 * pixelvalue
</BLOCKQUOTE>
<p>
where the pixelvalue ranges from 0 to 255.  Therefore, a temperature of
10C is a pixelvalue of 50, and 15C is 100.  To get a grayscale ranging
between these values, therefore, we create a linear function which maps
the 50th pixelvalue into grayvalue 1, and the 100th pixelvalue into
grayvalue 0.  That is what the awk line does; to see the actual numbers,
you could insert the line `<font color="#82140F"><code>write image grayscale to TMP</code></font>' and look at
the file `<fo