Image Segmentation/Background Subtraction

Question

My current project is to calculate the surface area of the paste covered on the cylinder.

Refer the images below. The images below are cropped from the original images taken via a phone camera.

I am thinking terms like segmentation but due to the light reflection and shadows a simple segmentation won’t work out.

Can anyone tell me how to find the surface area covered by paste on the cylinder?

Answer 1

First I'd simplify the problem by rectifying the perspective effect (you may need to upscale the image to not lose precision here). Then I'd scan vertical lines across the image.

Further, you can simplify the problem by segmentation of two classes of pixels, base and painted. Make some statistical analysis to find the range for the larger region, consisting of base pixels. Probably will make use of mathematical median of all pixels.

Then you expand the color space around this representative pixel, until you find the highest color distance gap. Repeat the procedure to retrieve the painted pixels. There's other image processing routines you may have to do such as smoothing out the noise, removing outliers and background, etc.