/* samplerect.cpp - downsample check image based on corner coordinates
 */

static char usage[] = "usage: %s coords.txt in.png out.png width\n";

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include "imageLib.h"

#define RATIO24 1.525
#define RATIO140 1.402

void interp(int x0, int y0, int x1, int y1, int i, int max, int *xx, int *yy) {
  int dx = (x1 - x0) * i / max;
  int dy = (y1 - y0) * i / max;
  *xx = x0 + dx;
  *yy = y0 + dy;
}


int main(int argc, char **argv)
{
  int verbose = 1;
  if (argc != 5) {
    fprintf(stderr, usage, argv[0]);
    exit(1);
  }
  int optind = 1;
  char *coordname = argv[optind++];
  char *imname = argv[optind++];
  char *outname = argv[optind++];
  int imw = atoi(argv[optind++]);

  try {
    FILE *fp = fopen(coordname, "r");
    int x[4], y[4];
    for (int k = 0, *px = x, *py = y; k < 4; k++, px++, py++)
      fscanf(fp, "%d %d", px, py);
    fclose(fp);
    int w1 = x[1] - x[0];
    int w2 = x[3] - x[2];
    int h1 = y[2] - y[0];
    int h2 = y[3] - y[1];
    float r11 = (float)w1/h1;
    float r12 = (float)w1/h2;
    float r21 = (float)w2/h1;
    float r22 = (float)w2/h2;
    float r = (r11 + r12 + r21 + r22) / 4.0;
    printf("aspect ratios:\n %.3f\n %.3f\n %.3f\n %.3f\navg\n %.3f \n", r11, r12, r21, r22, r);
    float ratio;
    if (fabs(r - RATIO24) < fabs(r - RATIO140)) {
      printf("24 checkers: using ratio %g  ", RATIO24);
      ratio = RATIO24;
    } else {
      printf("140 checkers: using ratio %g  ", RATIO140);
      ratio = RATIO140;
    }
    int imh = (int)(imw / ratio);
    printf("image size: %d x %d\n", imw, imh);

    CByteImage im;
    ReadImageVerb(im, imname, verbose);
    CShape shim = im.Shape();
    int nB = shim.nBands;
    CShape sh(imw, imh, nB);
    CByteImage outim(sh);

    int xx0, yy0, xx1, yy1, xx, yy;
    for (int oy = 0; oy < imh; oy++) {
      interp(x[0], y[0], x[2], y[2], oy, imh-1, &xx0, &yy0);
      interp(x[1], y[1], x[3], y[3], oy, imh-1, &xx1, &yy1);
      for (int ox = 0; ox < imw; ox++) {
	interp(xx0, yy0, xx1, yy1, ox, imw-1, &xx, &yy);
	for (int b = 0; b < nB; b++)
	  outim.Pixel(ox, oy, b) = im.Pixel(xx, yy, b);
      }
    }

    WriteImageVerb(outim, outname, verbose);
  }
  catch (CError &err) {
    fprintf(stderr, err.message);
    fprintf(stderr, "\n");
    exit(1);
  }

  return 0;
}