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lbb resampler comments

This commit is contained in:
Nicolas Robidoux 2010-03-26 00:31:11 +00:00
parent 001bd943eb
commit a1ab80443b
1 changed files with 21 additions and 1 deletions
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22
libvips/resample/lbb.cpp
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@ -213,7 +213,7 @@ lbbicubic( const double c00,
/*
* Computation of the four min and four max over 3x3 input data
* sub-blocks of the 4x4 input stencil (involves 28 flag
* computations):
* computations if done with conditional moves):
*/
const double m1 = (dos_two <= dos_thr) ? dos_two : dos_thr;
const double M1 = (dos_two <= dos_thr) ? dos_thr : dos_two;
@ -249,6 +249,26 @@ lbbicubic( const double c00,
const double max01 = LBB_MAX( M9, M12 );
const double min11 = LBB_MIN( m9, m13 );
const double max11 = LBB_MAX( M9, M13 );
/*
* The remainder of the computation involves the computation of:
*
* --8 conditional moves,
*
* --8 signs (in which the sign of zero is unimportant),
*
* --12 minima of two values,
*
* --8 maxima of two values,
*
* --8 absolute values,
*
* for a grand total of 29 minima, 25 maxima, 8 conditional moves, 8
* signs, and 8 absolute values. (If everything is done with
* conditional moves, "only" 28+8+8+12+8+8=72 flags are involved.)
*
* This part of the computation also involves 109 arithmetic (*,+,-)
* arithmetic operations (to be double checked).
*/
/*
* Distances to the local min and max: