How to find a noisy line in a picture Hi I would like to find a line in a noisy image as showed bellow. I tried gabor filter and cany edge detection, but it didn't produce anything usefull. I am looking for lines of specific orientation and I don't want to segment them, just to find if the line exist in the picture. 

Example pictures with lines





Example pictures without lines
What about an algorithm in image domain?

For every pixel, check into the direction you desire to know (up-down in your images above, I guess) if there is a pixel with "the same" value (i.e. a value inside an acceptance band, of course. Let's say +/- 10%) as the pixel under investigation. If so, go further into that direction. Count every pixel that you find. If the number of counts exceeds a certain threshold (i.e. 1/4 FOV or so in your case), then there is a line.

I would first try to use something simple like that instead of using more complicated algorithms that might be suitable for different kinds of images. Yours pretty much look like MRI phase images that can be nasty ;) )