Compare Images

[SMcNeill]

Code: (Select All)

'int memcmp(const void *str1, const void *str2, size_t n)

Declare CustomType Library
    Function memcmp% (ByVal s1%&, Byval s2%&, Byval n As _Offset)
End Declare



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 resul


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 = 1000
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)
    Static m(1) As _MEM
    m(0) = _MemImage(handle1): m(1) = _MemImage(handle2)
    If m(0).SIZE <> m(1).SIZE Then Exit Function 'not identical
    If m(0).ELEMENTSIZE <> m(1).ELEMENTSIZE Then Exit Function 'not identical
    If memcmp(m(0).OFFSET, m(1).OFFSET, m(0).SIZE) = 0 Then x = -1 Else x = 0
    CompareImages = x
End Function

Copied from deep inside another topic and shared here for ease of search and reference.