Color related functions

<spinmap> - Spin color map.

SPINMAP Spin color map.

SPINMAP cyclically rotates the color map for about 3 seconds.

SPINMAP(T) rotates it for about T seconds.

SPINMAP(inf) is an infinite loop, break with <ctrl-C>.

SPINMAP(T,inc) uses the specified increment. The default is

inc = 2, so inc = 1 is a slower rotation, inc = 3 is faster,

inc = -2 is the other direction, etc.

To avoid multiple redraws, set(gcf,'sharecolors','off') and

set(gcf,'renderer','painters').

See also colormap, rgbplot.

Reference page in Help browser

doc spinmap

<rgbplot> - Plot color map.

RGBPLOT Plot color map.

RGBPLOT(MAP) plots a color map, i.e. an m-by-3 matrix which

is appropriate input for COLORMAP. The three columns of the

colormap matrix are plotted in red, green, and blue lines.

See also colormap, rgb2hsv.

Reference page in Help browser

doc rgbplot

<colstyle> - Parse color and style from string.

COLSTYLE Parse color and style from string.

[L,C,M,MSG] = COLSTYLE('linespec') parses the line specification

'linespec' and returns the linetype part in L, the color part in C,

and the marker part in M. L,C and M are empty arguments for

parts that are not specified or if there is a parsing error. In

case of error, MSG will contain the error message string.

<ind2rgb> - Convert indexed image to RGB image.

IND2RGB Convert indexed image to RGB image.

RGB = IND2RGB(X,MAP) converts the matrix X and corresponding

colormap MAP to RGB (truecolor) format.

Class Support

-------------

X can be of class uint8, uint16, or double. RGB is an

M-by-N-by-3 array of class double.

See also rgb2ind.

Reference page in Help browser

doc ind2rgb

<rgb2ind> - Convert RGB image to indexed image.

RGB2IND Convert RGB image to indexed image.

RGB2IND converts RGB images to indexed images using one of three

different methods: uniform quantization, minimum variance quantization,

and colormap approximation. RGB2IND dithers the image unless you specify

'nodither' for DITHER_OPTION.

[X,MAP] = RGB2IND(RGB,N) converts the RGB image to an indexed image X

using minimum variance quantization. MAP contains at most N colors. N

must be <= 65536.

X = RGB2IND(RGB,MAP) converts the RGB image to an indexed image X with

colormap MAP by matching colors in RGB with the nearest color in the

colormap MAP. SIZE(MAP,1) must be <= 65536.

[X,MAP] = RGB2IND(RGB,TOL) converts the RGB image to an indexed image X

using uniform quantization. MAP contains at most (FLOOR(1/TOL)+1)^3

colors. TOL must be between 0.0 and 1.0.

[...] = RGB2IND(...,DITHER_OPTION) enables or disables

dithering. DITHER_OPTION is a string that can have one of these values:

'dither' dithers, if necessary, to achieve better color

resolution at the expense of spatial

resolution (default)

'nodither' maps each color in the original image to the

closest color in the new map. No dithering is

performed.

Class Support

-------------

The input image can be uint8, uint16, single, or double. The output image is

uint8 if the length of MAP is less than or equal to 256, or uint16

otherwise.

Example

-------

RGB = imread('ngc6543a.jpg');

[X,map] = rgb2ind(RGB,128);

figure, image(X), colormap(map)

axis off

axis image

See also cmunique, dither, imapprox, ind2rgb.

Reference page in Help browser

doc rgb2ind

<dither> - Convert image using dithering.

DITHER Convert image using dithering.

X = DITHER(RGB,MAP) creates an indexed image approximation of the RGB image

in the array RGB by dithering the colors in colormap MAP. MAP cannot have

more than 65536 colors.

X = DITHER(RGB,MAP,Qm,Qe) creates an indexed image from RGB, specifying the

parameters Qm and Qe. Qm specifies the number of quantization bits to use

along each color axis for the inverse color map, and Qe specifies the number

of quantization bits to use for the color space error calculations. If Qe <

Qm, dithering cannot be performed and an undithered indexed image is

returned in X. If you omit these parameters, DITHER uses the default values

Qm = 5, Qe = 8.

BW = DITHER(I) converts the intensity image in the matrix I to the binary

image BW by dithering.

Class Support

-------------

RGB can be uint8, uint16, single, or double. I can be uint8, uint16, int16,

single, or double. All other input arguments must be double. BW is

logical. X is uint8 if it is an indexed image with 256 or fewer colors;

otherwise, it is uint16.

Example

-------

Convert intensity image to binary using dithering.

RGB = imread('street1.jpg');

G = RGB(:,:,2);

BW = dither(G);

figure, imagesc(G), colormap(gray)

figure, image(BW), colormap(gray(2))

See also rgb2ind.

Reference page in Help browser

doc dither