In the first of this 'FOSS v proprietary' series we looked at some of the best software for editing and manipulating bitmap images. With digital photography such programs replace the earlier darkroom processes used for film, and the software borrows workflows and terminology from that earlier technology.
With vector graphics, the image is usually created entirely within the software application. In this case the software takes the place of the commercial artist's drafting table and borrows terminology and techniques from that world.
The advantage of vector images are that they scale well and have an efficient memory footprint, although they are also processor-intensive. As a result, highly detailed vector images can take a long time to render and redraw.
Part two (coming in September) looks at Adobe Illustrator and two simpler desktop applications — Microsoft's Visio and LibreOffice Draw. We'll also briefly examine some iPad drawing apps.
The technique of using layers in art goes back a long way. The early masters of oil painting learned how to use several layers of transparent paint applied over an opaque white base to create dazzling effects of light, shade and colour. Later, in commercial art and in animation, a stack of transparent sheets was used to build up a composite image with parts of the image on each layer. This allowed the creation of a number of different versions of, for example, an advertisement, by adding, exchanging and removing layers. Layers could easily be changed without having to recreate the entire image.
Vector editors borrow the older stack-of-transparencies technique, and the use of layers is basic to their operation. Good layer management and manipulation is vital in vector-editing software.
Rulers, guides and dimensions
For many commercial art applications, precise control of position and dimension within digital artwork is essential. Images for web or print pages can be rescaled to a degree, but artwork that relates to physical objects — product labels for example, or control files for CNC machining, or for laser cutting and engraving — must be accurate. The details of the user interface for units, rulers, guides and dimensions, and the control of snapping to guides, is one differentiator between vector graphics editors.
Accurate colour management is also vital in commercial art. Reproduced paint and print colours must appear as the designer intends, and remain consistent over a product range and over the products' lifetimes. Graphics software should include the ability to select input and output device profiles and to perform soft-proofing.
Apple is the pioneer in digital colour management, which is very well supported in Mac OS X and in Apple applications. Microsoft has now caught up, and colour management is well supported in its software too. Commercial calibration and profiling products are available for these proprietary operating systems. Colour management is still a little rough around the edges in Linux, but is possible via utilities such as LittleCMS, Argyll and dispcalGUI.
The SVG standard
The family of specifications for Scalable Vector Graphics (SVG) is significant because it's an open standard that's been in development by the World Wide Web Consortium (W3C) since 1999. SVG is XML-based and all the current leading browsers have at least some degree of support for it — early versions of Microsoft's Internet Explorer did not have native SVG support. SVG is currently at version 1.1 and supports not only vector graphics, but also raster graphics and text objects.
SVG is the native file format for the FOSS vector-editor Inkscape. Inkscape has full compliance with SVG version 1.1 as one of its design aims in order to be able to announce the release of Inkscape version 1.0 (the current version is 0.48). The SVG specification defines sRGB as the reference colour space, and so Inkscape uses sRGB as its working colour space.
The SVG standard does not include layers, but it does include groups and Inkscape layers are simply SVG groups with some extra Inkscape-specific parameters attached. Unfortunately these are not recognised by most other vector editors, but Inkscape layers can be preserved within an SVG file for import into other editors by first explicitly defining each layer as a group. Once imported, these groups can be cut and pasted into fresh layers.
Most vector editing software will display a long list of file types — either standards or native to other applications — that can be opened, saved and supposedly exchanged.
Closely related applications — Adobe's Photoshop and Premiere, for example — can often exchange files without problems, but exchanging files between an open-source application and a proprietary application — between Inkscape and Illustrator, for exmple — is almost always troublesome. Illustrator can save files in SVG but, like Inkscape, it uses a modified format with some Adobe-specific data attached.
In practice the process of exchanging files between one application and another frequently involves workarounds and reconstruction to arrive at a functionally identical copy open in another program.
File exchange, fonts and text
One obvious, but not insurmountable, problem is with text. Although the font files on a Windows system won't correspond with the font files on a Linux system, Windows TrueType font files can be copied to a Linux system and installed and managed using a utility like GNOME Font Manager or Fontmatrix. In Ubuntu, opening the Nautilus file manager and double-left-clicking on a font file will open the GNOME font viewer, which includes an install button. (Font copyrights should, of course, be observed.)
To ensure that an image displays with the correct fonts — no matter which system it is displayed on — it's helpful to make a note of the fonts used and to keep a backup of font files so they can be added to a system if required. The MyFonts website can be used to attempt to identify a font by uploading a bit map image. This functionality is built into CorelDRAW via the menu option Text / WhatTheFont?!.
Font dependencies can be removed by converting text to 'outline' — for example in Inkscape using the Path / Object to path menu choice, or similarly to 'curves' in CorelDraw using Layout / Convert to curves. However, once this is done it can no longer be edited as text.
When sending a completed piece of artwork off for further processing (for example to a commercial press printer), all layering and dependencies should be removed to produce as simple a file as possible in the required format.