efficient way to compare 2 images?

[SMcNeill]

bplus's demo, modified to just check alpha levels and not colors themselves:

Code: (Select All)

Screen _NewImage(800, 600, 32)
Dim i As Long
For i = 0 To 255
    Cls
    Line (100, 100)-Step(100, 100), _RGB32(255, 0, 0, i), BF
    Line (300, 100)-Step(100, 100), _RGB32(255, 0, 0), BF
    If _Alpha32(Point(150, 150)) = _Alpha32(Point(350, 150)) Then
        Print "When alpha ="; i; " have NO difference, zzz ..."
    Else
        Print "When alpha ="; i; " have difference, zzz ..."
    End If
    Print Hex$(Point(150, 150)), Hex$(Point(350, 150))
    Sleep
Next

Modified to print the actual color values that are on the screen for you.