This script can be used to create a "spoke pattern" image in the style of the ones featured in the following paper:
Downing K.H., Glaeser R.M., Restoration of weak phase-contrast images recorded with a high degree of defocus: The "twin image" problem associated with CTF correction, Ultramicroscopy 108 (2008), 921-928
All tweakable parameters are defined in the first lines of the script, which can be edited before the script is executed. The script generates the image, opens a viewer to show it and saves it in the current folder with the name specified by the user.
Usage:
dng spoke_pattern.py <output image>
import math import sys import ost.img.alg # Tweakable parameters wedge_start = 20 # Width of wedge at the narrower point wedge_end = 500 # Width of wedge at the broader point number_of_bands = 11 # Number of alternating bands (must be odd) size_of_image_x = 500 # Size of the image (X) size_of_image_y = 500 # Size of the image (Y) pixel_sampling = 1.0 * Units.A # Pixel width threshold = 2.0 * Units.A # Threshold for low pass filtering amplitude = 255 # amplitude of the obscillations # Image is created image=img.CreateImage(img.Size(size_of_image_x,size_of_image_y)) image.CenterSpatialOrigin() image.SetSpatialSampling(pixel_sampling) # For a cleaner code, 4 shorthands are defined image_extent=image.GetExtent() start_y=image_extent.GetStart()[1] end_y=image_extent.GetEnd()[1] start_x=image_extent.GetStart()[0] end_x=image_extent.GetEnd()[0] # Wedge is written in the image for y in range (start_y,end_y+1): wedge_width=wedge_start+(y-start_y)*(wedge_end-wedge_start)/(end_y-start_y) for x in range (start_x,end_x+1): half_wedge=wedge_width/2.0 outer_bands=(number_of_bands-1)/2 factor=(0.5+outer_bands)*math.pi/half_wedge if float(x)>-half_wedge and float(x)<half_wedge: value=255*math.cos(float(x)*factor) image.SetReal(img.Point(x,y),value) # Image is low-pass filtered filter=ost.img.alg.GaussianLowPassFilter(threshold) image.ApplyIP(filter) # Viewer is launched to show the result v=gui.CreateDataViewer(image,"Modulated Image")