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Re: IDL ROI Objects [message #90110 is a reply to message #90107] Wed, 28 January 2015 06:12 Go to previous messageGo to previous message
David Fanning is currently offline  David Fanning
Messages: 11724
Registered: August 2001
Senior Member
David B writes:

> Thanks for taking a look anyhow! I seem to have a talent for breaking IDL functions lately.

A useful talent. :-)

Here is a piece of code that I think dramatically shows the problem:

;*********************************************************** *******
PRO ROI_BUG
poly = [[5, 10, 10, 5, 5], [5, 5, 10, 10, 5]]
cgDisplay, 600, 600, WID=0, Title = 'Polygon Fill'
cgPlot, [1], XRange=[0,20], YRange=[0,20], /NoData, ASPECT=1.0, $
YTickLen=1.0, XTickLen=1.0
cgPolygon, poly[*,0], poly[*,1], COLOR='dodger blue', /Fill

cgDisplay, 600, 600, WID=1, Title='Polygon Pixel Fill - PolyFillV'
testImage = BytArr(20,20)+1B
pixels = PolyfillV(poly[*,0], poly[*,1], 20, 20)
testImage[pixels]=255
TVLCT, cgColor('red6', /Triple), 255
TVLCT, cgColor('white', /Triple), 1
cgPlot, [1], XRange=[0,20], YRange=[0,20], /NoData, ASPECT=1.0
cgImage, testImage, XRange=[0,20], YRange=[0,20], /Overplot
cgPlot, [1], XRange=[0,20], YRange=[0,20], /NoData, ASPECT=1.0, $
YTickLen=1.0, XTickLen=1.0, /NoErase

cgDisplay, 600, 600, WID=2, Title='Polygon Interior Pixel Fill -
IDLanROI'
p = OBJ_NEW('IDLanROI', poly[*,0], poly[*,1])
mask = p -> ComputeMask(DIMENSIONS=[20,20], MASK_RULE=1)
pixels = Where(mask EQ 255)
anImage = BytArr(20,20)+1B
anImage[pixels] = 255
cgPlot, [1], XRange=[0,20], YRange=[0,20], /NoData, ASPECT=1.0
cgImage, anImage, XRange=[0,20], YRange=[0,20], /Overplot
cgPlot, [1], XRange=[0,20], YRange=[0,20], /NoData, ASPECT=1.0, $
YTickLen=1.0, XTickLen=1.0, /NoErase

cgDisplay, 600, 600, WID=3, Title='Polygon All Pixel Fill - IDLanROI'
p = OBJ_NEW('IDLanROI', poly[*,0], poly[*,1])
mask = p -> ComputeMask(DIMENSIONS=[20,20], MASK_RULE=2)
pixels = Where(mask EQ 255)
anImage = BytArr(20,20)+1B
anImage[pixels] = 255
cgPlot, [1], XRange=[0,20], YRange=[0,20], /NoData, ASPECT=1.0
cgImage, anImage, XRange=[0,20], YRange=[0,20], /Overplot
cgPlot, [1], XRange=[0,20], YRange=[0,20], /NoData, ASPECT=1.0, $
YTickLen=1.0, XTickLen=1.0, /NoErase
END
;*********************************************************** *******

With IDLanROI, if you try to take interior pixels, the box is one pixel
too short. If you try to take *all* the pixels, the box is one pixel too
long. It seems impossible to get the box "just right", given a
particular polygon description.

Cheers,

David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.idlcoyote.com/
Sepore ma de ni thue. ("Perhaps thou speakest truth.")

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