test/testpalette.c

/*
 * testpalette.c
 *
 * A simple test of runtime palette modification for animation
 * (using the SDL_SetPalette() API). 
 */

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

/* This isn't in the Windows headers */
#ifndef M_PI
#define M_PI	3.14159265358979323846
#endif

#include "SDL.h"

/* screen size */
#define SCRW 640
#define SCRH 480

#define NBOATS 5
#define SPEED 2

#ifndef MIN
#define MIN(a, b) ((a) < (b) ? (a) : (b))
#endif
#ifndef MAX
#define MAX(a, b) ((a) > (b) ? (a) : (b))
#endif

/*
 * wave colours: Made by taking a narrow cross-section of a wave picture
 * in Gimp, saving in PPM ascii format and formatting with Emacs macros.
 */
static SDL_Color wavemap[] = {
    {0, 2, 103}, {0, 7, 110}, {0, 13, 117}, {0, 19, 125},
    {0, 25, 133}, {0, 31, 141}, {0, 37, 150}, {0, 43, 158},
    {0, 49, 166}, {0, 55, 174}, {0, 61, 182}, {0, 67, 190},
    {0, 73, 198}, {0, 79, 206}, {0, 86, 214}, {0, 96, 220},
    {5, 105, 224}, {12, 112, 226}, {19, 120, 227}, {26, 128, 229},
    {33, 135, 230}, {40, 143, 232}, {47, 150, 234}, {54, 158, 236},
    {61, 165, 238}, {68, 173, 239}, {75, 180, 241}, {82, 188, 242},
    {89, 195, 244}, {96, 203, 246}, {103, 210, 248}, {112, 218, 250},
    {124, 224, 250}, {135, 226, 251}, {146, 229, 251}, {156, 231, 252},
    {167, 233, 252}, {178, 236, 252}, {189, 238, 252}, {200, 240, 252},
    {211, 242, 252}, {222, 244, 252}, {233, 247, 252}, {242, 249, 252},
    {237, 250, 252}, {209, 251, 252}, {174, 251, 252}, {138, 252, 252},
    {102, 251, 252}, {63, 250, 252}, {24, 243, 252}, {7, 225, 252},
    {4, 203, 252}, {3, 181, 252}, {2, 158, 252}, {1, 136, 251},
    {0, 111, 248}, {0, 82, 234}, {0, 63, 213}, {0, 50, 192},
    {0, 39, 172}, {0, 28, 152}, {0, 17, 132}, {0, 7, 114}
};

/* Call this instead of exit(), so we can clean up SDL: atexit() is evil. */
static void
quit (int rc)
{
    SDL_Quit ();
    exit (rc);
}

static void
sdlerr (char *when)
{
    fprintf (stderr, "SDL error: %s: %s\n", when, SDL_GetError ());
    quit (1);
}

/* create a background surface */
static SDL_Surface *
make_bg (SDL_Surface * screen, int startcol)
{
    int i;
    SDL_Surface *bg =
        SDL_CreateRGBSurface (SDL_SWSURFACE, screen->w, screen->h,
                              8, 0, 0, 0, 0);
    if (!bg)
        sdlerr ("creating background surface");

    /* set the palette to the logical screen palette so that blits
       won't be translated */
    SDL_SetColors (bg, screen->format->palette->colors, 0, 256);

    /* Make a wavy background pattern using colours 0-63 */
    if (SDL_LockSurface (bg) < 0)
        sdlerr ("locking background");
    for (i = 0; i < SCRH; i++) {
        Uint8 *p = (Uint8 *) bg->pixels + i * bg->pitch;
        int j, d;
        d = 0;
        for (j = 0; j < SCRW; j++) {
            int v = MAX (d, -2);
            v = MIN (v, 2);
            if (i > 0)
                v += p[-bg->pitch] + 65 - startcol;
            p[j] = startcol + (v & 63);
            d += ((rand () >> 3) % 3) - 1;
        }
    }
    SDL_UnlockSurface (bg);
    return (bg);
}

/*
 * Return a surface flipped horisontally. Only works for 8bpp;
 * extension to arbitrary bitness is left as an exercise for the reader.
 */
static SDL_Surface *
hflip (SDL_Surface * s)
{
    int i;
    SDL_Surface *z = SDL_CreateRGBSurface (SDL_SWSURFACE, s->w, s->h, 8,
                                           0, 0, 0, 0);
    /* copy palette */
    SDL_SetColors (z, s->format->palette->colors,
                   0, s->format->palette->ncolors);
    if (SDL_LockSurface (s) < 0 || SDL_LockSurface (z) < 0)
        sdlerr ("locking flip images");

    for (i = 0; i < s->h; i++) {
        int j;
        Uint8 *from = (Uint8 *) s->pixels + i * s->pitch;
        Uint8 *to = (Uint8 *) z->pixels + i * z->pitch + s->w - 1;
        for (j = 0; j < s->w; j++)
            to[-j] = from[j];
    }

    SDL_UnlockSurface (z);
    SDL_UnlockSurface (s);
    return z;
}

int
main (int argc, char **argv)
{
    SDL_Color cmap[256];
    SDL_Surface *screen;
    SDL_Surface *bg;
    SDL_Surface *boat[2];
    unsigned vidflags = 0;
    unsigned start;
    int fade_max = 400;
    int fade_level, fade_dir;
    int boatcols, frames, i, red;
    int boatx[NBOATS], boaty[NBOATS], boatdir[NBOATS];
    int gamma_fade = 0;
    int gamma_ramp = 0;

    if (SDL_Init (SDL_INIT_VIDEO) < 0)
        sdlerr ("initialising SDL");

    while (--argc) {
        ++argv;
        if (strcmp (*argv, "-hw") == 0)
            vidflags |= SDL_HWSURFACE;
        else if (strcmp (*argv, "-fullscreen") == 0)
            vidflags |= SDL_FULLSCREEN;
        else if (strcmp (*argv, "-nofade") == 0)
            fade_max = 1;
        else if (strcmp (*argv, "-gamma") == 0)
            gamma_fade = 1;
        else if (strcmp (*argv, "-gammaramp") == 0)
            gamma_ramp = 1;
        else {
            fprintf (stderr,
                     "usage: testpalette "
                     " [-hw] [-fullscreen] [-nofade] [-gamma] [-gammaramp]\n");
            quit (1);
        }
    }

    /* Ask explicitly for 8bpp and a hardware palette */
    if ((screen =
         SDL_SetVideoMode (SCRW, SCRH, 8, vidflags | SDL_HWPALETTE)) == NULL)
    {
        fprintf (stderr, "error setting %dx%d 8bpp indexed mode: %s\n",
                 SCRW, SCRH, SDL_GetError ());
        quit (1);
    }

    if (vidflags & SDL_FULLSCREEN)
        SDL_ShowCursor (SDL_FALSE);

    if ((boat[0] = SDL_LoadBMP ("sail.bmp")) == NULL)
        sdlerr ("loading sail.bmp");
    /* We've chosen magenta (#ff00ff) as colour key for the boat */
    SDL_SetColorKey (boat[0], SDL_SRCCOLORKEY | SDL_RLEACCEL,
                     SDL_MapRGB (boat[0]->format, 0xff, 0x00, 0xff));
    boatcols = boat[0]->format->palette->ncolors;
    boat[1] = hflip (boat[0]);
    SDL_SetColorKey (boat[1], SDL_SRCCOLORKEY | SDL_RLEACCEL,
                     SDL_MapRGB (boat[1]->format, 0xff, 0x00, 0xff));

    /*
     * First set the physical screen palette to black, so the user won't
     * see our initial drawing on the screen.
     */
    memset (cmap, 0, sizeof (cmap));
    SDL_SetPalette (screen, SDL_PHYSPAL, cmap, 0, 256);

    /*
     * Proper palette management is important when playing games with the
     * colormap. We have divided the palette as follows:
     *
     * index 0..(boatcols-1):           used for the boat
     * index boatcols..(boatcols+63):   used for the waves
     */
    SDL_SetPalette (screen, SDL_LOGPAL,
                    boat[0]->format->palette->colors, 0, boatcols);
    SDL_SetPalette (screen, SDL_LOGPAL, wavemap, boatcols, 64);

    /*
     * Now the logical screen palette is set, and will remain unchanged.
     * The boats already have the same palette so fast blits can be used.
     */
    memcpy (cmap, screen->format->palette->colors, 256 * sizeof (SDL_Color));

    /* save the index of the red colour for later */
    red = SDL_MapRGB (screen->format, 0xff, 0x00, 0x00);

    bg = make_bg (screen, boatcols);    /* make a nice wavy background surface */

    /* initial screen contents */
    if (SDL_BlitSurface (bg, NULL, screen, NULL) < 0)
        sdlerr ("blitting background to screen");
    SDL_Flip (screen);          /* actually put the background on screen */

    /* determine initial boat placements */
    for (i = 0; i < NBOATS; i++) {
        boatx[i] = (rand () % (SCRW + boat[0]->w)) - boat[0]->w;
        boaty[i] = i * (SCRH - boat[0]->h) / (NBOATS - 1);
        boatdir[i] = ((rand () >> 5) & 1) * 2 - 1;
    }

    start = SDL_GetTicks ();
    frames = 0;
    fade_dir = 1;
    fade_level = 0;
    do {
        SDL_Event e;
        SDL_Rect updates[NBOATS];
        SDL_Rect r;
        int redphase;

        /* A small event loop: just exit on any key or mouse button event */
        while (SDL_PollEvent (&e)) {
            if (e.type == SDL_KEYDOWN || e.type == SDL_QUIT
                || e.type == SDL_MOUSEBUTTONDOWN) {
                if (fade_dir < 0)
                    fade_level = 0;
                fade_dir = -1;
            }
        }

        /* move boats */
        for (i = 0; i < NBOATS; i++) {
            int old_x = boatx[i];
            /* update boat position */
            boatx[i] += boatdir[i] * SPEED;
            if (boatx[i] <= -boat[0]->w || boatx[i] >= SCRW)
                boatdir[i] = -boatdir[i];

            /* paint over the old boat position */
            r.x = old_x;
            r.y = boaty[i];
            r.w = boat[0]->w;
            r.h = boat[0]->h;
            if (SDL_BlitSurface (bg, &r, screen, &r) < 0)
                sdlerr ("blitting background");

            /* construct update rectangle (bounding box of old and new pos) */
            updates[i].x = MIN (old_x, boatx[i]);
            updates[i].y = boaty[i];
            updates[i].w = boat[0]->w + SPEED;
            updates[i].h = boat[0]->h;
            /* clip update rectangle to screen */
            if (updates[i].x < 0) {
                updates[i].w += updates[i].x;
                updates[i].x = 0;
            }
            if (updates[i].x + updates[i].w > SCRW)
                updates[i].w = SCRW - updates[i].x;
        }

        for (i = 0; i < NBOATS; i++) {
            /* paint boat on new position */
            r.x = boatx[i];
            r.y = boaty[i];
            if (SDL_BlitSurface (boat[(boatdir[i] + 1) / 2], NULL,
                                 screen, &r) < 0)
                sdlerr ("blitting boat");
        }

        /* cycle wave palette */
        for (i = 0; i < 64; i++)
            cmap[boatcols + ((i + frames) & 63)] = wavemap[i];

        if (fade_dir) {
            /* Fade the entire palette in/out */
            fade_level += fade_dir;

            if (gamma_fade) {
                /* Fade linearly in gamma level (lousy) */
                float level = (float) fade_level / fade_max;
                if (SDL_SetGamma (level, level, level) < 0)
                    sdlerr ("setting gamma");

            } else if (gamma_ramp) {
                /* Fade using gamma ramp (better) */
                Uint16 ramp[256];
                for (i = 0; i < 256; i++)
                    ramp[i] = (i * fade_level / fade_max) << 8;
                if (SDL_SetGammaRamp (ramp, ramp, ramp) < 0)
                    sdlerr ("setting gamma ramp");

            } else {
                /* Fade using direct palette manipulation (best) */
                memcpy (cmap, screen->format->palette->colors,
                        boatcols * sizeof (SDL_Color));
                for (i = 0; i < boatcols + 64; i++) {
                    cmap[i].r = cmap[i].r * fade_level / fade_max;
                    cmap[i].g = cmap[i].g * fade_level / fade_max;
                    cmap[i].b = cmap[i].b * fade_level / fade_max;
                }
            }
            if (fade_level == fade_max)
                fade_dir = 0;
        }

        /* pulse the red colour (done after the fade, for a night effect) */
        redphase = frames % 64;
        cmap[red].r = (int) (255 * sin (redphase * M_PI / 63));

        SDL_SetPalette (screen, SDL_PHYSPAL, cmap, 0, boatcols + 64);

        /* update changed areas of the screen */
        SDL_UpdateRects (screen, NBOATS, updates);
        frames++;
    }
    while (fade_level > 0);

    printf ("%d frames, %.2f fps\n",
            frames, 1000.0 * frames / (SDL_GetTicks () - start));

    if (vidflags & SDL_FULLSCREEN)
        SDL_ShowCursor (SDL_TRUE);
    SDL_Quit ();
    return 0;
}