You might be wondering how to capture a website screenshot (as thumbnail) but you dont know how to do it. Although PHP GD library is available, it is just not possible to do the task with php. You will need a linux server running xwindow system and a browser like KDE konquerer or firefox. In this tutorial i am going to show you how to capture a website screenshot with khtml2png in a Centos/RHEL server. I am documenting here the experiment i conducted in my VPS so that my work could be helpful.
What is Needed?
Linux Server with Centos/RHEL
KDE Desktop Environment
Cmake - http://www.cmake.org
Most linux servers will usually not have a graphics card or output device like monitor. This is usually called headless server and the alternate way is using a Xvfb or Vncserver (Xserver with virtual frame buffer). It is basically a virtual display that doesnt need a graphics device and monitor. Anything written to Xvfb, can be captured as screenshot. In this tutorial, I will be using Xvfb without making use of khtml2png and it is the most simple method of doing it.
First install Xvfb server and ImageMagick
yum install Xvfb ImageMagick
yum install firefox
start the virtual display
> Xvfb :2 -screen 0 1024x768x24&
// This starts the virtual server with display no 2, screen no 1 on resolution 1024x768 with color depth of 24 bit.
Run the firefox on the virtual display in the command line
> DISPLAY=:2 firefox http://www.example.com
Wait for 5 seconds until, it loads and then capture a screenshot with ImageMagick's import tool
> import -window root example.png
once this is done, you can resize the images later with convert tool
khtml2png is another way of capturing a website screenshot of specified width and height from Xvfb virtual server. More information can be found at http://khtml2png.sourceforge.net.
khtml2png requires KDE, gcc compiler, cmake and kde-devel libraries,
If you have a new linux server, prepare your server with c compiler and other utilities
Install Basic Tools
yum install gcc gcc-c++ automake autoconf nano zlib zlib-devel
Install KDE desktop environment
yum groupinstall "X Window System" "KDE (K Desktop Environment)"
Install KDE developer libraries
yum install kdelibs kdelibs-devel
Install Xvfb Virtual Frame Buffer
yum install Xvfb xorg xorg-x11-font*
Cmake is cross plaform make utility. You cannot install using yum so you have to download the source files and compile it.
tar zxf cmake-2.7.1.tar.gz
Download the source files from sourceforge.
tar xzf khtml2png-2.7.5
Start Xvfb virtual server, then launch the khtml2png to grab a website screenshot
> Xvfb :2 -screen 0 1024x768x24&
> export DISPLAY=localhost:2.0
then run khtml2png2
> khtml2png2 --sw 200 --sh 150 http://www.example.com example.png
--sh and --sw indicates both scaled width and height
To view the image in the browser copy those created screenshot to apache /var/www/html and point your browser to http://your.ip.address/example.png
If you want khtml2png run as daemon you might want to install kthmld available from sourceforge.
Mozgrab - Web page
screen shot grabber using Mozilla.
html2jpg - A screenshot grabber written in Perl.
khtmld - A daemon for khtml2png
I am documenting the common errors i got and how i fixed those. Few i was able to fix while others i couldnt fix.
khtml2png2: cannot connect to X server
[This means you have not assigned the display where Xvfb is running. Try export DISPLAY=localhost:2.0 in the commandline
Couldn't open RGB_DB '/usr/share/X11/rgb'
[Xvfb might throw this error if you set the resolution to 32 bit color depth.
Lower the resolution to 24 or 16bit color.
Example: Xvfb :2 -screen 0 800x600x24&]
error opening security policy file /usr/lib/xserver/SecurityPolicy
[Login as a user other than root]
Could not init font path element /usr/share/X11/fonts/TTF/, removing
Could not init font path element /usr/share/X11/fonts/OTF, removing from list!
Could not init font path element /usr/share/X11/fonts/Type1/, removing from list!
Could not init font path element /usr/share/X11/fonts/CID/, removing from list!
Could not init font path element /usr/share/X11/fonts/100dpi/, removing from list!
Could not init font path element /usr/share/X11/fonts/75dpi/, removing from list!
[Try yum install xorg-x11-font*]
CMake Error: The following variables are used in this project,
but they are set to NOTFOUND.
Please set them or make sure they are set and tested correctly in the CMake files:
[Install qt and qt-devel packages. If that doesnt work, try rebooting the server and this might go off! ]
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