/*
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For Open Source Computer Vision Library
(3-clause BSD License)
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Copyright (C) 2015-2016, OpenCV Foundation, all rights reserved.
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*/
/*
Contributed by Gregor Kovalcik <gregor dot kovalcik at gmail dot com>
based on code provided by Martin Krulis, Jakub Lokoc and Tomas Skopal.
References:
Martin Krulis, Jakub Lokoc, Tomas Skopal.
Efficient Extraction of Clustering-Based Feature Signatures Using GPU Architectures.
Multimedia tools and applications, 75(13), pp.: 8071�8103, Springer, ISSN: 1380-7501, 2016
Christian Beecks, Merih Seran Uysal, Thomas Seidl.
Signature quadratic form distance.
In Proceedings of the ACM International Conference on Image and Video Retrieval, pages 438-445.
ACM, 2010.
*/
#ifndef _OPENCV_XFEATURES_2D_PCT_SIGNATURES_GRAYSCALE_BITMAP_HPP_
#define _OPENCV_XFEATURES_2D_PCT_SIGNATURES_GRAYSCALE_BITMAP_HPP_
#ifdef __cplusplus
namespace cv
{
namespace xfeatures2d
{
namespace pct_signatures
{
/**
* @brief Specific implementation of grayscale bitmap. This bitmap is used
* to compute contrast and entropy features from surroundings of a pixel.
*/
class GrayscaleBitmap
{
public:
/**
* @brief Initialize the grayscale bitmap from regular bitmap.
* @param bitmap Bitmap used as source of data.
* @param bitsPerPixel How many bits occupy one pixel in grayscale (e.g., 8 ~ 256 grayscale values).
* Must be within [1..8] range.
*/
GrayscaleBitmap(InputArray bitmap, int bitsPerPixel = 4);
/**
* @brief Return the width of the image in pixels.
*/
int getWidth() const
{
return mWidth;
}
/**
* @brief Return the height of the image in pixels.
*/
int getHeight() const
{
return mHeight;
}
/**
* @brief Return the height of the image in pixels.
*/
int getBitsPerPixel() const
{
return mBitsPerPixel;
}
/**
* @brief Compute contrast and entropy at selected coordinates.
* @param x The horizontal coordinate of the pixel (0..width-1).
* @param y The vertical coordinate of the pixel (0..height-1).
* @param contrast Output variable where contrast value is saved.
* @param entropy Output variable where entropy value is saved.
* @param radius Radius of the rectangular window around selected pixel used for computing
* contrast and entropy. Size of the window side is (2*radius + 1).
* The window is cropped if [x,y] is too near the image border.
*/
void getContrastEntropy(
int x,
int y,
float& contrast,
float& entropy,
int windowRadius = 3);
/**
* @brief Converts to OpenCV CV_8U Mat for debug and visualization purposes.
* @param bitmap OutputArray proxy where Mat will be written.
* @param normalize Whether to normalize the bitmap to the whole range of 255 values
* to improve contrast.
*/
void convertToMat(OutputArray bitmap, bool normalize = true) const;
private:
/**
* @brief Width of the image.
*/
int mWidth;
/**
* @brief Height of the image.
*/
int mHeight;
/**
* @brief Number of bits per pixel.
*/
int mBitsPerPixel;
/**
* @brief Pixel data packed in 32-bit uints.
*/
std::vector<uint> mData;
/**
* @brief Tmp matrix used for computing contrast and entropy.
*/
std::vector<uint> mCoOccurrenceMatrix;
/**
* @brief Get pixel from packed data vector.
* @param x The horizontal coordinate of the pixel (0..width-1).
* @param y The vertical coordinate of the pixel (0..height-1).
* @return Grayscale value (0 ~ black, 2^bitPerPixel - 1 ~ white).
*/
uint inline getPixel(int x, int y) const
{
int pixelsPerItem = 32 / mBitsPerPixel;
int offset = y*mWidth + x;
int shift = (offset % pixelsPerItem) * mBitsPerPixel;
uint mask = (1 << mBitsPerPixel) - 1;
return (mData[offset / pixelsPerItem] >> shift) & mask;
}
/**
* @brief Set pixel in the packed data vector.
* @param x The horizontal coordinate of the pixel (0..width-1).
* @param y The vertical coordinate of the pixel (0..height-1).
* @param val Grayscale value (0 ~ black, 2^bitPerPixel - 1 ~ white).
*/
void inline setPixel(int x, int y, uint val)
{
int pixelsPerItem = 32 / mBitsPerPixel;
int offset = y*mWidth + x;
int shift = (offset % pixelsPerItem) * mBitsPerPixel;
uint mask = (1 << mBitsPerPixel) - 1;
val &= mask;
mData[offset / pixelsPerItem] &= ~(mask << shift);
mData[offset / pixelsPerItem] |= val << shift;
}
/**
* @brief Perform an update of contrast matrix.
*/
void inline updateCoOccurrenceMatrix(uint a, uint b)
{
// co-occurrence matrix is symmetric
// merge to a variable with greater higher bits
// to accumulate just in upper triangle in co-occurrence matrix for efficiency
int offset = (int)((a > b) ? (a << mBitsPerPixel) + b : a + (b << mBitsPerPixel));
mCoOccurrenceMatrix[offset]++;
}
};
}
}
}
#endif
#endif