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Keywords and properties (in function graphics) [message #87488]

Fri, 07 February 2014 11:12

Gordon Farquharson
Messages: 48
Registered: December 2010

Member

Hi All

The IDL documentation states that keywords are applied only during the initial creation of the graphic, whereas properties can be set as keywords to the function during creation, or retrieved or changed using the "." notation after creation (e.g., [1]).

Below is a simple program to display an image using a map projection. In the first case (im1), I set all keywords and properties in the function call. In the second case (im2), I only set keywords in the function call, and set properties after the function call.

---
file1 = FILEPATH('Night.jpg', SUBDIRECTORY=['examples','data'])

ret = query_jpeg(file1, info)

lon = findgen(info.dimensions[0]) / info.dimensions[0] * 360. - 180.
lat = findgen(info.dimensions[1]) / info.dimensions[1] * 180. - 90.

read_jpeg, file1, data

im1 = image(data, lon, lat, DIMENSIONS=[1024,512], MARGIN=0., $
GRID_UNITS="degrees", MAP_PROJECTION="Mollweide")

im2 = image(data, lon, lat, DIMENSIONS=[1024,512], MARGIN=0.)

im2.grid_units = "degrees"
im2.map_projection = "Mollweide"

END
---

im1 displays the image as I would expect (warped to the map projection). However, IDL returns the following error when the map_projection property is set for im2.

% Unable to retrieve map projection.
% Execution halted at: $MAIN$ 16 /home/gordon/tmp/test_map.pro

For reference, line 16 is

im2.map_projection = "Mollweide"

Why? Specifically, why I can't change the map projection *property* after the image has been created?

Gordon

[1] http://www.exelisvis.com/docs/image.html

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[Message index]

		Keywords and properties (in function graphics) By: Gordon Farquharson on Fri, 07 February 2014 11:12
		Re: Keywords and properties (in function graphics) By: David Fanning on Fri, 07 February 2014 12:13
		Re: Keywords and properties (in function graphics) By: Gordon Farquharson on Fri, 07 February 2014 12:41
		Re: Keywords and properties (in function graphics) By: David Fanning on Fri, 07 February 2014 13:02
		Re: Keywords and properties (in function graphics) By: Gordon Farquharson on Fri, 07 February 2014 13:16

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