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The pixel coordinate picker

Raster graphics programs often display the coordinate of the pixel under the mouse pointer in some corner. How often have you loaded some raster figure, taken a sheet of paper and a pencil and then laborously copied coordinates down? Well, when I was about to do it one time too often, I thought to myself that this situation can be improved, searched on the internet for something to do the work for me, didn't find anything and therefore wrote it myself: PixPick, the pixel coordinate picker.

It loads a raster image (in ppm format, but each format can be converted on the fly easily), displays it, and outputs the coordinates of the mouse clicks into the image in ASCII form into a file (it reopens it for each coordinate pair, so that you can make notes and commments into the file in parallel). If you want to extract the values corresponding to data points from a figure (especially in the scientific trade this is sometimes necessary), you first click some x- and y-tics, note down the quantities they correspond to, and then click on all the data points (lines corresponding to erroneous clicks can be deleted during acquisition). Converting these coordinate values to the original quantities is then straightforward to script.

Partly for my education, I wrote this program in C, using only X11. Therefore it should be a matter of a few seconds for anybody with a UNIX-like system (which nowadays is mostly Linux, BSD and Mac OS X) to get it working. For Microsoft Windows you would probably need to get the X11 library and a C-compiler.

Here is the source code, available under the GNU General Public Licence Version 2.

N.b.: I have been made aware of the existence of the program Plot2Data, a commercial closed-source Windows utility, which purportedly includes the same basic functionality (specifically, I have not plagiarized the above ''Ever had this problem? Ever had that problem? Here is the solution''-structure of the introduction!). I know which one I would prefer even if I hadn't written it myself.
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