Dear Saba Noor

What do you mean by multiple numerical data from image 2D from pdf. Is the image in pdf format?  How do you choose two types of data points? 

Do you mean "extract features from a pdf image1 and then extract same features from another pdf image2 and want to find similarity or dissimilarity between two features?

Please reframe in the question that helps all to think about and give proper question.

thank you to pay attention and your guidance.

It is single image which I taken from a pdf file. Image is actually a graph (2D graph,x axis and y axis ). And in  graph there is two separate lines(eq.u,v). I want to calculate data points (numerical values) of  both of these separate lines(eq. u1,u2,..,v1,v2,..) and take difference (eg. u1 - v1,u2-v2,...). 

Is it clear now?

Yes I got it. 

You can use scan lines on the graph and find the point of intersection at every point for each line. Store separately the data and you can use any metric on that.

(Refer scan line polygon filling algorithm for the basic idea of scan lines)

imread( img, reads the image files and stores the numerical values in matlab. Then using imsubtract function  we can find the difference 

Hi,

First of all, I am not sure how do you go about extracting the image (graph in this case) from the PDF file? Do you do that manually? Second, make sure that when the image was embedded in the PDF file it was not rescaled or at least the rescale has maintained the aspect ratio, because otherwise the x axis and y axis will be distorted and thus you cannot rely on.

Once you have your graph image (usually a monochrome) grabbed, you can load it, detect the straight lines (hopefully they remain continuous = don't break) and then generate their respective statistics (e.g., regionprops in MATLAB).

ok

Thanks alot for reading &  giving attention to my question.

Your answers gives valuable information..

I think Graphixy may be helpful to some extent.  x and y coordinates data can be extracted  manually by hovering. Check the link: https://sourceforge.net/projects/graphixy/

Thanks a lot all of you for sharing your valuable knowledge.