Specifications

Interpolation in
Geometric Transform Functions
B-1
B
This appendix describes the interpolation algorithms used in the geometric
transformation functions of the Image Processing Library. For more
information about each of the geometric transform functions, see
Chapter 11, Geometric Transforms.
Overview of Interpolation Modes
In geometric transformations, the grid of input image pixels is not
necessarily mapped onto the grid of pixels in the output image. Therefore,
to compute the pixel intensities in the output image, the geometric
transform functions need to interpolate the intensity values of several input
pixels that are mapped to a certain neighborhood of the output pixel.
Geometric transformations can use various interpolation algorithms. When
calling the geometric transform functions of the Image Processing Library,
the application code specifies the interpolation mode (that is, the type of
interpolation algorithm) by using the parameter
interpolate . The library
supports the following interpolation modes:
• nearest neighbor interpolation (
interpolate = IPL_INTER_NN)
• linear interpolation (
interpolate = IPL_INTER_LINEAR)
• cubic interpolation (
interpolate = IPL_INTER_CUBIC)
• super-sampling (
interpolate = IPL_INTER_SUPER)