This is the command webcam that can be run in the OnWorks free hosting provider using one of our multiple free online workstations such as Ubuntu Online, Fedora Online, Windows online emulator or MAC OS online emulator
webcam - capture images and upload them to a webserver using ftp
webcam [ config file ]
webcam captures images from a video4linux device like bttv, annotates them and and uploads
them to a webserver using ftp in a endless loop.
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):
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
host = www
user = webcam
pass = x
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
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.
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