Ubuntu Unleashed 2017 Edition (2017)

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Sometimes, a file you want to manipulate in some way is in a format that cannot be used by either your graphics application or the final application. The solution is to convert the image file—sometimes through several formats. The convert utility from ImageMagick is useful, as is the netpbm family of utilities. If it is not already installed, you can easily install ImageMagick from the Ubuntu repositories; the netpbm tools are always installed by default. convert is super simple to use from the command line. Here is an example:

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matthew@seymour~:$ convert image.gif image.png

The convert utility converts between image formats recognized by ImageMagick. You can also manipulate color depth and size during the conversion process. You can use ImageMagick to append images, surround them with borders, add labels, rotate and shade them, and perform other manipulations well suited to scripting. Other commands associated with ImageMagick include display, animate, identify, and import. The application supports more than 130 different image formats (all listed in the man page for ImageMagick).

The netpbm tools are installed by default because they compose the underpinnings of graphics format manipulation. The man page for each image format lists related conversion utilities; the number of those utilities gives you some indication of the way that format is used and shows how one is built on another:

The man page for ppm, the portable pixmap file format, lists 47 conversion utilities related to ppm. This makes sense because ppm, or portable pixmap, is considered the lowest common denominator for color image files. It is therefore often used as an intermediate format.

The man page for pgm, the portable graymap file format, lists 22 conversion utilities. This makes sense because pgm is the lowest common denominator for grayscale image files.

The man page for pnm, the portable anymap file format, lists 31 conversion utilities related to it. However, there is no format associated with PNM because it operates in concert with ppm, pgm, and pbm.

An examination of the man page for pbm, the portable bitmap file format, reveals no conversion utilities. It’s a monochrome format and serves as the foundation of the other related formats.

The easiest way to resize or rotate image files is to install the nautilus-image-converter package from the repositories. This enables you to right-click an image when you are viewing files in the File Browser (for example, from Places, Pictures) and choose menu options to resize or rotate one or multiple images without opening another program.

Capturing Screen Images

You can use graphics-manipulation tools to capture images that are displayed on your computer screen. Although this technique was used for the production of this book, it has broader uses; there is truth to the cliché that a picture is worth a thousand words. Sometimes it is easier to show an example than it is to describe it.

You can use a captured screen image (also called a screen grab or a screenshot) to illustrate an error in the display of an application (a font problem, for example) or an error dialog that is too complex to copy down by hand. You might just want to share an image of your beautifully crafted custom desktop configuration with your friends or illustrate your written documents.

When using the default desktop, you can take advantage of the built-in screenshot mechanism (gnome-screenshot). You can use this tool by pressing the Print Screen key. (Alt+Print Screen takes a screenshot of only the window that has focus on a desktop.) Captured images are saved in PNG format. You can also find the tool in the Dash by searching for screenshot.

Other Graphics Manipulation Options

If you have very specific requirements for working with graphics, you may find one of the following better suits your needs than the general options and comments above. Some of these are in the Ubuntu repositories, but not all of them.

Blender is a 3-D image and animation editor that you can find at http://www.blender.org/.

CinePaint is a powerful and complex tool used by many Hollywood studios that you can find at http://www.cinepaint.org/.

darktable is a RAW editor and can be found at http://www.darktable.org/.

digiKam is photo management software and can be found at http://www.digikam.org/.

Hugin is a panoramic photo stitcher and can be found at http://hugin.sourceforge.net/.

Inkscape is a vector graphics creation and editing tool that you can find at http://inkscape.org/.

POV-Ray is a powerful and complex 3-D graphics program that uses ray tracing and can be found at http://www.povray.org/.

Radiance is intended for the analysis and visualization of lighting in design and can be found at http://www.radiance-online.org/.

Xara Xtreme is a general purpose graphics editor that you can find at http://www.xaraxtreme.org/.

Using Digital Cameras with Ubuntu

Most digital cameras used with Ubuntu fall into one of two categories: webcams (small, low-resolution cameras connected to the computer’s interface) or handheld digital cameras that record image data on disks or memory cards for downloading and viewing on a PC. Ubuntu supports both types. Other types of cameras, such as surveillance cameras that connect directly to a network via wired or wireless connections, need no special support (other than a network connection and viewing software) to be used with a Linux computer.

Ubuntu supports hundreds of different digital cameras, from early parallel-port (CPiA chipset-based) cameras to today’s USB-based cameras. You can even use Intel’s QX3 USB microscope with Ubuntu. The following sections describe some of the more commonly used types of still camera hardware and software supported by Ubuntu.

Handheld Digital Cameras

Because of the good development carried out in the Linux world, you can plug almost any digital camera in to your computer through a USB interface, and Ubuntu automatically recognizes the camera as a USB mass storage device. You can even set Ubuntu to recognize when a camera is plugged in so that it automatically imports your photographs for you.

Using Shotwell Photo Manager

Ubuntu comes by default with a pretty good photo manager called Shotwell Photo Manager that includes simple adjustment tools (see Figure 6.9). You can import your photos into Shotwell, assign tags to them, sort and arrange them, and even upload them to your favorite Internet photo-hosting sites such as Facebook, Flickr, and Picasa.

FIGURE 6.9 Browse your photo collection and correct minor problems with Shotwell Photo Manager.

Burning CDs and DVDs in Ubuntu

Linux is generally distributed via the Internet as disc images called ISOs that are ready to be written to CDs or DVDs. Therefore, learning how to burn discs is essential if you have to download and install a Linux distribution. You can use CDs and DVDs to do the following:

Record and store multimedia data, such as backup files, graphics images, and music.

Rip audio tracks from music CDs (ripping refers to extracting music tracks from a music CD) and compile your own music CDs for your personal use.

Although USB storage devices such as thumb drives are making CDs and DVDs almost as rare as floppy disks, they aren’t quite gone, and many people still find them useful. As long as that remains true, we want to make sure this information is available.

Creating CDs and DVDs with Brasero

Although adequate for quick burns and use in shell scripting, the command-line technique for burning CDs and DVDs is an awkward choice for many people (but we still cover doing so later in this chapter because others find it useful and desirable). Fortunately, Ubuntu provides several graphical clients; the most useful is Brasero.

Brasero is an easy-to-use graphical CD and DVD burning application that is installed by default.

Brasero takes a project-based approach to disc burning, opening up with a wizard from which you can select from four different tasks that people commonly want to do. Figure 6.10 shows the opening screen. Brasero also remembers previous “projects,” enabling you to quickly create several copies of a disc, which is ideal if you’re planning to pass on copies of Ubuntu to your friends and family.

FIGURE 6.10 Brasero gives you an intuitive way to create data and audio CDs and DVDs.

Burning a data CD or DVD is as easy as selecting the option in the opening screen and dragging and dropping the files you want to include from the directory tree on the left to the drop area on the right. If you insert a blank CD or DVD in your writer, Brasero keeps an eye on the disc size and tells you when you reach or exceed the limits. It also creates ISO files, which are disc images that contain everything that would exist on the medium if you burned a real CD or DVD in one file that can be mounted by computer file systems, which is useful if you want to create multiple copies of the same disc or if you want to share a disc image, perhaps using a USB thumb drive or over the Internet.

Finally, click the Burn button, input a label for the disc, and Brasero starts creating your new CD or DVD or image file. How long it takes to create a CD or DVD depends on the amount of data you are writing and the speed of your drive.

Creating CDs from the Command Line

In Linux, creating a CD at the command line is a two-step process. You first create the ISO9660-formatted image, and you then burn or write the image onto the CD. The ISO9660 is the default file system for CD-ROMs.

Use the mkisofs command to create the ISO image. The mkisofs command has many options (see the man page for a full listing), but use the following for quick burns:

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matthew@seymour~:$ mkisofs -r -v -J -l -o /tmp/our_special_cd.iso /source_directory

The options used in this example are as follows:

-r—Sets the permission of the files to more useful values. UID and GID (individual and group user ID requirements) are set to 0, all files are globally readable and searchable, and all files are set as executable (for Windows systems).

-v—Displays verbose messages (rather than terse messages) so that you can see what is occurring during the process; these messages can help you resolve problems if they occur.

-J—Uses the Joliet extensions to ISO9660 so that your Windows-using buddies can more easily read the CD. The Joliet (for Windows), Rock Ridge (for UNIX), and HSF (for Mac) extensions to the ISO9660 standard are used to accommodate long filenames rather than the eight-character DOS filenames that the ISO9660 standard supports.

-l—Allows 31-character filenames; DOS does not like it, but everyone else does.

-o—Defines the directory where the image will be written (that is, the output) and its name. The /tmp directory is convenient for this purpose, but the image could go anywhere you have write permissions.

/source_directory—Indicates the path to the source directory; that is, the directory containing the files you want to include. There are ways to append additional paths and exclude directories (and files) under the specified path; it is all explained in the man page, if you need that level of complexity. The simple solution is to construct a new directory tree and populate it with the files you want to copy and then make the image using that directory as the source.

Many more options are available, including options to make the CD bootable.

After you have created the ISO image, you can write it to the CD with the cdrecord command:

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matthew@seymour~:$ cdrecord -eject -v speed=12 dev=0,0,0 /tmp/our_special_cd.iso

The options used in this example are as follows:

-eject—Ejects the CD when the write operation is finished.

-v—Displays verbose messages.

speed=—Sets the speed; the rate depends on the individual drive’s capabilities. If the drive or the recordable medium is poor, you can use lower speeds to get a good burn.

dev=—Specifies the device number of the CD writer.