Checking to see if two 'HBITMAP's are the same?? (PLEASE help)

**SyntaxBubble** · 09-14-2003

Hi. Thanks for reading this. In my application I would like to see if a bitmap on a static control is the same as a bitmap I load in a loop. It looks like this:

Code:

	HBITMAP hBitmap;    // Handle to current tile's bitmap object
	FILE *pFile = fopen("myMap.txt", "wb");

	// TODO: Loop through the tile vector objects and write
	//       them to the specified file
	for (int current = 0; current < m_wndTile.size(); current++) 
	{
		hBitmap = m_wndTile[current]->GetBitmap();    // Get current tile's bitmap data
		for (int rsrc = 131; rsrc <= 132; rsrc++)   // Loop resource bitmaps
		{
			/* This section will check for a matching */
			/* resource id. if one is found, it will  */
			/* write the tile data to the file        */

		}
	}
	fclose(pFile);      // Close the file

Inside the 'for' loop containing the 'rsrc' of type 'int' is where I need to compare the two. I am making a level editor in MFC for a game I was working on a while back. How would I check to see if the 'hBitmap' object is equal to the bitmap loaded with the resource ID 'rsrc'? Please help if possible.

Thanks,
Matt U.

**novacain** · 09-14-2003

You would first check sizes, colour depth ect.

GetObject() with a BITMAP struct

Then check the actual bits.

Realy all you need to do is convert both to byte arrays (inc header) and compare one to the other in a loop.

GetDIBits() may help.

But the images may be the same 'picture' but diff sizes, colour depths ect and you will not be able to tell.

Could perform a threshold (all values above/below the threshold are turned black or white) or stretch ( all values are multiplied by a constant ie 4 to accentuate the image) or a histogram (the differnce from on pixcell to another is recorded looking peaks which are edges) but it depends on what you are looking for.

**Sebastiani** · 09-15-2003

This *might* work as long as the original bitmap was loaded with LoadImage() *and* it wasn't loaded from a file *and* the LR_SHARED flag is always used.

Code:

if(hBitmap == (HBITMAP)
   LoadImage(hInstance, MAKEINTRESOURCE(rsrc), IMAGE_BITMAP, 0, 0, LR_SHARED))
 // do something

Just a thought anyway. Note that it doesn't really compare the bitmaps, it just sees if they have the same handle, which may well be improbable, depending on your circumstances.

**Hunter2** · 09-15-2003

Realy all you need to do is convert both to byte arrays

GetPixel(hDC, x, y)

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