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<section id="color">
<h1>color<a class="headerlink" href="#color" title="Permalink to this heading">¶</a></h1>
<img alt="_images/colors.png" src="_images/colors.png" />
<p>Every graphical object has a <code class="xref py py-attr docutils literal notranslate"><span class="pre">color</span></code>. The attribute <code class="xref py py-attr docutils literal notranslate"><span class="pre">color</span></code> is a vector whose components are <code class="docutils literal notranslate"><span class="pre">R</span></code> (red), <code class="docutils literal notranslate"><span class="pre">G</span></code> (green), and <code class="docutils literal notranslate"><span class="pre">B</span></code> (blue). You can specify your own color by specifying RGB components, or you can use one of the colors from the VPython library:</p>
<ul class="simple">
<li><p><code class="docutils literal notranslate"><span class="pre">color.white</span></code> is defined as <code class="docutils literal notranslate"><span class="pre">vec(1,1,1)</span></code></p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">color.red</span></code> is defined as <code class="docutils literal notranslate"><span class="pre">vec(1,0,0)</span></code></p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">color.green</span></code> is defined as <code class="docutils literal notranslate"><span class="pre">vec(0,1,0)</span></code></p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">color.blue</span></code> is defined as <code class="docutils literal notranslate"><span class="pre">vec(0,0,1)</span></code></p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">color.cyan</span></code> is defined as <code class="docutils literal notranslate"><span class="pre">vec(0,1,1)</span></code></p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">color.magenta</span></code> is defined as <code class="docutils literal notranslate"><span class="pre">vec(1,0,1)</span></code></p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">color.yellow</span></code> is defined as <code class="docutils literal notranslate"><span class="pre">vec(1,1,0)</span></code></p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">color.orange</span></code> is defined as <code class="docutils literal notranslate"><span class="pre">vec(1,0.6,0)</span></code></p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">color.purple</span></code> is defined as <code class="docutils literal notranslate"><span class="pre">vec(0.4,0.2,0.6)</span></code></p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">color.black</span></code> is defined as <code class="docutils literal notranslate"><span class="pre">vec(0,0,0)</span></code></p></li>
</ul>
<p>In the RGB color system, a color is specified in terms of fractions of red, green, and blue, corresponding to the intensity of the tiny red, green, and blue dots of the computer screen. In the RGB scheme, white is the color with a maximum of red, blue, and green (1, 1, 1). Black has minimum amounts (0, 0, 0). The brightest red is represented by (1, 0, 0); that is, it has the full amount of red, no green, and no blue.</p>
<p>In addition to the colors in the color library you can also create your own colors, such as these:</p>
<p><code class="docutils literal notranslate"><span class="pre">vector(0.5,</span> <span class="pre">0.5,</span> <span class="pre">0.5)</span></code> a rather dark gray
Alternatively you can say <code class="docutils literal notranslate"><span class="pre">color=color.gray(0.5)</span></code> or <code class="docutils literal notranslate"><span class="pre">color.white*0.5</span></code> to mean <code class="docutils literal notranslate"><span class="pre">vec(0.5,0.5,0.5)</span></code></p>
<p><code class="docutils literal notranslate"><span class="pre">vector(1,0.7,0.2)</span></code> a coppery color</p>
<p>Colors may appear differently on different computers, and under different 3D lighting conditions. The named colors above are most likely to display appropriately, because RGB values of 0 or 1 are unaffected by differing color corrections (“gamma” corrections).</p>
<p>The VPython demo program <a class="reference external" href="https://www.glowscript.org/#/user/GlowScriptDemos/folder/Examples/program/Color-RGB-HSV-VPython">Color-RGB-HSV</a> lets you adjust RGB sliders to visualize colors and print color triples that you copy into your program. It also provides HSV sliders to adjust hue, saturation, and value.</p>
<section id="converting-between-rgb-and-hsv-color-descriptors">
<h2>Converting between RGB and HSV color descriptors<a class="headerlink" href="#converting-between-rgb-and-hsv-color-descriptors" title="Permalink to this heading">¶</a></h2>
<p>HSV (hue, saturation, and value) is an alternate scheme for describing colors. Although VPython only accepts RGB colors, there are functions for converting between RGB and HSV.</p>
<dl class="py function">
<dt class="sig sig-object py" id="color.rgb_to_hsv">
<span class="sig-prename descclassname"><span class="pre">color.</span></span><span class="sig-name descname"><span class="pre">rgb_to_hsv</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">c</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#color.rgb_to_hsv" title="Permalink to this definition">¶</a></dt>
<dd></dd></dl>
<p>The argument c is a vector representing a color.</p>
<dl class="py function">
<dt class="sig sig-object py" id="color.hsv_to_rgb">
<span class="sig-prename descclassname"><span class="pre">color.</span></span><span class="sig-name descname"><span class="pre">hsv_to_rgb</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">c</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#color.hsv_to_rgb" title="Permalink to this definition">¶</a></dt>
<dd></dd></dl>
<div class="highlight-python notranslate"><div class="highlight"><pre><span></span><span class="n">c</span> <span class="o">=</span> <span class="n">vector</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">0</span><span class="p">)</span>
<span class="n">c2</span> <span class="o">=</span> <span class="n">color</span><span class="o">.</span><span class="n">rgb_to_hsv</span><span class="p">(</span><span class="n">c</span><span class="p">)</span> <span class="c1"># convert RGB to HSV</span>
<span class="nb">print</span><span class="p">(</span><span class="n">hsv</span><span class="p">)</span> <span class="c1"># vector(0.16667, 1, 1)</span>
<span class="n">c3</span> <span class="o">=</span> <span class="n">color</span><span class="o">.</span><span class="n">hsv_to_rgb</span><span class="p">(</span><span class="n">c2</span><span class="p">)</span> <span class="c1"># convert back to RGB</span>
<span class="nb">print</span><span class="p">(</span><span class="n">c3</span><span class="p">)</span> <span class="c1"># vector(1, 1, 0)</span>
</pre></div>
</div>
<p>The functions can be embedded in object constructors. For example:</p>
<p><code class="docutils literal notranslate"><span class="pre">sphere(</span> <span class="pre">radius=2,</span> <span class="pre">color=color.hsv_to_rgb(vector</span> <span class="pre">(0.5,1,0.8)</span> <span class="pre">)</span></code></p>
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