EdgeFinder

class sonic.EdgeFinder
Method Summary
static getActiveBorder(u_illum_obj)

Determines which image borders are active, meaning which image borders have light coming in

Inputs:

  • u_illum_obj (1x1 sonic.Points2): Sonic Points2 object containing the uv direction of illumination from the sun to the body in the image

Outputs:

  • active_mask (1x4 logical): Logical array containing true for and active edge and false for an inactive edge in the clockwise order of [top, right, bottom, left]

static getSubPixel(im_obj, pixelEdge, BlurWidth, kernel_type, M)

The getSubPixel function computes the subpixel edge location and orientation from an image, pixel-level edge map, and information about the image blur. This function is intended for use on ISOLATED EDGES (that is, edges that are not within about 5 pixels of another edge). The algorithm is based on the method published in:

Christian, J.A., “Accurate Planetary Limb Localization for Image-Based Spacecraft Navigation,” Journal of Spacecraft and Rockets, Vol. 54, No. 3, 2017, pp 708-730. doi: 10.2514/1.A33692. Online: https://arc.aiaa.org/doi/abs/10.2514/1.A33692

Inputs:

  • im_obj (1x1 sonic.Image): grayscale image containing the body on which to find limb points

  • pixelEdge (1,1 sonic.Points2): pixel level points in the image where edges are found. Must be rounded to nearest pixel.

  • BlurWidth (1x1 double) width of Gaussian blur in image

  • kernel_type (1x1 double) flag for type of Zernike moment kernels. Input 5 for 5x5 moment or 7 for 7x7 moment.

  • M (nxn logical): optional forground mask to only include a masked part of the image in the search

Outputs:

  • subPixelEdge (1x1 sonic.Points2): edge points

  • subPixelNormals (1x1 sonic.Points2): normal of edge points, corresponding to edge points by index

The edge normals are defined positive going from background (darker region) to foreground (brighter region).

Last revised: 3/28/2024 Author: Dr. John A. Christian Edited: Ava Thrasher

static runScan(im_obj, scan_lines, min_consec, run_start_thresh)

Performs a scan across the provided image in the direction of sun illumination to find candidate edge points.

Inputs:

  • im_obj (1x1 sonic.Image): SONIC Image object containing the limb to find points on.

  • scans_lines (1x1 sonic.ScanLines): Lines in the image to perform scan along.

  • min_consec (1x1 double): Minimum number of consecutive bright pixels found on a scan for the first bright pixel to be considered a limb point. Used to keep hot pixels, stars, or debries from being falsely identified as an edge

  • run_start_thresh (1x1 double): Minimum digital number to flag as a limb point

Outputs:

  • limb_pts (1x1 sonic.Points2): SONIC Points2 object containing the determined u v coordinate limb points. U in first row V in second row.

Last revised: 3/28/24 Last author: Ava Thrasher

static sobel(im_obj, gradThresh)

Computes edge locations based on local extrema in Gu or Gv gradients

Inputs:

  • im_obj (1,1 sonic.Image): image object to find edges in

  • gradThresh (1,1 double): Threshhold above which a gradient i considered as a potential edge

Outputs:

  • E (nxm logical): mask which is true where edges were detecte