A caption to an image is provided in ASCIIDoctor document as follows:
.This is a caption
However, the caption is aligned to the left by default.
text-center on it does not work:
.This is a caption
This problem has been discussed in this Github issue. The solution provided to add a few lines to
imageblock in the stylesheet does not work. Instead, I changed the default behavior itself in the stylesheet to be center.
- To do this first find out where gems are installed:
$ gem environment
- Go to the
INSTALLATION DIRECTORY output in the above command and to the subdirectory holds ASCIIDoctor stylesheets:
$ cd gems/asciidoctor-1.5.2/data/stylesheets/
Tried with: ASCIIDoctor 1.5.2, Ruby 2.1.0 and Ubuntu 14.04
PDF files can have images embedded in them. Since PDF is the defacto format used for research papers, it can be sometimes necessary to extract these images. Images in a PDF file can be extracted easily using the
pdfimages tool from the
$ sudo apt install poppler-utils
- To list the details of images embedded in a PDF file:
$ pdfimages -list foo.pdf
page num type width height color comp bpc enc interp object ID
1 0 image 80 100 icc 3 8 image yes 11 0
1 1 smask 80 100 gray 1 8 image yes 11 0
1 2 image 80 100 icc 3 8 image yes 13 0
1 3 smask 80 100 gray 1 8 image yes 13 0
1 4 image 80 100 icc 3 8 image yes 15 0
1 5 smask 80 100 gray 1 8 image yes 15 0
1 6 image 80 100 icc 3 8 image yes 17 0
- To extract the images embedded in a PDF file provide a prefix for the extracted image filenames:
$ pdfimages foo.pdf foo_img
$ ls foo_img*
Tried with: PopplerUtils 0.24.5 and Ubuntu 14.04
An image is inserted into a LaTeX document using the
includegraphics command. The size of the image can be specified in a variety of techniques:
- Specify height or width or both in terms of
- Specify width as fraction of width of text column:
Tried with: Ubuntu 14.04
Ranger is a great console tool to explore directories and files. You can find the instructions to install and configure it in this post. As you explore files in the center column, Ranger displays a preview of the file contents in the right column. If the file is an image, then Ranger displays a color ASCII version of the image using the Caca library.
However, if you use XTerm or a terminal with similar capabilities, Ranger can show an actual image preview with full color and pixels! Remember that this works only on XTerm or similar terminals.
To preview images like this, Ranger requires the
w3mimgdisplay program. You can get it by installing:
$ sudo apt install w3m-img
After this, you need to set the
preview_images option to
true in the
.config/ranger/rc.conf file. You will have this file only if you followed the instructions given above during Ranger installation.
Once you have done this, open an XTerm and enjoy full-color image previews! Note that this did not work in RXVT for me 🙂
Tried with: W3m-Img 0.5.3-15, Ranger 1.6.0 and Ubuntu 14.04
ShellPic is a program that can be used to view images at any terminal. It renders the image using ASCII art and in color.
ShellPic is not packaged for Ubuntu yet. So, it can be installed from PyPI instead:
$ sudo pip install ShellPic
After installation, it can be invoked directly on any image:
$ shellpic foo.jpg
Tried with: ShellPic 1.6 and Ubuntu 14.04
Framebuffer Image Viewer (fbi) is a program that can be used to view images at the terminal. However, it only works with actual terminals (
/dev/tty), that is the terminals you get when you press
Ctrl + Alt + F1 to
Ctrl + Alt + F6. It does not work in pseudo terminals (
/dev/pts) that are used by terminal programs running in X, like GNOME Terminal.
To install fbi:
$ sudo apt install fbi
Before using the viewer, your username needs to be added to the
video group. For example, to add user
$ sudo adduser joe video
After this, any image can be viewed at a real terminal using fbi:
$ fbi foo.jpg
Tried with: FBI 2.07-11 and Ubuntu 14.04
You may sometimes want to convert a PDF file into an image format like PNG or JPG. Doing this is easy using the convert application from ImageMagick.
If you do not have it, first install ImageMagick:
$ sudo apt install imagemagick
To convert a PDF with a single page into a JPG:
$ convert foo.pdf foo.jpg
If the PDF has multiple pages, one image file is produced per page:
$ convert foo.pdf foo.png
By default, the image file is produced at 96 DPI resolution of the PDF. If you need higher DPI, use the density option. For example, to generate at 300 DPI:
$ convert -density 300 foo.pdf foo.png
-density parameter has to come first. If you place it anywhere else, the program runs silently without complaining, but the output image will be in the default DPI.
Tried with: ImageMagick 6.7.7-10 and Ubuntu 14.04
HoverZoom is a neat little extension I use on Chrome. Thumbnail Zoom Plus is a great alternative to this if you are using Firefox. It has all the same features and works on the same websites. Just hover the mouse on an image to see the fullsize version of it, if it exists.
Settings I use with this extension:
- Set the Delay before display to 0.5 sec.
- Set Default zoom to 100 percent.
- Disable Show picture using all available space.
- Turn off all keyboard shortcuts.
Tried with: Thumbnail Zoom Plus 2.7, Firefox 29.0 and Ubuntu 14.04
HoverZoom is one of those Chrome extensions that you wonder how you lived without! This is because a lot of images are shared today using links, like on Twitter. Most websites, like Facebook, show small size images which need to be clicked to view the full size image. HoverZoom makes viewing the full-size image hidden behind links and thumbnails a piece of cake.
On hovering the mouse cursor over any link or image, HoverZoom downloads the full size image and displays it. There is no need to click anything, which reduces the friction of using this operation.
Tried with: HoverZoom 4.29, Chrome 31.0.1650.63 and Ubuntu 12.04