efficient way to compare 2 images?

[bplus]

Well my idea didn't take so long for one compare, just blink and there's your answer:

Code: (Select All)

Randomize Timer

Screen _NewImage(1280, 720, 32)

'let's make this an unique and pretty image!
For i = 1 To 100
    Line (Rnd * _Width, Rnd * _Height)-(Rnd * width, Rnd * _Height), &HFF000000 + Rnd * &HFFFFFF, BF
Next

image2 = _CopyImage(0) 'identical copies for testing
image3 = _CopyImage(0) 'identical copy...  BUT
_Dest image3
PSet (Rnd * _Width, Rnd * _Height), &HFF000000 + Rnd * &HFFFFFF 'We've just tweaked it so that there's no way in hell it's the same as the other two now!
_Dest 0 'image3 is EXACTLY one pixel different from the other two.  Can we detect that?
image4 = _CopyImage(0) 'an identical copy once again, because 0 will change once we print the results

result1 = CompareImages(0, image2)
result2 = CompareImages(0, image3)
result3 = CompareImages(image2, image3)

Print "Current Screen and Image 1 Compare:  "; result1
Print "Current Screen and Image 2 Compare:  "; result2
Print "Image1 and Image 2 Compare        :  "; result3

Print
Print "Press <ANY KEY> for a speed test!"
Sleep

t# = Timer
Limit = 100
For i = 1 To Limit
    result = CompareImages&(image2, image3)
    result = CompareImages&(image2, image4)
Next
Print
Print Using "####.####### seconds to do"; Timer - t#;
Print Limit * 2; "comparisons."


Function CompareImages& (handle1 As Long, handle2 As Long)
    Dim As _Unsigned Long p1
    For y = 0 To _Height(handle1) - 1
        For x = 0 To _Width(handle1) - 1
            _Source handle1
            p1 = Point(x, y)
            _Source handle2
            If Point(x, y) <> p1 Then Exit Function
        Next
    Next
    CompareImages& = -1
End Function

Not nearly as quick as memory methods though.