[Insight-users] Hough Lines Transform

[Julien Jomier]

Hi Pavan,

As you know, the Hough transform describes a parameter space as angle 
v.s distance. In 2D this parameter space is 2 dimensional: one axis 
representing the angle and the other the distance.
SetAngleAxisSize() sets the size of the angle axis, i.e the size in Y of 
the image that contains the accumulator.
The angle resolution defines the step of search for the angle 
(PI/angleResolution). This means that these two values should be 
approximately the same. If these values are high, your parameter space 
will be more precise but it'll take more time to compute it and will 
take more memory.

If you have any issues, try to visualize the accumulator image (i.e the 
parameter space) and see if you have local maxima where they should be.
Take also a look at the example in the Examples directory as well as the 
test in the Testing directory.

The filter is not limiting the search to a particular direction of the 
line. You can modify the filter to do it though.

Hope that helps,

Julien

Pavan Podila wrote:
> Hello,
>    I am having problems using the Hough Lines Transform. I am not sure 
> on how to use the SetAngleResolution() and SetAngleAxisSize() APIs. The 
> default values are set at 500. How should I interpret these values? My 
> purpose is to extract all (nearly) horizontal lines in the image. Any 
> help is appreciated.
> 
> Thanks,
> Pavan
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