NAME: digit PURPOSE: (one line) Digitize from a displayed gif file. DESCRIPTION: CATEGORY: Image display CALLING SEQUENCE: digit, image, outfile INPUTS: image : Image to be displayed. May be a string scalar containing the name of an image file to be loaded and displayed, or an image array to be displayed. File is read with READ_IMAGE. outfile : File into which collected points are saved. OPTIONAL INPUT PARAMETERS: KEYWORD INPUT PARAMETERS: NATURAL = If set, the natural screen coordinates are used. No control points are solicited and no coordinate transformations are computed. NOSCALE = If set, the image is displayed without being scaled. ROTATE = Rotation angle (in degrees) for the gif image. Allowed values are 90, 180, and 270 counterclockwise. OUTPUTS: KEYWORD OUTPUT PARAMETERS: XVEC, YVEC = If both of these keywords are present, the collected coordinates are returned as vectors to the variables specified in the keywords. The collected coordinates are always written to the output file. COMMON BLOCKS: SIDE EFFECTS: RESTRICTIONS: PROCEDURE: Unless the 'NATURAL' keyword is specified, four control points and four associated values are requested in order to define the x and y axes and scale factors. The first two points are the x-axis control points (and their values) and the second two are the y-axis control points (and their values). Control vectors are computed from the requested control points and coordinate transformations are computed using simple vector algebra. MODIFICATION HISTORY: Written by Doug Loucks, Lowell Observatory, April, 1993. 94/10/04 - MWB - moved cr to front of print statement (v3.6 bug workaround) 2000/01/31, MWB, fixed bug that was introduced by some IDL version that changed the way CURSOR worked. 2009/01/13, MWB, changed to use READ_IMAGE to read external file.