ImfSampleCountChannel.h

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#ifndef INCLUDED_IMF_SAMPLE_COUNT_CHANNEL_H
#define INCLUDED_IMF_SAMPLE_COUNT_CHANNEL_H

//----------------------------------------------------------------------------
//
//      class SampleCountChannel
//
//      For an explanation of images, levels and channels,
//      see the comments in header file Image.h.
//
//----------------------------------------------------------------------------

#include "ImfImageChannel.h"
#include "ImfExport.h"

OPENEXR_IMF_INTERNAL_NAMESPACE_HEADER_ENTER

class DeepImageLevel;

//
// Sample count channel for a deep image level:
//
// Each deep image level has a number of samples channel.  For each
// pixel location (x,y) within the data window of the level, the sample
// count channel stores a single integer, n(x,y).  A deep channel, c,
// in the level as the sample count channel stores n(x,y) samples at
// location (x,y) if
//
//          x % c.xSampling() == 0 and y % c.ySampling() == 0.
//
// The deep channel stores no samples at location (x,y) if
//
//          x % c.xSampling() != 0 or y % c.ySampling() != 0,
//

class IMF_EXPORT SampleCountChannel : public ImageChannel
{
  public:

    //
    // The OpenEXR pixel type of this channel (HALF, FLOAT or UINT).
    //

    virtual PixelType   pixelType () const;
    

    //
    // Construct an OpenEXR frame buffer slice for this channel.
    // This function is needed reading an image from an OpenEXR
    // file and for saving an image in an OpenEXR file.
    // 

    Slice                   slice () const;


    //
    // Access to the image level to which this channel belongs.
    //

    DeepImageLevel &        deepLevel ();
    const DeepImageLevel &  deepLevel () const;


    //
    // Access to n(x,y), without bounds checking.  Accessing a location
    // outside the data window of the image level results in undefined
    // behavior.
    //

    const unsigned int &    operator () (int x, int y) const;


    //
    // Access to n(x,y), with bounds checking.  Accessing a location outside
    // the data window of the image level throws an Iex::ArgExc exception.
    //

    const unsigned int &    at (int x, int y) const;

    //
    // Faster access to n(x,y) for all pixels in a single horizontal row of
    // the channel.  Rows are numbered from 0 to pixelsPerColumn()-1, and
    // each row contains pixelsPerRow() values.
    // Access is not bounds checked; accessing out of bounds rows or pixels
    // results in undefined behavior.
    //

    const unsigned int *    row (int r) const;


    //
    // Change the sample counts in one or more pixels:
    //
    // set(x,y,m)   sets n(x,y) to m.
    //
    // set(r,m)     sets n(x,y) for all pixels in row r according to the
    //              values in array m.  The array  must contain pixelsPerRow()
    //              entries, and the row number must be in the range from 0
    //              to pixelsPerColumn()-1.
    //
    // clear()      sets n(x,y) to 0 for all pixels within the data window
    //              of the level.
    //
    // If the sample count for a pixel is increased, then new samples are
    // appended at the end of the sample list of each deep channel.  The
    // new samples are initialized to zero.  If the sample count in a pixel
    // is decreased, then sample list of each deep channel is truncated by
    // discarding samples at the end of the list.
    //
    // Access is bounds-checked; attempting to set the number of samples of
    // a pixel outside the data window throws an Iex::ArgExc exception.
    //
    // Memory allocation for the sample lists is not particularly clever;
    // repeatedly increasing and decreasing the number of samples in the
    // pixels of a level is likely to result in serious memory fragmentation.
    //
    // Setting the number of samples for one or more pixels may cause the
    // program to run out of memory.  If this happens, the image is resized
    // to zero by zero pixels and an exception is thrown.  Note that the
    // resizing operation deletes this sample count channel and the image
    // level to which it belongs.
    //

        void                set(int x, int y, unsigned int newNumSamples);
        void                set(int r, unsigned int newNumSamples[]);
        void                clear();


    //
    // OpenEXR file reading support / make sample counts editable:
    //
    //  beginEdit()     frees all memory that has been allocated for samples
    //                  in the deep channels, and returns a pointer to an
    //                  array of pixelsPerRow() by pixelsPerColumn() sample
    //                  counts in row-major order.
    //
    //                  After beginEdit() returns, application code is
    //                  free to change the values in the sample count array.
    //                  In particular, the application can fill the array by
    //                  reading the sample counts from an OpenEXR file.
    //
    //                  However, since memory for the samples in the deep
    //                  channels has been freed, attempting to access any
    //                  sample in a deep channel results in undefined
    //                  behavior, most likely a program crash.
    //
    //  endEdit()       allocates new memory for all samples in the deep
    //                  channels of the layer, according to the current
    //                  sample counts, and sets the samples to zero.
    //
    // Application code must take make sure that each call to beginEdit()
    // is followed by a corresponding endEdit() call, even if an
    // exception occurs while the sample counts are acessed.  In order to
    // do that, application code may want to create a temporary Edit
    //  object instead of calling beginEdit() and endEdit() directly.
    //
    // Setting the number of samples for all pixels in the image may
    // cause the program to run out of memory.  If this happens, the image
    // is resized to zero by zero pixels and an exception is thrown.
    // Note that the resizing operation deletes this sample count channel
    // and the image level to which it belongs.
    //

        unsigned int *      beginEdit();
        void                endEdit();

    class Edit
    {
      public:

        //
        // Constructor calls level->beginEdit(),
        // destructor calls level->endEdit().
        //

         Edit (SampleCountChannel& level);
        ~Edit ();

        //
        // Access to the writable sample count array.
        //

        unsigned int *          sampleCounts () const;

      private:

        SampleCountChannel &    _channel;
        unsigned int *          _sampleCounts;
    };


    //
    // Functions that support the implementation of deep image channels.
    //

    const unsigned int *    numSamples () const;
    const unsigned int *    sampleListSizes () const;
    const size_t *          sampleListPositions () const;
    size_t                  sampleBufferSize () const;


  private:

    friend class DeepImageLevel;

    //
    // The constructor and destructor are not public because
    // image channels exist only as parts of a deep image level.
    //

    SampleCountChannel (DeepImageLevel &level);
    virtual ~SampleCountChannel();

    virtual void        resize ();

    void                resetBasePointer ();

    unsigned int *  _numSamples;            // Array of per-pixel sample counts
                                           
    unsigned int *  _base;                  // Base pointer for faster access
                                            // to entries in _numSamples

    unsigned int *  _sampleListSizes;       // Array of allocated sizes of
                                            // per-pixel sample lists

    size_t *        _sampleListPositions;   // Array of positions of per-pixel
                                            // sample lists within sample list
                                            // buffer

    size_t          _totalNumSamples;       // Sum of all entries in the
                                            // _numSamples array

    size_t          _totalSamplesOccupied;  // Total number of samples within
                                            // sample list buffer that have
                                            // either been allocated for sample
                                            // lists or lost to fragmentation

    size_t          _sampleBufferSize;      // Size of the sample list buffer.
};



//-----------------------------------------------------------------------------
// Implementation of templates and inline functions
//-----------------------------------------------------------------------------

inline
SampleCountChannel::Edit::Edit (SampleCountChannel &channel):
    _channel (channel),
    _sampleCounts (channel.beginEdit())
{
    // empty
}


inline
SampleCountChannel::Edit::~Edit ()
{
    _channel.endEdit();
}


inline unsigned int *
SampleCountChannel::Edit::sampleCounts () const
{
    return _sampleCounts;
}


inline const unsigned int *
SampleCountChannel::numSamples () const
{
    return _numSamples;
}


inline const unsigned int *
SampleCountChannel::sampleListSizes () const
{
    return _sampleListSizes;
}


inline const size_t *
SampleCountChannel::sampleListPositions () const
{
    return _sampleListPositions;
}


inline size_t
SampleCountChannel::sampleBufferSize () const
{
    return _sampleBufferSize;
}


inline const unsigned int &
SampleCountChannel::operator () (int x, int y) const
{
    return _base[y * pixelsPerRow() + x];
}


inline const unsigned int &
SampleCountChannel::at (int x, int y) const
{
    boundsCheck (x, y);
    return _base[y * pixelsPerRow() + x];
}


inline const unsigned int *
SampleCountChannel::row (int n) const
{
    return _base + n * pixelsPerRow();
}


OPENEXR_IMF_INTERNAL_NAMESPACE_HEADER_EXIT

#endif