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/*****************************************************************************/
// Copyright 2006-2007 Adobe Systems Incorporated
// All Rights Reserved.
//
// NOTICE: Adobe permits you to use, modify, and distribute this file in
// accordance with the terms of the Adobe license agreement accompanying it.
/*****************************************************************************/
/* $Id: //mondo/dng_sdk_1_4/dng_sdk/source/dng_spline.cpp#1 $ */
/* $DateTime: 2012/05/30 13:28:51 $ */
/* $Change: 832332 $ */
/* $Author: tknoll $ */
/*****************************************************************************/
#include "dng_spline.h"
#include "dng_assertions.h"
#include "dng_exceptions.h"
/******************************************************************************/
dng_spline_solver::dng_spline_solver ()
: X ()
, Y ()
, S ()
{
}
/******************************************************************************/
dng_spline_solver::~dng_spline_solver ()
{
}
/******************************************************************************/
void dng_spline_solver::Reset ()
{
X.clear ();
Y.clear ();
S.clear ();
}
/******************************************************************************/
void dng_spline_solver::Add (real64 x, real64 y)
{
X.push_back (x);
Y.push_back (y);
}
/******************************************************************************/
void dng_spline_solver::Solve ()
{
// This code computes the unique curve such that:
// It is C0, C1, and C2 continuous
// The second derivative is zero at the end points
int32 count = (int32) X.size ();
DNG_ASSERT (count >= 2, "Too few points");
int32 start = 0;
int32 end = count;
real64 A = X [start+1] - X [start];
real64 B = (Y [start+1] - Y [start]) / A;
S.resize (count);
S [start] = B;
int32 j;
// Slopes here are a weighted average of the slopes
// to each of the adjcent control points.
for (j = start + 2; j < end; ++j)
{
real64 C = X [j] - X [j-1];
real64 D = (Y [j] - Y [j-1]) / C;
S [j-1] = (B * C + D * A) / (A + C);
A = C;
B = D;
}
S [end-1] = 2.0 * B - S [end-2];
S [start] = 2.0 * S [start] - S [start+1];
if ((end - start) > 2)
{
std::vector<real64> E;
std::vector<real64> F;
std::vector<real64> G;
E.resize (count);
F.resize (count);
G.resize (count);
F [start] = 0.5;
E [end-1] = 0.5;
G [start] = 0.75 * (S [start] + S [start+1]);
G [end-1] = 0.75 * (S [end-2] + S [end-1]);
for (j = start+1; j < end - 1; ++j)
{
A = (X [j+1] - X [j-1]) * 2.0;
E [j] = (X [j+1] - X [j]) / A;
F [j] = (X [j] - X [j-1]) / A;
G [j] = 1.5 * S [j];
}
for (j = start+1; j < end; ++j)
{
A = 1.0 - F [j-1] * E [j];
if (j != end-1) F [j] /= A;
G [j] = (G [j] - G [j-1] * E [j]) / A;
}
for (j = end - 2; j >= start; --j)
G [j] = G [j] - F [j] * G [j+1];
for (j = start; j < end; ++j)
S [j] = G [j];
}
}
/******************************************************************************/
bool dng_spline_solver::IsIdentity () const
{
int32 count = (int32) X.size ();
if (count != 2)
return false;
if (X [0] != 0.0 || X [1] != 1.0 ||
Y [0] != 0.0 || Y [1] != 1.0)
return false;
return true;
}
/******************************************************************************/
real64 dng_spline_solver::Evaluate (real64 x) const
{
int32 count = (int32) X.size ();
// Check for off each end of point list.
if (x <= X [0])
return Y [0];
if (x >= X [count-1])
return Y [count-1];
// Binary search for the index.
int32 lower = 1;
int32 upper = count - 1;
while (upper > lower)
{
int32 mid = (lower + upper) >> 1;
if (x == X [mid])
{
return Y [mid];
}
if (x > X [mid])
lower = mid + 1;
else
upper = mid;
}
DNG_ASSERT (upper == lower, "Binary search error in point list");
int32 j = lower;
// X [j - 1] < x <= X [j]
// A is the distance between the X [j] and X [j - 1]
// B and C describe the fractional distance to either side. B + C = 1.
// We compute a cubic spline between the two points with slopes
// S[j-1] and S[j] at either end. Specifically, we compute the 1-D Bezier
// with control values:
//
// Y[j-1], Y[j-1] + S[j-1]*A, Y[j]-S[j]*A, Y[j]
return EvaluateSplineSegment (x,
X [j - 1],
Y [j - 1],
S [j - 1],
X [j ],
Y [j ],
S [j ]);
}
/*****************************************************************************/
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