PolarUnwrap will resample an image using an annulus sector ("donut") shaped ROI.  This will e.g. straighten text written along a circle, for example the text/barcodes typically found near the hub opening of a CD/DVD. You can set the inner and outer radii of the ROI, and the extent of the sector (angles). The size of the resampled image can be specified as mean pitch or as an absolute value.

Original picture with ROI plotted

Unwrapped picture

Setup

Reference - Reference system selection

ROI - region of interest

• Center-X - circle center in X direction
• Center-Y - circle center in Y direction
• Inner radius - distance from center to inner edge for resampling
• Outer radius - distance from center to outer edge for resampling
• Angle start - start angle (relative to the X axis)
• Angle end - end angle (must be > Angle start). Direction is counterclockwise

Resampling - Set size of resampled image

• Specify pitch - mean pitch (pixels per unit). Smaller pitch means larger output image
  • Radial pitch - along straight lines ("spokes") extending from the center
  • Tangential pitch - along circle segments. Pitch is only correct in the middle
• Specify size - absolute output image size
  • Height - radial direction
  • Width - tangential direction

Output image - name of image to present result

Visualisation

Results