ignore a rectangular area in a bmp image during image comparison

Question

0.00/5 (No votes)

See more:

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

Objective-C

#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

Posted 15-Mar-15 22:20pm

rahul15001

Add a Solution

1 solution

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Frankie-C · Answer 1 · 2015-03-16T01:13:00

Read the four bytes together as DWORD, or unsigned int as you prefer, dimension your image arrays as same var type and you're done ;)

C++

#include <stdio.h>

#define WID 200
#define DEP 600
 
typedef struct {
int left;
int top;
int right;
int bot;
} rect;
 
DWORD image1[WID*DEP];
DWORD 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 (DWORD *im1, DWORD *im2, int wid, int dep, rect *rarr,   int rects) 
{
   int x, y, n, ignore;
   DWORD k; //You have not defined it in your code! 
   for (y=0; y<dep; y++)
    for (x=0; x<wid; x++) {
    int read_bytes = fread(&k, 4, 1, image1); // read four bytes
        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;
}