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Re: texture_coord [message #27683]

Sun, 04 November 2001 13:23

Mark Hadfield
Messages: 783
Registered: May 1995

Senior Member

From: "Karl Schultz" <kschultz@researchsystems.com>
>>> Mark Hadfield (m.hadfield@niwa.cri.nz) writes:
>>>> Your test image ('rose.jpg') is 227 x 149 pixels.
>>>> Texture-map image dimensions are supposed to be a
>>>> power of 2 (or so I was informed some time ago
>>>> when I complained to RSI about misalignment problems).
> IDL will scale it if you don't. But that scaling may not have been
> what you wanted, and may have caused the misalignment problems?

Yes. I realise now this has nothing to do with the interesting effects
encountered by David. But IDL's automatic re-sizing of images when it
needs to use them as a texture map is unsatisfactory, in my opinion. Below
is a test program to illustrate this. It creates & displays an image on its
own and then as a texture-map. If it is run with argument "num" set to any
number that is not a power of 2 the texture-mapped image is shifted up & to
the right.

Actually, I've found IDL's image-oriented mathematical operations
(interpolation, ROIs) often have pretty dodgy geometry when used with a
small number of pixels.

---
Mark Hadfield
m.hadfield@niwa.cri.nz http://katipo.niwa.cri.nz/~hadfield
National Institute for Water and Atmospheric Research

pro mgh_test_image2, NUM=num

compile_opt IDL2

if n_elements(num) eq 0 then num = 16

if n_elements(option) eq 0 then option = 0

; Create a symmetrical 2D array

thedata = bytarr(num,num)
thedata[0:num-2,0:num-2] = bytscl(dist(num-1))
thedata[num-1,*] = thedata[num-2,*]
thedata[*,num-1] = thedata[*,num-2]

; Load the data into an IDLgrImage

theimage = obj_new('IDLgrImage', thedata, LOCATION=[0,0] $
, DIMENSIONS=[1,1])

; Display the image alone

xobjview, theimage

; Display the image mapped onto an IDLgrPolygon

xobjview, obj_new('IDLgrPolygon', [0,1,1,0], [0,0,1,1] $
, COLOR=[255,255,255], TEXTURE_MAP=theimage $
, TEXTURE_COORD=[[0,0],[1,0],[1,1],[0,1]])

end

--
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[Message index]

		Re: texture_coord By: Mark Hadfield on Sun, 04 November 2001 13:23
		Re: texture_coord By: David Fanning on Sun, 04 November 2001 08:53
		Re: texture_coord By: Karl Schultz on Fri, 02 November 2001 09:49
		Re: texture_coord By: David Fanning on Fri, 02 November 2001 09:30
		Re: texture_coord By: Pavel A. Romashkin on Fri, 02 November 2001 09:16
		Re: texture_coord By: David Fanning on Fri, 02 November 2001 09:04
		Re: texture_coord By: Karl Schultz on Fri, 02 November 2001 08:46
		Re: texture_coord By: Karl Schultz on Fri, 02 November 2001 08:39
		Re: texture_coord By: David Fanning on Fri, 02 November 2001 07:09
		Re: texture_coord By: Mark Hadfield on Thu, 01 November 2001 18:48
		Re: texture_coord By: David Fanning on Thu, 01 November 2001 17:31
		Re: texture_coord By: Mark Hadfield on Thu, 01 November 2001 17:07
		Re: texture_coord By: David Fanning on Thu, 01 November 2001 16:34
		Re: texture_coord By: Harald von der Osten-[1] on Thu, 01 November 2001 10:48
		Re: texture_coord By: David Fanning on Thu, 01 November 2001 09:57
		Re: texture_coord By: David Fanning on Thu, 01 November 2001 09:53
		Re: texture_coord By: Karl Schultz on Thu, 01 November 2001 08:11
		Re: texture_coord By: David Fanning on Thu, 01 November 2001 07:18

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