shotgun

A minimal screenshot utility for X11. Shotgun was written to replace maim in my workflow.

Features:

• Exports PNG screenshots to file or stdout
• Masks off-screen areas on multi-head setups
• Supports selections by window ID and geometry
• On average, shotgun is more than twice as fast as maim

Usage

Usage: shotgun [options] [file]

Options:
    -i, --id ID         Window to capture
    -g, --geometry WxH+X+Y
                        Area to capture
    -h, --help          Print help and exit

To use with slop (as a replacement for maim -s):

#!/usr/bin/env bash

set -e

$sel=$(slop -f "-i %i -g %g")
shotgun $sel $*

shotgun vs maim

• Only PNG is supported
• Does not attempt to wrap slop
• No cursor blending
• Properly detects that stdout is a TTY, and defaults to a time-stamped file instead of dumping raw PNG data into your terminal (unless - is specified as the output file name)
• Most command-line flags were omitted
• The XShape extension is not supported
• shotgun is written in Rust, maim in C++
• The code base is kept as small and simple as possible (as much as Rust permits)

There are several reasons for omitting these features:

• Features that can be replaced trivially by external programs and wrapper scripts:
  • Use ImageMagick's convert for JPEG output
  • slop output is easy to process in a shell script
  • Use sleep instead of -d, since slop has to be called separately, this flag is not necessary
  • -x shouldn't even exist in the first place, set $DISPLAY instead
• I never use cursor blending, and I know that most users do not actually care for it
• -w (geometry relative to another window) is difficult to use and hardly useful, instead, shotgun always interprets the input geometry relative to the root window (maim's default is the captured window itself)
• There is rarely a reason to take a screenshot of an XShape window, most of them are special like slop's selection window or keynav's crosshair. Supporting XShape properly could add a significant amount of overhead, both in code length and performance, which are not desirable.

Performance

I've claimed that shotgun is twice as fast as maim, here's some supporting evidence:

streetwalrus@Akatsuki:~/source/shotgun(master)
>>> xrandr --fb 3840x2160
streetwalrus@Akatsuki:~/source/shotgun(master)
>>> for i in {1..10}; do time maim > /dev/null; done
maim > /dev/null  0.78s user 0.00s system 107% cpu 0.731 total
maim > /dev/null  0.79s user 0.01s system 104% cpu 0.764 total
maim > /dev/null  0.75s user 0.02s system 104% cpu 0.727 total
maim > /dev/null  0.74s user 0.01s system 110% cpu 0.678 total
maim > /dev/null  0.76s user 0.01s system 108% cpu 0.717 total
maim > /dev/null  0.73s user 0.02s system 104% cpu 0.711 total
maim > /dev/null  0.74s user 0.01s system 106% cpu 0.703 total
maim > /dev/null  0.74s user 0.01s system 109% cpu 0.682 total
maim > /dev/null  0.82s user 0.02s system 104% cpu 0.799 total
maim > /dev/null  0.75s user 0.01s system 105% cpu 0.719 total
streetwalrus@Akatsuki:~/source/shotgun(master)
>>> for i in {1..10}; do time ./target/release/shotgun > /dev/null; done
./target/release/shotgun > /dev/null  0.31s user 0.01s system 99% cpu 0.320 total
./target/release/shotgun > /dev/null  0.33s user 0.01s system 108% cpu 0.311 total
./target/release/shotgun > /dev/null  0.35s user 0.01s system 109% cpu 0.322 total
./target/release/shotgun > /dev/null  0.35s user 0.01s system 111% cpu 0.327 total
./target/release/shotgun > /dev/null  0.31s user 0.01s system 107% cpu 0.296 total
./target/release/shotgun > /dev/null  0.32s user 0.01s system 109% cpu 0.302 total
./target/release/shotgun > /dev/null  0.36s user 0.00s system 105% cpu 0.338 total
./target/release/shotgun > /dev/null  0.32s user 0.01s system 102% cpu 0.322 total
./target/release/shotgun > /dev/null  0.34s user 0.00s system 105% cpu 0.318 total
./target/release/shotgun > /dev/null  0.33s user 0.01s system 111% cpu 0.303 total

Further profiling has shown that the bottleneck in shotgun lies fully within the PNG encoder.

Installation

• Manual: Make sure you have a recent Rust toolchain. Clone this repo, then run cargo install.
• Arch Linux: AUR package
• Other distros: make a pull request to add your package or build script!