Averaging color of an Image - vb.net

Question

I'm using this code to calculate the average color of an image but this is not working as desired. The result is inaccurate.
How to find the average color of the image ?
Private Sub btnAvg_Click() Handles btnAvg.Click
Dim x, y As Integer
bmp = New Bitmap(picBox.Tag.ToString)
For y = picBox.Top To picBox.Bottom
For x = picBox.Left To picBox.Right
With bmp.GetPixel(x, y)
totalR = totalR + .R : totalG = totalG + .G : totalB = totalB + .B
End With
Next x
Next y
avgR = totalR / ((picBox.Bottom - picBox.Top) * (picBox.Right - picBox.Left))
avgG = totalG / ((picBox.Bottom - picBox.Top) * (picBox.Right - picBox.Left))
avgB = totalB / ((picBox.Bottom - picBox.Top) * (picBox.Right - picBox.Left))
End Sub
I'm looking for a hi-speed, more than 80% accurate result. This is not a duplicate question as other questions deals with C# only

Answer 1

This should work:
Private Function getAverageColor(ByVal imageFilePath As String) As Color
Dim bmp As New Bitmap(imageFilePath)
Dim totalR As Integer = 0
Dim totalG As Integer = 0
Dim totalB As Integer = 0
For x As Integer = 0 To bmp.Width - 1
For y As Integer = 0 To bmp.Height - 1
Dim pixel As Color = bmp.GetPixel(x, y)
totalR += pixel.R
totalG += pixel.G
totalB += pixel.B
Next
Next
Dim totalPixels As Integer = bmp.Height * bmp.Width
Dim averageR As Integer = totalR \ totalPixels
Dim averageg As Integer = totalG \ totalPixels
Dim averageb As Integer = totalB \ totalPixels
Return Color.FromArgb(averageR, averageg, averageb)
End Function

Answer 2

Averaging colors doesn't make much sense in general. What's the average of hot pink and navy yellow? The way you are calculating it now produces a completely different color.
You'll need to work in a different color space. HSB is an easy one to work with and directly supported by the Color type. Albeit that it doesn't deal with the strongly non-linear color perception of the human eye. Color.GetHue() returns the hue, a value that's directly proportional to the color. You also ought to create a histogram so that the background of the photo doesn't disturb the results too much. Or at least work from the center of photo outwards. Whether that's good enough to detect skin color is fairly doubtful.

Answer 3

You could try this code and see if the results suit you. It reduces the image to a single pixel thumbnail:
Private Function getAverageColor(ByVal imageFilePath As String) As Color
Dim bmp As New Bitmap(imageFilePath)
Dim thumb As New Bitmap(bmp.GetThumbnailImage(1, 1, Nothing, IntPtr.Zero))
Return thumb.GetPixel(0, 0)
End Function