cgcliptomap.pro
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; docformat = 'rst'
;
; NAME:
; cgClipToMap
;
; PURPOSE:
; Allows an image or geoTiff file to be clipped or subset to a map projected boundary.
;
;******************************************************************************************;
; ;
; Copyright (c) 2012, by Fanning Software Consulting, Inc. All rights reserved. ;
; ;
; Redistribution and use in source and binary forms, with or without ;
; modification, are permitted provided that the following conditions are met: ;
; ;
; * Redistributions of source code must retain the above copyright ;
; notice, this list of conditions and the following disclaimer. ;
; * Redistributions in binary form must reproduce the above copyright ;
; notice, this list of conditions and the following disclaimer in the ;
; documentation and/or other materials provided with the distribution. ;
; * Neither the name of Fanning Software Consulting, Inc. nor the names of its ;
; contributors may be used to endorse or promote products derived from this ;
; software without specific prior written permission. ;
; ;
; THIS SOFTWARE IS PROVIDED BY FANNING SOFTWARE CONSULTING, INC. ''AS IS'' AND ANY ;
; EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES ;
; OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT ;
; SHALL FANNING SOFTWARE CONSULTING, INC. BE LIABLE FOR ANY DIRECT, INDIRECT, ;
; INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED ;
; TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; ;
; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ;
; ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT ;
; (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS ;
; SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. ;
;******************************************************************************************;
;
;+
; Allows an image or geoTiff file to be clipped or subset to a map projected boundary.
;
; :Categories:
; Map Utilities
;
; :Returns:
; The clipped or subsetted image is returned.
;
; :Params:
; imageIn: in, required, type=varies
; Either a 2D or true-color image (in which, in both cases, a map coordinate object must be provided with the
; MAP keyword) or the name of the GeoTiff file from which an image and a map coordinate object
; can be obtained.
; boundary: in, required, type=fltarr
; A four-element array containing the map boundary to which the image should be clipped.
;
; :Keywords:
; latlonbox: out, optional, type=fltarr
; A four-element array representing the boundary of the output image in
; the Google Map preferred form of [north, south, east, west] in decimal
; degrees.
; map: in, required, type=object
; A map coordinate object (cgMap) that maps or georeferences the input image.
; outboundary: out, optional, type=fltarr
; A four-element array containing the final map boundary of the clipped image.
; The boundary will be in XY coordinates (projected meters).
; outmap: out, optional, type=object
; An output map coordinate object (cgMap) that describes the output image.
; outposition: out, optional, type=intarr
; A four-element array containing the pixel locations of the output image
; in the input image pixel coordinate system: [x0,y0,x1,y1]. In other words,
; these are the values used to subset the input image.
;
; :Author:
; FANNING SOFTWARE CONSULTING::
; David W. Fanning
; 1645 Sheely Drive
; Fort Collins, CO 80526 USA
; Phone: 970-221-0438
; E-mail: david@idlcoyote.com
; Coyote's Guide to IDL Programming: http://www.idlcoyote.com
;
; :History:
; Change History::
; Written, 16 August 2012. DWF.
; If the absolute value of the maximum of the boundary is LE 360, assume you need to convert
; from lat/lon space to projected meter space. 23 Aug 2012. DWF.
; Added MAPOUT and LATLONBOX keywords. 1 Nov 2012. DWF.
; Added OUTPOSITION keywords. 29 Nov 2012. DWF.
; I have reason to believe the way I was creating the location vectors and
; and image subset in this program was causing me to be 1 pixel off in
; creating the image subset. The algorithm has been tweaked to correct this. 12 Dec 2012. DWF.
;
; :Copyright:
; Copyright (c) 2012, Fanning Software Consulting, Inc.
;-
FUNCTION cgCliptoMap, imageIn, boundary, $
LATLONBOX=latlonbox, $
MAP=map, $
OUTBOUNDARY=outboundary, $
OUTMAP=outmap, $
OUTPOSITION=outposition
Compile_Opt idl2
; Return to caller if there is an error.
On_Error, 2
IF N_Elements(imageIn) EQ 0 THEN Message, 'Calling Syntax: clippedImage = cgClipToMap(image, boundary, MAP=map)'
; Is the imageIn variable a string. If so, it could be the
; have of a GeoTiff file for which you can gather the map
; projection information.
IF Size(imageIn, /TNAME) EQ 'STRING' THEN BEGIN
map = cgGeoMap(imageIn, Image=image, GeoTiff=geotiff, Palette=pal)
ENDIF ELSE image = imageIn
; You need a boundary at this point.
IF N_Elements(boundary) EQ 0 THEN Message, 'A clipping boundary is required.'
IF N_Elements(boundary) NE 4 THEN Message, 'A clipping boundary must be a four-element array.'
; You MUST have a map coordinate object at this point.
IF N_Elements(map) EQ 0 THEN Message, 'A map coordinate object is required.'
; If the absoulte value of the maximum of the boundary is less that 360, then assume the boundary
; is given in lat/lon space and convert it.
IF Abs(Max(boundary)) LE 360 THEN BEGIN
xy = map -> Forward(boundary[[0,2]], boundary[[1,3]])
thisBoundary = [xy[0,0], xy[1,0], xy[0,1], xy[1,1]]
ENDIF ELSE thisBoundary = boundary
; Current dimension of the image.
dims = Image_Dimensions(image, XSIZE=xsize, YSIZE=ysize, TRUEINDEX=trueindex, XINDEX=xindex, YINDEX=yindex)
IF (trueindex NE -1) && (trueindex NE 2) THEN image = Transpose(image, [xindex, yindex, trueindex])
; Get the current image range.
map -> GetProperty, XRange=xr, YRange=yr
; Create image vectors.
xvec = cgScaleVector(DIndgen(dims[0]+1), xr[0], xr[1])
yvec = cgScaleVector(DIndgen(dims[1]+1), yr[0], yr[1])
; Clip to get new image subscripts.
xsubs = 0 > Value_Locate(xvec, [thisBoundary[0],thisBoundary[2]]) < (dims[0]-1)
ysubs = 0 > Value_Locate(yvec, [thisBoundary[1],thisBoundary[3]]) < (dims[1]-1)
; Output boundary.
outboundary = [ xvec[xsubs[0]], yvec[ysubs[0]], xvec[xsubs[1]], yvec[ysubs[1]] ]
outposition = [ xsubs[0], ysubs[0], xsubs[1], ysubs[1] ]
; Clip the image.
IF trueIndex NE -1 THEN BEGIN
imageType = Size(image, /TYPE)
subimage = Make_Array(xsubs[1]-xsubs[0], ysubs[1]-ysubs[0], 3, Type=imageType)
subimage[*,*,0] = image[xsubs[0]:xsubs[1]-1, ysubs[0]:ysubs[1]-1, 0]
subimage[*,*,1] = image[xsubs[0]:xsubs[1]-1, ysubs[0]:ysubs[1]-1, 1]
subimage[*,*,2] = image[xsubs[0]:xsubs[1]-1, ysubs[0]:ysubs[1]-1, 2]
ENDIF ELSE subimage = image[xsubs[0]:xsubs[1]-1, ysubs[0]:ysubs[1]-1]
; Create an output map coordinate object.
map -> GetProperty, MAP_PROJECTION=projection, ELLIPSOID=ellipsoid, ZONE=zone
mapout = Obj_New('cgmap', projection, Ellipsoid=ellipsoid, ZONE=zone, $
XRange=[xvec[xsubs[0]],xvec[xsubs[1]]], $
YRange=[yvec[ysubs[0]],yvec[ysubs[1]]])
mapOut -> GetProperty, LATLONBOX=latlonBox
RETURN, subimage
END