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Re: [pdf-devel] pdf_function.c
From: |
jemarch |
Subject: |
Re: [pdf-devel] pdf_function.c |
Date: |
Mon, 17 Sep 2007 23:47:08 +0200 |
User-agent: |
Wanderlust/2.14.0 (Africa) SEMI/1.14.6 (Maruoka) FLIM/1.14.8 (Shijō) APEL/10.6 Emacs/22.1.50 (powerpc-unknown-linux-gnu) MULE/5.0 (SAKAKI) |
> Do a general formula to solve m-dimensional cubic splines
> exist? Something like that (the link talks about multi-linear
> interpolation):
> http://kanushu.uwaterloo.ca/~tveldhui/papers/MAScThesis/node3
>2.html
Ah. "Interpolating a single value involves 2^D function
values - one function value for each node in the enclosing
element."
This explains the warnings in the spec:
"The dimensionality of a sampled function is restricted only by
implementation limits. However, the number of samples required
to represent functions with high dimensionality multiplies
rapidly unless the sampling resolution is very low. Also,
the process of multilinear interpolation becomes computationally
intensive if the number of inputs m is greater than 2.
The multidimensional spline interpolation is even more
computationally intensive"
Yes. The tricky part is to extract a pair of interpolation functions
for each dimension from the samples array.
> I have finished an implementation of type 2 functions.
> Many thanks!
Shall I send a patch for review?
I would wait to have the types 0, 2 and 3 (stitching functions works
with type 1 and type 0 functions) implemented.
The type 4 functions (postscript calculator) requires a postscript
stack, a mini-parser to read values, operators and { } from the
stream, and is diffent enough to install it separately.
> BTW: are you using the `pdf_stm_peek' function?
Not yet :-) pdf_create_func_2() uses only a dictionary.
I intend to store the sample table as byte array, reading it
from a stream is *very* simple.
Ok.
--
Jose E. Marchesi <address@hidden>
<address@hidden>
GNU Spain http://es.gnu.org
GNU Project http://www.gnu.org