convolve.h

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// Copyright (c) 2007, 2008, 2011 libmv authors.
//
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// The above copyright notice and this permission notice shall be included in
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#ifndef LIBMV_IMAGE_CONVOLVE_H_
#define LIBMV_IMAGE_CONVOLVE_H_
 
#include "libmv/image/image.h"
#include "libmv/numeric/numeric.h"
 
namespace libmv {
 
// TODO(keir): Find a better place for these functions. gaussian.h in numeric?
 
// Zero mean Gaussian.
inline double Gaussian(double x, double sigma) {
  return 1 / sqrt(2 * M_PI * sigma * sigma) * exp(-(x * x / 2 / sigma / sigma));
}
// 2D gaussian (zero mean)
// (9) in http://mathworld.wolfram.com/GaussianFunction.html
inline double Gaussian2D(double x, double y, double sigma) {
  return 1.0 / (2.0 * M_PI * sigma * sigma) *
         exp(-(x * x + y * y) / (2.0 * sigma * sigma));
}
inline double GaussianDerivative(double x, double sigma) {
  return -x / sigma / sigma * Gaussian(x, sigma);
}
// Solve the inverse of the Gaussian for positive x.
inline double GaussianInversePositive(double y, double sigma) {
  return sqrt(-2 * sigma * sigma * log(y * sigma * sqrt(2 * M_PI)));
}
 
void ComputeGaussianKernel(double sigma, Vec* kernel, Vec* derivative);
void ConvolveHorizontal(const FloatImage& in,
                        const Vec& kernel,
                        FloatImage* out_pointer,
                        int plane = -1);
void ConvolveVertical(const FloatImage& in,
                      const Vec& kernel,
                      FloatImage* out_pointer,
                      int plane = -1);
void ConvolveGaussian(const FloatImage& in,
                      double sigma,
                      FloatImage* out_pointer);
 
void ImageDerivatives(const FloatImage& in,
                      double sigma,
                      FloatImage* gradient_x,
                      FloatImage* gradient_y);
 
void BlurredImageAndDerivatives(const FloatImage& in,
                                double sigma,
                                FloatImage* blurred_image,
                                FloatImage* gradient_x,
                                FloatImage* gradient_y);
 
// Blur and take the gradients of an image, storing the results inside the
// three channels of blurred_and_gradxy.
void BlurredImageAndDerivativesChannels(const FloatImage& in,
                                        double sigma,
                                        FloatImage* blurred_and_gradxy);
 
void BoxFilterHorizontal(const FloatImage& in,
                         int window_size,
                         FloatImage* out_pointer);
 
void BoxFilterVertical(const FloatImage& in,
                       int window_size,
                       FloatImage* out_pointer);
 
void BoxFilter(const FloatImage& in, int box_width, FloatImage* out);
 
void LaplaceFilter(unsigned char* src,
                   unsigned char* dst,
                   int width,
                   int height,
                   int strength);
 
}  // namespace libmv
 
#endif  // LIBMV_IMAGE_CONVOLVE_H_