Image Analyst: Segmentation (Extraction) of area between two red line

I 'm woriking on Segmentation of Historical documents, so far i have identified the text lines in the historical documents using seam carving method and result image is attached, i wnat to extract or segment those identified lines, which is saperated by red line.

Answer 1

[Image Analyst]

Use poly2mask() to create a mask image. Then mask the image

% Mask the image using bsxfun() function to multiply the mask by each channel individually.
maskedRgbImage = bsxfun(@times, rgbImage, cast(mask, 'like', rgbImage));

[Chandru G]

i tried with poly2mask() and roipoly(), didn't get the desired output, please elobrate the above function and try explain with code sample pertain to my above image..tq