qgscontrastenhancement.h

一个非常好的GIS开源新版本

/* **************************************************************************
                qgscontrastenhancement.h -  description
                       -------------------
begin                : Mon Oct 22 2007
copyright            : (C) 2007 by Peter J. Ersts
email                : [e-mail]

This class contains code that was originally part of the larger QgsRasterLayer 
class originally created circa 2004 by T.Sutton, Gary E.Sherman, Steve Halasz
****************************************************************************/

/* **************************************************************************
 *                                                                         *
 *   This program 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 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 ***************************************************************************/

#ifndef QGSCONTRASTENHANCEMENT_H
#define QGSCONTRASTENHANCEMENT_H

#include <limits>

class QgsContrastEnhancementFunction;

class CORE_EXPORT QgsContrastEnhancement {
 
public:
    
  /** \brief This enumerator describes the types of contrast enhancement algorithms that can be used.  */
  enum CONTRAST_ENHANCEMENT_ALGORITHM
  {
    NO_STRETCH, //this should be the default color scaling algorithm
    STRETCH_TO_MINMAX, //linear histogram stretch
    STRETCH_AND_CLIP_TO_MINMAX,
    CLIP_TO_MINMAX,
    USER_DEFINED
  };
    
  /** These are exactly the same as GDAL pixel data types
   ** This was added so that the python bindings could be built, 
   ** which initially was a problem because GDALDataType was passed
   ** around as an argument to numerous method, including the constructor.
   **
   ** It seems like there should be a better way to do this...
   */
  enum QgsRasterDataType {
    QGS_Unknown = 0,
    /*! Eight bit unsigned integer */           QGS_Byte = 1,
    /*! Sixteen bit unsigned integer */         QGS_UInt16 = 2,
    /*! Sixteen bit signed integer */           QGS_Int16 = 3,
    /*! Thirty two bit unsigned integer */      QGS_UInt32 = 4,
    /*! Thirty two bit signed integer */        QGS_Int32 = 5,
    /*! Thirty two bit floating point */        QGS_Float32 = 6,
    /*! Sixty four bit floating point */        QGS_Float64 = 7,
    /*! Complex Int16 */                        QGS_CInt16 = 8,
    /*! Complex Int32 */                        QGS_CInt32 = 9,
    /*! Complex Float32 */                      QGS_CFloat32 = 10,
    /*! Complex Float64 */                      QGS_CFloat64 = 11,
    QGS_TypeCount = 12          /* maximum type # + 1 */
  };
   
  QgsContrastEnhancement(QgsContrastEnhancement::QgsRasterDataType theDatatype=QGS_Byte);
  ~QgsContrastEnhancement();
  
  /*
   *
   * Static methods
   *
   */
  /** \brief Helper function that returns the maximum possible value for a GDAL data type */
  static double getMaximumPossibleValue(QgsRasterDataType);
  /** \brief Helper function that returns the minimum possible value for a GDAL data type */
  static double getMinimumPossibleValue(QgsRasterDataType);
 
  /*
   *
   * Non-Static Inline methods
   *
   */
  /** \brief Return the maximum value for the contrast enhancement range. */
  double getMaximumValue() { return mMaximumValue; }
     
  /** \brief Return the minimum value for the contrast enhancement range. */
  double getMinimumValue() { return mMinimumValue; }
  
  CONTRAST_ENHANCEMENT_ALGORITHM getContrastEnhancementAlgorithm() { return mContrastEnhancementAlgorithm; }
  
  /*
   *
   * Non-Static methods
   *
   */  
  /** \brief Return true if pixel is in stretable range, false if pixel is outside of range (i.e., clipped) */
  bool isValueInDisplayableRange(double);
  /** \brief Set the contrast enhancement algorithm */
  void setContrastEnhancementAlgorithm(CONTRAST_ENHANCEMENT_ALGORITHM, bool generateTable=true);
  /** \brief A public method that allows the user to set their own custom contrast enhancment function */
  void setContrastEnhancementFunction(QgsContrastEnhancementFunction*);
  /** \brief Set the maximum value for the contrast enhancement range. */
  void setMaximumValue(double, bool generateTable=true);
  /** \brief Return the minimum value for the contrast enhancement range. */
  void setMinimumValue(double, bool generateTable=true);
  /** \brief Apply the contrast enhancement to a value. Return values are 0 - 254, -1 means the pixel was clipped and should not be displayed */
  int stretch(double);
  
private:
  /** \brief Current contrast enhancement algorithm */
  CONTRAST_ENHANCEMENT_ALGORITHM mContrastEnhancementAlgorithm;
  /** \brief Data type of the band */
  QgsRasterDataType mRasterDataType;
  /** \brief Maximum range of values for a given data type */
  double mRasterDataTypeRange;
  /** \brief Flag indicating if the lookup table needs to be regenerated */
  bool mEnhancementDirty;
  
  QgsContrastEnhancementFunction* mContrastEnhancementFunction;

  /** \brief User defineable minimum value for the band, used for stretching */
  double mMinimumValue;
  /** \brief user defineable maximum value for the band, used for stretching */
  double mMaximumValue;

  /** \brief Scalar so that values can be used as array indicies */
  double mLookupTableOffset;
  /** \brief Pointer to the lookup table */
  int *mLookupTable;

  /** \brief Method to generate a new lookup table */
  bool generateLookupTable();
  /** \brief Method to calculate the actual stretched value(s) */
  int calculateContrastEnhancementValue(double);
};
 
#endif