Fie on Photoshop: Image Editing in Linux

By: Carla Schroder
Thursday, January 24, 2008 01:50:46 PM EST
URL: http://www.linuxplanet.com/linuxplanet/reviews/6455/1/

Overpriced Photoshop Begone

It has been said (so many times that I'm ready to start twapping people) that the most important missing killer app for Linux is a free Adobe Photoshop clone. Photoshop is a mature graphics editor with hundreds of features and plugins, the de-facto industry standard, and it retails for over $600. So a free-beer Linux clone would be a lovely thing indeed. But is all that Photoshop glory really necessary? In this series we'll answer that question, and then move on to bringing high-quality digital images to life in Linux itself, without having to use icky old Windows, or spending a pot of money.

Most Photoshop users barely touch its capabilities, and just like the idea of having it. Rather like my friend who buys only Snap-on hand tools, and carefully organizes them in their little red nests, and admires them, but hardly ever uses them. Snap-on tools are excellent, no doubt about it, but his needs would be served by a $30 kit from the local rejects outlet store. I suspect that a sizable number of Photoshop users find a way to acquire it without paying anything near its price tag, anyway, unlike my friend who pays full freight. So what does Linux offer for the discerning graphics artist and digital photo editor? Certainly far more than a $30 reject kit equivalent.

Gimp (GNU Image Manipulation Program) is the most popular Linux image editor. It's the oldest and most mature. Unfortunately, the poor thing is hardly allowed to stand on its own merits, but is continually compared to Photoshop, which is a bogus comparison. Gimp is first-rate at what it does, which is not to be a free-as-in-freeloader Photoshop imitation, but a perfectly good photo and image editor, especially for Web images. It uses similar tools and concepts to Photoshop (and every other graphics editor), but it is not Photoshop, which is a source of deep woe for a large, vocal number of people. I have the cure for your woe, fine people- stop it. The Gimp developers do not have the goal of duplicating Photoshop for your benefit, but creating a high-quality cross-platform image editor than runs on Linux, Unix, Mac OS X, and Windows.

So what, then, do you need Photoshop for? For best-quality professional color printing. Gimp does not support the CMYK or Pantone color spaces, which are essential for the most accurate commercial color printing. Gimp works in the RGB space.

RGB, CMYK, Pantone

So what are these RGB, CMYK and Pantone thingies? RGB is red, green, and blue. CMYK = cyan, magenta, yellow, and black. Pantone means the Pantone Color Matching System.

RGB is the basis for all colors emitted by computer monitors. We were taught in grade school that all the colors of the visible spectrum can be created by combining red, green, and blue light, even white light, though computer monitors only display a limited gamut. (Gamut is a term you'll see a lot; it means range of colors.) If you were a confused kid like me, you tried to make white by combining red, green, and blue paints. But this never worked, because pigments don't work the same way as light.

So for printing inks CMYK works best, and is the color system used by virtually all commercial printers, and better-quality home inkjet printers. You've seen the blah muddy colors output by low-end RGB inkjet printers, and the murky blacks that aren't really black, but more like the muck that results from grade school kids trying to make white with colored paints. CMYK produces nice crisp true blacks and true colors.

The Pantone Color Matching System goes beyond the CMYK gamut and defines thousands of additional colors, including special colors like flourescent and metallic colors. Colors that are not duplicated in the CMYK gamut are called spot colors. The Pantone company sells printed guides with swatches of each color and their index numbers, like PMS 100. So designers and printers and everyone involved have a common, standard system for specifying what colors to use. Even a lot of supposed professionals don't understand the differences between RGB and CMYK, and think that using a RGB-to-CMYK converter is sufficient. Unfortunately it's not, not even Photoshop's converter; you don't get perfect fidelity, but suffer noticeable color shifts.

Adding Pantone support to Gimp would open a legal morass. It's not entirely clear what Pantone, Inc. "owns". They don't own colors, and they don't own numbers. Copying and re-distributing their color swatch books is an obvious no-no, but what about building some sort of Pantone reference guide into Gimp? Adobe pays licensing fees to Pantone so they can build in a Pantone color-picker.

But the lack of a built-in Pantone color picker isn't such a big deal. Computer monitors vary in color, brightness, and contrast representation, so getting the best fidelity still comes down to matching swatches in a Pantone book. A bigger problem is Gimp not supporting CMYK natively, or higher bit depths. Someday it will--the problem is the core graphics engine is inadequate. It limits Gimp to 8-bit RGB. Modern graphics editors that are not hobbled by legacy code support 16- and 32-bit CMYK. Patience, Gimp fans, the day will come. Meanwhile, what's a Linux user to do?

The Krita Chronicles

The Krita image creation and editing program, part of the KOffice suite, was designed from the beginning with the needs of graphics professionals in mind. It has 32-bit color management, supports color profiling, supports RGB and CMYK natively, has a streamlined workflow, and whole batch of modern, sophisticated features that make Krita the real Photoshop Killer, for those who must have killers. Come back next week and we'll get going on learning how to use this wonderful application.

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