Richard Suchenwirth 2002-05-15 - The following code gets maps of predicted precipitation (for North Atlantic, Europe, and parts of adjacent continents) for the next 15 days, in 12 hour steps, from a German weather station via HTTP and displays them in a canvas.
proc cycle listName {
upvar 1 $listName list
set res [lindex $list 0]
set list [concat [lrange $list 1 end] [list $res]]
}
proc every {ms body} {eval $body; after $ms [info level 0]}
package require http
# http::config -proxyhost proxy -proxyport 80
set prefix http://129.13.102.67/pics/Rvtmrf
set suffix 4.gif
pack [canvas .c -width 800 -height 680] -expand 1 -fill both
wm title . "Loading..."
for {set i 12} {$i<=504} {incr i 12} {
set gif [http::data [http::geturl $prefix$i$suffix]]
if ![catch {lappend ims [image create photo im$i -data $gif]}] {
.c create image 0 0 -anchor nw -image im$i -tag im$i
}
}
wm title . "Film"
bind . q exit
bind . <Control-c> exit
every 1000 {.c raise [lindex [cycle ::ims] 0]}KBK I found that the above caused my Windows desktop to, uhhhm, "become unresponsive." Apparently, the Windows implementation, at least on my machine, can't cope with 32 images of that size inside a canvas at once.
Changing so that the canvas has only two image objects and loading them in alternation helps a lot. (It also allows the animation to start while the images are still downloading, if done right.) Here's an alternative implementation:
proc every {ms body} {eval $body; after $ms [info level 0]}
proc cycleImages { } {
variable ims
variable imsIndex
variable buffer
if { [llength $ims] > 0 } {
.c raise buffer$buffer
wm title . "image $imsIndex"
set buffer [expr { 2 - $buffer }]
incr imsIndex
if { $imsIndex >= [llength $ims] } {
set imsIndex 0
}
.c itemconfig buffer$buffer -image [lindex $ims $imsIndex]
}
}
proc loadImage { i } {
variable prefix
variable suffix
if { $i > 504 } return
http::geturl $prefix$i$suffix -command [list loadFinished $i]
}
proc loadFinished { i token } {
variable ims
lappend ims [image create photo -data [http::data $token]]
http::cleanup $token
after 0 [list loadImage [expr { $i + 12 }]]
}
package require http
# http::config -proxyhost webcache -proxyport 8080
set prefix http://129.13.102.67/pics/Rvtmrf
set suffix 4.gif
pack [canvas .c -width 800 -height 680 -bg white] -expand 1 -fill both
.c create image 10 10 -anchor nw -tag buffer1
.c create image 10 10 -anchor nw -tag buffer2
set ims {}
set imsIndex 0
set buffer 1
bind . q exit
bind . <Control-c> exit
every 1000 cycleImages
loadImage 12Donal Fellows - Now, I'm lucky enough to have a machine big enough to take all the images, but I don't like the way that they load; I'd like to issue a bunch of HTTP requests at once and get things back ASAP (I'm on quite a big network pipe here) so I do something like this (min. Tcl version 8.4):
package require http
# http::config -proxyhost proxy -proxyport 80
proc every {ms body} {eval $body; after $ms [info level 0]}
set prefix http://129.13.102.67/pics/Rvtmrf
set suffix 4.gif
set ims {}
pack [canvas .c -width 800 -height 680] -expand 1 -fill both
wm title . "Loading..."
update
set throttle 6
set cmds {}
proc loadImage {i step limit} {
global prefix suffix
if { $i > $limit } return
loadImageCore $prefix$i$suffix
after 150 loadImage [expr {$i + $step}] $step $limit
}
proc loadImageCore {url} {
global ims cmds throttle
set l [llength $ims]
lappend ims {}
if {$throttle < 1} {
lappend cmds [list \
http::geturl $url -command [list loadFinished $l]]
} else {
incr throttle -1
http::geturl $url -command [list loadFinished $l]
}
}
proc loadFinished { l token } {
global ims throttle
incr throttle
set image [image create photo -data [http::data $token]]
lset ims $l [.c create image 0 0 -anchor nw -image $image]
http::cleanup $token
after 1000 anotherCommand
}
proc anotherCommand {} {
global cmds
if {[llength $cmds]} {
set cmd [lindex $cmds 0]
set cmds [lrange $cmds 1 end]
uplevel #0 $cmd
}
}
set idx 0
proc cycleImage {} {
global ims idx
set item [lindex $ims $idx]
if {$item ne ""} {
.c raise $item
}
if {[incr idx] >= [llength $ims]} {
set idx 0
}
}
every [expr {1000/15}] {cycleImage}
loadImage 12 12 504
wm title . "Film"
bind . q exit
bind . <Control-c> exitAlas, asynchronous HTTP has quite a hefty synchronous start-up phase on this system. :^(
Multiply your possibilities by changing the trailing digit in the URL ("4.gif" above):
'Nother massive source of weather data is METAR [L1 ]. Not predictive but reporting current conditions (hourly, I think). Using a well-defined textual dataset with lines such as:
KCPC 190751Z AUTO 00000KT 10SM SCT015 OVC110 21/19 A3016 RMK AO2 705
That's an airport code, timecode, and then al sorts of weather info. There are several sources of collected data, e.g. [L2 ].
Hmm.... are there any countour plot solutions for Tcl? -jcw