| Blanking out regions [message #37963] |
Thu, 05 February 2004 00:43  |
Victorpoe
Messages: 2
Registered: February 2004
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Junior Member |
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I need to draw a contour plot of data on irregular 2d grid and blank
out regions outside the boundaries of multiconnected non-convex domain
A in R2.
; Draw contours
Contour, MyData, X, Y, /IRREGULAR
; Draw boundary
Oplot, BoundaryA
;Blank out exterior
?
Is there a way to fill the complement of A to circumscribed rectangle?
Any advice will be appreciated.
Victor.
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| Re: Blanking out regions [message #38011 is a reply to message #37963] |
Tue, 10 February 2004 05:42  |
hjalti
Messages: 13
Registered: October 2003
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Junior Member |
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Victorpoe@hotmail.com (Victor Podsechin) wrote in message news:<20b63ed6.0402050043.3aa30c29@posting.google.com>...
> I need to draw a contour plot of data on irregular 2d grid and blank
> out regions outside the boundaries of multiconnected non-convex domain
> A in R2.
> ; Draw contours
> Contour, MyData, X, Y, /IRREGULAR
> ; Draw boundary
> Oplot, BoundaryA
> ;Blank out exterior
> ?
> Is there a way to fill the complement of A to circumscribed rectangle?
> Any advice will be appreciated.
> Victor.
If I remember correctly it was David Fanning who discussed some time
ago how this can be done in case you have a masking array, in that
instance terrain elevation where the oceans with value zero were to be
blanked out. I have adapted Fanning's example for my own work and
added a method for creating a masking array from a polygon. I include
below the part of my program that does this job, and some comments
within.
-------
; You read your data into an array, then do
thisDevice = !D.Name ; Store the present device in a variable
xsize=500 & ysize=600 ; Define the dimensions of your plotting device
Set_Plot, 'Z' ; Set the Z-buffer as the current device
Device, Set_Resolution=[xsize, ysize]
; Here I read the masking polygon, a list of (x,y) coordinates
openr, lun, '../kortagr/boundary.xy', /get_lun
readf, lun, dummy
readf, lun, npoints
boundary=fltarr(2, npoints)
readf, lun, boundary
free_lun, lun
; Now the vertices of the polygon are stored in the array boundary
plot, boundary[0,*], boundary[1,*], /nodata, xstyle=1, ystyle=1,
/isotropic
; Plot the boundary with /nodata keyword
map=tvrd() ; Now read the image (axes) from the Z-buffer for later
use.
mask1=intarr(xsize,ysize)
id_mask1=where(map ne 0)
mask1[id_mask1]=1 ; set mask1 to one where the axes are
; Do the contour plot
contour, z, x, y, /irregular, nlevels=nlevels, /overplot,
c_labels=replicate(1, nlevels);, c_colors=c_colors, /fill, /overplot,
max_value=100, min_value=-100.
map=tvrd() ; read again the image from the Z-buffer
Set_Plot, thisDevice
window, xsize=xsize, ysize=ysize ; make a visible window
; Convert the boundary coordinates to device-coordinates
res=convert_coord(boundary[0,*], boundary[1,*], /data, /to_device)
res=fix(res[0:1,*]) ; Change to integer type - to be used as array
indices(actually not necessary).
id_mask=polyfillv(res[0,*], res[1,*], xsize, ysize); create an array
of all the array indices within the polygon defined by 'res'
mask=intarr(xsize, ysize)
mask[id_mask]=1
mask=mask+mask1 ; Region inside the polygon + the axes are to be
plotted
map=map*mask; Blanks map where mask is zero
tv, map ; puts map to the plotting window
END
This is it, hope it was helpful.
Regards, Hjalti
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| Re: Blanking out regions [message #38131 is a reply to message #38011] |
Mon, 23 February 2004 05:41 |
Victorpoe
Messages: 2
Registered: February 2004
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Junior Member |
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hjalti@vatnaskil.is (Hjalti Sig) wrote in message news:<e1330fff.0402100542.4df549a3@posting.google.com>...
> If I remember correctly it was David Fanning who discussed some time
> ago how this can be done in case you have a masking array, in that
> instance terrain elevation where the oceans with value zero were to be
> blanked out. I have adapted Fanning's example for my own work and
> added a method for creating a masking array from a polygon. I include
> below the part of my program that does this job, and some comments
> within.
> -------
> ; You read your data into an array, then do
>
> thisDevice = !D.Name ; Store the present device in a variable
> xsize=500 & ysize=600 ; Define the dimensions of your plotting device
> Set_Plot, 'Z' ; Set the Z-buffer as the current device
> Device, Set_Resolution=[xsize, ysize]
>
> ; Here I read the masking polygon, a list of (x,y) coordinates
> openr, lun, '../kortagr/boundary.xy', /get_lun
> readf, lun, dummy
> readf, lun, npoints
> boundary=fltarr(2, npoints)
> readf, lun, boundary
> free_lun, lun
> ; Now the vertices of the polygon are stored in the array boundary
>
> plot, boundary[0,*], boundary[1,*], /nodata, xstyle=1, ystyle=1,
> /isotropic
> ; Plot the boundary with /nodata keyword
> map=tvrd() ; Now read the image (axes) from the Z-buffer for later
> use.
> mask1=intarr(xsize,ysize)
> id_mask1=where(map ne 0)
> mask1[id_mask1]=1 ; set mask1 to one where the axes are
> ; Do the contour plot
> contour, z, x, y, /irregular, nlevels=nlevels, /overplot,
> c_labels=replicate(1, nlevels);, c_colors=c_colors, /fill, /overplot,
> max_value=100, min_value=-100.
>
> map=tvrd() ; read again the image from the Z-buffer
>
> Set_Plot, thisDevice
> window, xsize=xsize, ysize=ysize ; make a visible window
>
> ; Convert the boundary coordinates to device-coordinates
> res=convert_coord(boundary[0,*], boundary[1,*], /data, /to_device)
> res=fix(res[0:1,*]) ; Change to integer type - to be used as array
> indices(actually not necessary).
>
> id_mask=polyfillv(res[0,*], res[1,*], xsize, ysize); create an array
> of all the array indices within the polygon defined by 'res'
>
> mask=intarr(xsize, ysize)
> mask[id_mask]=1
> mask=mask+mask1 ; Region inside the polygon + the axes are to be
> plotted
>
> map=map*mask; Blanks map where mask is zero
> tv, map ; puts map to the plotting window
> END
>
>
> This is it, hope it was helpful.
> Regards, Hjalti
Thanks you, Hjalti,
your method works fine for me also.
I found another way to blank regions using polyfill procedure.
I assume that a boundary of domain A in R2 is closed and
counter-clockwise ordered.
Then it can be divided into four segments:
(xmin,*) - (*, ymin),
(*,ymin) - (xmax,*),
(xmax,*) - (*, ymax),
(*,ymax) - (xmin,*).
These segments can be closed by adding the points - corners of
circumscribed rectange:
(xmin, ymin)
(xmax, xmin)
(xmax, ymax)
(xmin,ymax).
By applying polyfill procedure to these closed segments the regions
outside the boundary will be blanked.
Victor.
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| Re: Blanking out regions [message #38206 is a reply to message #38131] |
Tue, 24 February 2004 05:40 |
hjalti
Messages: 13
Registered: October 2003
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Junior Member |
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Victorpoe@hotmail.com (Victor Podsechin) wrote in message news:<20b63ed6.0402230541.48b5d75e@posting.google.com>...
> hjalti@vatnaskil.is (Hjalti Sig) wrote in message news:<e1330fff.0402100542.4df549a3@posting.google.com>...
>> If I remember correctly it was David Fanning who discussed some time
>> ago how this can be done in case you have a masking array, in that
>> instance terrain elevation where the oceans with value zero were to be
>> blanked out. I have adapted Fanning's example for my own work and
>> added a method for creating a masking array from a polygon. I include
>> below the part of my program that does this job, and some comments
>> within.
>> -------
>> ; You read your data into an array, then do
>>
>> thisDevice = !D.Name ; Store the present device in a variable
>> xsize=500 & ysize=600 ; Define the dimensions of your plotting device
>> Set_Plot, 'Z' ; Set the Z-buffer as the current device
>> Device, Set_Resolution=[xsize, ysize]
>>
>> ; Here I read the masking polygon, a list of (x,y) coordinates
>> openr, lun, '../kortagr/boundary.xy', /get_lun
>> readf, lun, dummy
>> readf, lun, npoints
>> boundary=fltarr(2, npoints)
>> readf, lun, boundary
>> free_lun, lun
>> ; Now the vertices of the polygon are stored in the array boundary
>>
>> plot, boundary[0,*], boundary[1,*], /nodata, xstyle=1, ystyle=1,
>> /isotropic
>> ; Plot the boundary with /nodata keyword
>> map=tvrd() ; Now read the image (axes) from the Z-buffer for later
>> use.
>> mask1=intarr(xsize,ysize)
>> id_mask1=where(map ne 0)
>> mask1[id_mask1]=1 ; set mask1 to one where the axes are
>> ; Do the contour plot
>> contour, z, x, y, /irregular, nlevels=nlevels, /overplot,
>> c_labels=replicate(1, nlevels);, c_colors=c_colors, /fill, /overplot,
>> max_value=100, min_value=-100.
>>
>> map=tvrd() ; read again the image from the Z-buffer
>>
>> Set_Plot, thisDevice
>> window, xsize=xsize, ysize=ysize ; make a visible window
>>
>> ; Convert the boundary coordinates to device-coordinates
>> res=convert_coord(boundary[0,*], boundary[1,*], /data, /to_device)
>> res=fix(res[0:1,*]) ; Change to integer type - to be used as array
>> indices(actually not necessary).
>>
>> id_mask=polyfillv(res[0,*], res[1,*], xsize, ysize); create an array
>> of all the array indices within the polygon defined by 'res'
>>
>> mask=intarr(xsize, ysize)
>> mask[id_mask]=1
>> mask=mask+mask1 ; Region inside the polygon + the axes are to be
>> plotted
>>
>> map=map*mask; Blanks map where mask is zero
>> tv, map ; puts map to the plotting window
>> END
>>
>>
>> This is it, hope it was helpful.
>> Regards, Hjalti
>
>
> Thanks you, Hjalti,
> your method works fine for me also.
> I found another way to blank regions using polyfill procedure.
> I assume that a boundary of domain A in R2 is closed and
> counter-clockwise ordered.
> Then it can be divided into four segments:
> (xmin,*) - (*, ymin),
> (*,ymin) - (xmax,*),
> (xmax,*) - (*, ymax),
> (*,ymax) - (xmin,*).
> These segments can be closed by adding the points - corners of
> circumscribed rectange:
> (xmin, ymin)
> (xmax, xmin)
> (xmax, ymax)
> (xmin,ymax).
> By applying polyfill procedure to these closed segments the regions
> outside the boundary will be blanked.
> Victor.
OK, I may try this. But I was thinking - I guess the simplest way to
blank out regions is making a regular grid of your data, then
converting your (x,y) values to index numbers and same to the blanking
polygon, then finding the index numbers to be blanked using polyfillv,
assigning NaN to the corresponding z-values, and then doing countour
plotting. By this you can avoid manipulating images in the z-buffer.
Generally your data array has much smaller dimensions than the
plotting device, so this may result in a less refined blanking, but I
have not tried this out.
Hjalti
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