ImageMetaData.h

//# ImageMetaData.h: Meta information for Images
//# Copyright (C) 2009
//# Associated Universities, Inc. Washington DC, USA.
//#
//# This library is free software; you can redistribute it and/or modify it
//# under the terms of the GNU Library General Public License as published by
//# the Free Software Foundation; either version 2 of the License, or (at your
//# option) any later version.
//#
//# This library 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 Library General Public
//# License for more details.
//#
//# You should have received a copy of the GNU Library General Public License
//# along with this library; if not, write to the Free Software Foundation,
//# Inc., 675 Massachusetts Ave, Cambridge, MA 02139, USA.
//#
//# Correspondence concerning AIPS++ should be addressed as follows:
//#        Internet email: aips2-request@nrao.edu.
//#        Postal address: AIPS++ Project Office
//#                        National Radio Astronomy Observatory
//#                        520 Edgemont Road
//#                        Charlottesville, VA 22903-2475 USA
//#
//# $Id: ImageMetaData.h 21130 2011-10-18 07:39:05Z gervandiepen $

#ifndef IMAGES_IMAGEMETADATA_H
#define IMAGES_IMAGEMETADATA_H

#include <casacore/images/Images/ImageInterface.h>
#include <casacore/casa/aips.h>

namespace casacore { //# NAMESPACE CASACORE - BEGIN

// <summary>
// A class in which to store and allow read-only access to image metadata.
// </summary>

// <use visibility=export>

// <reviewed reviewer="" date="" tests="" demos="">
// </reviewed>

// <prerequisite>
//   <li> <linkto class=ImageInterface>ImageInterface</linkto>
// </prerequisite>

// <etymology>
// The ImageMetaData class name is derived from its role as holding image metadata.
// </etymology>

// <synopsis> 
// The ImageMetaData object is meant to allow access to image metadata (eg, shape,
// coordinate system info such as spectral and polarization axes numbers, etc).
// </synopsis>

// <example>
// Construct an object of this class by passing the associated image to the constructor.
// <srcblock>
// PagedImage<Float> myImage("myImage");
// ImageMetaData<Float> myImageMetaData(myImage);
// </srcblock>
// </example>

// <motivation> 
// This class is meant to provide an object-oriented interface for accessing
// image metadata without polluting the ImageInterface and CoordinateSystem
// classes with these methods.
// </motivation>
// <todo>
// Merge ImageInfo class into this class.
// </todo>


class ImageMetaData {

    public:
        template <class T> ImageMetaData(const ImageInterface<T>& image) :
			itsInfo(image.imageInfo()), itsUnits(image.units()),
            itsCoordinates(image.coordinates()), itsShape(image.shape()) {}

        // Get the axis number of the spectral axis of this image (0-based).
        Int spectralAxisNumber() const; 

        // Get the number of channels in this image.
	    uInt nChannels() const;

        // Is the specified channel number valid for this image?
        Bool isChannelNumberValid(const uInt chan) const;

        // Get the coordinate number of the spectral axis of this image (0-based). This
        // is generally not the same as the axis number because the direction (eg RA, Dec)
        // coordinate counts as only one coordinate, not two. Yes I know its confusing.
        // Here's an example, say you have an image with axes, RA, Dec, Stokes, Frequency.
        // The spectral coordinate number would be 2 since RA, Dec make up a single
        // direction coordinate. But, the spectral axis number would be 3, because RA
        // and Dec are counted seperately in this case. Its important (and very confusing)
        // to be clear about this difference or things will break.
        Int spectralCoordinateNumber() const;

        // Does this image have a spectral (frequency) axis?
        Bool hasSpectralAxis() const;

        // Get the coordinate number of the polarization axis of this image (0-based). This
        // is generally not the same as the axis number because the direction (eg RA, Dec)
        // coordinate counts as only one coordinate, not two. Yes I know its confusing.
        // Here's an example, say you have an image with axes, RA, Dec, Stokes, Frequency.
        // The polarization coordinate number would be 1 since RA, Dec make up a single
        // direction coordinate. But, the polarization axis number would be 2, because RA
        // and Dec are counted seperately in this case. Its important (and very confusing)
        // to be clear about this difference or things will break. Return -1
        // if this image does not have a polarization axis.
 
        Int polarizationCoordinateNumber() const;

        // Get the axis number of the polarization axis of this image (0-based). Return -1
        // if this image does not have a polarization axis.
        Int polarizationAxisNumber() const;

        // Does this image have a polarization axis?
        Bool hasPolarizationAxis() const;

        // Get the pixel number on the polarization axis of the specified stokes parameter.
        // If the specified stokes parameter does not exist in the image, the value returned
        // is not gauranteed to be anything other than outside the range of 0 to nStokes-1
        // inclusive. Return -1 if the specified stokes parameter is not present or
        // if this image does not have a polarization axis.
 
        Int stokesPixelNumber(const String& stokesString) const;

        // get the stokes parameter at the specified pixel value on the polarization axis.
        // returns "" if the specified pixel is out of range or if no polarization axis.

        String stokesAtPixel(const uInt pixel) const;

        // Get the number of stokes parameters in this image.
	    uInt nStokes() const;

        // is the specified stokes parameter present in the image?
        Bool isStokesValid(const String& stokesString) const;

        // Get the zero based direction coordinate number.
        Int directionCoordinateNumber() const;

        // does this image have a direction coordinate?
        Bool hasDirectionCoordinate() const;

        // Get the direction axes numbers for this image. Returns a two element
        // Vector if there is a direction coordinate, if not returns a zero element
        // vector.
        Vector<Int> directionAxesNumbers() const; 

        // Get the shape of the direction axes. Returns a two element
        // Vector if there is a direction coordinate, if not returns a zero element
        // vector.

        Vector<Int> directionShape() const;

        // if the specified stokes parameter is valid. A message suitable for
        // error notification is returned in the form of an in-out parameter
        //if one or both of these is invalid.
        Bool areChannelAndStokesValid(
            String& message, const uInt chan, const String& stokesString
        ) const;

        // Get beam volume if possible. Return true if beam area was determined.
        Bool getBeamArea(Quantity& beamArea) const;

        // Get the solid angle subtended by a direction pixel (eg ra,dec or lat, long)
        // Return False if this value cannot be determined.
        Bool getDirectionPixelArea(Quantity& pixelArea) const;

    private:
        const ImageInfo itsInfo;
        const Unit itsUnits;
        const CoordinateSystem& itsCoordinates;
        const IPosition itsShape;


};

} //# NAMESPACE CASACORE - END
#endif