Thread: ignore a rectangular area in a bmp image during image comparison

Below is the pseudo code to compare two image by ignoring the rectangular area which contains dynamic data

Code:

#include <stdio.h>

#define WID 200
#define DEP 600
 
typedef struct {
int left;
int top;
int right;
int bot;
} rect;
 
char image1[WID*DEP];
char image2[WID*DEP];
 
int inrect (int x, int y, rect r) {
if (x<r.left || x>r.right || y<r.top || y>r.bot)
    return 0;
return 1;
}
 
  int compareimages (char *im1, char* im2, int wid, int dep, rect *rarr,   int rects) 
{
   int x, y, n, ignore;
   for (y=0; y<dep; y++)
    for (x=0; x<wid; x++) {
    int read_bytes = fread(&k, 1, 1, image1); // 
        ignore = 0;
       for (n=0; n<rects; n++)
            ignore |= inrect (x, y, rarr[n]);
        if (!ignore)
            if (k != im2[y*wid+x])   // compare pixels
                return 0;
    }
return 1;
}
 
int main(void) {
rect rectarr[2] = { {10, 10, 50, 50}, { 40, 40, 90, 90 }};
// ... load images ...

// put pixel in one of the rectangles
image1[20*WID+20] = 1;
if (compareimages (image1, image2, WID, DEP, rectarr, 2))
    printf ("Same\n");
else
    printf ("Different\n");
 
// put pixel outside any rectangles
image1[0] = 1;
if (compareimages (image1, image2, WID, DEP, rectarr, 2))
    printf ("Same\n");
else
    printf ("Different\n");
return 0;
}

Above code works fine if each pixel has 1 byte but if i want to compare bmp image where each pixel has 4 byte each byte for red,green,blue and alpha channel how to do that please help