EVOLUTION-MANAGER

Edit File: manip_channel.html

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<table width="100%" summary="page for manip_channel {farver}"><tr><td>manip_channel {farver}</td><td style="text-align: right;">R Documentation</td></tr></table>

<h2>Modify colour space channels in hex-encoded colour strings</h2>

<h3>Description</h3>

<p>This set of functions allows you to modify colours as given by strings,
whithout first decoding them. For large vectors of colour values this should
provide a considerable speedup.
</p>

<h3>Usage</h3>

<pre>
set_channel(
  colour,
  channel,
  value,
  space = "rgb",
  white = "D65",
  na_value = NA
)

add_to_channel(
  colour,
  channel,
  value,
  space = "rgb",
  white = "D65",
  na_value = NA
)

multiply_channel(
  colour,
  channel,
  value,
  space = "rgb",
  white = "D65",
  na_value = NA
)

raise_channel(
  colour,
  channel,
  value,
  space = "rgb",
  white = "D65",
  na_value = NA
)

cap_channel(
  colour,
  channel,
  value,
  space = "rgb",
  white = "D65",
  na_value = NA
)

get_channel(colour, channel, space = "rgb", white = "D65", na_value = NA)
</pre>

<h3>Arguments</h3>

<table summary="R argblock">
<tr valign="top"><td><code>colour</code></td>
<td>
<p>A character string giving colours, either as hexadecimal
strings or accepted colour names.</p>
</td></tr>
<tr valign="top"><td><code>channel</code></td>
<td>
<p>The channel to modify or extract as a single letter, or
<code>'alpha'</code> for the alpha channel.</p>
</td></tr>
<tr valign="top"><td><code>value</code></td>
<td>
<p>The value to modify with</p>
</td></tr>
<tr valign="top"><td><code>space</code></td>
<td>
<p>The colour space the channel pertains to. Allowed values are:
<code>"cmy"</code>, <code>"cmyk"</code>, <code>"hsl"</code>, <code>"hsb"</code>, <code>"hsv"</code>, <code>"lab"</code> (CIE L*ab), <code>"hunterlab"</code>
(Hunter Lab), <code>"lch"</code> (CIE Lch(ab) / polarLAB), <code>"luv"</code>, <code>"rgb"</code> (sRGB),
<code>"xyz"</code>, <code>"yxy"</code> (CIE xyY), or <code>"hcl"</code> (CIE Lch(uv) / polarLuv)</p>
</td></tr>
<tr valign="top"><td><code>white</code></td>
<td>
<p>The white reference of the channel colour space. Will only have
an effect for relative colour spaces such as Lab and luv. Any value accepted
by <code><a href="as_white_ref.html">as_white_ref()</a></code> allowed.</p>
</td></tr>
<tr valign="top"><td><code>na_value</code></td>
<td>
<p>A valid colour string or <code>NA</code> to use when <code>colour</code> contains
<code>NA</code> elements. The general approach in farver is to carry <code>NA</code> values over,
but if you want to mimick <code><a href="../../grDevices/html/col2rgb.html">col2rgb()</a></code> you should set
<code>na_value = 'transparent'</code>, i.e. treat <code>NA</code> as transparent white.</p>
</td></tr>
</table>

<h3>Value</h3>

<p>A character vector of the same length as <code>colour</code> (or a numeric
vector in the case of <code>get_channel()</code>)
</p>

<p>Other encoding and decoding functions: 
<code><a href="decode_colour.html">decode_colour</a>()</code>,
<code><a href="encode_colour.html">encode_colour</a>()</code>
</p>

<h3>Examples</h3>

<pre>
spectrum &lt;- rainbow(10)

# set a specific channel
set_channel(spectrum, 'r', c(10, 50))
set_channel(spectrum, 'l', 50, space = 'lab')
set_channel(spectrum, 'alpha', c(0.5, 1))

# Add value to channel
add_to_channel(spectrum, 'r', c(10, 50))
add_to_channel(spectrum, 'l', 50, space = 'lab')

# Multiply a channel
multiply_channel(spectrum, 'r', c(10, 50))
multiply_channel(spectrum, 'l', 50, space = 'lab')

# set a lower bound on a channel
raise_channel(spectrum, 'r', c(10, 50))
raise_channel(spectrum, 'l', 20, space = 'lab')

# set an upper bound on a channel
cap_channel(spectrum, 'r', c(100, 50))
cap_channel(spectrum, 'l', 20, space = 'lab')

</pre>

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