Area calculation from image

[rbulph]

How can I calculate the green area in the attachment? Or simply the number of green pixels it contains would be enough to get me there.

[mandelbrot]

Are we talking pure green (i.e. 0,255,0) or shades of green? If we're also looking at shades, then what's your tolerance? What about the areas of white, if it's the interior of the building you're looking at?...

[rbulph]

Are we talking pure green (i.e. 0,255,0) or shades of green? If we're also looking at shades, then what's your tolerance? What about the areas of white, if it's the interior of the building you're looking at?...

 

The image has been produced by scanning a diagram, maximising the contrast, and then using the fill function in MS Paint to fill in all the internal areas in green. So I'm simply interested in the area that MS Paint has filled in. So the answer to your question is simply "whatever green MS Paint has provided."

 

I've found that it doesn't take my computer more than a minute to check each pixel in the diagram, and it's easy to code, so that's what I've now done in fact.

[mandelbrot]

LOL! That's what I was going to recommend. Another option, especially in larger images, would be to allow the user to set crop regions...

[snarfblam]

How are you examining the pixels?

[rbulph]

How are you examining the pixels?

 

Like this

 

 Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

       With Me.PictureBox1
           Dim b As New Bitmap(.Image.Width, .Image.Height)
           b = .Image
           Dim s As Integer
           For n As Integer = 1 To .Image.Width
               For m As Integer = 1 To .Image.Height
                   Dim q As Color = b.GetPixel(n - 1, m - 1)
                   If q.G = 0 And q.R > 250 Then s = s + 1 'plan had red infill. Check for no green as well so white is excluded.
               Next
           Next
           MsgBox(s)
       End With

   End Sub

[snarfblam]

You could make this much, much faster by examining the raw image data rather than using the GetPixel method. I'll see if I can find the tutorial I wrote on the topic.

[snarfblam]

Link (this is padding to shut up vB).