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.

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

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

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

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

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

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.