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more lbb resampler comments

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This commit is contained in:
Nicolas Robidoux 2010-03-24 19:16:56 +00:00
parent ad2ba14d16
commit f9f9c5192c
1 changed files with 11 additions and 9 deletions
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20
libvips/resample/lbb.cpp
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@ -92,15 +92,17 @@
*
* Instead of forcing the reconstructed surface to lie between two
* GLOBALLY defined planes, LBB constrains one patch at a time to lie
* between local min and max. It does so by constraining the
* derivatives (x, y and cross) at each input pixel location so that
* if the constraint was applied everywhere the surface would fit
* between the min and max of the values at the 9 closest pixel
* locations. Because this is done with each of the four pixel
* locations which define the bicubic patch constrains the
* reconstructed surface between the min and max of the values at the
* 16 closest values pixel locations (each corner defines its own 9x9
* subgroup of the 4x4 stencil).
* between LOCALLY defined planes. This is accomplished by
* constraining the derivatives (x, y and cross) at each input pixel
* location so that if the constraint was applied everywhere the
* surface would fit between the min and max of the values at the 9
* closest pixel locations. Because this is done with each of the four
* pixel locations which define the bicubic patch, this forces the
* reconstructed surface to lie between the min and max of the values
* at the 16 closest values pixel locations. (Each corner defines its
* own 3x3 subgroup of the 4x4 stencil. Consequently, the surface is
* necessarily above the minimum of the four minima, which happens to
* be the minimum over the 4x4. Similarly with the maxima.)
*/
#ifdef HAVE_CONFIG_H