class cv::LineIterator

Overview

Line iterator. More…

#include <imgproc.hpp>

class LineIterator
{
public:
    // fields

    int count;
    int elemSize;
    int err;
    int minusDelta;
    int minusStep;
    int plusDelta;
    int plusStep;
    uchar* ptr;
    const uchar* ptr0;
    int step;

    // construction

    LineIterator(
        const Mat& img,
        Point pt1,
        Point pt2,
        int connectivity = 8,
        bool leftToRight = false
        );

    // methods

    uchar*
    operator*();

    LineIterator&
    operator++();

    LineIterator
    operator++(int);

    Point
    pos() const;
};

Detailed Documentation

Line iterator.

The class is used to iterate over all the pixels on the raster line segment connecting two specified points.

The class LineIterator is used to get each pixel of a raster line. It can be treated as versatile implementation of the Bresenham algorithm where you can stop at each pixel and do some extra processing, for example, grab pixel values along the line or draw a line with an effect (for example, with XOR operation).

The number of pixels along the line is stored in LineIterator::count. The method LineIterator::pos returns the current position in the image:

// grabs pixels along the line (pt1, pt2)
// from 8-bit 3-channel image to the buffer
LineIterator it(img, pt1, pt2, 8);
LineIterator it2 = it;
vector<Vec3b> buf(it.count);

for(int i = 0; i < it.count; i++, ++it)
    buf[i] = *(const Vec3b)*it;

// alternative way of iterating through the line
for(int i = 0; i < it2.count; i++, ++it2)
{
    Vec3b val = img.at<Vec3b>(it2.pos());
    CV_Assert(buf[i] == val);
}

Construction

LineIterator(
    const Mat& img,
    Point pt1,
    Point pt2,
    int connectivity = 8,
    bool leftToRight = false
    )

intializes the iterator

creates iterators for the line connecting pt1 and pt2 the line will be clipped on the image boundaries the line is 8-connected or 4-connected If leftToRight=true, then the iteration is always done from the left-most point to the right most, not to depend on the ordering of pt1 and pt2 parameters

Methods

uchar*
operator*()

returns pointer to the current pixel

LineIterator&
operator++()

prefix increment operator (++it). shifts iterator to the next pixel

LineIterator
operator++(int)

postfix increment operator (it++). shifts iterator to the next pixel

Point
pos() const

returns coordinates of the current pixel