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<span id="Blend-Modes"></span><div class="header">
<p>
Next: <a href="Images.html" accesskey="n" rel="next">Images</a>, Previous: <a href="Rendering.html" accesskey="p" rel="prev">Rendering</a>, Up: <a href="API-Reference.html" accesskey="u" rel="up">API Reference</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Index.html" title="Index" rel="index">Index</a>]</p>
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<hr>
<span id="Blend-Modes-1"></span><h3 class="section">3.8 Blend Modes</h3>
<div class="example">
<pre class="example">(use-modules (sdl2 blend-mode))
</pre></div>
<p>SDL2 provides several of the most commonly used blend modes:
</p>
<dl>
<dt id="index-none">Variable: <strong>none</strong></dt>
<dd><p>No blending.
</p></dd></dl>
<dl>
<dt id="index-blend">Variable: <strong>blend</strong></dt>
<dd><p>Alpha blending.
</p></dd></dl>
<dl>
<dt id="index-add">Variable: <strong>add</strong></dt>
<dd><p>Additive blending.
</p></dd></dl>
<dl>
<dt id="index-mul">Variable: <strong>mul</strong></dt>
<dd><p>Multiplicative blending.
</p></dd></dl>
<dl>
<dt id="index-mod">Variable: <strong>mod</strong></dt>
<dd><p>Color modulation.
</p></dd></dl>
<p>Custom blend modes can be created using the <code>make-blend-mode</code>
procedure.
</p>
<dl>
<dt id="index-make_002dblend_002dmode">Procedure: <strong>make-blend-mode</strong> <em>src-color-factor dst-color-factor color-operation src-alpha-factor dst-alpha-factor alpha-operation</em></dt>
<dd><p>Return a new custom blend mode for renderers.
</p>
<p><var>src-color-factor</var> applies to the red, green, and blue components
of the source pixels.
</p>
<p><var>dst-color-factor</var> applies to the red, green, and blue components of the
destination pixels.
</p>
<p><var>color-operation</var> specifies how to combine the red, green, and blue
components of the source and destination pixels.
</p>
<p><var>src-alpha-factor</var> applies to the alpha component of the source pixels.
</p>
<p><var>dst-alpha-factor</var> applies to the alpha component of the destination
pixels.
</p>
<p><var>alpha-operation</var> specifies how to combine the alpha component of the
source and destination pixels.
</p>
<p>Possible values for factors are <code>zero</code>, <code>one</code>,
<code>src-color</code>, <code>one-minus-src-color</code>, <code>src-alpha</code>,
<code>one-minus-src-alpha</code>, <code>dst-color</code>,
<code>one-minus-dst-color</code>, <code>dst-alpha</code>, and <code>one-minus-dst
alpha</code>.
</p>
<p>Possible values for operations are <code>add</code>, <code>subtract</code>,
<code>rev-subtract</code>, <code>minimum</code>, and <code>maximum</code>.
</p></dd></dl>
<dl>
<dt id="index-blend_002dmode_003f">Procedure: <strong>blend-mode?</strong> <em>obj</em></dt>
<dd><p>Return <code>#t</code> if <var>obj</var> is a blend mode object.
</p></dd></dl>
<dl>
<dt id="index-blend_002dmode_002dsrc_002dcolor_002dfactor">Procedure: <strong>blend-mode-src-color-factor</strong> <em>blend-mode</em></dt>
<dd><p>Return the source red, green, and blue channel blend factor for
<var>blend-mode</var>.
</p></dd></dl>
<dl>
<dt id="index-blend_002dmode_002ddst_002dcolor_002dfactor">Procedure: <strong>blend-mode-dst-color-factor</strong> <em>blend-mode</em></dt>
<dd><p>Return the destination red, green, and blue channel blend factor for
<var>blend-mode</var>.
</p></dd></dl>
<dl>
<dt id="index-blend_002dmode_002dcolor_002doperation">Procedure: <strong>blend-mode-color-operation</strong> <em>blend-mode</em></dt>
<dd><p>Return the red, green, and blue channel blend operation for
<var>blend-mode</var>.
</p></dd></dl>
<dl>
<dt id="index-blend_002dmode_002dsrc_002dalpha_002dfactor">Procedure: <strong>blend-mode-src-alpha-factor</strong> <em>blend-mode</em></dt>
<dd><p>Return the source alpha channel blend factor for <var>blend-mode</var>.
</p></dd></dl>
<dl>
<dt id="index-blend_002dmode_002ddst_002dalpha_002dfactor">Procedure: <strong>blend-mode-dst-alpha-factor</strong> <em>blend-mode</em></dt>
<dd><p>Return the destination alpha channel blend factor for
<var>blend-mode</var>.
</p></dd></dl>
<dl>
<dt id="index-blend_002dmode_002dalpha_002doperation">Procedure: <strong>blend-mode-alpha-operation</strong> <em>blend-mode</em></dt>
<dd><p>Return the alpha channel blend operation for <var>blend-mode</var>.
</p></dd></dl>
<hr>
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