CVRaulMurOrb.cpp File Reference

Declares the Raul Mur ORB feature detector and descriptor. More...

#include <iterator>
#include <CVRaulMurExtNode.h>
#include <CVRaulMurOrb.h>

Include dependency graph for CVRaulMurOrb.cpp:

Go to the source code of this file.

Macros
#define	GET_VALUE(idx)

Functions
static float	IC_Angle (const CVMat &image, CVPoint2f pt, const vector< int > &u_max)
	Returns the angle of the image patch around a keypoint based on the center of gravity. More...
static void	computeOrbDescriptor (const CVKeyPoint &kpt, const CVMat &img, const CVPoint *pattern, uchar *desc)
	Calculate the Orb descriptor for a keypoint. More...
static void	computeOrientation (const CVMat &image, CVVKeyPoint &keypoints, const vector< int > &umax)
	Compute the angle for a keypoint and save it. More...
static void	computeDescriptors (const CVMat &image, CVVKeyPoint &keypoints, CVMat &descriptors, CVVPoint &pattern)
	Computes the descriptors for all passed keypoints. More...

Variables
const int	PATCH_SIZE = 31
const int	HALF_PATCH_SIZE = 15
const int	EDGE_THRESHOLD = 19
const float	factorPI = (float)(CV_PI / 180.f)
static int	bit_pattern_31_ [256 *4]

Detailed Description

Declares the Raul Mur ORB feature detector and descriptor.

This File is based on the ORB Implementation of ORB_SLAM https://github.com/raulmur/ORB_SLAM2

Date

Spring 2017

Remarks

Please use clangformat to format the code. See more code style on https://github.com/cpvrlab/SLProject4/wiki/SLProject-Coding-Style

Authors

Pascal Zingg, Timon Tschanz, Michael Goettlicher, Marcus Hudritsch

Copyright

http://opensource.org/licenses/GPL-3.0

Definition in file CVRaulMurOrb.cpp.

Macro Definition Documentation

GET_VALUE

#define GET_VALUE

(

idx

)

Value:

    center[cvRound(pattern[idx].x * b + pattern[idx].y * a) * step + \
           cvRound(pattern[idx].x * a - pattern[idx].y * b)]

Function Documentation

computeDescriptors()

static void computeDescriptors ( const CVMat &  image, CVVKeyPoint &  keypoints, CVMat &  descriptors, CVVPoint &  pattern  )

static

Computes the descriptors for all passed keypoints.

Definition at line 792 of file CVRaulMurOrb.cpp.

{
    descriptors = CVMat::zeros((int)keypoints.size(), 32, CV_8UC1);
 
    for (size_t i = 0; i < keypoints.size(); i++)
        computeOrbDescriptor(keypoints[i],
                             image,
                             &pattern[0],
                             descriptors.ptr((int)i));
}

computeOrbDescriptor()

static void computeOrbDescriptor ( const CVKeyPoint &  kpt, const CVMat &  img, const CVPoint *  pattern, uchar *  desc  )

static

Calculate the Orb descriptor for a keypoint.

Definition at line 62 of file CVRaulMurOrb.cpp.

{
 
    float angle = (float)kpt.angle * factorPI;
    float a = (float)cos(angle), b = (float)sin(angle);
 
    const uchar* center = &img.at<uchar>(cvRound(kpt.pt.y), cvRound(kpt.pt.x));
    const int    step   = (int)img.step;
// Define a rotation invariant get_value function which gets the correct pixel for the comparison
#define GET_VALUE(idx) \
    center[cvRound(pattern[idx].x * b + pattern[idx].y * a) * step + \
           cvRound(pattern[idx].x * a - pattern[idx].y * b)]
 
    // clang-format off
    // Do the actual comparisons
    for (int i = 0; i < 32; ++i, pattern += 16)
    {
        int t0, t1, val;
        t0 = GET_VALUE(0);  t1 = GET_VALUE(1);  val = t0 < t1;
        t0 = GET_VALUE(2);  t1 = GET_VALUE(3);  val |= (t0 < t1) << 1;
        t0 = GET_VALUE(4);  t1 = GET_VALUE(5);  val |= (t0 < t1) << 2;
        t0 = GET_VALUE(6);  t1 = GET_VALUE(7);  val |= (t0 < t1) << 3;
        t0 = GET_VALUE(8);  t1 = GET_VALUE(9);  val |= (t0 < t1) << 4;
        t0 = GET_VALUE(10); t1 = GET_VALUE(11); val |= (t0 < t1) << 5;
        t0 = GET_VALUE(12); t1 = GET_VALUE(13); val |= (t0 < t1) << 6;
        t0 = GET_VALUE(14); t1 = GET_VALUE(15); val |= (t0 < t1) << 7;
 
        desc[i] = (uchar)val;
    }
    // clang-format on
 
#undef GET_VALUE
}

computeOrientation()

static void computeOrientation ( const CVMat &  image, CVVKeyPoint &  keypoints, const vector< int > &  umax  )

static

Compute the angle for a keypoint and save it.

Definition at line 436 of file CVRaulMurOrb.cpp.

{
    for (CVVKeyPoint::iterator keypoint    = keypoints.begin(),
                               keypointEnd = keypoints.end();
         keypoint != keypointEnd;
         ++keypoint)
    {
        keypoint->angle = IC_Angle(image, keypoint->pt, umax);
    }
}

IC_Angle()

static float IC_Angle ( const CVMat &  image, CVPoint2f  pt, const vector< int > &  u_max  )

static

Returns the angle of the image patch around a keypoint based on the center of gravity.

Definition at line 27 of file CVRaulMurOrb.cpp.

{
    int m_01 = 0, m_10 = 0;
 
    const uchar* center = &image.at<uchar>(cvRound(pt.y), cvRound(pt.x));
 
    // Treat the center line differently, v=0
    for (int u = -HALF_PATCH_SIZE; u <= HALF_PATCH_SIZE; ++u)
        m_10 += u * center[u];
 
    // Go line by line in the circuI853lar patch
    int step = (int)image.step1();
    for (int v = 1; v <= HALF_PATCH_SIZE; ++v)
    {
        // Proceed over the two lines
        int v_sum = 0;
        int d     = u_max[(uint)v];
        for (int u = -d; u <= d; ++u)
        {
            int val_plus = center[u + v * step], val_minus = center[u - v * step];
            v_sum += (val_plus - val_minus);
            m_10 += u * (val_plus + val_minus);
        }
        m_01 += v * v_sum;
    }
 
    return fastAtan2((float)m_01, (float)m_10);
}

Variable Documentation

bit_pattern_31_

int bit_pattern_31_[256 *4]

static

This is the hardcoded comparison pattern which the creators of ORB have found to give the best results.

Definition at line 103 of file CVRaulMurOrb.cpp.

EDGE_THRESHOLD

const int EDGE_THRESHOLD = 19

Definition at line 22 of file CVRaulMurOrb.cpp.

factorPI

const float factorPI = (float)(CV_PI / 180.f)

Definition at line 58 of file CVRaulMurOrb.cpp.

HALF_PATCH_SIZE

const int HALF_PATCH_SIZE = 15

Definition at line 21 of file CVRaulMurOrb.cpp.

PATCH_SIZE

const int PATCH_SIZE = 31

Definition at line 20 of file CVRaulMurOrb.cpp.