Phil Wherry: update: have working code; now need to
make it a little easier to use.
Phil Wherry: amazingly, the code to do this turned out
to be two lines long.
Phil Wherry: well, that was the proof-of-concept. the
actual version will probably be 20 lines or so when
done.
drofnasw: You know that we're going to save
640x480 images from the Webcam, right? Would like
to be able resize 'em to 320x240 and 160x120. Can
do?
Phil Wherry: scales available will be 1/2, 1/4, and 1/8
(i'm using the cjpeg/djpeg tools as the guts of the tool;
that's what they can do)
drofnasw: 320x240 is 1/2; 160x120 is 1/4.
Phil Wherry: yep, so it'll work fine.
drofnasw: Beautifully!
drofnasw: I see a file called "resizer.php" has appeared
in the webcam/earthdial directory -- does that mean
that the utility will work only in that directory?
Phil Wherry: it'll work in the directories in which it
appears (i.e. you'll want to copy it elsewhere. It needs
to be in the same directory as the files upon which it
operates for security reasons.
drofnasw: But I can copy it into any directory -- incl.
my own Webspace -- right?
Phil Wherry: yes. let me get it done and i'll give you
some lessons on it.
Phil Wherry: Have a look at this:
http://www.wsanford.com/webcam/earthdial/resizer.ph
p?filename=fcps-earthdial.jpg&scale=2
Phil Wherry: The scale factor at the end can be either
2 or 4 or 8.
drofnasw: O.K., I tested all sizes (2, 4, 8). Works
well! One mystery: where are the files that the resizer
generates? I don't see any new files in the directory.
Phil Wherry: It's not creating new files; it's generating
the JPEG data on the fly and sending it to the browser
without creating an intermediate file.
drofnasw: Extraordinary! And this will also work w/in
the <IMG SRC> tag?
Phil Wherry: Yes, it will work anywhere you can use
an image.
Phil Wherry: This does bring me to an important point,
though: the file has to be in the same directory. If the
filename is wrong, the tool will just silently fail; there's
nothing in the way of error messages since it's
generating an image.
drofnasw: My colleague Gary runs a Webcam in his
pltrm. -- could he copy the PHP file and run it on his
Webserver?
Phil Wherry: Doubtful. It depends on the existence of
the cjpeg and djpeg tools (Unix), which are doing the
hard work. In addition, the Web server has to
understand how to handle PHP scripts.
drofnasw: No problem re: error msgs. -- the files will
be named consistently, so the utility should not fail.
Phil Wherry: no problem - just pointing out that when
you get the "broken image" icon when testing, that's
probably what's wrong.
drofnasw: Do you think we should save Webcam
images to a separate subdirectory?
Phil Wherry: Full invocation sequence is:

resizer.php?filename=filename&scale=x&quality=y

scale is 2, 4, or 8; quality is 0-100. Defaults are 2 and
90, respectively. No default for the filename.
Phil Wherry: Don't think it matters, to tell you the
truth.
drofnasw: "Quality" as in JPEG compression?
Phil Wherry: correct.
drofnasw: Please send me another sample URL that
includes all specs., incl. quality.
Phil Wherry: If you've still got the earlier URL, just
tack "&quality=90" onto the end of it.
Phil Wherry:
http://www.wsanford.com/webcam/earthdial/resizer.ph
p?filename=fcps-earthdial.jpg&scale=2&quality=90
drofnasw: Just curious -- is the output quality of the
new utility identical to photoweb?
Phil Wherry: Yes; it uses the same tools that
photoweb does internally. The pictures should be
bit-for-bit identical given the same settings, in fact.
drofnasw: Using the <IMG SRC> tag in combo. w.
your utility, how should I spec the IMG WIDTH and
HEIGHT -- the actual size of the image before or after
resizing?
Phil Wherry: Use the "after resizing" size.
drofnasw: Hmmm. The image you see of the Webcam
is actually 640x480; I'm using HTML to force the
browser to resize it to 320x240. I'm concerned that the
HTML will over-ride your utility.
Phil Wherry: No, the browser will display it at
whatever resolution is specified. If the underlying image
is the same size, no scaling will occur. If you're in
doubt, just leave out the HEIGHT and WIDTH tags;
the image is quite small so it won't cause a big
performance hit.
http://www.wsanford.com/webcam/earthdial/extras/resi
zer.php?filename=eggcam_test_still-img.jpg&scale=2&
quality=90
Phil Wherry: Good deal. Note that scale=2 and
quality=90 are both defaults so you can omit them if
you'd like.
drofnasw: Looks good at a scale factor of 4 too!
Phil Wherry: Even 8 looks good to me.
Phil Wherry: (though it's probably too small for your
needs for this project)
drofnasw: When one FTPs files, why doesn't the app
prompt you re: overwriting files?
Phil Wherry: it's not directly supported by the FTP
protocol.
drofnasw: So if we just overwrite the same files every
10 min., then the Web page(s) will grab the most
current images and resize 'em accordingly, right?
Phil Wherry: That's correct.
drofnasw: Piece of cake!
Phil Wherry: Yep, should be simple.

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Walter Sanford, Director           Carl Sandburg Middle School
Center for Sky Awareness           8428 Fort Hunt Road
Sandburg Planetarium               Alexandria, VA 22308
Fairfax County Public Schools      Work: 703-799-6169 -6197 (fax)
E-mail: wsanford@wsanford.com      Home: 703-765-9392
AMS Project ATMOSPHERE Atmospheric Education Resource Agent
SCSA, Geosystems, & Camp T-Equity - URL: http://www.wsanford.com/
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