How to access image histogram values in python-fu?

Question

I have been writing code in the python-fu console of gimp and I wanted to find the minimum of an image histogram (the pixel intensity value with the least frequency).

There are two functions in the procedural database that deals with histograms - pdb.gimp_drawable_histogram() and pdb.python_fu_histogram_export(). The first function pdb.gimp_drawable_histogram() is not useful for me because it does not give me the histogram minimum. The second function pdb.python_fu_histogram_export() does exactly what I want, but it exports the result into a .csv file and prevents me from accessing the values within the console.

I can get around this by exporting the .csv function first, followed by importing the .csv file back into the console and accessing the values. But this seems like a rather ugly and inefficient way to do it.

Is there a way to access the histogram values without exporting it to a .csv and then back into the console?

Answer 1

You can use the gimp_drawable_histogram while iterating a window, for instance:

hist=[pdb.gimp_drawable_histogram(drawable,HISTOGRAM_VALUE,x/255.,(x+1)/255.) for x in range(255)]

On an 8Mpix image it takes a couple of seconds. If you don't need that much precision you can use wider windows to make it run faster.

PS: it turns out that the CSV export you mention, written in Python, does exactly that (so won't run any faster). You can find it in your Gimp installation, as lib/gimp/2.0/plug-ins/histogram-export/histogram-export.py, under /usr in a regular Linux install, or your Gimp install tree in Windows.