Image areas

Obviously 1 is the biggest white area in the picture, but how do I check that?
I can only get all the pixels of the white colors at once.

That language you post the result in doesn't really matter too much, I'll just convert it to the language I need (Java).
I just need to find some logic in how to do this.

Just to clear things up, I have a method, lets call it getWhite(). When I call getWhite(), it returns all the white pixels in the image. With those pixels, I need to get the biggest white area of the area's of white pixels on the screen.

I hope you understand.

Form groups of white rectangles.

Choose a white pixel, and continually move left, right, up or down until you reach a non-white edge, and set that as your height or width. Do this over and over again until you've exhausted all the white areas in the image, and you'll end up with a list of rectangles. Then it's simply calculating which rectangle has the largest area.

@Nathan Not an efficient method but returns the largest rectangle based on the longest height of white pixels. Written in VB.NET:

Code:

Public Class Form1
    Structure WhiteBlock
        Dim Width As Integer
        Dim Height As Integer
    End Structure
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Dim Match = Color.White
        Dim Image As Bitmap = pb.Image
        Dim Heights As New List(Of Integer)
        Dim BlockList As New List(Of WhiteBlock)
        Dim CurrentWhiteBlock As New WhiteBlock
        For x As Integer = 0 To Image.Width - 1
            For y As Integer = 0 To Image.Height - 1
                If Image.GetPixel(x, y).ToArgb() = Match.ToArgb() Then
                    Image.SetPixel(x, y, Color.White)
                    CurrentWhiteBlock.Width += 1
                    CurrentWhiteBlock.Height += 1
                Else
                    Image.SetPixel(x, y, Color.Green)
                    If Not CurrentWhiteBlock.Height = 0 Then
                        If Not Heights.Contains(CurrentWhiteBlock.Height) Then
                            Heights.Add(CurrentWhiteBlock.Height)
                        End If
                    End If
                    CurrentWhiteBlock = New WhiteBlock
                End If
            Next
        Next
        Dim Largest As Integer = Heights(0)
        For Each n As Integer In Heights
            If n > Largest Then
                Largest = n
            End If
        Next
        lbl.Text = "Height of largest rectangle is: " & Largest
    End Sub
End Class