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GIMP 2.6 for Photographers

De
385 pages

Image editing has become a crucial element in the photographic workflow. Image editing tools, most notably Photoshop, are usually sophisticated and deep applications, and are fairly expensive. The only open source tool in this market is the GIMP, which has developed into a powerful, multiplatform system running on Linux, Mac OS X, and Microsoft Windows.

GIMP 2.6 for Photographers is a beginner's guide to the only open source image editing tool that provides a low-cost alternative to expensive programs such as Photoshop. Topics include the basics of image editing and simple adjustments, as well as advanced techniques using layers and masks, stitching panoramic images, and preparing high-quality black and white images. The most important editing functions are presented in individual, easy-to-follow workshops.

GIMP 2.6 for Photographers has evolved from classroom materials that the author developed and taught in courses and workshops on image editing with the GIMP.

The upgrade to GIMP 2.8 that is discussed in the book can be found at rockynook.com for a preview and more details.


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GIMP 2.6 for Photographers Image Editing with Open Source Software
Klaus Goelker
GIMP 2.6 for Photographers Image Editing with Open Source Software
Klaus Goelker, klaus.goelker@goelker-online.de Editor: Gerhard Rossbach Copyeditor: Judy Flynn Layout and Type: Jan Martí, Command Z Cover Design: Helmut Kraus,www.exclam.de Printer: Tara TPS Co., Ltd. through Four Colour Print Group Printed in Korea
ISBN 978-1-933952-49-9 1st Edition © 2011 by Klaus Goelker
Rocky Nook Inc. 26 West Mission Street Ste 3 Santa Barbara, CA 93101 www.rockynook.com
Library of Congress Cataloging-in-Publication Data
Goelker, Klaus. [Fotobearbeitung und Bildgestaltung mit GIMP 2.6. English] Gimp 2.6 for photographers : image editing with open source software / Klaus Goelker.  p. cm. ISBN 978-1-933952-49-9 (soft cover : alk. paper) 1. GIMP (Computer file) 2. Photography--Digital techniques. 3. Image processing--Digital techniques. I. Title. TR267.5.G56G64413 2011 775--dc22  2010027984
Distributed by O‘Reilly Media 1005 Gravenstein Highway North Sebastopol, CA 95472
Many of the designations used by manufacturers and sellers to distinguish their products are claimed as trademarks of their respective companies. Where those designations appear in this book, and Rocky Nook was aware of a trademark claim, the designations have been printed in caps or initial caps. They are used in editorial fashion only and for the benefit of such companies. They are not intended to convey endorsement or other affiliation with this book.
No part of the material protected by this copyright notice may be reproduced or utilized in any form, electronic or mechan-ical, including photocopying, recording, or by any information storage and retrieval system, without written permission of the copyright owner. While reasonable care has been exercised in the preparation of this book, the publisher and author assume no responsibility for errors or omissions, or for damages resulting from the use of the information contained herein.
This book is printed on acid-free paper.
T A B L E O F C O N T E N T S
Table of Contents
Chapter 1  Basics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
1.1 Preface to the Extended Second Edition . . . . . . . . . . . . . . . . . 4
1.2 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 1.2.1 Using GIMP 2.6 – About This Book . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 1.2.2 About GIMP 2.6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.3 Introduction to Digital Image Editing . . . . . . . . . . . . . . . . . . . . 7 1.3.1 Characteristics of Pixel Images. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 1.3.2 Resolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 1.3.3 Screen Colors – Color Models and GEGL, the New Graphics Library . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 1.3.4 Important File Formats for Practical Work . . . . . . . . . . . . . . . . . . . . 14
1.4 Loading and Managing Digital Photos on the Computer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18 1.4.1 Using the Operating System’s File Management Tools to Import Images from a Camera . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 1.4.2 Using Wizards to Import Images . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 1.4.3 Using the Operating System’s File Management to Organize Photo Collections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 1.4.4 Helpers: Image Management Programs for Windows, Mac OS X, and Linux . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 1.4.5 Converting Camera RAW Image Formats under Windows, Mac OS X, and Linux: Freeware and Plug-Ins . . . . . . . . . . . . . . . . . 24
1.5 Get GIMP Running . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28 1.5.1 Where Can I Get GIMP?. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
1.5.2 Installing GIMP and Plug-Ins. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 1.5.3 Starting GIMP for the First Time. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 1.5.4 Is GIMP Insecure? Some Comments and Tips . . . . . . . . . . . . . . . . 35 1.5.5 GIMP’s Program Windows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 1.5.6 The Image Window, the Main GIMP Interface . . . . . . . . . . . . . . . . 41 1.5.7 Real Help – GIMP’s Help Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
Chapter 2  Using GIMP: Correcting and Touching Up Your Images. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .51
2.1
2.2
JPEG versus RAW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .52
Opening and Developing a RAW Format, or Digital Negative, with GIMP. . . . . . . . . . . . . . . . . . . . . . . . . . . . .53 2.2.1 Opening an Image in UFRaw . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 2.2.2 Features and Elements of UFRaw’s Main Window. . . . . . . . . . . . . 57 2.2.3 RawTherapee for Developing Raw Images . . . . . . . . . . . . . . . . . . . 75
2.3 Editing Images in GIMP. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .77 2.3.1 Opening, Setting, and Storing an Image—the Steps . . . . . . . . . 77
2.3.2 Opening an Image . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78 2.3.3 The Image Window – Your Workspace . . . . . . . . . . . . . . . . . . . . . . . 82 2.3.4 Rotating an Image by Fixed Values. . . . . . . . . . . . . . . . . . . . . . . . . . . 85 2.3.5 Changing the Image View Size (Zooming) . . . . . . . . . . . . . . . . . . . 86 2.3.6 Setting the Image Size and Resolution . . . . . . . . . . . . . . . . . . . . . . . 88 2.3.7 Scaling the Print Size of Images – An Example for Converting Resolution and Size . . . . . . . . . . . . . . 90
T A B L E O F C O N T E N T S
C O N T E N T ST A B L E O F
2.3.8 Cropping (Clipping) an Image . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
2.3.9 Saving Your Image . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
2.3.10 Before Printing – Calibrating Monitors and Color Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
2.3.11 Printing Images. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .103
2.4 Working with Scanned Images . . . . . . . . . . . . . . . . . . . . . . . 105 2.4.1 Prerequisites for Scanning. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .105
2.4.2
How Scanners Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .106
2.4.3 Problems When Scanning Printed Originals— the Moiré Effect. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .107
2.4.4 Calculations to Consider before Scanning. . . . . . . . . . . . . . . . . . .107
2.5 Scanning and Editing an Image . . . . . . . . . . . . . . . . . . . . . . . 110 2.5.1 The Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .110
2.5.2 Scanning Your Image . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .110
2.5.3 Editing a Scanned Image . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .113
2.5.4 Setting the Image and Determining the Angle – Measuring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .114
2.5.5 Rotating an Image – Using the Rotate Tool . . . . . . . . . . . . . . . . . .115
2.5.6 Cropping an Image – The Crop Tool . . . . . . . . . . . . . . . . . . . . . . . .117
2.5.7 Using the Gaussian Blur Filter to Remove the Moiré Effect . . .118
2.5.8 Setting the Contrast and Color— Levels (Tonality Correction) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .120
2.5.9 Setting the Contrast, Brightness and Color Intensity – Curves. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .123
2.5.10 Adjusting Hue and Saturation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .128
2.5.11 Overview of some of the Functions in the Colors Menu . . . . .130
2.5.12 Saving an Image in Compressed Format (JPG/JPEG) f or the Internet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .132
2.6 Touchup Work 1—Removing Color Cast. . . . . . . . . . . . . . . 136 2.6.1 What Is Touchup Work? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .136 2.6.2 Color Correcting Options. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .136 2.6.3 Using the Levels Function to Correct Color Cast . . . . . . . . . . . . .137 2.6.4 A Second Method to Remove Color Cast—Color Balance . . . .140
2.7 Touchup Work 2—Removing Spots, Dust, and Scratches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142 2.7.1 Why You Need Smooth Brushes—the Clone Tool . . . . . . . . . . . .142
2.7.2 Creating New Brush Pointers in GIMP and Importing Adobe Photoshop Brushes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .143 2.7.3 Preparing the Clone Tool Options. . . . . . . . . . . . . . . . . . . . . . . . . . .145 2.7.4 Using the Clone Tool for Touchup Work . . . . . . . . . . . . . . . . . . . . .146 2.7.5 The Healing Tool . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .149
2.8 Performing Magic – Editing Photographs with Graphic Filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150 2.8.1 Sharpening Images and Image Elements . . . . . . . . . . . . . . . . . . .151 2.8.2 Noise Reduction and “Smoothening” Images. . . . . . . . . . . . . . . .154 2.8.3 Simulating Film Grain – Covering Up Blemishes with Noise and Pixels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .161
T A B L E O F C O N T E N T S
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