Operating system: FreeBSD 13.0
Note:
In code excerpts and examples, the long lines are folded and then indented to make sure they fit the page.
Install py-png package. At the time of writing, python version is 3.8.
$ sudo pkg install py38-png
Install netpbm - a toolkit for conversion of images between different formats.
$ sudo pkg install netpbm
% ls /usr/local/include/netpbm
colorname.h pammap.h pgm.h pm_system.h
mallocvar.h pbm.h pm_c_util.h pm.h
pam.h pbmfont.h pm_config.h pnm.h
pamdraw.h pbmfontdata.h pm_gamma.h ppm.h
ppmcmap.h runlength.h
ppmdfont.h shhopt.h
ppmdraw.h
ppmfloyd.h
% man -k netpbm | wc -l
64
% man -k pbm | wc -l
143
% xdpyinfo | wc -l
4270
% xdpyinfo | grep -n -i pixmap
10:number of supported pixmap formats: 7
11:supported pixmap formats:
% xdpyinfo | head -20
name of display: :0.0
version number: 11.0
vendor string: The X.Org Foundation
vendor release number: 12011000
X.Org version: 1.20.11
maximum request size: 16777212 bytes
motion buffer size: 256
bitmap unit, bit order, padding: 32, LSBFirst, 32
image byte order: LSBFirst
number of supported pixmap formats: 7
supported pixmap formats:
depth 1, bits_per_pixel 1, scanline_pad 32
depth 4, bits_per_pixel 8, scanline_pad 32
depth 8, bits_per_pixel 8, scanline_pad 32
depth 15, bits_per_pixel 16, scanline_pad 32
depth 16, bits_per_pixel 16, scanline_pad 32
depth 24, bits_per_pixel 32, scanline_pad 32
depth 32, bits_per_pixel 32, scanline_pad 32
keycode range: minimum 8, maximum 255
focus: window 0x40000c, revert to PointerRoot
% xwininfo -root | wc -l
24
% xwininfo -root | grep -i depth
Depth: 24
For a window with a depth of 24
% xwininfo | grep 'Window id'
xwininfo: Window id: 0x1e0000f "LibreOffice"
% xwininfo | grep -i depth
Depth: 24
piping xwd(1) with xwdtopnm(0) and pnmtopng(0) works:
% xwd | xwdtopnm | pnmtopng > screenshot.png
xwdtopnm: writing PPM file
% ls -lh screenshot.png
-rw-r--r-- 1 dusko dusko 23K Feb 6 12:01 screenshot.png
% file screenshot.png
screenshot.png: PNG image data, 830 x 391, 8-bit/color RGB, non-interlaced
Open the screenshot.
% xv screenshot.png
For a window with a depth > 24
% xwininfo | grep 'Window id'
xwininfo: Window id: 0x1402c2d "Mozilla Firefox"
% xwininfo | grep -i depth
Depth: 32
% xwd | xwdtopnm | pnmtopng > screenshot.png
xwdtopnm: can't handle X11 pixmap_depth > 24
pnmtopng: Error reading first byte of what is expected to be a Netpbm
magic number. Most often, this means your input file is empty
piping xwd(1) with xwdtopnm(0) and pnmtopng(0) doesn’t work.
Workaround for Taking Screenshots with xwd(1) with Pixmap Size (Depth) Bigger than 24
Modify and use a tool xwd2png (convert output of xwd to PNG), https://github.com/drj11/xwd2png.
NOTE:
This is a quick and dirty workaround. For example, I’m removing Python exception handling, NotImplementedError. although there is a possibility that the author of the source code left it to perhaps indicate a TODO placeholder, as a reminder to implement handling other cases (that is visual classes different than 4) later.
Location where I keep my helper binaries, useful tools and scripts:
% ls -ld /mnt/usbflashdrive/bin
drwxr-xr-x 6 dusko dusko 512 Dec 9 12:27 /mnt/usbflashdrive/bin
% cd /mnt/usbflashdrive/bin/xwd2png
% fetch https://raw.githubusercontent.com/drj11/xwd2png/main/XWDFile.h
XWDFile.h 4031 B 22 MBps 00s
% fetch https://raw.githubusercontent.com/drj11/xwd2png/main/xwd.py
xwd.py 7958 B 34 MBps 00s
Python version:
% ls -ld /usr/local/bin/python*
-r-xr-xr-x 1 root wheel 5248 Nov 3 18:13 /usr/local/bin/python3.8
-r-xr-xr-x 1 root wheel 3153 Nov 3 18:13 /usr/local/bin/python3.8-config
lrwxr-xr-x 1 root wheel 50 Jan 1 18:31 /usr/local/bin/pythontex -> ../share/texmf-dist/scripts/pythontex/pythontex.py
% cp -i xwd.py xwd.py.original.bak
% vi xwd.py
% diff --unified=0 xwd.py.original.bak xwd.py
--- xwd.py.original.bak 2022-02-06 12:35:23.701781000 -0800
+++ xwd.py 2022-02-06 12:36:15.213548000 -0800
@@ -1 +1 @@
-#!/usr/bin/env python3
+#!/usr/bin/env python3.8
@@ -57,15 +56,0 @@
- # Check visual_class.
- # The following table from http://www.opensource.apple.com/source/tcl/tcl-87/tk/tk/xlib/X11/X.h is assumed:
- # StaticGray 0
- # GrayScale 1
- # StaticColor 2
- # PseudoColor 3
- # TrueColor 4
- # DirectColor 5
-
- if self.visual_class != 4:
- # TrueColor
- raise NotImplemented(
- "Cannot handle visual_class {!r}".format(self.visual_class)
- )
-
@@ -291 +276 @@
- apng.write(out)
+ apng.save(out)
% xwininfo | grep 'Window id'
xwininfo: Window id: 0x1402c2d "Mozilla Firefox"
% xwininfo | grep -i depth
Depth: 32
% xwd | /mnt/usbflashdrive/bin/xwd2png/xwd.py > ~/screenshot.png
% ls -lh ~/screenshot.png
-rw-r--r-- 1 dusko dusko 580K Feb 6 12:47 /home/dusko/screenshot.png
% file ~/screenshot.png
/home/dusko/screenshot.png: PNG image data, 1260 x 1079,
8-bit/color RGB, non-interlaced
Open the screenshot.
% xv ~/screenshot.png
Alternatively:
Install ImageMagick (sudo pkg install ImageMagick7) and use one of its tools, import for taking screenshots.