Most professional print products are created in Adobe's InDesign, Illustrator, and Photoshop products. However, the free Scribus [1] and Inkscape [2] application offer alternatives with which you can create technically flawless artwork for offset printing.

Sample CD Cover

Inkscape is still the most useful vector graphic program for design purposes. It provides a wide variety of tools and effects that give you the creative flow you need. You can also use it to integrate external bitmaps and texts.

Figure 1 shows the design for a CD cover in Inkscape. At the top, you can see the preparation for print setup that is used during the design for page size. The three millimeters wide red border is the so-called bleed that falls away during the sheet cutting. Because of the tolerances of the cutting machines, the design in this regard needs to proceed flawlessly.

Figure 1: This is how the design was created in Inkscape: The page size follows the template of the printing press. The light wedges at the bottom still appear at this stage without the strong blur added later.

The photo highlighted through cross-hatching was brought in directly in RGB color format. The conversion to press format of CMYK color space takes place while exporting the entire cover. The green polygons on the front and back side will get a blur of 90% in the setting for the object fill, resulting later in soft light spots. The text on the front side will get a soft blur through the Shadows and Glows | Drop Glow effect. The small wedge highlighted in magenta at the left edge of the ochre-colored border adds Blur on one side. For a useful introduction to the drawing and painting program, refer to the Inkscape guide [3].

True Colors

To have on-screen colors not deviate too much from what's printed, set the appropriate color profile for your monitor. You can find profiles on the Internet under icc profile , icm profile , or color profile and your monitor's model number.

You can often find the ICC or ICM file directly on the CD that came with your monitor when you install the driver in Windows. The Windows 7 setup copied the author's Asus monitor profile into the spool\drivers\color\ directory in C:\Windows\System32\ .

Some newer monitors have an sRGB mode [4] that adapts to the color representation in the profile of the same name. You can obtain these and other consistent profiles from Adobe [5]. Copy the ICC or ICM file into the /usr/share/color/icc/ folder that all Linux applications access. Some distributions also provide an adobe-profiles package or something of the sort.

Inkscape manages the profiles in File | Inkscape Preferences | Color Management as Display Profile and Device Profile (Figure 2). The Display Profile normalizes the screen reproduction and the Device Profile simulates the printing device's color rendering on the computer. Activate the printing color preview with Simulate output on screen . Check the Black Point Compensation box to optimize the brightness display. For Display Adjustment and Display Rendering Intent , choose Perceptual . Inkscape represents the print colors on screen so that they match human perception as much as possible.

Figure 2: Inkscape color management provides accuracy with the matching profiles for the screen (in blue) and printer (in red).

Generics

Print firms that don't use a standard profile, such as sRGB or CMYK, usually have their own profile that they can send you. If in doubt, ask for the color profile from the firm. Less pricy printers often save themselves this effort and work without any color management.

Such was the case in producing the sample CD cover (Figure 3). It shows a distinct, yet tolerable deviation between the screen display and print. I used the device profile common in Europe known as ISO Coated v2 . Tailored to common offset printing machines, it comes close enough in color reproduction, even when the printer works without color management.

Figure 3: On the left, you can see the final product; on the right, you see the view in Scribus. Although the differences are relatively small, they're nonetheless perceivable.

When selecting generic profiles use Coated for coated paper and Uncoated for uncoated paper (colors appear less bright). In any case, use generic profiles for monitors and printers without color management preference, because at least the conversion from RGB to CMYK color space gets done (see the "RGB and CMYK" box).

Figure 4: Subtractive color mixing in which the color pigments filter out spectral components from the white paper requires other primary colors (cyan, magenta, and yellow) as the additive color mixing of the red, green, and blue pixels of the monitor.

Profiling

To provide a color profile for the document, open File | Document Properties | Color Management and link the desired profile with the document. So far, Inkscape simulates the print colors in the CMYK color space only on screen. Even if you use the CMYK tab in the color picker, the program internally calculates the RGB colors. To change this, left-click an object with color fill and open the context menu Fill and Stroke . Change to the CMS tab and choose the color profile already selected for the simulation of the printing colors (Figure 5).

Figure 5: On the CMS tab of the Fill and Stroke dialog, you can link the colors of the object with the profile used for the printer property.

Inkscape doesn't create consistent CMYK documents, but instead assigns individual colors to the CMYK color space. These arrive as such in Scribus when importing the SVG files created in Inkscape. This color management and SVG import into Scribus create an unbroken workflow between the two programs, even with continuous color management – at least in theory. In practice, however, the shortcomings of the Scribus import filter make it far from perfect.

Thus, all graphic effects are lost during the SVG import. Even the simple blur of the green color wedge disappears, along with the drop glow in the text. To package these effects with help from Scribus into a standardized CMYK PDF, the only way is through a bitmap export from Inkscape. To make matters worse, the drawing program exports bitmaps and PDFs exclusively in RGB color space, which is why it's not suited for generating true color print templates.

Above Bands

To solve this shortcoming, you should first export all elements from Inkscape that Scribus can process as PNG bitmaps of 300-dpi resolution. Inkscape puts partial selections in separate files and keeps track of the associated filenames.

In the CD cover project, the front and back sides were exported in one piece and moved into a full-page graphic frame. Because the software produces low-resolution previews, even large bitmaps of many megabytes are not a problem. Before integrating the RGB bitmaps created in Inkscape, they must be converted to the CMYK color space. Use the convert command-line tool from the ImageMagick package (Listing 1).

$ convert rbg_image.png -intent perceptual -black-point-compensation \
  -profile /usr/share/color/icc/ISOcoated_v2_eci.icc cmyk_image.tiff

Give the convert command the path to the color profile that you used to simulate the printing color in Inkscape. The bitmaps then contain the CMYK color shading that Inkscape simulated on the screen. PNGs don't support CMYK colors, so you should use the TIFF format. You must also set the Rendering Intention and Blackpoint compensation as you did in Inkscape.

The back cover text was omitted when exporting from Inkscape. Because of sharpness factors, the body text is best developed in Scribus. To colorize it according to the design, import the Inkscape SVG files with File | Import | Get Vector File . Ignore all error messages and delete the import when you're done. The colors imported from the Inkscape files stay behind in the Scribus color palette (Figure 6).

Figure 6: Even if the Scribus import filter has its flaws, at least it accepts the colors associated with a color profile from Inkscape.

Be sure that all the colors in the Inkscape document that you want to access in Scribus are associated with the printing color profile, as mentioned earlier. If you want to define more colors in Scribus (Edit | Colors | New ), choose the CMYK color model and disable the Spot Color option, which requires a separate printing plate that can drive up costs unnecessarily.

As with texts, caution should be taken with printing colors in graphic elements. Because the printers don't rasterize, edges in resolutions less than 800 dpi tend to produce jagged effects. For optimal quality, therefore, you should use resolutions of at least 1200 dpi when exporting such objects, or save them as normal SVG . As long as they don't contain effects, Scribus imports such formats without a problem. The PDF export embeds the SVG elements just as Scribus does for texts as vector graphics that can be printed at any resolution.

The same applies to vector shapes that you draw directly. Among them are Bézier curves, polygons, and standard shapes such as circles and ellipses, but also arrows and smileys. The Scribus tools, however, don't have nearly the same scope of functionality as those in Inkscape.

Almost There

In Scribus, access Color Management in File | Document Settings (Figure 7). As before, choose the Monitor and Printer profiles. Use the printer profile for CMYK Images and CMYK Solid Colors . Don't even think of using RGB Images and RGB Solid Colors if you are going for technically correct printing processes.

Figure 7: As in Inkscape, Scribus color management is based on an RGB screen profile (in blue) and a CMYK printer profile (in red). Activate the check boxes at the bottom of the dialog for a simulation of the printer colors.

Next, select the Page Display and paper size via File | Document Setup | Document according to the master template and choose a Double Sided layout. Remember to leave a bleed of about three millimeters. Set the desired number of pages (Page | Insert ). For the front cover, use the frame tool to drag it into a full-page frame. Highlight it after inserting it using the Select tool (the white arrow) and adjust its position with the Properties palette (or F2) as to page size and bleed. Finally, load the Inkscape bitmap with Ctrl+I.

Ready to Go

Unlike Inkscape, Scribus is ideally suited for creating print templates. I created compliant PDFs according to the X-3 standard used in printing. You'll find the settings to do this in File | Export | Save as PDF . On the General tab, the Lossless – ZIP selection for the Compression Method prevents ugly compression artifacts (Figure 8). Compatibility sets the PDF subformat for the export. Only PDF/X-3 allows embedding color profiles and, thus, the correct color management at the print shop. Unfortunately, not all printers support this relatively new format. Check with your printer in advance about which PDF format they expect. The print shop used for the demo CD, for example, could support only the older PDF 1.4 format, which Scribus also supports.

Figure 8: Scribus can handle the PDF/X-3 format developed specially for printing. The Lossless – ZIP choice as Compression Method avoids degrading the quality of embedded images.

On the Fonts tab, you either embed all possible fonts (Embed all ) or convert them to curves, which avoids deviations more reliably. Under Colors , choose Output Intent: Printer for PDF 1.3 through PDF 1.5. Only X-3 PDFs allow embedding printer color profiles on the Pre-Press tab under Output Profile . Here, you activate at least the options Crop Marks and Bleed Marks (Figure 9), which the shop needs for printsetting. The Crop Marks define the inside dimensions of the artwork for the printer. The other marks outside this area are the Registration Marks , Color Bars , and Page Information that might make the printer's work easier, so activating them doesn't hurt.

Figure 9: On the Pre-Press tab, you'll find the physical print settings.

Conclusion

The bitmap export at 300 dpi and the color conversion with ImageMagick's convert makes a CMYK workflow possible with the Inkscape drawing program and the Scribus desktop publishing program. The former provides the graphically appealing design, and the latter generates industry-standard PDF files that printshops can process further.

The steps might not flow as seamlessly as with Adobe's Illustrator or InDesign programs. You may find, for example, that converting the vector shapes into high-resolution bitmaps can swell the size of the print template PDFs, and that unrasterized full-color images often get jagged effects in resolutions of 300 dpi, especially in texts. Many of these pitfalls, however, can be avoided with some extra legwork.