asked on

[VB6] Compare two images and show percentage that one matches the other ?

I use the GetDIBits() API function to compare two images to tell if they're the same or different much quicker than using GetPixel or other methods. But is there any way to show percentage that one matches the other ? Here is the project
CompareImages.zip

aikimark

The correct approach for best performance is to populate two arrays as efficiently as possible and then compare the pixel locations. Count the number of times the pixel values are different and divide by the total number of pixels (=rows*columns)

Lukie Luke

ASKER

Can you specify the code ? Thank you in advance :)

aikimark

If you are using the API function, you already have the arrays populated. Nest two For...Next loops, one for the row value and one for the column value.
Example:

For lngRow=0 to ubound(dibarray,1)
   For lngCol=0 to ubound(dibarray,2)
   Next
Next

Open in new window

Lukie Luke

ASKER

Sorry I don't want to bother you but please read, edit the project and upload it again. My main problem is to show the percentage between two images. I don't really understand your code.

aikimark

@Lukie Luke

please read, edit the project and upload it again

Is this your program?
Do you know how to program?

Lukie Luke

ASKER

I'm new to VB. I found it from vbforum

aikimark

Do you know how to program in any language?

Lukie Luke

ASKER

@aikimark Yes, I know a bit of programing in Visual Basic 6.0

ASKER CERTIFIED SOLUTION

aikimark

membership

This solution is only available to members.

To access this solution, you must be a member of Experts Exchange.

Start Free Trial

Lukie Luke

ASKER

Thank you, sir

PortletPaul

The .bas file in that zip is represented here.

There is a nested loop at the end of that VB code, "Private Function ComparePixels() As Boolean "

If you create a similar function with a nested loop, counting when pixels are true, or false, or both, then you have the basis for a percentage calculation. (nb: if you have the total size to start with then you don't need both but you could do it that way.)

Note the existing function has an "Exit For" escape, so it does not compare all pixels if a difference is found (so it is just determining "different" or "not-different").

ps: I haven't touched VB in a million years (or thereabouts) so I'm not offering more than this

Lukie Luke

ASKER

Thank you sir for the advise :)