Video and Image Processing Suite User Guide

ID 683416
Date 2/12/2021

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24.3.1. Warp Definition Equations

To specify the required mapping, the Warp Lite IP uses a perspective transform matrix to define the inverse transformation from the output space (X,Y) to the input space (U,V).
Matrix Form

This matrix applies a mapping that converts the 2-dimensional (X,Y) coordinate space to the 3-dimensional (U’, V’, W’) homogeneous coordinate space.

Conversion Matrix

To convert to the required 2-dimensional (U, V) space, the IP applies a scaling to the U’ and V’ coordinates by dividing by the third coordinate W’.

Based on this matrix form, you control the operation of the Warp IP with these eight values:

  • Xscale
  • Xskew
  • Xoffset
  • Yscale
  • Yskew
  • Yoffset
  • Xpersp
  • Ypersp

For the vertical keystone mapping, only five of the eight transform parameters: Xscale, Xskew, Xoffset, Yscale and Ypersp. The Xpersp, Yskew and Yoffset are zero.

The run time control register programs each of these values.

The IP defines the vertical keystone distortion within a 1920x1080 screen image with only two parameters: X1 and X3 (refer to figure Vertical Keystone Region Definition), the required horizontal offsets in the output coordinate space at the top and bottom of the distorted image respectively.