 1.0f, gain_g = 1.0f, gain_b = 1.0f;
  36
  37 enum textures {
  38         SOURCE_IMAGE = 1,
  39         SRGB_LUT = 2,
  40         SRGB_REVERSE_LUT = 3,
  41         HSV_WHEEL = 4,
  42 };
  43
  44 // assumes h in [0, 2pi> or [-pi, pi>
  45 void hsv2rgb(float h, float s, float v, float *r, float *g, float *b)
  46 {
  47         if (h < 0.0f) {
  48                 h += 2.0f * M_PI;
  49         }
  50         float c = v * s;
  51         float hp = (h * 180.0 / M_PI) / 60.0;
  52         float x = c * (1 - fabs(fmod(hp, 2.0f) - 1.0f));
  53
  54         if (hp >= 0 && hp < 1) {
  55                 *r = c;
  56                 *g = x;
  57                 *b = 0.0f;
  58         } else if (hp >= 1 && hp < 2) {
  59                 *r = x;
  60                 *g = c;
  61                 *b = 0.0f;
  62         } else if (hp >= 2 && hp < 3) {
  63                 *r = 0.0f;
  64                 *g = c;
  65                 *b = x;
  66         } else if (hp >= 3 && hp < 4) {
  67                 *r = 0.0f;
  68                 *g = x;
  69                 *b = c;
  70         } else if (hp >= 4 && hp < 5) {
  71                 *r = x;
  72                 *g = 0.0f;
  73                 *b = c;
  74         } else {
  75                 *r = c;
  76                 *g = 0.0f;
  77                 *b = x;
  78         }
  79
  80         float m = v - c;
  81         *r += m;
  82         *g += m;
  83         *b += m;
  84 }
  85
  86 GLhandleARB read_shader(const char* filename, GLenum type)
  87 {
  88         static char buf[131072];
  89         FILE *fp = fopen(filename, "r");
  90         if (fp == NULL) {
  91                 perror(filename);
  92                 exit(1);
  93         }
  94
  95         int len = fread(buf, 1, sizeof(buf), fp);
  96         fclose(fp);
  97
  98         GLhandleARB obj = glCreateShaderObjectARB(type);
  99         const GLchar* source[] = { buf };
 100         const GLint length[] = { len };
 101         glShaderSource(obj, 1, source, length);
 102         glCompileShader(obj);
 103
 104         GLchar info_log[4096];
 105         GLsizei log_length = sizeof(info_log) - 1;
 106         glGetShaderInfoLog(obj, log_length, &log_length, info_log);
 107         info_log[log_length] = 0;
 108         printf("shader compile log: %s\n", info_log);
 109
 110         GLint status;
 111         glGetShaderiv(obj, GL_COMPILE_STATUS, &status);
 112         if (status == GL_FALSE) {
 113                 exit(1);
 114         }
 115
 116         return obj;
 117 }
 118
 119 void draw_picture_quad(GLint prog, int frame)
 120 {
 121         glUseProgramObjectARB(prog);
 122         check_error();
 123
 124         glActiveTexture(GL_TEXTURE0);
 125         glBindTexture(GL_TEXTURE_2D, SOURCE_IMAGE);
 126         glUniform1i(glGetUniformLocation(prog, "tex"), 0);
 127
 128         glActiveTexture(GL_TEXTURE1);
 129         glBindTexture(GL_TEXTURE_1D, SRGB_LUT);
 130         glUniform1i(glGetUniformLocation(prog, "srgb_tex"), 1);
 131
 132         glActiveTexture(GL_TEXTURE2);
 133         glBindTexture(GL_TEXTURE_1D, SRGB_REVERSE_LUT);
 134         glUniform1i(glGetUniformLocation(prog, "srgb_reverse_tex"), 2);
 135
 136         glUniform3f(glGetUniformLocation(prog, "lift"), lift_r, lift_g, lift_b);
 137         //glUniform3f(glGetUniformLocation(prog, "gamma"), gamma_r, gamma_g, gamma_b);
 138         glUniform3f(glGetUniformLocation(prog, "inv_gamma_22"),
 139                     2.2f / gamma_r,
 140                     2.2f / gamma_g,
 141                     2.2f / gamma_b);
 142         glUniform3f(glGetUniformLocation(prog, "gain_pow_inv_gamma"),
 143                     pow(gain_r, 1.0f / gamma_r),
 144                     pow(gain_g, 1.0f / gamma_g),
 145                     pow(gain_b, 1.0f / gamma_b));
 146         glUniform1f(glGetUniformLocation(prog, "saturation"), saturation);
 147
 148         glDisable(GL_BLEND);
 149         check_error();
 150         glDisable(GL_DEPTH_TEST);
 151         check_error();
 152         glDepthMask(GL_FALSE);
 153         check_error();
 154
 155         glMatrixMode(GL_PROJECTION);
 156         glLoadIdentity();
 157         glOrtho(0.0, 1.0, 0.0, 1.0, 0.0, 1.0);
 158
 159         glMatrixMode(GL_MODELVIEW);
 160         glLoadIdentity();
 161
 162         glClearColor(1.0f, 0.0f, 0.0f, 1.0f);
 163 //      glClear(GL_COLOR_BUFFER_BIT);
 164         check_error();
 165
 166         glBegin(GL_QUADS);
 167
 168         glTexCoord2f(0.0f, 1.0f);
 169         glVertex2f(0.0f, 0.0f);
 170
 171         glTexCoord2f(1.0f, 1.0f);
 172         glVertex2f(1.0f, 0.0f);
 173
 174         glTexCoord2f(1.0f, 0.0f);
 175         glVertex2f(1.0f, 1.0f);
 176
 177         glTexCoord2f(0.0f, 0.0f);
 178         glVertex2f(0.0f, 1.0f);
 179
 180         glEnd();
 181         check_error();
 182 }
 183
 184 void draw_hsv_wheel(float y, float rad, float theta, float value)
 185 {
 186         glUseProgramObjectARB(0);
 187         check_error();
 188         glActiveTexture(GL_TEXTURE0);
 189         check_error();
 190         glEnable(GL_TEXTURE_2D);
 191         check_error();
 192         glBindTexture(GL_TEXTURE_2D, HSV_WHEEL);
 193         check_error();
 194         glActiveTexture(GL_TEXTURE1);
 195         check_error();
 196         glBindTexture(GL_TEXTURE_2D, 0);
 197         check_error();
 198         glActiveTexture(GL_TEXTURE0);
 199         glEnable(GL_BLEND);
 200         check_error();
 201         glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
 202         check_error();
 203
 204         // wheel
 205         glBegin(GL_QUADS);
 206
 207         glTexCoord2f(0.0f, 1.0f);
 208         glVertex2f(0.0f, y);
 209
 210         glTexCoord2f(1.0f, 1.0f);
 211         glVertex2f(0.2f * 9.0f / 16.0f, y);
 212
 213         glTexCoord2f(1.0f, 0.0f);
 214         glVertex2f(0.2f * 9.0f / 16.0f, y + 0.2f);
 215
 216         glTexCoord2f(0.0f, 0.0f);
 217         glVertex2f(0.0f, y + 0.2f);
 218
 219         glEnd();
 220
 221         // wheel selector
 222         glDisable(GL_TEXTURE_2D);
 223         glColor3f(0.0f, 0.0f, 0.0f);
 224         glPointSize(5.0f);
 225         glBegin(GL_POINTS);
 226         glVertex2f((0.1f + rad * cos(theta) * 0.1f) * 9.0f / 16.0f, y + 0.1f - rad * sin(theta) * 0.1f);
 227         glEnd();
 228
 229         // value slider
 230         glDisable(GL_TEXTURE_2D);
 231         glBegin(GL_QUADS);
 232
 233         glColor3f(0.0f, 0.0f, 0.0f);
 234         glVertex2f(0.22f * 9.0f / 16.0f, y);
 235         glVertex2f(0.24f * 9.0f / 16.0f, y);
 236
 237         glColor3f(1.0f, 1.0f, 1.0f);
 238         glVertex2f(0.24f * 9.0f / 16.0f, y + 0.2f);
 239         glVertex2f(0.22f * 9.0f / 16.0f, y + 0.2f);
 240
 241         glEnd();
 242
 243         // value selector
 244         glColor3f(0.0f, 0.0f, 0.0f);
 245         glPointSize(5.0f);
 246         glBegin(GL_POINTS);
 247         glVertex2f(0.23f * 9.0f / 16.0f, y + value * 0.2f);
 248         glEnd();
 249
 250         glColor3f(1.0f, 1.0f, 1.0f);
 251 }
 252
 253 void draw_saturation_bar(float y)
 254 {
 255         glUseProgramObjectARB(0);
 256         check_error();
 257
 258         // value slider
 259         glDisable(GL_TEXTURE_2D);
 260         glBegin(GL_QUADS);
 261
 262         glColor3f(0.0f, 0.0f, 0.0f);
 263         glVertex2f(0.0f * 9.0f / 16.0f, y + 0.02f);
 264         glVertex2f(0.0f * 9.0f / 16.0f, y);
 265
 266         glColor3f(1.0f, 1.0f, 1.0f);
 267         glVertex2f(0.2f * 9.0f / 16.0f, y);
 268         glVertex2f(0.2f * 9.0f / 16.0f, y + 0.02f);
 269
 270         glEnd();
 271
 272         // value selector
 273         glColor3f(0.0f, 0.0f, 0.0f);
 274         glPointSize(5.0f);
 275         glBegin(GL_POINTS);
 276         glVertex2f(0.2f * (saturation / 4.0f) * 9.0f / 16.0f, y + 0.01f);
 277         glEnd();
 278
 279         glColor3f(1.0f, 1.0f, 1.0f);
 280 }
 281
 282 void make_hsv_wheel_texture()
 283 {
 284         static unsigned char hsv_pix[HSV_WHEEL_SIZE * HSV_WHEEL_SIZE * 4];
 285         for (int y = 0; y < HSV_WHEEL_SIZE; ++y) {
 286                 for (int x = 0; x < HSV_WHEEL_SIZE; ++x) {
 287                         float yf = 2.0f * y / (float)(HSV_WHEEL_SIZE) - 1.0f;
 288                         float xf = 2.0f * x / (float)(HSV_WHEEL_SIZE) - 1.0f;
 289                         float rad = hypot(xf, yf);
 290                         float theta = atan2(yf, xf);
 291
 292                         float r, g, b;
 293                         hsv2rgb(theta, rad, 1.0f, &r, &g, &b);
 294                         hsv_pix[(y * HSV_WHEEL_SIZE + x) * 4 + 0] = lrintf(r * 255.0f);
 295                         hsv_pix[(y * HSV_WHEEL_SIZE + x) * 4 + 1] = lrintf(g * 255.0f);
 296                         hsv_pix[(y * HSV_WHEEL_SIZE + x) * 4 + 2] = lrintf(b * 255.0f);
 297
 298                         if (rad > 1.0f) {
 299                                 hsv_pix[(y * HSV_WHEEL_SIZE + x) * 4 + 3] = 0;
 300                         } else {
 301                                 hsv_pix[(y * HSV_WHEEL_SIZE + x) * 4 + 3] = 255;
 302                         }
 303                 }
 304                 printf("\n");
 305         }
 306
 307         glBindTexture(GL_TEXTURE_2D, HSV_WHEEL);
 308         check_error();
 309         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
 310         check_error();
 311         glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, HSV_WHEEL_SIZE, HSV_WHEEL_SIZE, 0, GL_RGBA, GL_UNSIGNED_BYTE, hsv_pix);
 312         check_error();
 313 }
 314
 315 void update_hsv()
 316 {
 317         hsv2rgb(lift_theta, lift_rad, lift_v, &lift_r, &lift_g, &lift_b);
 318         hsv2rgb(gamma_theta, gamma_rad, gamma_v * 2.0f, &gamma_r, &gamma_g, &gamma_b);
 319         hsv2rgb(gain_theta, gain_rad, gain_v * 4.0f, &gain_r, &gain_g, &gain_b);
 320
 321         if (saturation < 0.0) {
 322                 saturation = 0.0;
 323         }
 324
 325         printf("lift: %f %f %f\n", lift_r, lift_g, lift_b);
 326         printf("gamma: %f %f %f\n", gamma_r, gamma_g, gamma_b);
 327         printf("gain: %f %f %f\n", gain_r, gain_g, gain_b);
 328         printf("saturation: %f\n", saturation);
 329         printf("\n");
 330 }
 331
 332 void read_colorwheel(float xf, float yf, float *rad, float *theta, float *value)
 333 {
 334         if (xf < 0.2f && yf < 0.2f) {
 335                 float xp = 2.0f * xf / 0.2f - 1.0f;
 336                 float yp = -(2.0f * yf / 0.2f - 1.0f);
 337                 *rad = hypot(xp, yp);
 338                 *theta = atan2(yp, xp);
 339                 if (*rad > 1.0) {
 340                         *rad = 1.0;
 341                 }
 342         } else if (xf >= 0.22f && xf <= 0.24f) {
 343                 *value = yf / 0.2f;
 344         }
 345 }
 346
 347 void mouse(int x, int y)
 348 {
 349         float xf = (x / (float)WIDTH) * 16.0f / 9.0f;
 350         float yf = (HEIGHT - y) / (float)HEIGHT;
 351
 352         if (yf < 0.2f) {
 353                 read_colorwheel(xf, yf, &lift_rad, &lift_theta, &lift_v);
 354         } else if (yf >= 0.2f && yf < 0.4f) {
 355                 read_colorwheel(xf, yf - 0.2f, &gamma_rad, &gamma_theta, &gamma_v);
 356         } else if (yf >= 0.4f && yf < 0.6f) {
 357                 read_colorwheel(xf, yf - 0.4f, &gain_rad, &gain_theta, &gain_v);
 358         } else if (yf >= 0.6f && yf < 0.62f && xf < 0.2f) {
 359                 saturation = (xf / 0.2f) * 4.0f;
 360         }
 361
 362         update_hsv();
 363 }
 364
 365 void load_texture(const char *filename)
 366 {
 367         SDL_Surface *img = IMG_Load(filename);
 368         if (img == NULL) {
 369                 fprintf(stderr, "Load of '%s' failed\n", filename);
 370                 exit(1);
 371         }
 372
 373         // Convert to RGB.
 374         SDL_PixelFormat *fmt = img->format;
 375         SDL_LockSurface(img);
 376         unsigned char *src_pixels = (unsigned char *)img->pixels;
 377         unsigned char *dst_pixels = (unsigned char *)malloc(img->w * img->h * 3);
 378         for (unsigned i = 0; i < img->w * img->h; ++i) {
 379                 unsigned char r, g, b;
 380                 unsigned int temp;
 381                 unsigned int pixel = *(unsigned int *)(src_pixels + i * fmt->BytesPerPixel);
 382
 383                 temp = pixel & fmt->Rmask;
 384                 temp = temp >> fmt->Rshift;
 385                 temp = temp << fmt->Rloss;
 386                 r = temp;
 387
 388                 temp = pixel & fmt->Gmask;
 389                 temp = temp >> fmt->Gshift;
 390                 temp = temp << fmt->Gloss;
 391                 g = temp;
 392
 393                 temp = pixel & fmt->Bmask;
 394                 temp = temp >> fmt->Bshift;
 395                 temp = temp << fmt->Bloss;
 396                 b = temp;
 397
 398                 dst_pixels[i * 3 + 0] = r;
 399                 dst_pixels[i * 3 + 1] = g;
 400                 dst_pixels[i * 3 + 2] = b;
 401         }
 402         SDL_UnlockSurface(img);
 403
 404 #if 1
 405         // we will convert to sRGB in the shader
 406         glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, img->w, img->h, 0, GL_RGB, GL_UNSIGNED_BYTE, dst_pixels);
 407         check_error();
 408 #else
 409         // implicit sRGB conversion in hardware
 410         glTexImage2D(GL_TEXTURE_2D, 0, GL_SRGB8, img->w, img->h, 0, GL_RGB, GL_UNSIGNED_BYTE, dst_pixels);
 411         check_error();
 412 #endif
 413         free(dst_pixels);
 414         SDL_FreeSurface(img);
 415 }
 416
 417 void write_ppm(const char *filename, unsigned char *screenbuf)
 418 {
 419         FILE *fp = fopen(filename, "w");
 420         fprintf(fp, "P6\n%d %d\n255\n", WIDTH, HEIGHT);
 421         for (unsigned y = 0; y < HEIGHT; ++y) {
 422                 unsigned char *srcptr = screenbuf + ((HEIGHT - y - 1) * WIDTH) * 4;
 423                 for (unsigned x = 0; x < WIDTH; ++x) {
 424                         fputc(srcptr[x * 4 + 2], fp);
 425                         fputc(srcptr[x * 4 + 1], fp);
 426                         fputc(srcptr[x * 4 + 0], fp);
 427                 }
 428         }
 429         fclose(fp);
 430 }
 431
 432 int main(int argc, char **argv)
 433 {
 434         int quit = 0;
 435
 436         SDL_Init(SDL_INIT_EVERYTHING);
 437         SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 0);
 438         SDL_GL_SetAttribute(SDL_GL_STENCIL_SIZE, 0);
 439         SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
 440         SDL_SetVideoMode(WIDTH, HEIGHT, 0, SDL_OPENGL);
 441         SDL_WM_SetCaption("OpenGL window", NULL);
 442
 443         // geez
 444         glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
 445         glPixelStorei(GL_PACK_ALIGNMENT, 1);
 446
 447         glBindTexture(GL_TEXTURE_2D, SOURCE_IMAGE);
 448         check_error();
 449         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
 450         check_error();
 451
 452         load_texture("blg_wheels_woman_1.jpg");
 453         //glGenerateMipmap(GL_TEXTURE_2D);
 454         //glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_BASE_LEVEL, 4);
 455         //check_error();
 456
 457         //load_texture("maserati_gts_wallpaper_1280x720_01.jpg");
 458         //load_texture("90630d1295075297-console-games-wallpapers-wallpaper_need_for_speed_prostreet_09_1920x1080.jpg");
 459         //load_texture("glacier-lake-1280-720-4087.jpg");
 460
 461 #if 0
 462         // sRGB reverse LUT
 463         glBindTexture(GL_TEXTURE_1D, SRGB_REVERSE_LUT);
 464         check_error();
 465         glTexParameteri(GL_TEXTURE_1D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
 466         glTexParameteri(GL_TEXTURE_1D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
 467         check_error();
 468         float srgb_reverse_tex[4096];
 469         for (unsigned i = 0; i < 4096; ++i) {
 470                 float x = i / 4095.0;
 471                 if (x < 0.0031308f) {
 472                         srgb_reverse_tex[i] = 12.92f * x;
 473                 } else {
 474                         srgb_reverse_tex[i] = 1.055f * pow(x, 1.0f / 2.4f) - 0.055f;
 475                 }
 476         }
 477         glTexImage1D(GL_TEXTURE_1D, 0, GL_LUMINANCE16F_ARB, 4096, 0, GL_LUMINANCE, GL_FLOAT, srgb_reverse_tex);
 478         check_error();
 479
 480         // sRGB LUT
 481         glBindTexture(GL_TEXTURE_1D, SRGB_LUT);
 482         check_error();
 483         glTexParameteri(GL_TEXTURE_1D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
 484         glTexParameteri(GL_TEXTURE_1D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
 485         check_error();
 486         float srgb_tex[256];
 487         for (unsigned i = 0; i < 256; ++i) {
 488                 float x = i / 255.0;
 489                 if (x < 0.04045f) {
 490                         srgb_tex[i] = x * (1.0f / 12.92f);
 491                 } else {
 492                         srgb_tex[i] = pow((x + 0.055) * (1.0 / 1.055f), 2.4);
 493                 }
 494         }
 495         glTexImage1D(GL_TEXTURE_1D, 0, GL_LUMINANCE16F_ARB, 256, 0, GL_LUMINANCE, GL_FLOAT, srgb_tex);
 496         check_error();
 497 #endif
 498
 499         // generate a PDO to hold the data we read back with glReadPixels()
 500         // (Intel/DRI goes into a slow path if we don't read to PDO)
 501         glBindBuffer(GL_PIXEL_PACK_BUFFER_ARB, 1);
 502         glBufferData(GL_PIXEL_PACK_BUFFER_ARB, WIDTH * HEIGHT * 4, NULL, GL_STREAM_READ);
 503
 504         make_hsv_wheel_texture();
 505         update_hsv();
 506
 507         int prog = glCreateProgram();
 508         GLhandleARB vs_obj = read_shader("vs.glsl", GL_VERTEX_SHADER);
 509         GLhandleARB fs_obj = read_shader("fs.glsl", GL_FRAGMENT_SHADER);
 510         glAttachObjectARB(prog, vs_obj);
 511         check_error();
 512         glAttachObjectARB(prog, fs_obj);
 513         check_error();
 514         glLinkProgram(prog);
 515         check_error();
 516
 517         GLchar info_log[4096];
 518         GLsizei log_length = sizeof(info_log) - 1;
 519         log_length = sizeof(info_log) - 1;
 520         glGetProgramInfoLog(prog, log_length, &log_length, info_log);
 521         info_log[log_length] = 0;
 522         printf("link: %s\n", info_log);
 523
 524         struct timespec start, now;
 525         int frame = 0, screenshot = 0;
 526         clock_gettime(CLOCK_MONOTONIC, &start);
 527
 528         while (!quit) {
 529                 SDL_Event event;
 530                 while (SDL_PollEvent(&event)) {
 531                         if (event.type == SDL_QUIT) {
 532                                 quit = 1;
 533                         } else if (event.type == SDL_KEYDOWN && event.key.keysym.sym == SDLK_ESCAPE) {
 534                                 quit = 1;
 535                         } else if (event.type == SDL_KEYDOWN && event.key.keysym.sym == SDLK_F1) {
 536                                 screenshot = 1;
 537                         } else if (event.type == SDL_MOUSEBUTTONDOWN && event.button.button == SDL_BUTTON_LEFT) {
 538                                 mouse(event.button.x, event.button.y);
 539                         } else if (event.type == SDL_MOUSEMOTION && (event.motion.state & SDL_BUTTON(1))) {
 540                                 mouse(event.motion.x, event.motion.y);
 541                         }
 542                 }
 543
 544                 ++frame;
 545
 546                 draw_picture_quad(prog, frame);
 547
 548                 glReadPixels(0, 0, WIDTH, HEIGHT, GL_BGRA, GL_UNSIGNED_INT_8_8_8_8_REV, BUFFER_OFFSET(0));
 549                 check_error();
 550
 551                 draw_hsv_wheel(0.0f, lift_rad, lift_theta, lift_v);
 552                 draw_hsv_wheel(0.2f, gamma_rad, gamma_theta, gamma_v);
 553                 draw_hsv_wheel(0.4f, gain_rad, gain_theta, gain_v);
 554                 draw_saturation_bar(0.6f);
 555
 556                 SDL_GL_SwapBuffers();
 557                 check_error();
 558
 559                 unsigned char *screenbuf = (unsigned char *)glMapBuffer(GL_PIXEL_PACK_BUFFER_ARB, GL_READ_ONLY);
 560                 check_error();
 561                 if (screenshot) {
 562                         char filename[256];
 563                         sprintf(filename, "frame%05d.ppm", frame);
 564                         write_ppm(filename, screenbuf);
 565                         printf("Screenshot: %s\n", filename);
 566                         screenshot = 0;
 567                 }
 568                 glUnmapBuffer(GL_PIXEL_PACK_BUFFER_ARB);
 569                 check_error();
 570
 571 #if 1
 572                 clock_gettime(CLOCK_MONOTONIC, &now);
 573                 double elapsed = now.tv_sec - start.tv_sec +
 574                         1e-9 * (now.tv_nsec - start.tv_nsec);
 575                 printf("%d frames in %.3f seconds = %.1f fps (%.1f ms/frame)\n",
 576                         frame, elapsed, frame / elapsed,
 577                         1e3 * elapsed / frame);
 578 #endif
 579         }
 580         return 0;
 581 }