Simple some function returns "Overflow Exception"

Question

This code always through Arithmetic overflow exception. Whats wrong ?

Function ChannelSum(ByVal C As System.Drawing.Color) As Integer
    Dim temp As Integer : temp = (C.R + C.G + C.B)
    Return temp
End Function

...

Dim x, y, R, G, B, a As Integer : Dim tmp As Color
bmp = New Bitmap(picBox.Tag.ToString)
xMax = bmp.Width - 1 : yMax = bmp.Height - 1
For x = 0 To xMax Step 1
    For y = 0 To yMax Step 1
        tmp = bmp.GetPixel(x, y) : a = ChannelSum(tmp)
    Next y
Next x

The loop breaks in the first encounter !

The loop breaks in the first encounter ! When X and Y is 0, But the debugger shows X,Y have passed the xMax,yMax. I've copied all the code. — Sourav
– Sourav, Commented Aug 2, 2012 at 14:52
I would bet that your C.R,C.G,c.B are not returning an integer as you expect. Maybe you will need to do cInt on each of those. — Yosem
– Yosem, Commented Aug 2, 2012 at 14:54
What does that mean ? I'm using all the built in function. and valid color ranges from 0-255 and you are saying it's not returning INT. #confuzd :( — Sourav
– Sourav, Commented Aug 2, 2012 at 14:54

Holger Brandt · Accepted Answer · 2012-08-02 14:53:48Z

3

C.R and the others are byte fields and can only hold a value up to 255. Adding byte fields together will result in a number larger than 255. Use CInt() on each color element first.

 temp = (CInt(C.R) + CInt(C.G) + CInt(C.B))

answered Aug 2, 2012 at 14:53

Holger Brandt

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3 Comments

Sourav Over a year ago

You can accept an answer in 4 minutes, So wait for 4 mins. Thnx :)

Comfortably Numb Over a year ago

@Holger Brandt. Very weird, I'd thing it would detect that result is being assigned to an Integer variable.

Holger Brandt Over a year ago

@Trekstuff, actually, it always evaluates the expression on the right side of the equation first and then takes the results and tries to cast it into the datatype of the variable. Otherwise something like Dim tmp As String = 2 + 3 would probably show as "23" instead of "5".

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