Extract curve value from a gray Image

Assuming that I have a raster log image like attached with the left boundary value = 0 and right boundary value = 100

How do I extract the value points on the curve?

Is there a name for this problem in general?

Sample code would be greatly appreciated

Thanks

[Huy Nguyen]

I'm looking for a method to clean the image, then automatically extract the data points. The user shouldn't have to manually pick the points

Answer 1

[Stephen23]

Try one of these FEX submissions:

http://www.mathworks.com/matlabcentral/fileexchange/7173-grabit

http://www.mathworks.com/matlabcentral/fileexchange/41560-img2curve

http://www.mathworks.com/matlabcentral/fileexchange/4316-reverseplot

http://www.mathworks.com/matlabcentral/fileexchange/36618-data-theif

http://www.mathworks.com/matlabcentral/fileexchange/15966-grab-2d-points

[Huy Nguyen]

Thank you for your answer

Before feeding the image into those tools, I need to remove grid lines first

Any idea how to do it effectively? especially when my data is noisy as you can see

[Huy Nguyen]

Btw, after looking at the links, I don't think this is what I'm looking for

I'm looking for a method to clean the image, then automatically extract the data points. The user shouldn't have to manually pick the points. They may have to specify the axis range thought.

[Stephen23]

You don't specify what you mean by "Clean" the image, but I guess you want to ignore the grid lines and just extract the curve points. Search for "detect straight lines in image"and for "skeletonize". You need to be prepared for the fact that importing noisy images will likely always need some user input.