// compute residual image for teaser firgure in paper

static char *usage ="\n  usage: %s in1.png in2.png residout.png\n";

#include "imageLib.h"
#include "math.h"
#include <stdlib.h>
#define VERBOSE 1

#define ROUND(x) ((x) >= 0? ((int)((x) + .5)) : ((int)((x) - .5)))

/*
http://www.eecs.harvard.edu/~ayanc/indep_polyc_n/CanonEOS5D-wb1i2e3.htm#b1d5
i_r = 0.936820 R + 0.331565 G + 0.111501 B
i_g = -0.076041 R + 0.987069 G + 0.141115 B
i_b = -0.062749 R + 0.117385 G + 0.991102 B

Red = -1.45e+00 + 1.61e+03 i + -5.72e+03 i^2 + 1.21e+04 i^3 + -1.36e+04 i^4 + 6.05e+03 i^5
Green = 2.66e+00 + 1.96e+03 i + -8.43e+03 i^2 + 2.20e+04 i^3 + -3.23e+04 i^4 + 2.05e+04 i^5
Blue = -1.15e+00 + 2.03e+03 i + -8.49e+03 i^2 + 1.94e+04 i^3 + -2.21e+04 i^4 + 9.78e+03 i^5
*/
#define deg 5
int main(int argc, char *argv[])
{
    double pol[3][deg+1] = /* B, G, R */
	{{-1.15e+00, 2.03e+03, -8.49e+03, 1.94e+04, -2.21e+04, 9.78e+03},
	 { 2.66e+00, 1.96e+03, -8.43e+03, 2.20e+04, -3.23e+04, 2.05e+04},
	 {-1.45e+00, 1.61e+03, -5.72e+03, 1.21e+04, -1.36e+04, 6.05e+03}};

    try {
	if (argc < 4)
	    throw CError(usage, argv[0]);
	int argn = 1;
	char *in1file = argv[argn++];
	char *in2file = argv[argn++];
	char *outfile = argv[argn++];

	CByteImage im1, im2;
	ReadImageVerb(im1, in1file, VERBOSE);
	ReadImageVerb(im2, in2file, VERBOSE);
	CShape sh = im1.Shape();
	int w = sh.width, h = sh.height;
	CByteImage resid(sh);
	for(int y = 0; y < h; y++){
	    for(int x = 0; x < w; x++){
		for (int b = 0; b < 3; b++){
		    double v1 = im1.Pixel(x, y, b);
		    double v2 = im2.Pixel(x, y, b);
		    if (0) { // apply polynomial
			//v1 /= 255;
			//v2 /= 255;
			double s = 0;
			double v = 1;
			for (int k = 0; k <= deg; k++) {
			    s += v * pol[b][k];
			    v *= v1;
			}
			v1 = s;
		    }
		    double diff = v1 - v2;
		    //if (diff < 0) diff = -diff;
		    diff *= 1; // scale
		    int idiff = 128 + (int)ROUND(diff);
		    resid.Pixel(x, y, b) = __min(255, __max(0, idiff));
		}
		resid.Pixel(x, y, 3) = 255; // full alpha
	    }
	}
	WriteImageVerb(resid, outfile, VERBOSE);
    }
    catch (CError &err) {
	fprintf(stderr, err.message);
	fprintf(stderr, "\n");
	return -1;
    }
  
    return 0;
}