|John Haine||05/05/2021 09:42:13|
|4116 forum posts|
I wonder if anyone could please help me find a program to help with digitising a graphic?
I have a graph printed in a journal and I would like to read the data into a spreadsheet so I can do further analysis on it. Ideally I would scan the graphic, view it on my monitor, and position the mouse cursor over points on the graphic, clicking the mouse to write the current cursor coordinates to the next line in a file. By doing this for the axes and the points, I could then scale the measurements to reconstruct the data.
Does anyone know of such a program is available please, preferably as freeware?
|jann west||05/05/2021 09:54:19|
|82 forum posts|
I just checked and paint.net (google it - free - works on windows) has a readout in the bottom of the screen that relates to the cursor position and can be set to show inches, cm or pixels.
|Dave Smith 14||05/05/2021 09:55:24|
|187 forum posts|
Ruler, pencil, calculator and scale it.
Put the image into a 2D CAD programme, Adjust size to 1:1 or a convenient size. Set the graph datum at the CAD drawing datum and lay down a series of points at suitable positions on the graph. Interrogate points for values.
You can do the same in Excel using lines, it is a bit more fiddly but it works well.
|557 forum posts|
Pending a better answer, what follows will do what you want.
Any CAD program will allow you to import a scanned .JPG file and use it as an underlay to the drawing.
It will also allow you to draw two orthogonal axes and rotate the scan until it coincides with these. This helps to correct any skew in the scan. Move the corrected scan around in the drawing until the coordinates of the scan axes match the drawing coordinates.
Draw a series of 'point' entities on the curve. Export the drawing as an ASCII dxf file and open in notepad. The coordinates for the point entities will be easily identifiable. Strip away all extraneous things in the file, just leaving X, Y pairs. Import these as .CSV into the spreadsheet.
|Clive Foster||05/05/2021 11:38:51|
|2817 forum posts|
Many years ago I used a program called NIH Image to do exactly what you are proposing. Worked well although the control side was primitive by todays standards. Certainly had to read the manual. As I recall it the output was in CSV format which I ported over to CricketGraph to replicate the graph and Excel to do some analysis.
NIH Image was a free to download program developed by the American National Institute of Mental Health for this and many other imaging analysis duties. Ran under the Classic Macintosh OS. Now long obsolete, although it seems still to be available for download, it has been replaced by ImageJ which runs on Java.
ImageJ in a much more sophisticated program but I presume has the same capabilities buried inside it.
ImageJ is also a free download.
Allegedly there are ways of running NIH Image on a PC or modern MacOS but locating the port or emulators may be a problem.
PS Quote from https://imagej.nih.gov/ij/docs/intro.html about what ImageJ can do.
"It can display, edit, analyze, process, save and print 8-bit, 16-bit and 32-bit images. It can read many image formats including TIFF, GIF, JPEG, BMP, DICOM, FITS and "raw". It supports "stacks", a series of images that share a single window. It is multithreaded, so time-consuming operations such as image file reading can be performed in parallel with other operations.
It can calculate area and pixel value statistics of user-defined selections. It can measure distances and angles. It can create density histograms and line profile plots. It supports standard image processing functions such as contrast manipulation, sharpening, smoothing, edge detection and median filtering.
It does geometric transformations such as scaling, rotation and flips. Image can be zoomed up to 32:1 and down to 1:32. All analysis and processing functions are available at any magnification factor. The program supports any number of windows (images) simultaneously, limited only by available memory.
Spatial calibration is available to provide real world dimensional measurements in units such as millimeters. Density or gray scale calibration is also available."
Edited By Clive Foster on 05/05/2021 11:45:21
|John Haine||05/05/2021 11:41:30|
|4116 forum posts|
Many thanks for the useful suggestions. Some more Googling came up with this:
which is just the job. Free 21 day evaluation licence, $30 to register after that but I hope I can do everything I need before then. In fact I've already digitised the graphs I want to!
|Michael Gilligan||05/05/2021 13:31:59|
18761 forum posts
That could almost have been bespoke for your job !!
... duly noted for future reference.
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