Color Specification

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来自 New York University Tandon School of Engineering 的课程

Information Visualization: Applied Perception

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New York University Tandon School of Engineering

Information Visualization: Applied Perception

个评分

课程 2（共 4 门，Specialization Information Visualization ）

This module aims at introducing fundamental concepts of visual perception applied to information visualization. These concepts help the student ideate and evaluate visualization designs in terms of how well they leverage the capabilities of the human perceptual machinery.

从本节课中

Color Perception and Color Spaces

Visualizing data with color7:13

Few Examples: Misusing Color in Visualization5:30

Color Perception15:39

Color Specification4:37

Color Space: RGB7:37

Color Space: HSV / HSL6:20

Color Space: CIE Lab/ Luv Part 14:13

Color Space: CIE Lab/ Luv Part 27:53

Color Space: CIE Lch/ HCL9:06

Quick Summary4:37

与讲师见面

Enrico Bertini
Associate Professor
Computer Science and Engineering
Cristian Felix
PhD. Candidate
Computer Science and Engineering

Now, after learning a little bit about how color is perceived by human vision,

the next step is to understand how to specify color.

What do I mean, specify color?

Well, I mean that when we want to practically use color,

especially in visualization as we will see later on, we want to be able to say,

I want this type of color.

Or I want these colors to have certain properties.

So how do we specify colors in a way that is helpful for

visual representation?

We need color specification systems.

And we need color specification systems that are reliable and

uniform across different devices.

If you think about it, that's not a trivial problem at all.

So if I want to reproduce a specific kind of color,

I want to be able to use a specification that can be reproduced

in different devices, which is a quite complex problem.

So, one important thing to know, as I already mentioned earlier,

is that every color can be expressed as the sum of three colors,

or in general, as we will see,

every color can be expressed in a three dimensional space.

So let's start with a somewhat simple example.

If you have three lights and one light is blue, one light is green, and

one light is red, what we can do is to change the intensity

of these lights to basically match an existing color.

If we can do that, we actually have a way to specify

numbers that describe a specific color.

Think about having a way to create a standard set of three lamps,

one is blue, one is green, and one is red.

And let's assume that it's easy to reproduce a standard

version of these lamps.

Then if I want you to reproduce a given color

that I've tested earlier, what I have to do is just to give you the number or

the value of these three intensities, the intensity of blue,

the uncertain intensity of green, and the intensity of red.

So this is the basis of a very large set of color spaces.

What is a color space?

A color space is a system typically of three variables,

in a three-dimensional space, that describes uniquely a color.

By giving, I give you three values, I'll tell you which space I'm using, and

you'll be able to reproduce exactly the color that I want to communicate to you.

So that's a very important concept and a very useful one in practice.

One thing to know about color spaces, before we dive into specific color spaces,

is that the three primary axis of each color space

basically define what is the gamut of the color space.

We choose the whole set of colors that can be

reproduced by this specific color space.

One important thing to know is that not all color spaces are equivalent.

What do I mean by that?

I mean that a given color space may reproduce a subset

of the full set of colors that humans can naturally perceive.

For instance, the RGB space, which I'm going to introduce next,

can cover a subset of all the possible colors that human can perceive.

In the next lesson, I'm going to walk you through different color spaces.

And as we will see, these color spaces have different

properties that make them more or less useful for

this organization design and color specification in general.

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