CImagePyramid.h

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/* +------------------------------------------------------------------------+
   |                     Mobile Robot Programming Toolkit (MRPT)            |
   |                          http://www.mrpt.org/                          |
   |                                                                        |
   | Copyright (c) 2005-2017, Individual contributors, see AUTHORS file     |
   | See: http://www.mrpt.org/Authors - All rights reserved.                |
   | Released under BSD License. See details in http://www.mrpt.org/License |
   +------------------------------------------------------------------------+ */

#ifndef __mrpt_vision_image_pyramid_H
#define __mrpt_vision_image_pyramid_H

#include <mrpt/utils/CImage.h>

namespace mrpt
{
namespace vision
{
/** Holds and builds a pyramid of images: starting with an image at full
 * resolution (octave=1), it builds
  *  a number of half-resolution images: octave=2 at 1/2 , octave=3 at 1/2^2,
 * octave=N at 1/2^(N-1).
  *
  *  Color (RGB) or grayscale pyramids can be built from color input images;
 * only grayscale pyramids can be built from
  *   grayscale images.
  *
  *  The algorithm to halve the images can be either a 1:2 decimation or a
 * smooth filter (arithmetic mean of every 4 pixels).
  *
  *  Pyramids are built by invoking the method \a buildPyramid() or \a
 * buildPyramidFast()
  *
  * Example of usage:
  * \code
  *   CImagePyramid  pyr;
  *
  *   CImage img = ...
  *
  *   pyr.buildPyramid(
  *      img,
  *      4,    // num. of octaves
  *      true  // smooth
  *      );
  *
  *   pyr.images[0].saveToFile("pyr0.jpg");
  *   pyr.images[1].saveToFile("pyr1.jpg");
  *   ...
  * \endcode
  *
  *  \note Both converting to grayscale and building the octave images have
 * SSE2-optimized implementations (if available).
  *
  * \sa mrpt::utils::CImage
  * \ingroup mrpt_vision_grp
  */
class CImagePyramid
{
   public:
        /** Default constructor, does nothing */
        CImagePyramid();
        /** Destructor, frees the stored images. */
        ~CImagePyramid();

        /** Fills the vector \a images with the different octaves built from the
         * input image.
          *  \param[in] img The input image. Can be either color or grayscale.
          *  \param[in] nOctaves Number of octaves to build. 1 means just the
         * original image, 2 means the original plus the 1/2 image, etc.
          *  \param[in] smooth_halves If true, use an arithmetic mean of every 2x2
         * pixel block when downsampling.
          *  \param[in] convert_grayscale If true, the pyramid is built in grayscale
         * even for color input images.
          * \sa buildPyramidFast
          */
        void buildPyramid(
                const mrpt::utils::CImage& img, const size_t nOctaves,
                const bool smooth_halves = true, const bool convert_grayscale = false);

        /**  Exactly like \a buildPyramid(), but if the input image has not to be
         * converted from RGB to grayscale, the image data buffer is *reutilized*
          *   for the 1st octave in \a images[0], emptying the input image.
          * \sa buildPyramid
          */
        void buildPyramidFast(
                mrpt::utils::CImage& img, const size_t nOctaves,
                const bool smooth_halves = true, const bool convert_grayscale = false);

        /** The individual images:
          *  - images[0]: 1st octave (full-size)
          *  - images[1]: 2nd octave (1/2 size)
          *  - images[2]: 3rd octave (1/4 size)
          */
        std::vector<mrpt::utils::CImage> images;
};
}
}

#endif