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@ -31,11 +31,11 @@
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<meta property="og:url" content="/SergeoLacruz/inventree-zebra-plugin" />
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<meta property="og:site_name" content="InvenTree" />
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<meta property="og:type" content="article" />
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<meta property="article:published_time" content="2025-02-03T01:08:16+00:00" />
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<meta property="article:published_time" content="2025-02-03T11:33:13+00:00" />
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<meta name="twitter:card" content="summary" />
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<meta property="twitter:title" content="Inventree Zebra Plugin" />
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<script type="application/ld+json">
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{"@context":"https://schema.org","@type":"BlogPosting","author":{"@type":"Person","name":"SergeoLacruz"},"dateModified":"2025-02-03T01:08:16+00:00","datePublished":"2025-02-03T01:08:16+00:00","description":"Zebra Label Printer Plugin for Inventree","headline":"Inventree Zebra Plugin","mainEntityOfPage":{"@type":"WebPage","@id":"/SergeoLacruz/inventree-zebra-plugin"},"url":"/SergeoLacruz/inventree-zebra-plugin"}</script>
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{"@context":"https://schema.org","@type":"BlogPosting","author":{"@type":"Person","name":"SergeoLacruz"},"dateModified":"2025-02-03T11:33:13+00:00","datePublished":"2025-02-03T11:33:13+00:00","description":"Zebra Label Printer Plugin for Inventree","headline":"Inventree Zebra Plugin","mainEntityOfPage":{"@type":"WebPage","@id":"/SergeoLacruz/inventree-zebra-plugin"},"url":"/SergeoLacruz/inventree-zebra-plugin"}</script>
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<!-- End Jekyll SEO tag -->
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</head>
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@ -77,9 +77,13 @@
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<p>Zebra Label Printer Plugin for Inventree</p>
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<p>This is a label printing plugin for <a href="https://inventree.org">InvenTree</a>, which provides
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support for Zebra Label printers. It was only tested with GK420T but should work for
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other ZPL printers too. It uses the ZPL library to convert the png data provided by
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InvenTree to Zebra’s bitmap format.</p>
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support for Zebra Label printers. It allows two modes of operation:</p>
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<ul>
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<li>Use the ZPL library to convert the png data provided by InvenTree to Zebra’s bitmap
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format and send this to the printer.</li>
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<li>Write a ZPL template and let the printer do the rendering.</li>
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</ul>
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<p>It can output the print data either to a local printer connected to the computer via
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USB or to a network printer with an IP address. The output can be configured in the
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@ -96,7 +100,9 @@ InvenTree plugin user interface.</p>
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<h2 id="configuration-options">Configuration Options</h2>
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<h3 id="printer-interface">Printer Interface</h3>
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<p>Here you can chose between Local printer or network printer. Default value is a local printer.</p>
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<p>Here you can chose between local printer, network printer or the labelary.com API.
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The last one is useful for preview of labels, especially when ZPL templates are used.
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Default value is a local printer.</p>
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<h3 id="ip-address">IP address</h3>
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<p>In case you use an IP printer set the IPv4 address here.</p>
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@ -133,6 +139,9 @@ change it according to your requirements. Please keep in mind that this string
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is passed directly to the printer without any checks. So be careful when editing
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here.</p>
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<h3 id="get-printer-info">Get Printer info</h3>
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<p>Turn this switch on to display a collection of all IP printers below on this page.</p>
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<h2 id="label-template">Label Template</h2>
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<p>The label needs a template described in html and css. The template should
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start with a page definition that defines the label size as shown below:</p>
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@ -171,11 +180,104 @@ in another printer.</p>
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<p>Only the IP address and darkness can be overwritten so far. All other settings remain.</p>
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<h2 id="quality-matters">Quality matters</h2>
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<p>The InvenTree printer system uses a graphical representation of the label. The label is described
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in HTML, converted to a pixel graphic and printed. The advantage is independency from printer
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models and systems. Disadvantage is larger data and quality problems with darkness and scaling.
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Let’s have a look at the following printout:</p>
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<p><img src="/assets/plugins/qr.png" alt="QRCodes"></p>
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<p>Both codes have been printed with the same printer on the same reel. The left one is
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hardly readable using my mobile. The right one reads easily even as it is smaller.</p>
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<h3 id="secret-1-scale">Secret 1, Scale</h3>
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<p>The printer resolution is 8 dots per mm resulting in a dot size of 0.125mm. The QR code pixel
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and the printer pixel size should be integrally divisible. The code in the picture has 21
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pixels plus one in the frame, so 23 pixel. The frame is set in the HTML description.</p>
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<div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>{% qrcode qr_data border=1 %}
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</code></pre></div></div>
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<p>I selected two dots per pixel. So 23 * 2 * 0.125 = 6.125mm. If the size is something different
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scaling takes place and the result might be worse. If you like a larger printout select more
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dots per pixel. From a certain size upwards the value does not matter any more because the code
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gets large enough to be readable in any quality.</p>
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<h3 id="secret-2-darkness">Secret 2: Darkness</h3>
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<p>Zebra printers allow to set the darkness of the print in values between 0 (white) and 30 (max)
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The left code was printed with a value of 30. The black dots tend to blur out a bit resulting
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in smaller white areas. The right code was printed with a value of 25 resulting in larger white
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pixels. The darkness values are just examples. Your values will differ based on printer model,
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media type and printer age. The printer head tends to wear out and the darkness value might
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need an adjustment from time to time.</p>
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<h2 id="in-printer-rendering">In printer rendering</h2>
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<p>You can also bypass the InvenTree print engine and render the label inside the printer.
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The printer knows how to render the label for best quality. Inspired by the
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inventree-zpl-plugin <a href="https://github.com/yellowcrescent/inventree-zpl-plugin">inventree-zpl-plugin</a> a similar
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function was aded to the zebra printer driver. You can write a ZPL template and upload
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it to the InvenTree Label templates as usual. Add a command to the template’s metadata:</p>
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<div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>{"zpl_template": "True"}
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</code></pre></div></div>
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<p>In that case the printer driver ignores the picture rendered by WeasyPrint. Instead
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it calls the render_to_string function of the template and sends the
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result to the printer. The result can look like:</p>
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<p><img src="/assets/plugins/example_label.png" alt="Label Example"></p>
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<p>The upper label was created using this template:</p>
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<div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>
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{% autoescape off %}
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^FT30,25^A0N,18,22^FDIPN^FS
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^FT150,30^FB100,1,,C,,^A0N,24,32^FDACME^FS
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^FT320,25^A0N,18,22^FD{{ item.pk }}^FS
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^FT100,70^FB200,2,,C,,^A0N,18,22^FD{{ part.name }}^FS
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^FT100,100^FB200,1,,C,,^A0N,18,22^FD{{ part.manufacturer_parts.first.manufacturer.name }}^FS
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^FT30,150^FB340,1,,C,,^A0N,30,40^FD{{ part.IPN }}^FS
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^FT20,210^FB360,3,,L,,^A0N,18,22^FD{{ part.description }}^FS
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^FT15,110^BQ,2,3^FDQA,{{ part.IPN }}^FS
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^FT310,130^BQ,2,3^FDQA,{{ qr_data }}^FS
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{% endautoescape %}
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</code></pre></div></div>
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<p>Autoescape must be off. We do not need &quot and similar escapes here.
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Context variables can be used as usual.</p>
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<p>!!! warning “Limitation”
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ZPL commands starting with backslash like \& cannot be used so far.</p>
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<h3 id="preview">Preview</h3>
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<p>The printer driver allows an output device called “preview”. If this is selected
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the ZPL code is sent to the API of labelary.com. The API sends back pdf data
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which is displayed in a new browser window. This is helpful while writing ZPL
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templates but works with HTML templates too. Please be careful and do not send
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confidential information to the API.</p>
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<p>In case you need to pass a proxy for the POST requests set the environment
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variables PROXY_CON and PROXY_URL on the server. The plugin does not have
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settings for this.</p>
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<h2 id="getting-printer-info">Getting printer info</h2>
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<p>With the multi printer feature it can happen that you have several printers in
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your setup. When the Get Printer Info switch is set ON, the driver calls each printer
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once a minute and collects some info about it. It calls the printer configured
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in the settings as well as all printers it finds in the label templates.
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In case a printer is unreachable, an error message is shown. If a printer is used
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in several templates it is listed only once.</p>
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<p>The printer info feature works for local USB printers too.</p>
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<p><img src="/assets/plugins/printer_info.png" alt="Printer Info"></p>
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<h2 id="how-it-works">How it works</h2>
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<p>First import all the stuff you need. Here we use the translation mechanism from
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Django for multi language support. The import the InvenTree libs and everything
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you need for plugin. Here we have ZPL for the Zebra bitmaps and socket for the
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IP connection to the printer.</p>
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<p>First import all the stuff you need. Here we use the translation mechanism from Django for multi language support.
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The import the InvenTree libs and everything you need for plugin. Here we have ZPL for the Zebra bitmaps and socket
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for the IP connection to the printer.</p>
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<p>The next part is this:</p>
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@ -184,17 +286,17 @@ IP connection to the printer.</p>
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<span class="n">AUTHOR</span> <span class="o">=</span> <span class="sh">"</span><span class="s">Michael Buchmann</span><span class="sh">"</span>
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<span class="n">DESCRIPTION</span> <span class="o">=</span> <span class="sh">"</span><span class="s">Label printing plugin for Zebra printers</span><span class="sh">"</span>
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<span class="n">VERSION</span> <span class="o">=</span> <span class="n">ZEBRA_PLUGIN_VERSION</span>
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<span class="n">NAME</span> <span class="o">=</span> <span class="sh">"</span><span class="s">Zebra</span><span class="sh">"</span>
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<span class="n">NAME</span> <span class="o">=</span> <span class="sh">"</span><span class="s">Zebra labels</span><span class="sh">"</span>
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<span class="n">SLUG</span> <span class="o">=</span> <span class="sh">"</span><span class="s">zebra</span><span class="sh">"</span>
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<span class="n">TITLE</span> <span class="o">=</span> <span class="sh">"</span><span class="s">Zebra Label Printer</span><span class="sh">"</span>
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</code></pre></div></div>
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<p>The name of the class can be freely chosen. You reference to it in the entry_points section of the setup.py file.
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<p>The name of the class can be freely chosen but should be different from SLUG. Otherwise it does not
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show up. You reference to it in the entry_points section of the setup.py file.
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The parameters need to be like in the example. Then there is the description block. The keywords are fixed and
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need to be like that. The values are found in the UI as shown in the pictures below.</p>
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need to be like that. The values are found in the UI as shown in the picture below.</p>
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<p><img src="/assets/plugins/plugin_admin.png" alt="Admin">
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<img src="/assets/plugins/plugin.png" alt="Config"></p>
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<p><img src="/assets/plugins/plugin.png" alt="Config"></p>
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<p>Then we add the configuration parameters.</p>
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<div class="language-python highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">SETTINGS</span> <span class="o">=</span> <span class="p">{</span>
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@ -263,43 +365,7 @@ can be chosen in the InvenTree settings. 800 is a good value because it gives hi
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<p>The rest of the code is just output to the printer on different interfaces.</p>
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<h2 id="quality-matters">Quality matters</h2>
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<p>The InvenTree printer system uses a graphical representation of the label. The label is described
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in HTML, converted to a pixel graphic and printed. The advantage is independency from printer
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models and systems. Disadvantage is larger data and quality problems with darkness and scaling.
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Let’s have a look at the following printout:</p>
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<p><img src="/assets/plugins/qr.png" alt="QRCodes"></p>
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<p>Both codes have been printed with the same printer on the same reel. The left one is
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hardly readable using my mobile. The right one reads easily even as it is smaller.</p>
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<h3 id="secret-1-scale">Secret 1, Scale</h3>
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<p>The printer resolution is 8 dots per mm resulting in a dot size of 0.125mm. The QR code pixel
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and the printer pixel size should be integrally divisible. The code in the picture has 21
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pixels plus one in the frame, so 23 pixel. The frame is set in the HTML description.</p>
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<div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>{% qrcode qr_data border=1 %}
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</code></pre></div></div>
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<p>I selected two dots per pixel. So 23 * 2 * 0.125 = 6.125mm. If the size is something different
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scaling takes place and the result might be worse. If you like a larger printout select more
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dots per pixel. From a certain size upwards the value does not matter any more because the code
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gets large enough to be readable in any quality.</p>
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<h3 id="secret-2-darkness">Secret 2: Darkness</h3>
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<p>Zebra printers allow to set the darkness of the print in values between 0 (white) and 30 (max)
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The left code was printed with a value 0r 30. The black dots tend to blur out a bit resulting
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in smaller white areas. The right code was printed with a value of 25 resulting in larger white
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pixels. The darkness values are just examples. Your values will differ based on printer model,
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media type and printer age. The printer head tends to wear out and the darkness value might
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need an adjustment from time to time.</p>
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<h3 id="alternative">Alternative</h3>
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<p>You can also bypass the InvenTree template and printing system and directly create ZPL from
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the parts data. The printer knows best how to render the label and the print quality is best.
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If you are interested in this way have a look at the <a href="https://github.com/yellowcrescent/inventree-zpl-plugin">inventree-zpl-plugin</a>
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that does exactly that.</p>
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<p>Happy printing.</p>
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</div>
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