`alphamap`

Gets or sets the alphamap, the table that turns data values into transparency.

Category: Graphics > Formatting and Annotation

Syntax

alphamap(name)

Sets a predefined map such as 'rampup', 'rampdown', 'vup', 'vdown', 'increase', 'decrease', 'opaque'.

alphamap(A)

Sets a custom map from a vector of values between 0 and 1.

A = alphamap

Returns the current alphamap.

Description

The alphamap is to transparency what the colormap is to color: each entry corresponds to a range of data values (set by alim) and gives the opacity for it. 'rampup' goes from transparent to opaque over 64 entries.

Input arguments

name: Name of a predefined shape.
A: Vector of alpha values between 0 and 1.

Output arguments

A: Column vector with the current alphamap.

Example

A rising ramp

alphamap('rampup')
m = alphamap;
disp(size(m))
disp(m(1:3)')

Output

ans = 64×1

         0
    0.0159
    0.0317
    0.0476
    0.0635
    0.0794
    0.0952
    0.1111
    0.1270
    0.1429
    0.1587
    0.1746
    0.1905
    0.2063
    0.2222
    0.2381
    0.2540
    0.2698
    0.2857
    0.3016
    0.3175
    0.3333
    0.3492
    0.3651
    0.3810
    0.3968
    0.4127
    0.4286
    0.4444
    0.4603
    0.4762
    0.4921
    0.5079
    0.5238
    0.5397
    0.5556
    0.5714
    0.5873
    0.6032
    0.6190
    0.6349
    0.6508
    0.6667
    0.6825
    0.6984
    0.7143
    0.7302
    0.7460
    0.7619
    0.7778
    0.7937
    0.8095
    0.8254
    0.8413
    0.8571
    0.8730
    0.8889
    0.9048
    0.9206
    0.9365
    0.9524
    0.9683
    0.9841
    1.0000
    64     1
         0    0.0159    0.0317

alphamap