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I want to compute an area of certain object on a picture using Monte Carlo method. The picture shows some shape on white background. To do so I figured out that I'd get the coordinates of non-white points and then I'd launch the rest of the routine in e.g. Excel. My problem however is that I don't know about any application or software that performs what I want - i.e. getting coordinates of pixels of some specified colour. Can someone suggest some application or software which can do what I want?

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Why use a Monte-Carlo method when identifying and counting all the pixels will be more accurate and almost surely faster and easier? In fact, merely opening the "picture"--if it's a standard image file--in a GIS will let you see an attribute table in which the pixel counts are already listed. The area is directly proportional to the pixel count. –  whuber Jan 5 '13 at 20:16
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The only motivation to use MC method is that I have to show that I know how to use this method. –  data Jan 5 '13 at 20:24
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@whuber is right in that counting pixels is the way to go for raster area calculations. I've never heard of a MC approach to determine pixel area. Consider using QGIS's raster calculator to perform the necessary mask: spatialgalaxy.net/2012/01/25/using-the-qgis-raster-calculator –  Aaron Jan 5 '13 at 20:29
    
@Aaron & whuber I've installed QGIS and honestly don't have any idea what to do next (except I managed to make QGIS open my picture file). I'm completly new to this kind of software. Could you please provide more detailed instruction on how should I proceed? –  data Jan 5 '13 at 22:12

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