[rrd-users] Trend to show cloud height -Weather Station Application

Simon Hobson linux at thehobsons.co.uk
Sat Feb 19 10:40:40 CET 2011

Robert Conway wrote:

>Is there a hex colour value for totally transparent ?

You can optionally specify a fourth byte for the colour value - and 
if you do it is used as a transparency value. It's useful where you 
want to plot an area (such as min-max band) without obliterating 
what's below it.

So for example, for a pale blue, you can either use "pale blue" 
(BFBFFF), or you can use "blue" (0000FF) with transparency 0000FF3F 
which will give a pale blue over a white background but allow the 
underlying features to show through.

The only way I could see of getting clouds would be to use an image 
as the plot area initial fill (which isn't supported, though I'd 
imagine it might not be hard to hack), then plot a solid white area 
up to the cloudbase to obliterate it.

Simon Hobson

Visit http://www.magpiesnestpublishing.co.uk/ for books by acclaimed
author Gladys Hobson. Novels - poetry - short stories - ideal as
Christmas stocking fillers. Some available as e-books.

More information about the rrd-users mailing list