Table Of ContentNUMBER
BY COLORS
Brand Fortner Theodore E. Meyer
B
C~L
A uide t Using Color
to Under t nd Technical Data
8rand Fortner Theodore E. Meyer
Fortner Research llC Fortner Research llC
Sterling, VA 20164 Sterling, VA 20164
USA USA
Publisher:Allan M.Wylde
Publishing Associate: Keisha Sherbecoe
Product Manager: Walter Borden
Production Manager: Robert Wexler
Manufacturing Supervisor:Jeffrey Taub
Cover Designer: lrene Irmfeld
Library of Congress Cataloging-in-Publication Data
Fortner, Brand, 1955-
Number by colors : a guide to using color to understand technical
data / Brand Fortner, Theodore E. Meyer.
p. cm.
Includes bibliographical references and index.
ISBN 978-1-4612-7327-1 ISBN 978-1-4612-1892-0 (eBook)
DOI 10.1007/978-1-4612-1892-0
1. Color. 2. Color separation-Data processing. 1. Meyer,
Theodore E. II. Tirle.
QC495.F6 1996
535.6-dc20 96-22982
Printed on acid-free paper.
© 1997 Springer Seienee+Business Media New York
Originally published by Springer-Verlag New York IBe. in 1997
Softcover reprint of the hardeover Ist edition 1997
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987654321
ISBN 978-1-4612-7327-1
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-Number by Colors
Prefac~e
Introduction
One of our favorite pastimes when we were small were those marvelous
"Color by Number" kits that you used to find in toy stores. These kits con
tained black and white drawings with a bunch of numbers on them. They also
included a fine collection of colored paints or pencils, and again each one had
a number.
What you did was find the number that was printed in a particular region
on the drawing, select the paint with that number on it, and fill in the region
with that color. After you had filled in enough of these regions, something
interesting happened.
What emerged on that drawing was not numbers, not color paints, but
something more: a painting that you yourself created, but also something that
was artistically vastly superior to anything that you could have made unaided.
It was almost magical, how you could turn numbers into colors.
In this book we start out by doing exactly the reverse: we will be turning
colors into I1Itmbers.1 In other words, we quantity colors as a way to understand
what on earth color is and how we can use it. In later chapters, we actually
1. Hence the title of this book: Number by Colors, the reverse of Color by Numbers.
Number by Colors vii
return to the original idea, by showing how numbers that represent scientific
data can be turned into colors, just like the old kits.
This book is designed for the working scientists and engineers who use col
or frequently. Perhaps they use color to distinguish different lines in a line
graph. Perhaps they use colors to illustrate different isosurface levels in a 3D
visualization of fluid flow. These researchers may feel that they are not making
the best use of color. In that case, this book is for them. On the other hand,
they may think that there is nothing subtle or interesting or deceptive about
using color. They are probably wrong, and this book is also for them.
To truly make the most use out of the visualization of technical data, you
must understand color, since many of the pitfalls of visualization revolve
around color perception. We feel that this book contains all the basic facts that
every technical person should know about using color.
Color vision is still a very hot research area. Many of the most basic facts of
color perception were unknown just a few decades ago. Even today we do not
know for sure why an object appears to be the same color, regardless of the
light source.
One final reason for this book is that we personally have found the topic
fascinating in its own right. We hope you do too.
A Quick Tour of This Book
Color starts with photons of light. It ends with comprehension of an image,
or insight into data that have generated that image. There are many steps be
tween that beginning and that end. In this book, we go over each of those
intermediate steps one by one.
We cover the first steps of going from photons to impulses in the brain to
the perception of color in Part I, "Color Physics, Physiology, Psychology." In
Part II, "Color Technology," we go from the perception of color to the de
scription of color, and then to the reproduction of color. Finally, in Part III,
"Color on Computers," we show how color reproductions can be stored in
computers, and how color can be used to represent data. A description of the
chapters in each of these parts is given in the following.
viii Number by Colors
Part I, "Color Physics, Physiology, Psychology"
Part I starts with the physics of photons, covers the physiology of the translation
of the photons into red, green, and blue signals, and then talks about the psy
chology of the translation of those RGB signals to the perception of hue, sat
uration, and intensity. The specific chapters are as follows.
• Chapter 1, "Spectral Analysis," gives a brief overview of concepts needed
in the rest of book about wavelengths, frequencies, spectra, light, and so
on. This material is included to make the book as self-contained as possi
ble. It may be skipped without loss of continuity.
• Chapter 2, "Eye, Ear, and Brain," talks about our senses of hearing and
sight. We start with a discussion of the ear, because it gives great insight
into color vision. We also discuss the physiology of the eye, focusing on
the details of color vision.
• Chapter 3, "Light Spectra to RGB," shows how light spectra translate into
the generation of red, green, and blue signals going to the brain.
• Chapter 4, "Hue, Saturation, Intensity," shows how the reception of red,
green, and blue signals in the eye translates to our perception of hue, satura
tion, and intensity in the brain.
Part II, "Color Technology"
In Part I we went over the fundamentals of color and biology. In Part II we
describe how we have chosen to describe and reproduce these colors. Today peo
ple define colors with a variety of mathematical models, which are described
in the first two chapters of this part. There is also a variety of technologies for
reproducing these colors, which are described in the last two chapters. The
specific chapters are as follows.
• Chapter 5, "Defining Colors-The CIE Color Diagram," goes into great
detail about the most important graphic in all of colordom, the CIE
Color Diagram. We show how the CIE diagram was constructed, why it
is so important, and how to use it.
• Chapter 6, "Defining Colors-Color Models," describes each of the most
commonly used mathematical models for colors, such as RGB, HSI,
CMYK, and so on. Many of these color models were created for specific
color reproduction technologies, which are described in the next two
chapters.
Number by Colors ix
• Chapter 7, "Reproduci11g Colors-Fundamentals," discusses the key concepts
needed to evaluate color reproduction technologies, such as pixels, reso
lutions, gamma correction, halftones, and dithering.
• Chapter 8, "Reprodllcing Colors-Teclmologies," enumerates in some detail
the most prevalent color reproduction technologies of today, such as pho
tography, printing, and video.
Part III, "Color on Computers"
For most researchers, interactions with color involve a computer. In the final
two chapters of this part we talk about how these colors can be stored on
computers, how they can be displayed, and how color can be used to visualize
technical data. The first chapter is needed to introduce fundamental informa
tion on the basics of storing and organizing any kind of technical data on
computers. This part contains the following chapters.
• Chapter 9, "Numbers in Computers," details the ways that data can be
stored digitally (as bytes, integers, fixed-point numbers, floating-point numbers,
ASCII text, etc.) and discusses the advantages and disadvantages of each
method. We then discuss the concepts of data dimensionality, data value, and
data location, and show how technical data can be categorized as column
data, 2D matrix data, 3D matrix data, and polygonal data.
• Chapter 10, "Color in Computers-Fundamentals," starts with the basics of
storing colors on computers, and then launches into a detailed discussion
of true color and index color images and their associated colortables. To
fully understand digitized computer images, it is vital that one have a fun
damental understanding of colortables and colortable manipulations.
• Chapter 11, "Color by Numbers-Using Color to Visualize Data," shows
how you can use the technology developed for index color images and
apply it to display 2D or 3D matrix data as pseudocolor or false color
images. We finish by showing how many of the facts that we have identi
fied throughout the book can be used to avoid visualization pitfalls.
x Number by Colors
Appendix
The one and only Appendix goes into some detail about how numbers, espe
cially color images, can be organized into graphics and scientific data formats.
Although this material is outside the main thrust of this book, it is pertinent
enough to include here.
• Appendix A, "Science and Graphics Data Formats," discusses the concepts
involved in standard data formats for science and graphics data. We finish the
Appendix with very brief summaries of the most popular science and
graphics data formats.
Navigational Tools
We have worked very hard so you will find it easy to locate information in
this book. Towards that end, we have included the following navigational and
organizational features:
• The book contains both a brief and an extended table of contents in the
preface, and an extended index at the end. Immediately before the index
is a glossary of key concepts and phrases.
• Each part in the book begins with a synopsis of the topics in that part.
• Every chapter in the book begins with an introduction and a series of
questions, and ends with a summary and responses to those questions.
Although Number by Colors could be used as a reference, we have designed it
to be readable straight through. If you wish to do this, we offer the following
suggestions.
Chapter 1 is background material, and can be safely skipped if you are fa
miliar with the basic concepts (see, e.g., if you can answer the questions posed
at the beginning of the chapter). The rest of Part I (Chapters 2 through 4) is
part of the core of the material of the book, and should be read straight
through.
The first three chapters of Part II (Chapters 5 through 7) are also core ma
terial and should be read carefully. The material in Chapter 8 on color tech
nologies can be sampled as need be. In Part III, Chapter 9 on Numbers in
Computers is pure reference, and can be safely skipped by the computer liter
ate. The last two chapters, 10 and 11, contain fundamental material dealing
with using color on computers, and should be read straight though.
Number by Colors XI
