NAME¶
webcam - capture images and upload them to a webserver using ftp
SYNOPSIS¶
webcam [ config file ]
DESCRIPTION¶
webcam captures images from a video4linux device like bttv, annotates
them and and uploads them to a webserver using ftp in a endless loop.
CONFIGURATION¶
At startup
webcam reads the configuration from the given config file or
~/.webcamrc if none is specified in the command line.
The config file has at least two sections. The "grab" section holds
the capture parameters. Any other section describes where the image should be
uploaded. Older versions used "ftp" as name for that section.
Recently the webcam utility got support for multiple connections, thus any
section name is accepted and you can have more than one ftp section (you have
to use another name for each section througth, name them by upload servers for
example).
Here is an sample config file (the given values are the defaults):
[grab]
device = /dev/video0
driver = libv4l
text = "webcam %Y-%m-%d %H:%M:%S"
infofile = filename
fg_red = 255
fg_green = 255
fg_blue = 255
width = 320
height = 240
delay = 3
wait = 0
input = composite1
norm = pal
rotate = 0
top = 0
left = 0
bottom = -1
right = -1
quality = 75
trigger = 0
once = 0
[ftp]
host = www
user = webcam
pass = xxxxxx
dir = public_html/images
file = webcam.jpeg
tmp = uploading.jpeg
passive = 1
debug = 0
auto = 0
local = 0
ssh = 0
The annotation
text is processed with strftime. Check the
strftime(3) or
date(1) manpage to see how you can format the timestamps. The text can also be
read from a extern file (use
infofile for that). The default color for
the text overlay is white (RGB=255,255,255). Entries in the range of 0 through
255 for
fg_red, fg_green, and
fg_blue can be used to
define a different color. Likewise
bg_red, bg_green, and
bg_blue can be used to set the background color (which defaults to
transparent).
input is the video source (TV/composite/whatever),
norm the TV
norm.
delay is the delay between two images in seconds.
wait is
the initial delay before the first image is grabbed (some cameras need some
time for adapting to lightning, thus don't return images with reasonable
quality within the first few seconds ...).
quality is the JPEG quality
for the stored images.
top, bottom, left, and
right in the grab section allow cropping
the image after it is grabbed. They should satisfy
0<=top<bottom<=height and 0<=left<right<=width. (0,0 is the
top, left corner.) If
rotate is positive, the output image will be
rotated counter-clockwise 90 degrees that number of times (1, 2, or 3).
With
trigger set to a non-zero value webcam will upload the image only if
the content of the image has changed. It just looks for the maximum difference
between the last uploaded and current image and if it is greater than the
specified value the image will be uploaded. If
once is set to 1 webcam
will upload a single frame and quit.
archive can be used to create a (local) archive of the webcam images.
Just specify the filename for the files as argument. The filename will be
processed with
strftime(3), so you can use the place the usual time format
controls into the string to get unique filenames. Non-existing directories are
created if needed.
If
debug in the ftp section is set to 1 the complete communication
between webcam and the ftp utility is printed to stderr.
auto enables
autologin via ~/.netrc (starts the ftp utility without the '-n' switch, check
the
ftp(1) man page for more info about the ~/.netrc file). If
local in
the ftp section is non-zero, files will be stored locally (using the
dir,
tmp, and
file parameters) rather than ftped.
ssh set to
non-zero makes webcam use ssh instead of ftp.
CORRECTION OF DISTORTION¶
contributed by Frederic Helin, the parameters belong into the [grab] section of
the config file too.
- distor = 1
- If distor param is set to 1, the correction of distortion
works.
- distor_k = 700
- This is the coefficient of distortion. This algorithm is
based on the paper "Correcting Distortion of Image by Image
Registration" of Toru Tamaki, Tsuyoshi Yamamura and Noboru Ahnishi.
More your lens has an important distortion, more 'distor_k' must be neared
of 0. 700 is the default value. Coefficient k of program is x100 than
article.
- distor_cx = 192
- distor_cy = 144
- Coordinates of the lens optical axis: width/2 and height/2
are the default values. The axis doesn't go through the image center. So,
you can change its coordinates around the center of image to affine
correction.
- distor_zoom = 30
- Zoom parameter is used to cache the distorted borders of
image, if you don't like this. Default value is 100.
- distor_sensorw = 320
- distor_sensorh = 240
- Dimensions of camera sensor. Default values are for 1/4p
sensor. This parameters used to have the same k coefficient than
article.
AUTHOR¶
Gerd Knorr <kraxel@bytesex.org>
COPYRIGHT¶
Copyright (C) 1997-2002 Gerd Knorr
This program is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
A PARTICULAR PURPOSE.