coyote: CGZIMAGE

Description
Allows the user to interactively zoom into an image. Program controls are available
by right-clicking in the full-sized image window. Zoom factors from 2x to 16x are
available. Use the left mouse button to draw a box on the full-sized image to locate
the region of the image to zoom.
Categories
Graphics
Examples
Code examples::
   IDL> image = cgDemoData(7)
   IDL> cgZImage, image ; 2D image
   IDL> image = cgDemoData(16)
   IDL> cgZImage, image ; True-Color 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, 20 September 2012 from previous FSC_ZImage program. DWF.
   Modernized the info structure handling to reflect modern sensibilities. 3 Oct 2012. DWF.
   Changes to allow this to work with very large images. Can now zoom to actual pixel values.
      Also fixed a problem that left zoom windows lying around unused if scroll bars were 
      needed. 18 October 2012. DWF.
   The color palette was not always being included when images were zoomed. Fixed. 17 Nov 2012. DWF.
   Added ZoomFactor keyword to allow the zoom factor to be set on start-up. 28 Nov 2012. DWF.
   Fixed a typo that caused bringing controls into the window to fail. 13 Jan 2014. DWF.
Copyright
Copyright (c) 2012-2014, Fanning Software Consulting, Inc.
t handler for the motion events coming from the zoom window. Find the location
value of the image at the cursor location and report it to the status bar in the
 image window.
Params
image: in, required, type=any
    A 2D or true-color image of any normal data type. If not a BYTE array,
    cgImage keywords for proper image scaling must be used to provide image
    scaling parameters.
Keywords
beta: in, optional, type=float, default=3.0
     The beta factor in a Hyperpolic Sine stretch. Available only with 2D images.
bottom: in, optional, type=integer, default=0
     If the SCALE keyword is set, the image is scaled before display so that all 
     displayed pixels have values greater than or equal to BOTTOM and less than 
     or equal to TOP. Available only with 2D images.
boxcolor: in, optional, type=string, default='gold'
     The name of the color of the rubber-band selection box.
clip: in, optional, type=float, default=2
     A number between 0 and 50 that indicates the percentage of pixels to clip
     off either end of the image histogram before performing a linear stretch.
     Available only with 2D images.
exclude: in, optional, type=numeric
     The value to exclude in a standard deviation stretch.
exponent: in, optional, type=float, default=4.0
     The logarithm exponent in a logarithmic stretch. Available only with 2D images.
filename: in, optional, type=string
     The name of a file that IDL can read with READ_IMAGE (e.g, GEOTIFF, TIF, JPEG, PNG, etc.).
gamma: in, optional, type=float, default=1.5
     The gamma factor in a gamma stretch. Available only with 2D images.
group_leader: in, optional, type=long
     The widget identifier of the group leader for this program. When the group leader
     dies, this program will be destroyed, too.
interpolate: in, optional, type=boolean, default=0
     Set this keyword to interpolate with bilinear interpolation the display image as it 
     is sized to its final position in the display window. Interpolation will potentially 
     create image values that do not exist in the original image. The default is to do no
     interpolation, so that image values to not change upon resizing. Interpolation can
     result in smoother looking final images.
map: in, optional, type=structure
     A cgMap object for navigating the input image.
maxvalue: in, optional, type=varies
     If this value is defined, the data is linearly scaled between MINVALUE
     and MAXVALUE. MAXVALUE is set to MAX(image) by default. Setting this 
     keyword to a value automatically sets `SCALE` to 1. If the maximum value of the 
     image is greater than 255, this keyword is defined and SCALE=1.
mean: in, optional, type=float, default=0.5
     The mean factor in a logarithmic stretch. Available only with 2D images.
minvalue: in, optional, type=varies
     If this value is defined, the data is linearly scaled between MINVALUE
     and `MAXVALUE`. MINVALUE is set to MIN(image) by default. Setting this 
     keyword to a value automatically sets SCALE=1. If the minimum value of the 
     image is less than 0, this keyword is defined and SCALE=1.
missing_color: in, optional, type=string, default='white'
     The color name of the missing value. Available only with 2D images.
missing_index: in, optional, type=integer, default=255 
     The index of the missing color in the final byte scaled image. Available only with 2D images.
missing_value: in, optional, type=integer
     The number that represents the missing value in the image. Available only with 2D images.
multiplier: in, optional, type=float
     The multiplication factor in a standard deviation stretch. The standard deviation
     is multiplied by this factor to produce the thresholds for a linear stretch.
ncolors: in, optional, type=integer, default=256
     If this keyword is supplied, the `TOP` keyword is ignored and the TOP keyword 
     is set equal to  NCOLORS-1. This keyword is provided to make cgImage easier 
     to use with the color-loading programs such as cgLOADCT::
          cgLoadCT, 5, NColors=100, Bottom=100
          cgImage, image, NColors=100, Bottom=100
     Setting this keyword to a value automatically sets SCALE=1. Available only with 2D images.
negative: in, optional, type=boolean, default=0
     Set this keyword if you want to display the image with a negative or reverse stretch.
     Available only with 2D images.
palette: in, optional, type=byte
     Set this keyword to a 3x256 or 256x3 byte array containing the RGB color 
     vectors to be loaded before the image is displayed. Such vectors can be 
     obtained, for example, from cgLoadCT with the RGB_TABLE keyword::
            cgLoadCT, 4, /BREWER, /REVERSE, RGB_TABLE=palette
            cgImage, cgDemoData(7), PALETTE=palette
scale: in, optional, type=boolean, default=0
     Set this keyword to byte scale the image before display. If this keyword is not set, 
     the image is not scaled before display. This keyword will be set automatically by using
     any of the keywords normally associated with byte scaling an image. Available only with 
     2D images. If set, STRETCH is set to 1, unless it is set to another value.
stretch: in, optional, type=integer/string, default=1
     The type of scaling performed prior to display. May be specified as a number 
     or as a string (e.g, 3 or "Log"). Available only with 2D images.
       Number   Type of Stretch
         0         None           No scaling whatsoever is done.
         1         Linear         scaled = BytScl(image, MIN=minValue, MAX=maxValue)
         2         Clip           A histogram stretch, with a percentage of pixels clipped at both the top and bottom
         3         Gamma          scaled = GmaScl(image, MIN=minValue, MAX=maxValue, Gamma=gamma)
         4         Log            scaled = LogScl(image, MIN=minValue, MAX=maxValue, Mean=mean, Exponent=exponent)
         5         Asinh          scaled = AsinhScl(image, MIN=minValue, MAX=maxValue, Beta=beta)
         6         SquareRoot     A linear stretch of the square root histogram of the image values.
         7         Equalization   A linear stretch of the histogram equalized image histogram.
         8         Gaussian       A Gaussian normal function is applied to the image histogram.
         9         MODIS          Scaling done in the differential manner of the MODIS Rapid Response Team
                                  and implemented in the Coyote Library routine ScaleModis.
sigma: in, optional, type=float, default=1.0
     The sigma scale factor in a Gaussian stretch. Available only with 2D images.
title: in, optional, type=string, default=""
     Set this keyword to the title of the plot window.
top: in, optional, type=integer, default=255
     If the SCALE keyword is set, the image is scaled before display so that all 
     displayed pixels have values greater than or equal to BOTTOM and less than 
     or equal to TOP. Available only with 2D images.
zoomfactor: in, optional, type=string, default=3
     Use this keyword to set the starting zoom factor. The values you can use are as follows::
          0: 'Actual'
          1: '2x'
          2: '3x'
          3: '4x'
          4: '5x'
          5: '6x'
          6: '7x'
          7: '8x'
          8: '12x'
          9: '16x'