Whether it is for debugging purposes, making images for tutorials or capturing a moment in a game, screenshots (screengrabs or screen captures) often come in handy. Most operating systems, including Raspbian, will have options to create screenshots by using the keyboard, but what if no keyboard is connected?
A screenshot is a digital image of what is visible on the screen at that specific point in time. It includes everything that is displayed. Often the Raspberry Pi is used as a standalone device without any peripherals connected to it, which makes using the keyboard impractical. A popular solution in this case is to make use of a remote system to trigger the screenshot command.
To be able to take screenshots from a remote location the Raspberry Pi needs to be connected to a network and the username, password and IP address is required. SSH access to the Raspberry Pi needs to be available. The process will be done using raspi2png and PuTTY from a computer connected on the same network. To install raspi2png a connection to the internet will be required.
raspi2png
raspi2png is an utility with the purpose of taking a “snapshot” of the Raspberry Pi screen. It is also reported to work well for Minecraft screen captures. For more information see Andrew Duncan’s raspi2png Github page.
After the raspi2png command is triggered, a screenshot is saved as a PNG file. The screenshot command is triggered on the Raspberry Pi itself using a terminal command, but because the command can be triggered from a remote location it can capture both GUI and terminal screens.
The utility and its dependencies are to be installed locally on the Raspberry Pi. The raspi2png project files need to be downloaded from Github, after which they need to be compiled.
The first step is to connect to the Raspberry Pi using PuTTY. After having terminal access to the Raspberry Pi, do an update/upgrade first:
sudo apt-get update sudo apt-get upgrade -y
The following commands will install the dependencies:
sudo apt-get install libpng12-dev -y sudo apt-get install git -y
It is recommended to download the raspi2png project files to the /home/pi/raspi2png directory. The /raspi2png directory will be created automatically, but to make sure you’re in the /home/pi/ directory, use:
cd /home/pi
To download the raspi2png project files from Github, use:
git clone https://github.com/AndrewFromMelbourne/raspi2png/
To compile the project files, simply use the make command while in the /raspi2png directory:
cd /home/pi/raspi2png make cd
If the make process was successful, a screenshot can then be triggered by running the raspi2png command:
/home/pi/raspi2png/raspi2png
The screenshot is saved as snapshot.png. It is saved in the same directory as from where the command was triggered from. The old screenshot will be replaced each time a new command was triggered. The location where the screenshot will be saved can also be set with the -p command line option (see below)
Captured screenshots can be renamed and copied to a different location using WinSCP.
raspi2png also has some handy command line options which can be used to extend the functionality. From the Github page, the following command line options are available:
Usage: raspi2png [-p pngname] [-v] [-w ] [-h ] [-t ] [-d ]
-p - name of png file to create (default is snapshot.png)
-v - verbose
-h - image height (default is screen height)
-w - image width (default is screen width)
-t - type of image captured
can be one of the following: RGB565 RGB888 RGBA16 RGBA32
-d - delay in seconds (default 0)
The most useful are -p , and -d. For example:
/home/pi/raspi2png/raspi2png -d 5 -p "snap_01.png"
will create an image file called snap_01.png after a delay of 5 seconds, and:
/home/pi/raspi2png/raspi2png -p "/home/pi/snap_02.png"
will create an image file called snap_02.png in the /home/pi directory (irrespective where the directory the command was triggered from).
