/* sRGB.cpp
 * Daniel Scharstein 2/11/09
 * applies inverse sRGB transform to (hopefully) linearize an image
 */

static char *usage = "\n  usage: %s [-quiet] sRGB.png linear.png\n";

#include <stdio.h>
#include <cmath>

#include "imageLib.h"

// convert from sRGB to linear
// see http://en.wikipedia.org/wiki/SRGB
void inv_sRGB(CByteImage im)
{
    CShape sh = im.Shape();
    int width = sh.width, height = sh.height;
    int ncols = __min(sh.nBands, 3);
    for (int y = 0; y < height; y++) {
	for (int x = 0; x < width; x++) {
	    uchar *p = &im.Pixel(x, y, 0);
	    for (int b = 0; b < ncols; b++) {
		double v = p[b] / 255.0;
		if (v <= 0.04045)
		    v /= 12.92;
		else
		    v = pow((v + 0.055) / 1.055, 2.4);
		int n = (int)( 255.0 * v + 0.5);
		if (n < 0) throw CError("n < 0");
		if (n > 255) throw CError("n > 255");
		p[b] = n;
	    }
	}
    }
}

int main(int argc, char *argv[])
{
    try {
	int verbose = 1;
	int argn = 1;
	if (argc > 1 && argv[1][0]=='-' && argv[1][1]=='q') {
	    verbose = 0;
	    argn++;
	}
	if (argn == argc-2) {
	    CByteImage im;
	    ReadImageVerb (im, argv[argn++], verbose);
	    inv_sRGB(im);
	    WriteImageVerb(im, argv[argn++], verbose);
	} else
	    throw CError(usage, argv[0]);
    }
    catch (CError &err) {
	fprintf(stderr, err.message);
	fprintf(stderr, "\n");
	return -1;
    }
    return 0;
}