This repository has been archived by the owner on Feb 11, 2021. It is now read-only.
testgamma.c
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/* Bring up a window and manipulate the gamma on it */
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <math.h>
#include "SDL.h"
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/* Call this instead of exit(), so we can clean up SDL: atexit() is evil. */
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static void
quit(int rc)
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SDL_Quit();
exit(rc);
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/* Turn a normal gamma value into an appropriate gamma ramp */
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void
CalculateGamma(double gamma, Uint16 * ramp)
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int i, value;
gamma = 1.0 / gamma;
for (i = 0; i < 256; ++i) {
value = (int) (pow((double) i / 256.0, gamma) * 65535.0 + 0.5);
if (value > 65535) {
value = 65535;
}
ramp[i] = (Uint16) value;
}
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}
/* This can be used as a general routine for all of the test programs */
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int
get_video_args(char *argv[], int *w, int *h, int *bpp, Uint32 * flags)
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int i;
*w = 640;
*h = 480;
*bpp = 0;
*flags = SDL_SWSURFACE;
for (i = 1; argv[i]; ++i) {
if (strcmp(argv[i], "-width") == 0) {
if (argv[i + 1]) {
*w = atoi(argv[++i]);
}
} else if (strcmp(argv[i], "-height") == 0) {
if (argv[i + 1]) {
*h = atoi(argv[++i]);
}
} else if (strcmp(argv[i], "-bpp") == 0) {
if (argv[i + 1]) {
*bpp = atoi(argv[++i]);
}
} else if (strcmp(argv[i], "-fullscreen") == 0) {
*flags |= SDL_FULLSCREEN;
} else if (strcmp(argv[i], "-hw") == 0) {
*flags |= SDL_HWSURFACE;
} else if (strcmp(argv[i], "-hwpalette") == 0) {
*flags |= SDL_HWPALETTE;
} else
break;
}
return i;
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}
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int
main(int argc, char *argv[])
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SDL_Surface *screen;
SDL_Surface *image;
float gamma;
int i;
int w, h, bpp;
Uint32 flags;
Uint16 ramp[256];
Uint16 red_ramp[256];
Uint32 then, timeout;
/* Check command line arguments */
argv += get_video_args(argv, &w, &h, &bpp, &flags);
/* Initialize SDL */
if (SDL_Init(SDL_INIT_VIDEO) < 0) {
fprintf(stderr, "Couldn't initialize SDL: %s\n", SDL_GetError());
return (1);
}
/* Initialize the display, always use hardware palette */
screen = SDL_SetVideoMode(w, h, bpp, flags | SDL_HWPALETTE);
if (screen == NULL) {
fprintf(stderr, "Couldn't set %dx%d video mode: %s\n",
w, h, SDL_GetError());
quit(1);
}
/* Set the window manager title bar */
SDL_WM_SetCaption("SDL gamma test", "testgamma");
/* Set the desired gamma, if any */
gamma = 1.0f;
if (*argv) {
gamma = (float) atof(*argv);
}
if (SDL_SetGamma(gamma, gamma, gamma) < 0) {
fprintf(stderr, "Unable to set gamma: %s\n", SDL_GetError());
quit(1);
}
#if 0 /* This isn't supported. Integrating the gamma ramps isn't exact */
/* See what gamma was actually set */
float real[3];
if (SDL_GetGamma(&real[0], &real[1], &real[2]) < 0) {
printf("Couldn't get gamma: %s\n", SDL_GetError());
} else {
printf("Set gamma values: R=%2.2f, G=%2.2f, B=%2.2f\n",
real[0], real[1], real[2]);
}
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#endif
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/* Do all the drawing work */
image = SDL_LoadBMP("sample.bmp");
if (image) {
SDL_Rect dst;
dst.x = (screen->w - image->w) / 2;
dst.y = (screen->h - image->h) / 2;
dst.w = image->w;
dst.h = image->h;
SDL_BlitSurface(image, NULL, screen, &dst);
SDL_UpdateRects(screen, 1, &dst);
}
/* Wait a bit, handling events */
then = SDL_GetTicks();
timeout = (5 * 1000);
while ((SDL_GetTicks() - then) < timeout) {
SDL_Event event;
while (SDL_PollEvent(&event)) {
switch (event.type) {
case SDL_QUIT: /* Quit now */
timeout = 0;
break;
case SDL_KEYDOWN:
switch (event.key.keysym.sym) {
case SDLK_SPACE: /* Go longer.. */
timeout += (5 * 1000);
break;
case SDLK_UP:
gamma += 0.2f;
SDL_SetGamma(gamma, gamma, gamma);
break;
case SDLK_DOWN:
gamma -= 0.2f;
SDL_SetGamma(gamma, gamma, gamma);
break;
case SDLK_ESCAPE:
timeout = 0;
break;
default:
break;
}
break;
}
}
}
/* Perform a gamma flash to red using color ramps */
while (gamma < 10.0) {
/* Increase the red gamma and decrease everything else... */
gamma += 0.1f;
CalculateGamma(gamma, red_ramp);
CalculateGamma(1.0 / gamma, ramp);
SDL_SetGammaRamp(red_ramp, ramp, ramp);
}
/* Finish completely red */
memset(red_ramp, 255, sizeof(red_ramp));
memset(ramp, 0, sizeof(ramp));
SDL_SetGammaRamp(red_ramp, ramp, ramp);
/* Now fade out to black */
for (i = (red_ramp[0] >> 8); i >= 0; --i) {
memset(red_ramp, i, sizeof(red_ramp));
SDL_SetGammaRamp(red_ramp, NULL, NULL);
}
SDL_Delay(1 * 1000);
SDL_Quit();
return (0);
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}