I think theta should only go to 1p1. I'd leave viewmat out of the main verb.
NB.*houghTransform v Produces a density diagram of image y in hough space NB. y is picture as an array with 1 at non-white points, NB. x is resolution (width,height) of resulting image houghTransform=:4 :0 'w h'=.x rho=. y hough~ o. (%~ 0.5+i.) w NB. rho for each pixel at each theta 'min max'=. (<./ , >./)@, rho rho=. <. 0.5+ h * (max-min) %~ min -~ rho NB. Rescale and round rho to int from 0 to h ([: <:@(#/.~) (i.h)&,)"1&.|: rho NB. consolidate into picture ) NB. Where hough is one of these equivalent verbs: NB.*hough v Returns rho values of each theta value x for picture y. NB. y is picture as an array with 1 at non-white points, NB. x is values to test at hough=:4 :0 ind=. 4$.$. y NB. Indices of points in y ind +/ .* 2 1 o./ x ) hough=: 4 :'(2 1 o./ x) +/ .*~ 4$.$.y' hough=: 2 1&(o./)@[ +/ .*~ 4 $. $...@] Note 'Example use:' require 'viewmat media/platimg' Img=: readimg jpath '~temp/pentagon.png' viewmat 320 240 houghTransform _1 > Img ) > From: Marshall Lochbaum > Sent: Wednesday, 15 September 2010 13:30 > > I think this gives the correct plot. It also uses viewmat, but just to plot > the final array. > > NB. Y is picture as an array with 1 at black points, x is values to test at > NB. Returns r values of each theta value x. > hough=:4 :0 > ind=. ($ #: I.@,) y NB. Indices of points in y > ind +/ .* 2 1 o./ x > ) > > NB. Y is picture, x is resolution. Produces and sends to viewmat a density > diagram > NB. In hough space with resolution x > drawhough=:4 :0 > 'w h'=.x > val=. y hough~ +:o. (%~ 0.5+i.) w NB. Test r values for each pixel at each > theta given by the centers of pixels > 'min max'=. (<./@, , >./@,) val > rel=.h * (max-min) %~ min -~ val NB. Rescale so that y values go from 0 to > h > pixels=.([: <:@(#/.~) (i.h) , ])"1&.|: <:@>. rel NB. Round y values; > consolidate into picture > viewmat pixels > ) > > I have tested this on |. =/~ i. 100, but not on the actual picture. Note > that it uses the top left corner as the natural coordinate center. > Also, I made theta go from 0 to 2p1. Should these be the bounds, or just 0 > to 1p1? > > Marshall > > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of Aai > Sent: Tuesday, September 14, 2010 10:16 AM > To: Programming forum > Subject: Re: [Jprogramming] Hough transform > > Hi David, > I don't know exactly what you expect but here's an alternative using > viewmat. > > require 'viewmat' > > Because you just increment coordinate values by 1 for every iteration it's > sufficient to compose a triple X Y Z in which Z is the 'height' or > 'density' of a point in hough space. > > hough2=: 4 : 0 > radii=: (>:length>:$y)*_0.5+grid {. x > angle=: 1r1p1*grid {: x > b=: 0 < ,y > inter=: b # , y > coord=: ($y) #: I. b > rhoug=: (coord,.1)+/ .*(1 0,0 _1,:_0.5 0.5*$y)+/ .*1 2 o./angle > r=: (<:@# - I.&rhoug)radii > 'X Y Z'=.|:({.,#)/.~,/r ,."1 i. {: x > viewmat Z (;/ X,.Y) } 0 $~ 0 _1 { x > ) > > > try e.g. > > 250 hough2 data > > > -- > Met vriendelijke groet, > =@@i > > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm > > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
