Image comparison

[harsha]

I want to know how to compare the image through vb code.
My requirement is that When I scan a same page many times, the scanned image has different file size. So when i try to compare the scanned images of the same page , I get the result that the images are differrent. So by opening the image file and comparing bit by bit does not work.
I want to know how to compare the two images without depending upon the file size.

Thanks in advance.

Sriharsha

[vbPoet]

I have posted the same thread today

[dglienna]

You cannot compare something with 2000 dots to something with 4000 dots. They will always be different. The images must be the same size to compare the bits.

[Jacob Roman]

If you were to compare images of the same size, you would do something like this:

Option Explicit
 
Private Type Picture_Type
 
    Size As Long
    Width As Long
    Height As Long
 
End Type
 
Private Sub Command1_Click()
    
    Dim Pic(1) As Picture_Type
    
    Dim X As Long, Y As Long
    
    Dim Is_The_Same As Long
    
    Dim Comparison As Single
    
    With Picture1
        
        .BorderStyle = False
        .Picture = LoadPicture("C:\Jacob's Stuff\Pics\Alice.jpg")
        .AutoSize = True
        .AutoRedraw = True
        .ScaleMode = 3
            
    End With
    
    With Picture2
        
        .BorderStyle = False
        .Picture = LoadPicture("C:\Jacob's Stuff\Pics\whiterabbit.jpg")
        .AutoSize = True
        .AutoRedraw = True
        .ScaleMode = 3
        
    End With
    
    With Pic(0)
    
        .Size = Picture1.ScaleWidth * Picture1.ScaleHeight
        .Width = Picture1.ScaleWidth
        .Height = Picture1.ScaleHeight
            
    End With
    
    With Pic(1)
    
        .Size = Picture2.ScaleWidth * Picture1.ScaleHeight
        .Width = Picture2.ScaleWidth
        .Height = Picture2.ScaleHeight
            
    End With
    
    If Pic(0).Size = Pic(1).Size Then
    
        For Y = 0 To Pic(0).Height - 1
        
            For X = 0 To Pic(0).Width - 1
            
                If Picture1.Point(X, Y) = Picture2.Point(X, Y) Then
                
                    Is_The_Same = Is_The_Same + 1
                
                End If
            
            Next X
            
        Next Y
        
        Comparison = (Is_The_Same / Pic(0).Size) * 100
        
        MsgBox "Both images are " & Comparison & "% the same", vbInformation
    
    Else
    
        MsgBox "The pictures are not the same size, so no comparison will be made.", vbCritical
    
    End If

[vbPoet]

hmm Jacob
thx 4 code Smart Code.

thx David as well.

I think if both images are not of same size.
then we can restrict our
2 for statements to the smaller value of both images.

like
1st image 100 X 100
2nd image 200 X 50


then we can restrict our For statements as
for X 100
for Y 50

[dglienna]

that wouldn't work, either.

[Jacob Roman]

hmm Jacob
thx 4 code Smart Code.

thx David as well.

I think if both images are not of same size.
then we can restrict our
2 for statements to the smaller value of both images.

like
1st image 100 X 100
2nd image 200 X 50


then we can restrict our For statements as
for X 100
for Y 50

It obviously wouldn't be the same image if the images were a different size, so there would be no point in comparing them. Think what would happen if you were to compare a horizontal rectangle with a vertical one. It just can't happen.

[vbPoet]

Oh yeah
But if you look right at the top of this thread
it is nearly 3 years OLD thread.

But today in my original thread i have also edited that i want to know
how much % both are same.
100 %
50%
1 % only ......

[dglienna]

I think it would only be 100% match or not. If the color was different it would be different, the same picture would be different if the sun was shining at different times of the day, for instance.