Plot a curve with ImageJ?

Hello !
Sorry in advance for my poor english (I am French).
My problem is that I have a reslice with a curve I had cropped. The curve is white, the background is black (I’ve use “Threshold”). How can I have the values (i.e. all the x and the y of my curve) ? Is it possible with ImageJ (I guess no).

Thanks !

Here is a macro example which I hacked together (Please change the path in the last line!):

run("Line Graph (21K)");
makeRectangle(91, 47, 135, 127);
setThreshold(0, 165);
setOption("BlackBackground", false);
run("Convert to Mask");
run("Save XY Coordinates...", "background=0 save=C:\\LineGraph.txt");

Essentially it thresholds the line, skeletonizes the mask (Process->Binary->Skeletonize) to remove unnecessary pixels and then saves the xy coodinates (see: Analyze->Tools->Save XY values).

Note that the values are recognized from top-left to bottom right. So maybe you have to transform the values
for calculus.