color segmentati​on/substra​ction of green screen from image

Hi i have taken photos of rocks using a green screen as a background. please see:- <http://www.flickr.com/photos/24335673@N04/7683980794/in/photostream/>>

i would like subtract the green bg as effectively as possible so that the boundary of the rock is preserved. would color segmentation be a good method? if so how can i achieve it? or perhaps a different seg method? thank sharif

Answer 1

[Image Analyst]

Get the separate color channels:

% Extract the individual red, green, and blue color channels.
redChannel = rgbImage(:, :, 1);
greenChannel = rgbImage(:, :, 2);
blueChannel = rgbImage(:, :, 3);

Then look where the blue and red channels are dark and the green channel is high.

mask = (redChannel < 50) & (blueChannel < 50) & (greenChannel > 50);
% Mask the image.
maskedRgbImage = bsxfun(@times, rgbImage, cast(mask,class(rgbImage)));

You copyrighted the image to prevent download, so that's about all I can do.

[Sharif]

first, thanks for getting back so quickly. sorry about copyright, flickr's default settings, fixed it now.

i tried it out but the uneven lighting is causing bad segmentation. i tried l.a.b color seg to avoid the lighting issue.('Color-Based Segmentation Using K-Means Clustering' you mentioned in a previous post) the results were much better. thanks again, sharif

[KSY]

Hi. I want to mask purple color what is the setting for red,green and blue channel?

[Image Analyst]

Red and blue will be high and green will be low. Use impixelinfo() to let you mouse around the image and see what the RGB values are.