curve_tools.h

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/*
    This file is part of darktable,
    Copyright (C) 2011-2020 darktable developers.
 
    darktable is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.
 
    darktable is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.
 
    You should have received a copy of the GNU General Public License
    along with darktable.  If not, see <http://www.gnu.org/licenses/>.
 
    part of this file is based on nikon_curve.h from UFraw
    Copyright 2004-2008 by Shawn Freeman, Udi Fuchs
*/
 
#pragma once
 
// Curve Types
#define CUBIC_SPLINE 0
#define CATMULL_ROM 1
#define MONOTONE_HERMITE 2
 
// Maximum resolution allowed due to space considerations.
#define MAX_RESOLUTION 65536
#define MAX_ANCHORS 20
 
// ERROR CODES
#define CT_SUCCESS 0
#define CT_ERROR 100
#define CT_WARNING 104
#define CT_SET_ERROR 200
 
 
// DATA STRUCTURES
/**********************************************************
CurveData:
    Structure for the curve data inside a NTC/NCV file.
***********************************************************/
typedef struct
{
  float x;
  float y;
} CurveAnchorPoint;
 
typedef struct
{
  // Type for this curve
  unsigned int m_spline_type;
 
  // Box data
  float m_min_x;
  float m_max_x;
  float m_min_y;
  float m_max_y;
 
  // Number of anchor points
  unsigned char m_numAnchors;
 
  // contains a list of anchors, 2 floats per each point, x-y format
  // max is 20 points
  CurveAnchorPoint m_anchors[MAX_ANCHORS];
 
} CurveData;
 
typedef struct
{
  // Number of samples to use for the curve.
  unsigned int m_samplingRes;
  unsigned int m_outputRes;
 
  // Sampling array
  unsigned short int *m_Samples; // jo: changed to short int to save memory
 
} CurveSample;
 
/*********************************************
CurveDataSample:
    Samples from a spline curve constructed from
    the curve data.
 
    curve   - Pointer to curve struct to hold the data.
    sample  - Pointer to sample struct to hold the data.
**********************************************/
int CurveDataSample(CurveData *curve, CurveSample *sample);
 
/***************************************************************
 * interpolate_set:
 *
 * convenience function for calculating the necessary parameters for
 * interpolation.
 *
 * input:
 *      n    - length of data arrays
 *      x    - x axis of the data array
 *      y    - y axis of the data array
 *      type - type of interpolation currently either CUBIC or HERMITE
 * output:
 *      ypp  - pointer to array of parameters
 *******************************************************************/
float *interpolate_set(int n, float x[], float y[], unsigned int type);
 
/***************************************************************
 * interpolate_val:
 *
 * convenience function for piecewise interpolation
 *
 * input:
 *      n    - length of data arrays
 *      x    - x axis of the data array
 *      xval - point where to interpolate
 *      y    - y axis of the data array
 *      tangents - parameters calculated with interpolate_set
 *      type - type of interpolation currently either CUBIC or HERMITE
 * output:
 *      yval  - interpolated value at xval
 *******************************************************************/
float interpolate_val(int n, float x[], float xval, float y[], float tangents[], unsigned int type);
 
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