Initial Pass Through Image¶

For each pixel above threshold the code looks to see if this is the highest making a first pass. in the box (n x n) surrounding the pixel. If this is the highest in the box, then the location is stored in a list of potential photons.

In addition to storing the location of potential photons, an image is formed with its value incremented by one for the box (n x n) around the pixel. This image initially starts with all values set to zero. After the images have been processed, this image can be used to find overlap between photon events. An example of such an image is shown in First pass image output

A graphical (flow chart) representation of the logic is shown in First pass through all images.

First pass image output¶

(top) Actual CCD image showing photon events. (bottom) Image output from first pass showing potential photon locations

$digraph first_pass { node[shape="box", style=rounded] start; end; node[shape="diamond", style=""] is_last_pixel[label="is last pixel?"] is_pixel_above_thresh[label="is pixel above\nthreshold"] is_pixel_highest[label="is pixel highest\nvalue in nxn box"] node[shape="parallelogram", style=""] get_pixel[label="get pixel value"] node[shape="box", style=""] set_start_pixel[label="move to first pixel"] move_to_next_pixel[label="move to next pixel"] store_loc[label="add location of\nphoton to photon list"] mark_loc[label="mark location\nof nxn box in image"] start -> set_start_pixel set_start_pixel -> get_pixel get_pixel -> is_pixel_above_thresh is_pixel_above_thresh -> is_last_pixel[label="no"] is_pixel_above_thresh -> is_pixel_highest[label="yes"] is_pixel_highest -> is_last_pixel[label="no"] is_pixel_highest -> store_loc[label="yes"] store_loc -> mark_loc mark_loc -> is_last_pixel move_to_next_pixel -> get_pixel is_last_pixel -> move_to_next_pixel[label="no"] is_last_pixel -> end[label="yes"] }$

First pass through all images¶