The Describe command generates a brief description of a procedure, module, or other Maple object based on information stored within it.

For procedures, the description is generated from any description strings in the procedure, and its calling sequence.

Module descriptions are generated from description strings in the module, followed by an indented list generated by calling Describe recursively on each exported member of the module.

The description of other Maple objects consists of the type of the object, and its value (possibly abbreviated).

$\mathrm{Describe}\left(\mathrm{Digits}\right)$

Digits::integer = 10

$\mathrm{Describe}\left(\mathrm{ImageTools}\right)$

# an image processing package
module ImageTools:

    # clip intensity to specified levels
    Clip( img::ImageTools:-Image,
          { high::{realcons, identical(NULL)} := NULL, inplace::truefalse := false, low::{realcons, identical(NULL)} := NULL, output::{ImageTools:-Image, identical(NULL)} := NULL }, $ )

    Create( height::{nonnegint, range(integer)} := 0, width::{nonnegint, range(integer)} := 0, layers::{1, 3, 4, identical(NULL), 1 .. {3, 4}} := NULL, data::{Array, Matrix, table, procedure, list(procedure), set(`=`), listlist(realcons), listlist(list(realcons))} := {},
            { background::{realcons, list(realcons), identical(black,white)} := ':-black', channels::identical(NULL,1,3,4) := NULL, copy::truefalse := false, fit::truefalse := false, format::identical(Array,Matrix) := Array, order::identical(C_order,Fortran_order) := 'C_order' }, $ ) :: ImageTools:-Image

    module Draw:

        Line( )

        Circle( )

        FilledCircle( )

        Text( )

        TextSize( )

        FilledRectangle( img, x0, y0, x1, y1, color )

    # embed images in an open worksheet
    Embed( imgarg::{list({list(Image), Image}), Image},
           { exterior::identical(group,all,none) := ':-all', interior::identical(group,all,none) := ':-all', mode::identical(direct,task) := ':-direct', tempdir::string := GetTempDir(), title::{string, identical(NoUserValue)} := ':-NoUserValue', titleposition::identical(top,bottom) := ':-bottom' }, $ )

    # compute the entropy of the layers of an image
    Entropy( img, N::posint := 256,
             { autorange::truefalse := false, range:::-range(numeric) := 0 .. 1 }, $ )

    # flip an image horizontally or vertically
    Flip( img::ImageTools:-Image, dir::identical(horizontal,vertical),
          { inplace::truefalse := false, output::{ImageTools:-Image, identical(NULL)} := NULL }, $ )

    Formats::set = {BMP, JPEG, TIFF}

    # adjust the gamma of an image; values < 1 lighten, values > 1 darken
    Gamma( img::ImageTools:-Image, gamma::realcons,
           { inplace::truefalse := false, output::{ImageTools:-Image, identical(NULL)} := NULL }, $ )

    # return height of image, in pixels
    Height( img::ImageTools:-Image, info::identical(size,range,lower,upper) := ':-size', $ )

    Image::symbol = ImageTools:-Image

    # return number of layers in image
    Layers( img::ImageTools:-Image, info::identical(size,lower,upper,range) := ':-size', $ )

    # mask intensity of an image with another image
    Mask( img::ImageTools:-Image, mask::ImageTools:-Image, $ )

    # preview an image in the worksheet as a thumbnail plot
    module Preview( img::ImageTools:-Image, maxH::{posint, identical(NULL)} := NULL, maxW::{posint, identical(NULL)} := NULL,
                    { chars::string := "@Oo*+=~- ", method::identical(bspline,nearest) := ':-bspline', output::identical(image,text) := ':-image' }, $ )

        # preview an image in the worksheet as a thumbnail plot
        Preview( img::ImageTools:-Image, maxH::{posint, identical(NULL)} := NULL, maxW::{posint, identical(NULL)} := NULL,
                 { chars::string := "@Oo*+=~- ", method::identical(bspline,nearest) := ':-bspline', output::identical(image,text) := ':-image' }, $ )

    # compute the quality of a reconstructed image
    Quality( img_r::ImageTools:-GrayImage, img_s::ImageTools:-GrayImage, meas::identical(mse,psnr,rmse,snr) := ':-mse',
             { peak::realcons := 1 }, $ )

    # read an image from a file or URL
    Read( input::string, img::{ImageTools:-Image, identical(NULL)} := NULL,
          { format::identical(BMP,JPEG,TIFF) := NULL, output::{ImageTools:-Image, identical(NULL)} := NULL }, $ )

    # rotate an image in increments of 90 degrees
    module Rotate( img::ImageTools:-Image, angle::{integer, identical(left,right)},
                   { output::{ImageTools:-Image, identical(NULL)} := NULL }, $ )

        # rotate an image in increments of 90 degrees
        Rotate( img::ImageTools:-Image, angle::{integer, identical(left,right)},
                { output::{ImageTools:-Image, identical(NULL)} := NULL }, $ )

    # scale the size of an image
    Scale( img::ImageTools:-Image, scaleY::{realcons, integer .. integer}, optScaleX::{realcons, identical(NULL), integer .. integer} := NULL,
           { antialias::{posint, identical(none)} := ':-none', method::identical(bspline,nearest) := ':-bspline' }, $ )

    # stack images horizontally or vertically
    Stack( img_list::list(ImageTools:-Image), dir::identical(horizontal,vertical) := ':-horizontal',
           { halign::identical(left,center,right) := ':-left', valign::identical(top,center,bottom) := ':-top' }, $ )

    # convert an image to an RGB representation
    ToRGB( img::ImageTools:-Image,
           { output::{ImageTools:-ColorImage, identical(NULL)} := NULL }, $ )

    # convert an image to an RGBA representation
    ToRGBA( img::ImageTools:-Image,
            { output::{ImageTools:-ColorAImage, identical(NULL)} := NULL }, $ ) :: ImageTools:-ColorAImage

    # display images in a maplet
    View( { borderheight::posint := 120, borderwidth::posint := 80, maxmapletheight::posint := 800, maxmapletwidth::posint := 800, tempdir::string := GetTempDir(), title::string := "Image View" } )

    # return width of image, in pixels
    Width( img::ImageTools:-Image, info::identical(size,range,lower,upper) := ':-size', $ )

    # write an image to a file
    Write( file::string, image::ImageTools:-Image,
           { format::identical(BMP,JPEG,TIFF) := FormatFromName(file,true), quality::{numeric, identical(NULL)} := NULL }, $ )

    # create a checkerboard image
    Checkerboard( n::posint := 20, height::posint := 8, width::posint := height,
                  { background::realcons := 0., foreground::realcons := 1.0 } )

    ColorAImage::symbol = ImageTools:-ColorAImage

    ColorImage::symbol = ImageTools:-ColorImage

    # linearly transform the colors of an image
    ColorTransform( img::{ImageTools:-ColorAImage, ImageTools:-ColorImage}, m::Matrix(And(realcons,Not(infinity))),
                    { inplace::truefalse := false, output::{ImageTools:-ColorAImage, ImageTools:-ColorImage, identical(NULL)} := NULL }, $ )

    # combine monochromatic images to create a color image
    CombineLayers( img1::ImageTools:-GrayImage, img2::ImageTools:-GrayImage, img3::ImageTools:-GrayImage, img4::{ImageTools:-GrayImage, identical(NULL)} := NULL,
                   { output::{ImageTools:-ColorAImage, ImageTools:-ColorImage, identical(NULL)} := NULL }, $ )

    # compute the complement of an image
    Complement( img::ImageTools:-Image, peak::realcons := 1,
                { inplace::truefalse := false, output::{ImageTools:-Image, identical(NULL)} := NULL }, $ )

    # apply a spatial convolution mask/kernel to an image
    Convolution( image::ImageTools:-Image, kernel::rtable,
                 { edges::{numeric, identical(compute,leave)} := ':-compute', exterior::{numeric, identical(ignore)} := ':-ignore', shape::identical(same,full,valid) := ':-same', weight::{numeric, identical(none)} := ':-none' }, $ )

    # scale intensity to a given range
    FitIntensity( img::ImageTools:-Image, intensity::range(And(realcons,Not(infinity))) := 0 .. 1, channel::{1, 2, 3, 4, identical(all)} := 'all',
                  { inplace::truefalse := false, output::{ImageTools:-Image, identical(NULL)} := NULL }, $ )

    # guess the image format from the filename
    FormatFromName( file::string, errorOnFailure::truefalse := false, $ )

    # extract one layer from a colored image
    GetLayer( img::{ImageTools:-ColorAImage, ImageTools:-ColorImage}, layer::{1, 2, 3, 4},
              { output::{ImageTools:-GrayImage, identical(NULL)} := NULL }, $ )

    # extract a subimage from an image
    GetSubImage( img::ImageTools:-Image, row::integer, col::integer, ht::posint, wd::posint,
                 { output::{ImageTools:-Image, identical(NULL)} := NULL, reindex::truefalse := false }, $ )

    GrayImage::symbol = ImageTools:-GrayImage

    # convert HSV color image to RGB
    module HSVtoRGB( img::{ImageTools:-ColorAImage, ImageTools:-ColorImage},
                     { inplace::truefalse := false, output::{ImageTools:-ColorAImage, ImageTools:-ColorImage, identical(NULL)} := NULL }, $ )

        # convert HSV color image to RGB
        HSVtoRGB( img::{ImageTools:-ColorAImage, ImageTools:-ColorImage},
                  { inplace::truefalse := false, output::{ImageTools:-ColorAImage, ImageTools:-ColorImage, identical(NULL)} := NULL }, $ )

    # compute a histogram of an image
    Histogram( img::ImageTools:-Image, buckets::posint := 256,
               { autorange::truefalse := false, centers::truefalse := false, cumulative::truefalse := false, normalized::truefalse := false, range:::-range(numeric) := 0 .. 1 }, $ )

    # measure intensity of layers of an image
    Intensity( img::ImageTools:-Image, meas::identical(minimum,maximum,range,mean,variance,rms,energy) := ':-range', $ )

    # pad image, increasing its size
    PadImage( img::ImageTools:-Image, ht_rng::{range(integer), identical(NULL)} := NULL, wd_rng::{range(integer), identical(NULL)} := NULL,
              { border::nonnegint := 0, bottom::{nonnegint, identical(NULL)} := NULL, fill::{numeric, list(numeric), identical(reflect,replicate)} := 0, left::{nonnegint, identical(NULL)} := NULL, reindex::truefalse := false, right::{nonnegint, identical(NULL)} := NULL, top::{nonnegint, identical(NULL)} := NULL }, $ )

    # plot intensity histogram of an image
    PlotHistogram( img::ImageTools:-Image, buckets::posint := 256,
                   { autorange::truefalse := false, cumulative::truefalse := false, decomb::truefalse := false, normalized::truefalse := false, range:::-range(numeric) := 0 .. 1 } )

    # convert an image to grayscale
    RGBtoGray( img::ImageTools:-Image,
               { output::{ImageTools:-GrayImage, identical(NULL)} := NULL }, $ ) :: ImageTools:-GrayImage

    # convert RGB to HSV
    module RGBtoHSV( img::{ImageTools:-ColorAImage, ImageTools:-ColorImage},
                     { inplace::truefalse := false, output::{ImageTools:-ColorAImage, ImageTools:-ColorImage, identical(NULL)} := NULL }, $ )

        # convert RGB to HSV
        RGBtoHSV( img::{ImageTools:-ColorAImage, ImageTools:-ColorImage},
                  { inplace::truefalse := false, output::{ImageTools:-ColorAImage, ImageTools:-ColorImage, identical(NULL)} := NULL }, $ )

    # convert RGB to YUV
    RGBtoYUV( img::{ImageTools:-ColorAImage, ImageTools:-ColorImage},
              { inplace::truefalse := false, output::{ImageTools:-ColorAImage, ImageTools:-ColorImage, identical(NULL)} := NULL }, $ )

    # scale the intensities of selected layers of an image
    ScaleIntensity( img::ImageTools:-Image, scale::realcons, offset::realcons := 0,
                    { inplace::truefalse := false, layers::{posint, list(posint), identical(all,color)} := 'all', output::{ImageTools:-Image, identical(NULL)} := NULL } )

    # insert a layer into an image
    SetLayer( img::ImageTools:-Image, img_layer::ImageTools:-GrayImage, layer::{1, 2, 3, 4},
              { inplace::truefalse := false, output::{ImageTools:-ColorAImage, ImageTools:-ColorImage, identical(NULL)} := NULL }, $ )

    # insert a subimage into a main image
    SetSubImage( img::ImageTools:-Image, sub::ImageTools:-Image, row::{integer, identical(NULL)} := NULL, col::{integer, identical(NULL)} := NULL,
                 { inplace::truefalse := false, output::{ImageTools:-Image, identical(NULL)} := NULL }, $ )

    # perform threshold operation on a grayscale image
    module Threshold( img, threshold::{numeric, identical(NULL)} := NULL,
                      { buckets::posint := 100, high::numeric := 1.0, low::numeric := 0., method::identical(both,above,below) := 'both' }, $ )

        # perform threshold operation on a grayscale image
        Threshold( img, threshold::{numeric, identical(NULL)} := NULL,
                   { buckets::posint := 100, high::numeric := 1.0, low::numeric := 0., method::identical(both,above,below) := 'both' }, $ )

    # convert an image to grayscale
    ToGrayscale( img::ImageTools:-Image,
                 { output::{ImageTools:-GrayImage, identical(NULL)} := NULL }, $ ) :: ImageTools:-GrayImage

    # transpose an image
    Transpose( img::ImageTools:-Image,
               { output::{ImageTools:-Image, identical(NULL)} := NULL }, $ )

    # return the type of an image
    WhatTypeImage( image )

    # convert YUV to RGB
    YUVtoRGB( img::{ImageTools:-ColorAImage, ImageTools:-ColorImage},
              { inplace::truefalse := false, output::{ImageTools:-ColorAImage, ImageTools:-ColorImage, identical(NULL)} := NULL }, $ )

    module ColouringProcedures:

        HueToRGB( img::Array(datatype = float[8]) )

        FlameToRGB( data::Array(datatype = float[8]), gam::numeric, samplesize::posint := 2 )