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Figure 2
(a) Calculation of the beam center from a defocused diffraction image. The diffraction image is summed in the x and y directions as shown at the top of and on the righthand side of the image, where the dotted line shows the threshold above which the corresponding pixels are considered `bright'. These define a bounding box around the defocused primary beam. (b) Cropped defocused diffraction pattern for image analysis. The position of the primary beam (defined as the center of the cropped image) is indicated by a red dot. The red squared area is used for image variance calculation using Equation (S4). (c) Segmented binary image of (b) with intensity cut-off percentiles of 10 and 20%, implemented by taking the third and fourth bins of a 20-binned intensity histogram from the image in (b). The yellow ring in (c) corresponds to the gradient between the primary beam and the background. (d) Blurred image of (c) by applying a two-dimensional Gaussian filter. The blue dot in (d) shows the calculated crystal center and is used for calculating the beam shift to apply (the vector between the blue and red dots).

Volume 6| Part 5| September 2019| Pages 854-867
ISSN: 2052-2525