/usr/share/doc/gdl-coyote/html/cgimgscl.html

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  <TITLE>coyote: CGIMGSCL</TITLE>
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  <H1><a href="index.html">coyote</a>: CGIMGSCL</H1>
  <ul>
  <li><a href=Graphics.html>coyote/Graphics</a></li>
<li><a href=Utilities.html>coyote/Utilities</a></li>
    <li><a href="/usr/share/gnudatalanguage/coyote/cgimgscl.pro">[Source code]</a></li>
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  <dl>
<dt>Description</dt>
<dd><pre>
This function scales an image using the same keywords and scaling available in 
cgImage and cgStretch. Set the `Stretch` keyword for the types of image scaling
or stretching available.
</pre></dd>
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<dl>
<dt>Categories</dt>
<dd><pre>
Graphics, Utilities
</pre></dd>
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<dl>
<dt>Returns</dt>
<dd><pre>
Returns a scaled image.
</pre></dd>
</dl>

<dl>
<dt>Params</dt>
<dd><pre>
image: in, required
   The input image that is to be scaled. Only 2D images can be scaled, although
   true-color images can be resized.
xsize: in, optional
   The output X size of the image.
ysize: in, optional
   The output Y size of the image.
</pre></dd>
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<dl>
<dt>Keywords</dt>
<dd><pre>
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`.
beta: in, optional, type=float, default=3.0
     The beta factor in a Hyperpolic Sine stretch.
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.
constant: in, optional, type=float, default=1.0
     A constant value applied in a logarithmic stretch.
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 compression stretch.
gamma: in, optional, type=float, default=1.5
     The gamma factor in a gamma stretch.
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.
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 compression stretch.
minus_one: in, optional, type=boolean, default=0
     The value of this keyword is passed along to the cgResizeImage
     command. It prevents cgResizeImage from adding an extra row and
     column to the resulting array, which can be a problem with
     small image arrays. 
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_index: in, optional, type=integer, default=255
     The index of the missing color in the final byte scaled image.
missing_value: in, optional, type=integer
     The number that represents the missing value in the image.
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 cgImgScl easier 
     to use with the color-loading programs such as cgLOADCT::
          cgLoadCT, 5, NColors=100, Bottom=100
          scaled = cgImgScl(image, NColors=100, Bottom=100)
     Setting this keyword to a value automatically sets SCALE=1 and STRETCH='LINEAR', if not
     defined otherwise. 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.
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.
stretch: in, optional, type=integer/string, default=0
     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. If  Min(image)
     is less than zero or Max(image) is greater than 255, then the default value for
     stretch is 1.
     Number   Type of Stretch::
         0         None           No scaling whatsoever is done.
         1         Linear         scaled = BytScl(image, MIN=minValue, MAX=maxValue)
         2         Linear 2%      A histogram stretch, with a percentage of pixels clipped at both the top and bottom
         3         Gamma          scaled = cgGmaScl(image, MIN=minValue, MAX=maxValue, Gamma=gamma)
         4         Log            scaled = cgLogScl(image, MIN=minValue, MAX=maxValue, Mean=mean, Exponent=exponent)
         5         Asinh          scaled = cgAsinhScl(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.
         10        StdDev         Standard deviation stretch. scaled = cgSDevScl(image, MULTIPLIER=2).
         11        Compression    Compress mid-tones in image with cgCompressScl.
sigma: in, optional, type=float, default=1.0
     The sigma scale factor in a Gaussian stretch.
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`.
</pre></dd>
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<dl>
<dt>Examples</dt>
<dd><pre>
Used to for image display::
   IDL> scaledImage = cgImgScl(image, Stretch=4, Exponent=2)
   IDL> cgImage, scaledImage[0:100, 200:400], /Keep_Aspect
</pre></dd>
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<dl>
<dt>Author</dt>
<dd><pre>
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
</pre></dd>
</dl>

<dl>
<dt>History</dt>
<dd><pre>
Change History::
  Written by David W. Fanning, 21 September 2012. 
  Only define MISSING_INDEX value if needed. Change to support TRANSPARENT keyword
     in cgImage. 18 October 2012. DWF.
  Only 2D images can be scaled. 18 October 2012. DWF.
  Made LOG stretch a real log stretch and add a compression stretch. 27 March 2015. DWF.
</pre></dd>
</dl>

<dl>
<dt>Copyright</dt>
<dd><pre>
Copyright (c) 2012-2015, Fanning Software Consulting, Inc.
</pre></dd>
</dl>

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gdl-coyote 2016.11.13-2 / usr / share / doc / gdl-coyote / html / cgimgscl.html
