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<html>
<head>
<title>POW and Color</title>
</head>
<body>
<h1>POW and X Colormaps</h1>
<p>
POW allows some interactive manipulation of the Colortable used
to display grayscale images. POW has detailed X Colormap
handling options. There are four different
ways of dealing with colormaps. The powColormap options are
available in fv by using the "-cmap" command line argument to
fv. The different options are:
<ul>
<li>0 - let POW attempt to determine the optimum colormap
setup for you. This is the default.
<li>1 - Force POW to setup a private colormap. POW will setup
this colormap to minimize (but not eliminate) flashing.
<li>2 - Force POW to use truecolor. If you have a 16 or
24 bit truecolor visual available, this looks very nice,
and allows different colortables for different images,
but interactive changes to the image colortable are slow.
If you only have 8 bit truecolor, this will look pretty
bad.
<li>3 - Force POW to use the screen default colormap. This
guarantees no flashing, but may force truecolor
image mode to be used with an 8-bit visual
which looks <em>really</em> awful.
</ul>
Generally, if you experience colormap problems, mode 1 is
probably the most robust unless you don't have any pseudocolor
visuals (e.g. a Linux machine running in 16 or 24 bit mode).
</p>
<h1>The POW Color Menu</h1>
<p>
The POW Color menu has four parts:
<ol>
<li>The top section contains three hierarchical menus listing
a bunch of colortables from which to choose. They are
divided into <B>Continuous</B> (colors vary in a smooth manner),
<B>Ramps</B> (colormap is divided into separate colors within
which the intensity varies from dark to bright), and <b>Steps</b>
(colormap is divided into blocks of a constant color/intensity).</li>
<li>You can reverse the "dark to light" direction of your
colortable by checking the <b>Invert Colortable</b> button.</li>
<li>There are four scalings of the colortable available in the
next section. The first three <B>linear</B>, <B>sqrt</B>, and
<B>log</B> apply the indicated function to the color table. The next
item -- <B>Histo Equalize</B> -- will compute a histogram of an image (within
a user-configurable range) and attempt to distribute colors equally
amongst the pixels. The <B>Rescale Image</B> command allows the user
to define what intensity range over which to apply the color table. The
window which comes up contains the original and current intensity range and
a histogram of the current image.
A new range can be either typed in directly or selected using
the histogram.</li>
<li>The final item -- <B>Create Colorbar</B> -- will create a new graph containing
a colorbar for the current image.
</ol>
</p>
<p>
You can interactively change the contrast and brightness of the
current image's colortable by dragging the left mouse button across
the image.
</p>
</body>
</html>
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