The ProbabilisticHoughLine command detects line segments in img, and returns the detected line segments as an $m$ by $4$ Array, lines. Each line segment corresponds to a row of lines: ${\mathrm{lines}}_i=\left[{\left(x_i\right)}_1\,{\left(y_i\right)}_1\,{\left(x_i\right)}_2\,{\left(y_i\right)}_2\right]$, where $\left[{\left(x_i\right)}_1\,{\left(y_i\right)}_1\right]$ and $\left[{\left(x_i\right)}_2\,{\left(y_i\right)}_2\right]$ are the two end points of the ith line segment.

This command is implemented by a call to the Intel Integrated Performance Primitives (IPP) library; in particular, its ippiHoughProbLine_8u32f_C1R command. For more details, see its documentation.

This command interprets integer coordinate values to represent the corners of pixels, like the commands in the ImageTools[Draw] package do. It always returns coordinates for the centers of pixels, so the coordinates returned are always half integers.

img should be a binary image, so calling EdgeDetect and Threshold are usually necessary before calling ProbabilisticHoughLine.

$\mathrm{with}\left(\mathrm{ImageTools}\right)\:$

$\mathrm{img}≔\mathrm{Read}\left(\mathrm{cat}\left(\mathrm{kernelopts}\left(\mathrm{datadir}\right)\,''/images/Maplesoft.png''\right)\right)$

$\mathrm{img}≔\begin{array}{c}\left[\begin{array}{ccccccccccc}0.968627450980392& 0.964705882352941& 0.964705882352941& 0.956862745098039& 0.956862745098039& 0.960784313725490& 0.968627450980392& 0.972549019607843& 0.972549019607843& 0.972549019607843& \dots \\ 0.956862745098039& 0.952941176470588& 0.952941176470588& 0.956862745098039& 0.956862745098039& 0.956862745098039& 0.960784313725490& 0.964705882352941& 0.964705882352941& 0.968627450980392& \dots \\ 0.956862745098039& 0.952941176470588& 0.952941176470588& 0.952941176470588& 0.952941176470588& 0.952941176470588& 0.956862745098039& 0.956862745098039& 0.956862745098039& 0.956862745098039& \dots \\ 0.949019607843137& 0.949019607843137& 0.952941176470588& 0.952941176470588& 0.952941176470588& 0.952941176470588& 0.952941176470588& 0.952941176470588& 0.952941176470588& 0.952941176470588& \dots \\ 0.949019607843137& 0.949019607843137& 0.949019607843137& 0.949019607843137& 0.949019607843137& 0.949019607843137& 0.952941176470588& 0.952941176470588& 0.952941176470588& 0.952941176470588& \dots \\ 0.945098039215686& 0.945098039215686& 0.945098039215686& 0.949019607843137& 0.945098039215686& 0.949019607843137& 0.949019607843137& 0.949019607843137& 0.949019607843137& 0.952941176470588& \dots \\ 0.941176470588235& 0.941176470588235& 0.941176470588235& 0.941176470588235& 0.941176470588235& 0.945098039215686& 0.941176470588235& 0.941176470588235& 0.941176470588235& 0.945098039215686& \dots \\ 0.933333333333333& 0.933333333333333& 0.933333333333333& 0.933333333333333& 0.933333333333333& 0.933333333333333& 0.933333333333333& 0.933333333333333& 0.937254901960784& 0.941176470588235& \dots \\ 0.925490196078431& 0.925490196078431& 0.925490196078431& 0.929411764705882& 0.929411764705882& 0.929411764705882& 0.941176470588235& 0.941176470588235& 0.941176470588235& 0.941176470588235& \dots \\ 0.925490196078431& 0.921568627450980& 0.921568627450980& 0.921568627450980& 0.921568627450980& 0.921568627450980& 0.929411764705882& 0.933333333333333& 0.929411764705882& 0.933333333333333& \dots \\ ⋮& ⋮& ⋮& ⋮& ⋮& ⋮& ⋮& ⋮& ⋮& ⋮& \ddots \end{array}\right]\\ \hfill \text{slice of 592 × 1330 × 4 Array}\end{array}$

$\mathrm{edge}≔\mathrm{Threshold}\left(\mathrm{EdgeDetect}\left(\mathrm{img}\right)\,1.5\right)$

$\mathrm{edge}≔\begin{array}{c}\left[\begin{array}{ccccccccccc}0.& 0.& 0.& 0.& 0.& 0.& 0.& 0.& 0.& 0.& \dots \\ 0.& 0.& 0.& 0.& 0.& 0.& 0.& 0.& 0.& 0.& \dots \\ 0.& 0.& 0.& 0.& 0.& 0.& 0.& 0.& 0.& 0.& \dots \\ 0.& 0.& 0.& 0.& 0.& 0.& 0.& 0.& 0.& 0.& \dots \\ 0.& 0.& 0.& 0.& 0.& 0.& 0.& 0.& 0.& 0.& \dots \\ 0.& 0.& 0.& 0.& 0.& 0.& 0.& 0.& 0.& 0.& \dots \\ 0.& 0.& 0.& 0.& 0.& 0.& 0.& 0.& 0.& 0.& \dots \\ 0.& 0.& 0.& 0.& 0.& 0.& 0.& 0.& 0.& 0.& \dots \\ 0.& 0.& 0.& 0.& 0.& 0.& 0.& 0.& 0.& 0.& \dots \\ 0.& 0.& 0.& 0.& 0.& 0.& 0.& 0.& 0.& 0.& \dots \\ ⋮& ⋮& ⋮& ⋮& ⋮& ⋮& ⋮& ⋮& ⋮& ⋮& \end{array}\right]\\ \hfill \text{592 × 1330 Array}\end{array}$

$\mathrm{Embed}\left(\mathrm{edge}\right)$

$\mathrm{line}≔\mathrm{ProbabilisticHoughLine}\left(\mathrm{edge}\,1\,\frac{\mathrm{\pi }}{1800}\,80\,50\,10\right)$

$\mathrm{line}≔\begin{array}{c}\left[\begin{array}{cccc}303.500000000000& 298.500000000000& 445.500000000000& 303.500000000000\\ 15.5000000000000& 324.500000000000& 719.500000000000& 506.500000000000\\ 510.500000000000& 305.500000000000& 855.500000000000& 317.500000000000\\ 622.500000000000& 347.500000000000& 855.500000000000& 359.500000000000\\ 580.500000000000& 470.500000000000& 836.500000000000& 535.500000000000\\ 387.500000000000& 331.500000000000& 468.500000000000& 335.500000000000\\ 757.500000000000& 280.500000000000& 855.500000000000& 281.500000000000\\ 511.500000000000& 307.500000000000& 855.500000000000& 320.500000000000\\ 951.500000000000& 238.500000000000& 1053.50000000000& 238.500000000000\\ 791.500000000000& 239.500000000000& 855.500000000000& 239.500000000000\\ ⋮& ⋮& ⋮& ⋮\end{array}\right]\\ \hfill \text{165 × 4 Array}\end{array}$

DrawLine := proc(img, line)
    local i;
    for i to upperbound(line, 1) do
        Draw:-Line(img, line[i, 1], line[i, 2], line[i, 3], line[i, 4], [255, 0, 0]);
    end do;
end proc:

$\mathrm{DrawLine}\left(\mathrm{img}\,\mathrm{line}\right)$

$\mathrm{Embed}\left(\mathrm{img}\right)$

The ImageTools[ProbabilisticHoughLine] command was introduced in Maple 2020.

For more information on Maple 2020 changes, see Updates in Maple 2020.