AN2621 Freescale Semiconductor / Motorola, AN2621 Datasheet - Page 2

• Manufacturer Part Number: AN2621
• Description: MPC8220i PF300 Image Coprocessor Operation
• Manufacturer: Freescale Semiconductor / Motorola

The Resampling Unit
The PF300 is controlled by registers and makes use of both dedicated and system memory in its operation.
1
1.1
The Resampling Unit (RU) operates on the locations (addresses) of pixels in the two-dimensional source
and destination reference coordinate systems. The RU performs a linear transformation of output
(destination) pixel coordinates to compute the required coordinates of the nearest neighbor input (source)
pixel. In general, this allows mapping of a rectangular source image to a parallelogram destination image.
The destination image can be rotated to an arbitrary angle and shifted by an arbitrary number of pixels with
respect to the source image coordinate system. The RU also generates a “shadow” image that is a 1-bit per
destination pixel mask indicating whether or not the corresponding destination pixel is valid (that is,
whether the associated source pixel was inside or outside of the source image). Most applications will
substitute white space or the current background color for destination pixel data that is not valid.
Algebraically, the coordinate transform can be expressed by two simultaneous equations as shown below.
Or, in matrix notation,
In these equations, Xdest and Ydest are the pixel coordinates of the destination image, and Xsrc and Ysrc
are the corresponding coordinates in the source image. a, b, tx, c, d, and ty are constants. tx and ty represent
translation (shift) in the x and y directions, respectively.
2
Source
Image
The Resampling Unit
Algorithm Description
Resampling
Unit
MPC8220i PF300 Image Coprocessor Operation
[Xdest Ydest 1]
Freescale Semiconductor, Inc.
Figure 1. PF300 Image Coprocessor Data Flow
For More Information On This Product,
Bus I/F Unit
Conversion
Xdest = a × Xsrc + b × Ysrc + tx
Ydest = c × Xsrc + d × Ysrc + ty
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Color
CCU
RAM
Unit
=
[Xsrc Ysrc 1]
Screening
RAM
Unit
Tile
tx ty 1
a c 0
b d 0
CMYK
Buffer
MOTOROLA
Destination
Image