.NET [VB.NET] Auto Crop Image - Printable Version

Code
Function Crop(ByVal p As Image) As Image

    Dim x, y As Int32 'for use of X,Y Coordinates of pixels

    Dim b As New Bitmap(p) 'image needed to crop

    Dim c As New Color() 'pixel color for use of identifying if background

    

    Dim intLeft As Int32 'furthest left X coordinate

    Dim intRight As Int32 'furthest right X coordinate

    Dim intBottom As Int32 'furthest to the bottom Y coordinate

    Dim intTop As Int32 'furthest to top Y coordinate

    y = 0

    Do Until y = b.Height 'loop through pixels on Y axis until end of image height

    x = 0

    Do Until x = b.Width 'loop through pixels on X axis until end of image width

    c = b.GetPixel(x, y) 'Get the color of the pixel

    'First we want to establish if the pixel is White (the color of our background)

    If c.R <> 0 And c.G <> 0 And c.B <> 0 Then

    'We'll also want to ignore colors close to the background color

    'I did this because some of the images I had were scanned, and 

    'the paper color didn't always scan at a perfect white

    If c.R < 250 Or c.G < 250 Or c.B < 250 Then

    'Determine if pixel is further left than the value we already have

    If intLeft <= 0 And intLeft < x Then

    intLeft = x

    End If

    'Determine if pixel is further to the top than the value we already have

    If intTop <= 0 And intTop < y Then

    intTop = y

    End If

    'Determine if pixel is further right than the value we already have

    If intRight <= b.Width And intRight < x Then

    intRight = x

    End If

    'Determine if pixel is further to the bottom than the value we already have

    If intBottom <= b.Height And intBottom < y Then

    intBottom = y

    End If

    End If

    End If

    x += 1

    Loop

    y += 1

    Loop

    Dim intNewWidth As Int32 = (intRight) 'Establish width of new cropped image

    Dim intNewHeight As Int32 = (intBottom) 'Establish height of new cropped image

    'Create new image with a 10 pixel buffer, so image won't be too close to edge

    Dim imgCropped As New Bitmap(intNewWidth + 10, intNewHeight + 10)

    'Create a Graphics object for drawing to the cropped image

    Dim objGraphics As Graphics = Graphics.FromImage(imgCropped)

    'set the background color to white (you can choose what you like

    objGraphics.Clear(System.Drawing.Color.White)

    'Determine where you'd like to start drawing from the Top (Y axis)

    Dim intStartTop As Int32 = 5 '-intTop / 40 + 5

    'Determine where you'd like to start drawing from the Left (X axis)

    Dim intStartLeft As Int32 = 5 '-intLeft / 40 + 5

    'you want to start drawing the image at the point where an actual image exists,

    'not just blank space. I negated the furthest top and left pixel points and

    'divided them by 40 and added 5 (half of the 10 pixel buffer, so 5x on each side)

    'The reason I divided was because the image would be too far to the left or top

    'sometimes and 40 just happened to work the best for the images I was cropping.

    'I believe this has to do with the horizontal an vertical resolution values,

    'bit depth, and image format

    'There must be room for improvement or a way to do this better, but it worked for

    'what I needed.

    'Draw the original image to your new cropped sized image

    objGraphics.DrawImage(b, intStartLeft, intStartTop)

    b.Dispose()

    objGraphics.Dispose()

    'return the Cropped image to the caller

    Return imgCropped

    End Function