ExtractChannel

Extracts a channel from a pixmap or a sound.

Syntax

• ExtractChannel(pm, fam, ch)

  • pm is a pixmap

  • fam is one of "rgb", "hsv", and "hsl"

  • ch is one of the characters in fam

• ExtractChannel(snd, n)

  • snd is a sound

  • n is a non-negative integer

Description

If pm is a pixmap, then ExtractChannel(pm, fam, ch) returns the specified RGB, HSV, or HSL channel from pm as a greyscale pixmap.

If snd is a sound, then ExtractChannel(snd, n) returns the channel with index n in snd as a single-channel sound. Sound channels indices are zero-based, so the first channel has index 0.

Examples

S ≔ ExampleData("Sally");
pm ≔ CreatePixmap(width(S), (4/3)⋅height(S));
spm ≔ scale(S, 1/3);
pm ≔ DrawRect(pm, S, 0, 0);
for(i, 1, 3,
  (
    pm ≔ DrawRect(
      pm,
      ExtractChannel(spm, "rgb", characters("rgb")[i]),
      width(spm)⋅(i − 1),
      height(S))
  )
);
pm

See also

• CombineChannels

• AdjustRGB

• AdjustHSV