3 Color Operations

▼ |  | Graphics: Legacy Library

1 | Basic Commands
2 | Position Operations
3 | Color Operations
4 | Draw, Clear, and Flip Operations
5 | World Operations
6 | Miscellaneous Operations
7 | An Example
8 | A More Complicated Example
9 | Protecting Graphics Operations
10 | Mouse Operations
11 | Keyboard Operations
12 | Flushing
13 | Graphics Library as a Unit

On this page:

rgb
change-color
default-display-is-color?

Racket
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## 3 Color Operations🔗ℹ

A color can be represented in three ways: as a color index (an integer in 0 to 299, inclusive), as a color name string, or as a rgb value. All drawing functions which take a color argument accept colors in any form. An rgb value is assigned to an index with change-color.

> > struct
> > (struct |  | rgb (red green blue)
> #:extra-constructor-name make-rgb)
> red : (real-in 0 1)
> green : (real-in 0 1)
> blue : (real-in 0 1)

Takes three values in the range 0 (dark) to 1 (bright) and returns an rgb (a color).

> procedure (change-color index rgb) → void?
> index : (integer-in 0 299)
> rgb : rgb?

Changes the color at index in the color table to the color specified in rgb. Only the first twenty-one indices are initialized; a color index should not be used until it has been initialized.

> procedure (default-display-is-color?) → boolean?

Returns #t if the default display screen for viewports is in color or #f otherwise.
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