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<li class="active"><a href="./">Image Operations</a>
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<h4>This Page</h4>
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<ul class="toc">
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<li><a href="#accessing-images">Accessing Images</a></li>
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<li><a href="#accessing-image-data">Accessing Image Data</a></li>
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<li><a href="#accessing-exif-data">Accessing EXIF Data</a></li>
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<li><a href="#generating-thumbnails">Generating Thumbnails</a></li>
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</ul>
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</div>
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<div class="col-sm-9 doc-styling">
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<h1>Image Operations</h1>
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<ul class=page-meta>
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</ul>
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<p>Images are separate files and as such just embedded into HTML files. However
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very often you want to perform modifications on these images that require
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interacting with those files directly. This can be conveniently done directly
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from the template code through the image APIs that Lektor provides.</p>
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<h2 id="accessing-images">Accessing Images</h2><p>To work with images one needs to get access to the image objects first. Images
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are returned from the attachments of a page. If you want to make sure you
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only operate with actual images the <code>.images</code> attribute can be used to filter
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the query. For instance this iterates over all attached images of a page:</p>
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<div class="hll"><pre><span></span><span class="cp">{%</span> <span class="k">for</span> <span class="nv">image</span> <span class="k">in</span> <span class="nv">this.attachments.images</span> <span class="cp">%}</span>
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<span class="p"><</span><span class="nt">div</span> <span class="na">class</span><span class="o">=</span><span class="s">"image"</span><span class="p">><</span><span class="nt">img</span> <span class="na">src</span><span class="o">=</span><span class="s">"</span><span class="cp">{{</span> <span class="nv">image</span><span class="o">|</span><span class="nf">url</span> <span class="cp">}}</span><span class="s">"</span><span class="p">></</span><span class="nt">div</span><span class="p">></span>
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<span class="cp">{%</span> <span class="k">endfor</span> <span class="cp">%}</span>
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</pre></div>
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<p><br/>
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To access images from a different content folder, you would use:</p>
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<div class="hll"><pre><span></span><span class="cp">{%</span> <span class="k">for</span> <span class="nv">image</span> <span class="k">in</span> <span class="nv">site.get</span><span class="o">(</span><span class="s1">'/myfolder'</span><span class="o">)</span><span class="nv">.attachments.images</span> <span class="cp">%}</span>
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<span class="p"><</span><span class="nt">div</span> <span class="na">class</span><span class="o">=</span><span class="s">"image"</span><span class="p">><</span><span class="nt">img</span> <span class="na">src</span><span class="o">=</span><span class="s">"</span><span class="cp">{{</span> <span class="nv">image</span><span class="o">|</span><span class="nf">url</span> <span class="cp">}}</span><span class="s">"</span><span class="p">></</span><span class="nt">div</span><span class="p">></span>
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<span class="cp">{%</span> <span class="k">endfor</span> <span class="cp">%}</span>
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</pre></div>
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<p><br/>
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To retrieve only a specific image or attachment with a certain name you would use</p>
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<div class="hll"><pre><span></span><span class="cp">{%</span> <span class="k">set</span> <span class="nv">my_image</span> <span class="o">=</span> <span class="nv">site.get</span><span class="o">(</span><span class="s1">'/myfolder'</span><span class="o">)</span><span class="nv">.attachments.get</span><span class="o">(</span><span class="s1">'imagenameexample.jpg'</span><span class="o">)</span> <span class="cp">%}</span>
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<span class="p"><</span><span class="nt">div</span> <span class="na">class</span><span class="o">=</span><span class="s">"image"</span><span class="p">><</span><span class="nt">img</span> <span class="na">src</span><span class="o">=</span><span class="s">"</span><span class="cp">{{</span> <span class="nv">my_image</span><span class="o">|</span><span class="nf">url</span> <span class="cp">}}</span><span class="s">"</span><span class="p">></</span><span class="nt">div</span><span class="p">></span>
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</pre></div>
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<h2 id="accessing-image-data">Accessing Image Data</h2><p>One of the more common operations is to access the direct image data. This
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is resolution and file format. The <code>width</code>, <code>height</code> and <code>format</code> parameters
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are provided for this. In some cases this is very useful to generate CSS code
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that needs to know about the original resolution. For instance this achieves a
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retina rendered background:</p>
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<div class="hll"><pre><span></span><span class="p"><</span><span class="nt">div</span> <span class="na">style</span><span class="o">=</span><span class="s">"</span>
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<span class="s"> background: url(</span><span class="cp">{{</span> <span class="nv">image</span><span class="o">|</span><span class="nf">url</span> <span class="cp">}}</span><span class="s">);</span>
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<span class="s"> background-size: </span><span class="cp">{{</span> <span class="nv">image.width</span> <span class="o">/</span> <span class="m">2</span> <span class="cp">}}</span><span class="s">px </span><span class="cp">{{</span> <span class="nv">image.height</span> <span class="o">/</span> <span class="m">2</span> <span class="cp">}}</span><span class="s">px</span>
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<span class="s">"</span><span class="p">></</span><span class="nt">div</span><span class="p">></span>
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</pre></div>
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<h2 id="accessing-exif-data">Accessing EXIF Data</h2><p>Lektor can also give you access to a lot of the EXIF information that is stored
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in the images. Not all EXIF information is available but the most common
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values are. For the full list of attributes see <a href="../../api/db/record/exif/" class="ref">EXIF data</a>.</p>
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<p>Here an example that shows the camera information:</p>
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<div class="hll"><pre><span></span><span class="p"><</span><span class="nt">div</span> <span class="na">class</span><span class="o">=</span><span class="s">"image"</span><span class="p">></span>
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<span class="p"><</span><span class="nt">img</span> <span class="na">src</span><span class="o">=</span><span class="s">"</span><span class="cp">{{</span> <span class="nv">image</span><span class="o">|</span><span class="nf">url</span> <span class="cp">}}</span><span class="s">"</span> <span class="na">alt</span><span class="o">=</span><span class="s">""</span><span class="p">></span>
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<span class="p"><</span><span class="nt">p</span><span class="p">><</span><span class="nt">strong</span><span class="p">></span>Camera:<span class="p"></</span><span class="nt">strong</span><span class="p">></span> <span class="cp">{{</span> <span class="nv">image.exif.camera</span> <span class="cp">}}</span>
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<span class="p"></</span><span class="nt">div</span><span class="p">></span>
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</pre></div>
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<h2 id="generating-thumbnails">Generating Thumbnails</h2><p>While browsers are reasonably good at downscaling images themselves, you
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still need to transmit the entire image. When you want smaller images it
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often makes sense to generate thumbnails automatically. In Lektor each
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image provides the <a href="../../api/db/record/thumbnail/" class="ref">thumbnail</a> method.</p>
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<p>It accepts the width and height of the target image. If either of these is not
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provided, it will be computed automatically. The return value can be converted
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into a URL with the <code>|url</code> filter:</p>
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<div class="hll"><pre><span></span><span class="p"><</span><span class="nt">img</span> <span class="na">src</span><span class="o">=</span><span class="s">"</span><span class="cp">{{</span> <span class="nv">image.thumbnail</span><span class="o">(</span><span class="m">320</span><span class="o">)|</span><span class="nf">url</span> <span class="cp">}}</span><span class="s">"</span><span class="p">></span>
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</pre></div>
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