[Image-SIG] Choosing arbitrary polygons

Jeffrey Kunce kuncej@mail.conservation.state.mo.us
Fri, 19 Apr 2002 10:34:20 -0500

> One of the most important things that I need 
>to do is to select arbitrary areas of an image (polygons), and then 
>extract statistics off that. 

Here is some code that should give you some ideas

def PolygonHistogram(anImage, aPolygon):
    '''computes the histogram of the portion of anImage within
    mask = Image.new('1', anImage.size, 0)
    draw = ImageDraw.Draw(mask)
    draw.polygon(aPolygon, fill=1, outline=1)
    return anImage.histogram(mask)

You can also do interesting things by using various ImageChops
operations on an image and a mask.