Interpolator

This is an extension of the document Helmut Dersch did on Testing Interpolator Quality

Panotools allows 7 different interpolator.  The interpolator is defined on the 'm' line of the script file using 'i'.  Valid values are 0-poly3 (default), 1-spline16, 2-spline36, 3-sinc256, 4-spline64, 5-bilinear, 6-nearest neighbor, 7-sinc1024

The following images have been rotated 5 degrees 36 separate times.  Then a lossless rotation of 180 deg to get back where it started.

	Ken Turkowski's Zone Plate	line image displayed here at 300% enlargement	Image of my back yard displayed with 80% jpg	Add to 3000 X 6000 pan (*1)	rotate a 6000 X 8000 image (*2)
Original
[6] Nearest Neighbor				22	32
[5] Bilinear				24	34
[0] Poly 3				22	39
[1] Spline 16				24	44
[2] Spline 36				24	56
[4] Spline 64				25	72
[3] Sinc 256				51	548
[7] Sinc 1024				101	1436
Original
PhotoShop BiCubic Normal
PhotoShop BiCubic Smoother
PhotoShop BiCubic Sharper

All times measured with stop watch.

*1 - Time in seconds to convert a 3.5 MP image into a 3000 X 6000 pan.  Image had hfov of 97°.  Time includes: converting image, creating mask, feathering, and flattening image.

*2 - Time in seconds to rotate a 6000 X 8000 pixel image 180°. Time includes converting image only.

When creating a panorama generally an image is transformed 5 or less times. 
Once to correct image from Chromatic Aberrations, light falloff, etc...
Second to transform from original into pan.
Third to transform patch area to rectangular.
Forth to transform patch back into pan.
Fifth to create cubes faces from pan.

The distortions above is after 36 separate transformations.  With only 5 transformations the distortion will be less.  When making a panorama I always shrink the final pan to 75% or smaller of original size.  This removes the interpolations introduced by the camera when creating pixels from the CCD.  Getting me to the true resolving power of my camera and lens.  Shrinking the image will also hide some of the distortion created from the transformations.
   

References, Links, and Notes:

• PanoTools developed by Helmut Dersch.
• PanoTools Next Generation.  PanoTools Mailing List on Yahoo
• PanoTools on SourceForge
  
• PTGui developed by Joost Nieuwenhuijse.
• PTMac developed by Kevin Kratzke
• PTAssembler developed by Max Lyons, and his changes to PT
• Hugin open source development.