算术运算导致溢出..以下高亮代码中的错误

debugcn 发表于 Dev

帕特尔

Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
    Compare(PictureBox1.Image, PictureBox2.Image)
End Sub

Public Function Compare(ByVal img1_ As Image, ByVal img2_ As Image) As Double
    Dim pixelNb As Integer = img1_.Width * img1_.Height
    Dim percent As Double = 100
    Dim resized_img2_ As Bitmap = ResizeBitmap(CType(img2_, Bitmap), img1_.Width, img1_.Height)
    For i As Integer = 0 To img1_.Width - 1
        For j As Integer = 0 To img1_.Height - 1
            percent -= ColorCompare((CType(img1_, Bitmap)).GetPixel(i, j), (CType(resized_img2_, Bitmap)).GetPixel(i, j)) / pixelNb
        Next
    Next

    Return percent
End Function

Public Function ResizeBitmap(ByVal b As Bitmap, ByVal nWidth As Integer, ByVal nHeight As Integer) As Bitmap
    Dim result As Bitmap = New Bitmap(nWidth, nHeight)
    Using g As Graphics = Graphics.FromImage(CType(result, Image))
        g.DrawImage(b, 0, 0, nWidth, nHeight)
    End Using

    Return result
End Function

Public Function ColorCompare(ByVal c1 As Color, ByVal c2 As Color) As Double
    Return Double.Parse((Math.Abs(c1.B - c2.B) + Math.Abs(c1.R - c2.R) + Math.Abs(c1.G - c2.G)).ToString()) * 100 / (3 * 255)
End Function

在这一行中给出错误

Return Double.Parse((Math.Abs(c1.B - c2.B) + Math.Abs(c1.R - c2.R) +
           Math.Abs(c1.G - c2.G)).ToString()) * 100 / (3 * 255)

玛丽

c1.B 返回一个字节。字节的值为 0-255 并且是无符号的，因此它不能保存负值。

Dim a As Byte = 200
Dim b As Byte = 201
Dim x  = a - b

导致相同的溢出错误。更改为整数可避免该错误。演员似乎没有必要，因为它正在扩大（无数据丢失）。

    Dim a As Byte = 200
        Dim b As Byte = 201
        Dim c As Integer = a
        Dim d As Integer = b
        Dim x = c - d

将颜色字节更改为整数，然后重试。

Dim g, h, i, j, k, l As Integer
g = c1.B
h = c2.B
i = c1.R
j = c1.R
k = c1.G
l = c1.G
Dim result As Double = CDbl(Math.Abs(g - h) + Math.Abs(i - j) + Math.Abs(k - l)) * 100 / (3 * 255)
    Return result

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