Help for the IDP3 Adjust Position Widget

    Scaling, shifting, resampling, rotating, etc. of individual images
is controlled in the Adjust Position Widget.  The widget is laid out
as a long vertical control panel.  At the top of the widget is the
name of the image (the current reference image) to which the current
status and values pertain.  The fields and buttons below the image
name are as follows:

   Flux Scale:  Multiplicative factor for the reference image.  This
		value may be adjusted in increments of the step field
		below the flux scale entry box with the + and - buttons.

   Resample Factor:  Factor for resampling the reference image.  May
		     be any positive real number.

   Image Bias:  Additive factor for the reference image.  This is 
		a convenient way to remove background from the image.
		(see ROI statistics.)

   Image Shifting:  Image offsets may be set in several ways.  The user
		    may specify both X and Y offsets in the appropriate
		    fields or by using the control pad with a non-zero
		    Move Amount.  Aligning by World Coordinates or by
		    centroids will set the necssary X and Y offsets to
		    align images.  These offsets will be reflected in
		    the X and Y offset fields of the Adjust Position
		    widget.

   Image Rotation:  A Rotation Center and Angle (measured clockwise)
		    must be specified in order to rotate the reference
		    image.  The default rotation center (center of image)
		    is set when an image is loaded.  The user may modify
		    the rotation center by modifying the numbers in the
		    the Rotation Center X and Y fields.  The rotation
		    angle may be incremented by the adjustment field
		    below the Angle field with the + and - buttons.

   Image Padding:   When images are rotated without first being padded
		    much of the image may be rotated out of the field
		    of view.  To avoid this occurence the user may pad
		    the image where padded pixels are set to 0.  Padding
		    must be the same for both x and y axes.  If Border
		    Pad is selected to be Yes the pad value is automatically
		    set to 40% of the major axis.  The user may override
		    this value by setting his own in the Number of Pixels
		    field.  Setting this field initially automatically
		    sets the Border Pad selection to Yes.

   Image Pixel Scaling: The user may adjust the pixel scale of the reference
			image with the IDP3 Set Pixel Scales Widget.  The
			widget is activated from the Pixel Scale button.
			See help for the IDP3 Set Pixel Scales Widget for
			more details.  Pixel scale corrections that have
			been applied may be "undone" with the Undo button.

   X/Y Position:  When an image is loaded the header is searched for keywords
		  which establish the image target position.  For HST data
		  these keywords are RA_TARG and DEC_TARG and for Spitzer
		  data the keywords are RA_REF and DEC_REF.  If these keywords
		  are present with a valid world coordinate system the x and
		  y position of the target coordinates is computed and stored
		  in the image structure.  The user may query the values of
		  the x and y positions as well as modify the values with the
		  popup IDP3 X/Y Position Widget.  The user may align images
		  by these X/Y positions with Align by X/Y Positions in the
		  ROI Align Menu.

   Image Clipping:  The user may clip the minimum and maximum values in the
		    image with the IDP3 Clip Image Min and IDP3 Clip Image
		    Max Widgets activated by the Clip Min and Clip Max
		    buttons.  The user specifies the minimum value and
		    the replacement value where all pixel values less than
		    or equal to the Minimum Value are set to the Replacement
		    Value.  The Clip Max function works in the same way that
		    all pixel values greater than or equal to the Maximum
		    Value are set to the Replacement Value.

   Help Button:  Displays the contents of this file.

   Done Button:  Closes the IDP3 Adjust Position Widget.