Vector graphics shoot-out: Inkscape v CorelDRAW

Vector-based images are the mainstay of digital graphic design. In this two-part article we compare some of the best free and open-source software (FOSS) for creating and manipulating (primarily 2D) vector images with the equivalent proprietary offerings.

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 one of this article looks at the history and background of vector image creation and examines Inkscape, an open-source application, and CorelDRAW, a proprietary program.

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.

Colour management

dispcalGUI, a GUI front end for Argyll, can be used with a number of commercial colorimeters to calibrate and profile Linux system displays.

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

GNOME Font Manager (top) and the font information box (bottom).

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.

Inkscape began life in 1999 as a Linux program called Gill (GNOME Illustrator), created by Ralph Levien. Around 2000 the code was adapted into SodiPodi by a team of developers under Lauris Kaplinski. SodiPodi (Estonian idiom for 'mish mash') was quite successful and at one point was ported to Microsoft Windows and other OSs. Then in 2003 four SodiPodi developers who wanted to focus on SVG compliance, improve the interface, and move to a more open development base, forked the code into the first version of Inkscape.

The maximised Inkscape workspace.

The latest stable release of Inkscape is version 0.48.2 (Ubuntu 12.04 LTS Software Centre includes version Inkscape is cross-platform and runs on Unix, Linux, Windows XP/Vista/7 and Apple Mac OS X. The free and open-source software is released under the GNU GPL 2 June 1991 licence.

Since Inkscape is FOSS it can be compiled in either 32-bit or 64-bit versions, and most Linux distributions will include the appropriate binary packages. Multi-threading support is provided for the processor-intensive filters — File / Inkscape Preferences / Filters / Number of threads. Memory use can be monitored through Help / About Memory. There's a page on the Inkscape wiki for those familiar with Illustrator, Inkscape for Adobe Illustrator users. Another page called Adobe Tool Map lists the control equivalencies, where they exist, between Illustrator and Inkscape. The release notes for version 0.48 of Inkscape are also a useful reference.

A number of Inkscape extensions are available from the Inkscape wiki.

Inkscape user interface

The window on the left shows Inkscape launched as Document 1. Document 2 on the right is the result of opening a new document from the File / New menu in the first window.

Unlike most other vector-editing programs, Inkscape has the slightly odd convention of opening as a small, rather unimpressive-looking window when launched. This may be because a new document opened from within Inkscape opens as a completely fresh instance, with no paging or window/document switching option available within the Inkscape menus. The File / New (document) menu offers a wealth of choices for preset document types (34 in all), including everything from DVD slip-covers to business cards.

Along the top of the Inkscape window is the standard application text with drop-down menus; below that is the icon-based Command bar, which duplicates some of the text menu choices, and below that the Tool Controls bar. There is a vertical Tool box along the left edge and vertical Snap menu along the right edge. At the bottom is a Palette bar and a Status bar. Inkscape designates the centre area of its display, where images are actually drawn, as the Canvas.

Layer control in Inkscape

The Inkscape Layer menu.
Inkscape layer switching from the Status bar.
The Inkscape Layer dialogue.

Compared to CoreDRAW for example, layer control in Inkscape is perhaps less elaborate, although there are three points of user interaction; the Layer drop-down from the top menu, Layer switching on the bottom Status bar and the Layer dialogue (Shift-Ctrl-L to open), which appears to the right of the Canvas.

Although the layer dialogue duplicates some of the functionality of the Layer drop-down and the Status control, such as renaming layers and changing their order, it's the only place where layer blend mode and opacity can be changed. Unlike CorelDRAW, it does not provide an expandable tree display of all the objects within a layer and of their groupings. Clicking on any drawing object automatically selects the layer that object is on.

Dimensions and guides in Inkscape
The dimension default for a freshly installed copy of Inkscape is 'px' (pixels) with A4 as the page size. Dimension units can be set as cm, ft, in, M, mm, pc, pt or px. The typographic terms picas and points are represented by 'pc' and 'pt' (a pica = 12 points or 1/72nd of a foot).

The pixels setting is a little misleading because it does not refer to the resolution of the display system, but defaults to 90dpi ('dots per inch' rather than 'pixels per inch'). The setting refers to the required output resolution.

The ruler zero point defaults to the bottom left corner of the drawing page, which is not so unusual. However, unlike CorelDRAW, by default Inkscape uses bottom-left as the zero reference for ALL drawing objects. This makes it difficult to centre, for example, ellipse objects representing drill holes on the intersection of guide lines. This is where the Snap menu on the left of the Inkscape workspace comes in: snap behaviour can be changed so that the centre of object snaps to guidelines by clicking the 'snap to rotation centre' button (it resembles a '+' sign) in the Snap menu.

The Inkscape guide coordinate entry box is opened by double-clicking on a guideline. Coordinates are given as X and Y rather than, as in CorelDRAW, H and W.

Also unlike CorelDRAW, guidelines are not treated like other drawing objects where the same H and W coordinate boxes are used. Instead, to position guides by entering coordinates requires double clicking on a guideline to open a floating coordinate entry box.

Inkscape Filters

Complex effects can be achieved quite quickly in Inkscape using Filters, although at the expense of performance.

Inkscape provides a good range of complex filters, over 200 of them, via the top-level Filters menu. Inkscape operates in RGB, and although CMYK colour values can be used, the filters are never disabled for CMYK as they are in some other vector editors. Using the appropriate filter it's easy to produce a graphic element for buttons, for example, or give a drawing object the texture of hand-laid paper.

Some of the filters are extremely processor-intensive and can slow zooming, or moving a drawing object, down to crawl. The performance impact can be minimised by choosing a lower display quality in Inkscape preferences / Filters, or by turning the filters off while editing an image from the View / Display mode menu.

Colour management in Inkscape

The colour management panel in Inkscape
In Inkscape the soft-proofing colour-managed display can be enabled and disabled by mouse-toggling the colour space symbol at the bottom right intersection of the scroll bars.

Like many open-source applications that require colour management, Inkscape uses the LittleCMS library. For rendering vector images into bitmaps it uses the Cairo library, which does not currently support colour separations for CMYK images. Consequently Inkscape cannot, for now, preview or perform separations.

With suitable display and print profiles installed, Inkscape's colour-management settings can be adjusted from the Inkscape Preferences / Colour Management panel. Images can be soft-proofed by toggling colour management on and off, simulating the appearance of the printed output, by clicking on the small colour-space symbol at the bottom right corner of the canvas.

An article from Libre Graphics World explains colour management and CMYK in Inkscape 0.48 in more depth.

Inkscape file import and export
Although SVG is the native file format, Inkscape can save files in any one of 23 formats, including PDF and PostScript. The import of some file types — CDR, PLT, SK1, and WMF — requires the use of a separate command-line tool called UniConvertor. This was originally developed for the sK1 project, another open-source vector illustration program that's now deprecated and being redeveloped as PrintDesign. A generic command for UniConvertor might be: uniconvertor drawing.cdr drawing.svg, to convert from Corel format (CDR) to Inkscape SVG.

UniConvertor version 1.1.4 is installed on Ubuntu 12.04 when Inkscape is installed.

Other FOSS vector graphics software
Other FOSS vector editors than those covered in this article are available. Some, like Xara Xtreme for Linux, are no longer under development. And as mentioned above, the sK1 project was recently restarted due to a change in direction.

Back in 1987 Canadian software company Corel decided it wanted a graphics program to bundle with its desktop publishing systems. CorelDRAW 1.0, written by Michel Bouillon and Pat Beirne, shipped in 1989 and ran on Microsoft Windows. Corel now ships CorelDRAW as part of a suite of eight programs. The current version, Graphics Suite X6, comprises PHOTO-PAINT, PowerTRACE, Website Creator (as a post-install download), CAPTURE, CONNECT, PhotoZoom Pro2 and ConceptShare, along with CorelDRAW.

Acknowledging the dominant market position of Adobe's Illustrator, CorelDRAW even has a workspace setting that more closely mimics that of Illustrator than Corel's default.

 CorelDRAW Graphics Suite X6 is supplied with a beautifully designed hardback guidebook of just over 300 glossy pages. The book demonstrates the use of many of CorelDRAW's features with examples, and comes in a slip cover with software DVD in a pocket on the inside cover. A quick-reference card is included, and the book is also available as a PDF.

Further free tutorial resources relating to specific tasks are available from Corel's website, along with various third-party tools and plug-ins.

CorelDRAW Graphics Suite X6 costs £478.80 (inc. VAT; £399 ex. VAT) from Corel's website for the box version (and, strangely, one penny less for the download version). Lower prices are available elsewhere.

See the April 2012 review of CorelDRAW Graphics Suite X6 by Mary Branscombe for more in-depth information.

CorelDRAW X6: User interface

The CorelDRAW X6 opening screen with the Help/About splash screen displayed. 
CorelDRAW X6 with an image file opened.

CorelDRAW X6's user interface is broadly similar to Illustrator and Inkscape: the majority of the display area is used for the image window and this is framed by the Menu bar, the Standard toolbar and the Property bar across the top. The Toolbox occupies the left edge, the Color Palette is on the right and across the bottom are the Image palette and the Status bar.

What's new in CorelDRAW X6?
With X6 Corel has introduced native 64-bit operation and multi-core processor optimisation, improving performance and allowing users to work with larger and more complex image files. Import and export compatibility has been improved with enhanced support for Adobe Creative Suite, Acrobat and Microsoft Publisher file formats. New or enhanced features in CorelDRAW X6 include a redesigned Object Properties docker, four new Shape tools, improved Master Layers, page numbering, new alignment guides, advanced OpenType support and new Color styles and Color harmonies.

Text effects and textures in CorelDRAW X6
Unlike Inkscape, CorelDRAW does not have menu selections for filters and textures, so to create something like the gold effect text on a textured background shown in the Inkscape screenshot takes a lot more work using the basic tools, such as contour, fill and outline.

Layer control in CorelDRAW X6

The layers and drawing objects used in this CD cover are displayed and can be manipulated from the Object Manager opened on the right of the display. Page tabs along the bottom access further pages in the file with different versions of the design.

Layers in CorelDRAW X6 are controlled entirely from the Object manager (Tools menu / Object manager); new layers and Master layers can be added or even deleted from there.

CorelDRAW X6: Rulers, guides and dimensions


CorelDRAW's rulers and guides, and the drawing object position and rotation boxes, are in the Property bar. 

Guides in Corel are dragged and dropped from the horizontal or vertical rulers just like Inkscape, but their position and inclination are displayed in the same boxes on the Property bar used for other drawing objects.

Position and angle of rotation can be precisely set to an accuracy of three digits (for mm units) by typing the required values directly into these boxes. By default, the centre of all drawing objects is used as the reference point, so when other drawing objects are aligned with guides through their centres, their coordinates are the same. This makes object positioning through entering coordinates very easy and objects can be resized without disturbing their position.

When an object tool is selected from the Toolbox to draw an object, the related properties displays for position, dimension and so on open in the Properties menu bar.


CorelDRAW's New Document panel with the web page format selected, showing all dimensions in pixels. 

Units of measurement in CorelDRAW are set according to the document type chosen when a new document is opened. CorelDRAW provides a wide range of preformatted document types: when an A4 document is chosen, for example, all dimensions grids and rulers are set to millimetres; if a web page document type is chosen the dimensions are set to pixels — and so on.

The units for page, grid and rulers can be set in the Options panel.

Measurement units can be set through the Options menu, independent of the document format chosen, to inches, feet, yards, miles, millimetres, centimetres, meters, kilometres, picas, points, ciceros, didots, Q and H. Ciceros and didots are French typographic measures where a cicero is 1/6th of a French inch and is equal to 12 didots. Q is used for metric fonts, where 1Q = 0.25mm, and is commonly used in Japan. H is the same size as Q but is used for spacing.

CorelDRAW X6: Colour management

The dialogue boxes for the global default colour management settings (top) and for individual documents (bottom) in CorelDRAW.

Colour management is a concept that many users — particularly less technical graphic artists — find difficult. Corel has tried to make its colour management settings more easily understood over the years, and has settled on an approach that quite closely resembles Adobe's.

CorelDRAW has both global default colour management settings and settings for individual documents. The default settings apply globally and are reflected in the individual document's dialogue until they are edited. Default colour mode and document colour mode can be set to either CMYK or RGB and these document options are also available when a new document is opened.

Documents can be soft-proofed by selecting Tools / Proof colors. The colour profile of the required output device must be selected in the Color Proof settings (Tools / Color proof settings).

CorelDRAW X6's print panel, showing the print separations selection in the Color tab. Further settings are available in the Separations tab.

Colour separations can be previewed or printed from the File / Print menu selection. A print control panel allows various separation options to be chosen.

Inkscape and CorelDraw: pros and cons
Although it has lost ground to Adobe and is now only available in a Windows version, CorelDRAW remains an extremely capable vector image editor and should not be overlooked. Sold as a well-appointed graphics suite, you also get seven other graphics applications and utilities in addition to CorelDRAW itself. The enhanced support for file exchange with Adobe products in X6 minimises interoperability problems and makes CorelDRAW X6 Graphics Suite a viable choice in an Adobe-dominated market.

Like the majority of FOSS creative software, Inkscape lags behind the proprietary products in terms of features, but it is cross-platform and, of course, free. The large choice of filters allows some complex effects to be achieved very quickly, and although it's not as user-friendly as CorelDRAW at first, the snap options are extensive. Because it's free, some designers use Inkscape to supplement and support their workflow with proprietary vector editors.

Inkscape does not use a native interface under Mac OS X, but runs on the X11 window layer. If you need spot colours, fully-developed colour management, CMYK and separations on any platform, Inkscape is not the best choice. However, print publication is less important these days than it was, and as it's based on the SVG specification, Inkscape is eminently suitable for use as a web graphics creator/editor.

(To be continued...)


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