LXF117.tut_gimp.pdf

Tutorial Gimp

Gimp Open source image-editing

software you can get your teeth into

Gimp: use other tools

Mixing raster, vector and text is easier than you think. Michael J Hammel

explains how to integrate Gimp with Inkscape, Scribus and OpenOffice.org.

Gimp’s Text tool provides a button for converting a text

layer to a path that can then be edited using the Path tool.

work with the Gimp to produce images for the

web, many have more varied needs. Cartoonists

need vector support to tweak drawings, office workers need

images for presentations and desktop publishing requires

both. Gimp can fill the needs of all these users. In fact, Gimp

integrates easily with many desktop applications; the trick is

to understand the requirements of each application and the

reason we use them.

This month we’re going to learn how to integrate Gimp

with three popular Linux desktop tools: Inkscape, Scribus and

OpenOffice.org. We’ll learn how to use the exported output

from any one application with the Gimp and how each can

import Gimp images. Where applicable we’ll also discuss use

of drag and drop between applications.

A common thread in this discussion is file formats. Gimp

works with many formats, including GIF, JPEG, PNG and TIFF

and can import both PostScript and SVG vector formats.

While JPEG and GIF suffice for the web, TIFF or PNG are

better choices when working on print documents. PNG is also

preferable for digital presentations, because its lossless

format is better suited to dynamic scaling and it offers a

range of transparency effects. Where EXIF data from digital

cameras needs to be retained, the TIFF format is often the

best choice. TIFF is also preferred for work that needs to use

alternate colour spaces, such as CMYK. For vector formats,

SVG is the best option for export or import between multiple

applications, though support for PostScript import might be of

higher quality in some cases.

Another common issue is dpi settings. For the web and

digital presentations 72dpi or 96dpi is fine. However, if you’re

printing, consider the quality of the output. A low 150dpi will do

for a flyer for the local children’s choir, while the high-end

restaurant menu is better served by 300dpi.

Keep these common threads in mind as we explore the

integration of the Gimp with Inkscape, a popular open source

vector graphic illustration tool.

Gimp and Inkscape

Gimp does wonders with pixels, but working with text is often

more than pixel editing. The latest version of Gimp enables you

to transform a text layer into a path so that the text can be

manipulated manually, but this isn’t Gimp’s forte. It’s best to

leave it to a vector tool such as Inkscape.

Inkscape’s text management features are more extensive

than Gimp’s and enable easy creation of text along a curve

with kerning adjustments. We’ll now look at how to do this and

how to adjust the the spacing of the letters, before we move

the text into the Gimp.

Start up Inkscape and you’ll see a blank page. Now choose

the Text tool from the toolbar and type ‘Integrating Gimp with

Inkscape. Use the Select tool to position the text in the centre

Our

expert

Michael J

Hammel

is a contributor to

the Gimp project

and the author of

three books on the

subject, including

his latest, The

Artist’s Guide to

Gimp Effects.

Last month We drank a toast to the completion of the wine bottle tutorial.

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W hile a vast number of desktop users are content to

Gimp Tutorial

Gimp: use other tools

In Inkscape,

the text can

be edited in

place and the

letter positions

can be edited

further either

independently or

as a group.

of the top half of the page. Next, choose the Bézier tool. Click

in the canvas once, then click again but drag before releasing

to create a curve. Release the mouse button, then click and

drag in one more spot. Release the mouse button and hit

Enter to complete the curve.

As a vector tool Inkscape creates objects, and selecting

these is similar to selecting a path in Gimp. Use the Select

tool and click on an object to select it. To place the text along

the curve, first choose the Select tool from the Toolbox and

then click on the text. Hold down the Shift key and click on

the curve. Now both objects are selected. Under the Text

menu at the top of the Inkscape window, choose ‘Put on Path’.

The text is aligned from left to right along the curve.

The text on the path is still in vector format, so it can be

edited some more. First we must expand the space between

letters to flow the entire distance of the curve. Choose the

Text tool from the toolbar and then click anywhere in the text

object. Hold down the Alt key and use the < and > keys (and

possibly the Shift key, depending on your keyboard layout) to

proportionally decrease or increase the space between

letters. Adjusting space in this way is known as kerning. Note

that the space between letters is not exactly the same. The

space is adjusted based on the two letters that bound it. This

produces a more natural flow for the letters.

A leading question

While both Gimp and Inkscape can adjust letter spacing, only

Inkscape makes it easy to adjust the vertical positioning of

letters. Use the arrow keys to move the text cursor in front of

the ‘I’ in ‘Inkscape. Hold down Shift and use the Right arrow to

select the letters ‘Ink. Hold down the Alt key and then tap the

Up arrow 24 times. Still holding Alt, tap the Right arrow 15

times. The letters move vertically and to the right, positioned

above the remaining letters.

If no letters had been selected then all characters after the

text cursor would have been moved (try this to see what

happens to the ‘e’ in ‘Inkscape’!). Similarly, if there had been

multiple lines of text, the spacing between the lines could

have been edited using Ctrl+Alt and the < and > keys.

To move this curved text to Gimp, save it in Inkscape and

load the file into Gimp manually. We have to do this because

drag and drop between the two doesn’t work with a vector

text object, and the Inkscape project can’t be saved to file and

opened in Gimp as the text isn’t yet in a path format.

Ideally text should be in path format for use in Gimp. To do

this, select the text object in Inkscape then click on the Path >

Object To Path menu option. Now save the project to a file.

The default format for Inkscape project files is SVG, which is

what’s required for importing into Gimp.

Open the file in Gimp. Don’t worry about the Page Size

dialog that appears, as Inkscape’s default page size will

import to 744x1052 pixels at 90dpi. Note that once you

become more familiar with Inkscape you may want to make

changes to the size of the image when opening it. More

important here is to make sure that the Import Paths option

in this dialog is set, but not the Merge Imported Paths option.

The former allows for the text to be imported as a path in the

Gimp, and having it in a path allows us to scale it without

losing the quality of the rendered text.

We can convert the path to a selection to fill it later on, or it

can be stroked after scaling. Don’t merge the paths from

Inkscape, because the curve itself (the curved line around

which the text is formed) is included with the curved text.

Half the job of migrating vector images from Inkscape to

Gimp is integrating these desktop tools. Inkscape can load

raster images created with Gimp. Since the images are linked

rather than embedded into an Inkscape project, changes

made to the Gimp image will cause the Inkscape project to be

updated the next time it’s reopened. It’s also possible to drag

Gimp layers directly into Inkscape, although doing so embeds

the image in the project file, with the consequence that later

updates to the layer won’t show up in the Inkscape file.

Vector artwork, such as cartoons, are often drawn using

tools such as Inkscape and painted in Gimp. The process for

migrating this from Inkscape to Gimp is similar to working

with text along a curve, without needing to convert the text an

object before saving the Inkscape project. Once imported, the

vector paths can be stroked or converted to a selection and

filled with solid colours, gradients and patterns. Making the

selection and filling it with a gradient is easier in the Gimp

because there’s no need to mask objects, as there would be if

the process were done in Inkscape.

Gimp and Scribus

Scribus is a page layout tool, meaning it’s useful for creating

posters and flyers, among many other types of print media. It

benefits Gimp users in its support for duotone, tritone and

quadtone images – these are halftone images printed with

The

default

Inkscape

toolbar is

a single

vertical row

on the left

of the main

window.

The tools

highlighted

are, from

top to

bottom,

the Select,

Bézier and

Text tools.

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April 2009 Linux Format 89

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Tutorial Gimp

This sort of

positioning of

individual or

subgroups of

letters cannot

be done in

Gimp without

fine-tuned path

editing. After

you’ve kerned

them, the letters

spread across

the length of the

curve.

pixels. The image will be placed in the image frame but may

not fit exactly. Right-click on the image and select Adjust

Frame to Image to shrink or grow the frame as is appropriate

to fit the image.

Scribus provides a limited but powerful set of image

effects. In the same right-click menu, select Image Effects to

open the Image Effects dialog. Select Duotone and click on

the ‘>>’ button to add it as an effect. The Options area of the

dialog enables you to choose the two colours to use for the

duotone. To achieve good midtone and highlights, choose a

high-contrast set of colours, including one that’s black. To

reduce printing costs, pick pure Cyan, Magenta, Yellow or

Black. Tritone and Quadtone can be created in the same way.

Scribus makes integration with Gimp easy, however it’s a

one-way integration. By default, the Scribus external tool for

editing raster images is Gimp, but this can be changed in the

Preferences dialog. With the image converted to duotone, it

can be edited directly in the Gimp. In the right-click menu

choose Edit Image. Because the image is linked to the Scribus

document and not embedded in it, the image that’s opened is

the one saved to disk, so the duotone effect is not directly

editable in the Gimp. Instead, export the page to an image file

by clicking File > Export > Save As Image. While there’s a

method of exporting just the image object, it requires the use

of the Crop tool in the Gimp Toolbox to clip the duotone

image out of the exported image from Scribus.

Gimp and OpenOffice.org

OpenOffice.org is a collection of office applications for word

processing, basic drawing, presentations and spreadsheets.

Each one supports the use of raster image files in various

formats and with varying amounts of image editing features.

Layers from Gimp images can be dragged directly into all

of these applications. Dragging a layer embeds the graphic in

the OpenOffice.org application file. Alternatively, save a Gimp

image to any common raster file format, then manually open

it in an OpenOffice.org application. This process links the file

so that changes to the Gimp image are picked up the next

time OpenOffice.org is started.

If you drag layers into an OpenOffice.org application, the

dpi settings from the Gimp image aren’t imported. If you want

the dpi settings to be honoured by OpenOffice.org, save the

Gimp file to disk first.

There are no special tricks to using Gimp images in

OpenOffice.org applications, but a little imagination can make

using Gimp with OpenOffice.org more creative. For example,

two, three or four inks. A halftone image is a single-colour

image created with collections of dots. The primary purpose

of a duotone is to bring out midtone and highlights in an

image. Tritone and quadtone processes increase depth, effect

and quality. Duotone images are less expensive to produce in

large-quantity, high-quality print runs.

Scribus enables you to easily create this type of image and

can convert existing Gimp images likewise. Scribus starts

with a blank page, much like Inkscape. Click Insert > Insert

Image Frame to add a frame then drag through the page with

the mouse to size it. The initial size doesn’t matter, we’ll resize

it to fit the image in a moment.

Right-click in the image frame to open a menu. Select Get

Image, then choose an image saved from Gimp. Scribus

supports many raster formats including JPEG, PNG and TIFF.

For the purposes of this tutorial, the image shown is 237x238

When opening an SVG, choose to import paths but don’t merge them. This

allows scaling and rendering of the text without rendering the curve itself.

This vector art from OpenClipart.org was imported from

SVG into Gimp. Selections and bi-linear gradients add depth.

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Gimp Tutorial

Scribus exports the

entire page as a single

layer using PNG or SVG,

even with multiple layers

in the Scribus document.

PNG may be easier to work

with since it provides a

solid white background.

Importing the image

is extremely easy with

a mature page layout

tool such as Scribus.

you can create various types of backgrounds with gradients,

outlines and patterns in Gimp and dragged into Impress

presentations on a slide-by-slide basis. Creative banners can

be added to Calc spreadsheets, and you can size to fit

cascading screenshots of desktop application windows for

print documentation using dpi settings in Gimp.

The Gimp’s editing features are far more extensive than

any of the OpenOffice.org applications alone provide – it’s a

matter of using the right tool for the job.

Draw is a less sophisticated graphics tool than Gimp, but it

does offer some interesting features. Any 2D graphic can be

quickly mapped to 3D in Draw, though the result is not always

ideal. Gimp’s Map Object filter is much slower and a bit less

interactive, but offers much higher-quality mapping on a

variety of shapes. But Draw is really useful to Gimp users

thanks to its predefined shapes. In Draw these shapes are in

vector format, which makes them easy to scale and modify.

For example, Draw provides us with multiple types of callout

shapes – the small bubbles that are associated with

characters speaking in a comic strip. These shapes can be

sized without losing quality in Draw. To get them into Gimp

simply copy them in Draw by clicking Edit > Copy or pressing

Ctrl+C. Then paste them in a Gimp image window. This is a

much easier process than trying to hand-draw the somewhat

odd shapes provided by the callouts.

Summary

This month’s tutorial could be viewed as a laundry list of

things the Gimp can’t do, but this isn’t about missing features.

Instead it’s about using the right tool for the job. No single

tool does everything and in truth, no one really wants such an

application. Such a program would be unwieldy to use, with

so many buttons, toolbars, and windows. Instead, it’s better

to define a workflow into a series of tasks that can be

accomplished with a variety of tools, then merge it all

together at the end. Use OpenOffice.org and Scribus for

document layout and management and leave the graphic

design to tools like the Gimp and Inkscape. LXF

Once the duotone effect is applied to the image frame, it

can be edited directly in the Gimp.

3D mapping is fast in Draw but its predefined shapes, like the callout and

puzzle piece shown here, are what attract Gimp users to the application.

Next month We’re turning simple effects into a classy advertising poster.

April 2009 Linux Format 91

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