Graphics Reference
In-Depth Information
Auxiliary grid
Source image grid
01
2
3
01
2
3
scanline
grid coordinates
0
1
2
3
012
3
0 1 2 3 4 5 6 7 8 . . .
pixel coordinates
0 1 2 3 4 5 6 7 8 . . .
3
3
2
2
1
1
0
0
0 1 2 3 4 5 6 7 8 . . .
pixel coordinates
pixel coordinate to grid coordinate
graph for auxiliary image
0 1 2 3 4 5 6 7 8 . . .
pixel coordinates
pixel coordinate to grid coordinate
graph for source image
3
3
2
2
1
1
0
0
0 1 2 3 4 5 6 7 8 . . .
Use the graph to see where the column
indices map to image pixels (here, half of
pixel 3 and all of pixels 4 and 5 are useful)
0 1 2 3 4 5 6 7 8 . . .
Use the graph to determine the image pixel's
range in terms of the column indices
(pixel 6 is shown)
FIGURE 4.45
For a given pixel in the auxiliary image, determine the range of pixel coordinates in the source image (e.g., pixel 6
of auxiliary grid maps to pixel coordinates 3.5 to 5 of the source image).
column-by-column basis by averaging auxiliary image pixel colors to form the intermediate image.
The columns are processed by using the horizontal grid curves to establish a common coordinate
system between the two images (see
Figure 4.46
)
.
This two-pass procedure is applied to both the source and the destination images with respect
to the intermediate grid. Once both images have been warped to the same intermediate grid, the
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