Computing water level based on difference in frame colors

I am trying to measure the water levels taken from a camera as a burst of waves is run. I have the camera recording of the water level as an avi file. I need to extract all the frames from this avi file, in order to measure the water level in each frame. A green dye was placed in the water to allow for easy examination of the water column (see attached picture).

Any ideas how I would do this on MATLAB?

Answer 1

[Image Analyst]

I would convert from RGB to HSV, then take the S channel. I'd then take the mean along rows (direction 2), then take the location of the hald way point. Something like

hsvImage = rgb2hsv(rgbImage);
verticalProfile = mean(hsvImage(:, :, 2), 2);
threshold = 0.5 * (min(verticalProfile) + max(verticalProfile))
topLine = find(verticalProfile > threshold, 1, 'first')
hold on;
line([1, size(rgbImage, 2)], [topLine, topLine], 'Color', 'r')

If it doesn't work, attach the image that it doesn't work for.

[Vivek]

I am not sure I follow. What I want to do is get the water column measurements throughout the entire avi file (so the water column measurement in each frame). The initial water level is 5 cm (in the pic attached in the first post).

Any ideas how I would go about doing this?