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<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML//EN">
<html>
<head>
<title>Pow Region Manipulation</title>
</head>
<body>
<h1>Pow Region Manipulation</h1>
<h2>Overview</h2>
POW provides the user with the ability to create and edit standard
region files through the <B>Region File</B> menu item under POW's <a
href="Tools.html">Tools menu</A>. The Region File dialog window
consists of a list of regions available for manipulation; a set of
buttons and an entry box which are used to modify the currently
selected region; and, at the bottom, buttons which open/save regions
in a file and delete all the regions. Region types supported are Box,
Circle, Ellipse, Polygon, Line, and Point. <p>
<h2>Creating Regions</h2>
When the region dialog box is open, a new region can be created by
placing the mouse at the desired location in the graph and
click-and-drag with the left mouse button down (Command-Click on Mac OS).
The shape of the
region created is determined by the current shape button in the dialog
box. For Circles, and Ellipses, the initial mouse location will be
the center of the region and the final location its radius or width
and/or height, as appropriate. For Boxes, the mouse movement traces
out opposite corners of the rectangle. For Polygons and Lines, the
mouse movement locations define the start and end of a line segment.
To add extra segments to the Polygon, let up on the mouse button then
press it again, without moving, then drag out the next side of the
polygon, repeating as necessary. For a Point shape, the final mouse
position defines its location. When the mouse button is released, the
new region is appended to the list of available regions and made the
current region. <p>
<h2>Current Region and Manipulation</h2>
The current region is the one highlighted in the dialog's list of
regions and "tagged" on the graph (see below). Upon selection
(clicking the left mouse button on a region in the list or on the
graph itself) or creation, the definition of the current region is
placed in the current region portion of the dialog box. <p>
A region consists of 3 parts: a sign indicating whether it defines a
region to be added (source) or subtracted (background) from the data
(these are indicated on the graph with blue or red region outlines,
respectively); a shape; and the parameters defining its location,
size, and possible rotation. The sign and shape of the current region
are represented by a pair of buttons. The <B>sign</B> button toggles
between "+" and "-" and the <B>shape</B> button brings up a popup menu
of the 6 available shapes to choose from. The region
<B>parameters</B> are placed in a final text entry box and can be
modified by hand. When changing shapes, POW does its best to
translate the current parameters into appropriate values and format
for the new shape. For example, in going from a circle to polygon,
the parameters change from a circle's (X,Y,R) format to a list of
points tracing out the circle's outline. Changing the current region
information in the dialog box does not actually affect the current
region until the <B>Apply</B> button is pressed. Prior to pressing
Apply, the region information can be restored by reselecting the
current region. (Note: the values initially placed in the entry box
are rounded off after 6 significant digits, so pressing Apply may
result in minor changes in the shape's size and location even though
the values were not modified.) <p>
Although the sign and shape of a region can only be modified via the
dialog box, the location, size, and rotation of regions can be changed
either in the dialog box (yuck!) or through direct manipulation of the
region on the graph with the mouse. The current region is "tagged"
with 2 types of handles: a <B>rotation</B> handle (green triangle) and
one or more <B>resize</B> handles (green squares). Circles, Polygons,
and Lines cannot be rotated, so they have only one or more (as
appropriate) resize handles. Boxes and Ellipses have one of each
type, but Points have neither. A shape is rotated or resized (for
Polygons and Lines, it is more a matter of repositioning points) by
clicking the relevant handle with the left mouse button and dragging
it to a new location. When the mouse cursor is over one of the
handles, the cursor changes to a double-arrow, indicating that point
can be dragged. When the mouse button is released the dialog's list
of regions and current region information are updated with the new
information. On the polygon, to drag a vertex, use Shife-Left Mouse
button to drag the intended vertex to new location.<p>
To <B>move a region</B>, simply click the left mouse button inside the
region and drag it to the new location. Because clicking on a region
makes it the current region, moving a region can be performed on any
region, not just the current one. When inside a region, the cursor
changes to a 4-sided arrow and the region's outline thickens. The
current region can also be moved via the keyboard. When the POW
window is in the foreground, <B>shift-arrow</B> will move the current
shape one screen pixel in the arrow's direction. <B>Control-arrow</B>
moves the shape 10 pixels. <p>
Polygons can be modified in two additional ways. Points can be
deleted by dragging a point onto one of its adjacent points. A point
can also be inserted by clicking and dragging one of the handles with
the left mouse button (Command-Click on Mac OS). This inserts the new
point before the one clicked. If this is incorrect, immediately drag the new point back
onto the first to delete it (no need to release the mouse button) and
then click and drag on the next point. Vertex can be dragged by
click and drag with right mouse button. <p>
The <B>Delete</B> button in the Region dialog deletes the current
region, and the next region in the list (or previous region if
deleting the last region) becomes the current region. All the regions
can be deleted with the <B>Clear All</B> button. <p>
<h2>Coordinate Systems</h2>
Region parameters can be displayed in one of several formats
selectable by a popup menu just below the list of regions in the
Region dialog. The first is <B>Image</B> format wherein positions and
size parameters are reported in the pixel coordinates of the image.
If the image has a linear scaling, the <B>Linear</B> format will
report coordinates in this scaled coordinate system instead of pixels.
If WCS information is available for the graph, region parameters can
be displayed in celestial coordinates as degrees. The formats
<B>FK4</B>, <B>FK5</B>, <B>Galactic</B>, <B>Ecliptic</B>, and
<B>ICRS</B> each report region positions and sizes as degrees, but POW
currently does not convert between these formats; the user must
specify the appropriate system which will then be written to the
region file when saved. Finally, the <B>Degrees</B> format signifies
a mixed style used by SAOtng wherein positions are in degrees, but
sizes are in pixels.<p>
The final 2 elements of the popup menu select the formatting to use
when displaying degree values. <B>Decimal Degrees</B> format shows
values as ordinary decimals with RA ranging over 0-360 and Declination
over -90 to +90. <B>HHMMSS Degrees</B> instead displays decimals in
hour:minute:second format. <p>
<h2>Statistics Calculation</h2>
3 entries indicate the statistics of a region selected (or combine
of regions). The statistics include number of pixel enclosed, total
flux and mean flux in the region(s). <p>
For statistic of 2 or more regions on the image, number of pixels
is determined by several factors, such as if a region intersects with
one another, the sign of region (+: include, -: exclude). Pow calls
CFITSIO routine and pass the region(s) descriptions to determine if
a given pixel is part of the ROI (region of interests). And if so,
that pixel's value is been recorded to be part of calculation of
total flux and mean flux of the ROI. <p>
<h2>Saving/Opening Region Files</h2>
At the bottom of the Region dialog are a pair of <B>Open</B> and
<B>Save</B> buttons which will read and write region files in the
standard format, compatible with SAOtng. If regions already exist
when opening a region file, the user will have the option of deleting
the old regions or appending the new ones to the list. When saving
regions, the parameters will be written in the coordinate system
currently selected in the Region dialog. <p>
</body>
</html>
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