Package: feret
Feret: A Python Module to calculate the Feret Diameter of Binary ImagesThis python module can calculate the following parameters for binary images:maximum Feret diameter (maxferet, maxf)minimum Feret diameter (minferet, minf)Feret diameter 90 ° to the minferet (minferet90, minf90)Feret diameter 90 ° to maxferet (maxferet90, maxf90)See thisWikipedia pageto get the definition of those parameters.This module gives the exact results as ImageJ (useedge=Trueas shown below), all the parameters are exactly calculated andnotapproximated.InstallationsThis project is available via pip:pip install feretPieces of InformationConvex HullThe definition of the maxferet and minferet uses the image of a caliper. Therefore, only the points which correspond to the convex hull of the object play a role. That is why before any calculations the convex hull is determined to reduce the runtime.MaxferetThe maxferet is calculated as the maximum Euclidean distance of all pixels.MinferetThe minferet is exactly calculated andnotapproximated. My algorithm uses the fact, that the calipers that define the minferet run on one side through two points and on the other through one point. The script iterates over all edge points and defines a line through the point and the one next to it. Then all the distances to the other points are calculated and the maximum is taken. The minimum of all those maximums is the minferet. The maximum of all those maximums isnotthe maxferet, that is the reason it is calculated separately. The runtime of this is already pretty good but hopefully I can improve it in the future.UseThe module can be used as followed:First you need a binary image for which the feret diameter should be calculated. The background has to have the value zero, the object can have any nonzero  value. The object doesn't have to be convex. At the moment the module only supports one object per image.This means, that if there are multiple not connected regions, the script will calculate a convexhull which include all regions and for this hull the feret diameter is calculated.Thr calls are:importferet# tifffile is not required nor included in this module.importtifffileastifimg=tif.imread('example.tif')# Image has to be a numpy 2d-array.# get the valuesmaxf,minf,minf90,maxf90=feret.all(img)# get only maxferetmaxf=feret.max(img)# get only minferetminf=feret.min(img)# get only minferet90minf90=feret.min90(img)# get only maxferet90maxf90=feret.max90(img)# get all the informationsres=feret.calc(img)maxf=res.maxfminf=res.minfminf90=res.minf90minf_angle=res.minf_angleminf90_angle=res.minf90_anglemaxf_angle=res.maxf_anglemaxf90_angle=res.maxf90_angleThere is an option to calculate the Feret diameters for the pixel edges instead of the centers. Just add anedge=Truein the call as shown below. This works for all calls analogous.importferet# tifffile is not required nor included in this module.importtifffileastifimg=tif.imread('example.tif')# Image has to be a numpy 2d-array.# get only maxferetmaxf=feret.max(img,edge=True)This module can also plot the result. Just useimportferet# tifffile is not required nor included in this module.importtifffileastifimg=tif.imread('example.tif')# Image has to be a numpy 2d-array.# plot the resultferet.plot(img)#edge=True can be passed here tooThe reason for the two MinFeret points on the left is described above. The MinFeret line does not have to run in between its two base points or through one of them. MaxFeret and MinFeret do not have to be 90° to each other. To calculate the 90° to MaxFeret and MinFeret useferet.max90(img)andferet.min90(img)methods.