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Asset Color Extractor

This plugin for Movable Type will look at any image asset and extract a set of colors from the image.

Prerequisites

  • Image Magick
  • Movable Type 6.2+
  • run-periodic-tasks must be set up

Configuration

The maximum number of colors to be extracted can be specified on a per-blog basis. Visit Tools > Plugins > Asset Color Extractor > Settings to specify this option. Note that the option is the maximum number of colors to be extracted. Simple or small images can return few results. "5" is likely a good balance between what can be extracted from images; some less complex images may only find one, two, or three colors and only the most complex images will return more than ten.

The colors are identified based upon commonality and frequency of use in the image histogram. Most typically, this means that the images background colors are going to appear in the palette first while less common colors will be at the end of the palette. The plugin reduces the image's complexity to find a color palette and this can also mean that a given color's frequency is not high enough in the histogram to extract that color. In other words, it's not a perfect tool.

If you want to use a color to blend in with the image, the first extracted color is likely a good choice. Better accent color choices can likely be found further along in the palette -- perhaps the 3rd or 5th color extracted, for example.

Use

The Asset Color Extractor plugin can be used to extract colors in a number of ways:

  • Automatically, on upload.
  • With the "Extract Colors" Page Action on the Edit Asset screen.
  • With the "Extract Colors" List Action on the Manage Assets screen. (Choose assets then select "Extract Colors" from the "Actions..." dropdown.)

Need to extract colors from all existing assets, and you've got a lot of assets? Included is a small script to help: extract-colors.pl. From your MT_HOME, run ./plugins/AssetColorExtractor/extract-colors.pl to process all image assets in the system. Restrict it by adding the blog ID, for example ./plugins/AssetColorExtractor/extract-colors.pl 7 to extract colors only for assets in blog ID 7.

All of these extraction methods work the same way, creating a new Worker for each asset. This is where run-periodic-tasks comes in: the extraction worker is run by run-periodic-tasks (informally, the "Publish Queue"). This also means that when choosign to extract colors they are typically not going to be available immediately; you must wait until the Worker finishes. Why do it this way? Most image assets can extract a color palette pretty quickly, but I found that some assets would take a long time to parse (often upwards of one minute). The commonality I found amongst image assets that took a long time to process wasn't file size or pixel dimensions, but sharpness. Images that are not quite sharp took quite a while. The only reasonable way to handle this, then, was to offload the extraction to another process that wouldn't leave the user waiting.

Extracted colors can be reviewed in two ways:

  • The Edit Asset screen will show an "Extracted Colors" section which presents large samples of the extracted colors.
  • The Manage Assets screen includes a new column for the Listing Framework, "Extracted Colors," which presents small samples of the extracted colors.

Template Tags

Two template tags are provided to make working with the extracted colors easy. Your template must be in the Asset context to use these tags.

AssetExtractedColors

The AssetExtractedColors block tag provides access to all of the extracted colors. It has no arguments. The meta variables __first__, __last__, __even__, __odd__, and __counter__ can be used with this tag. Example use is below.

The AssetExtractedColors block tag takes one argument: generate. Setting this argument to true (1) will cause the tag to extract colors from the image if not already availabe. This can be a good way to extract colors from older assets, but note that it can be resource intensive!

AssetExtractedColor

The AssetExtractedColor function tag outputs the extracted color. This can be used with the AssetExtractedColors block tag. Example:

<mt:Assets>
<p>
    <mt:AssetLabel>:
    <mt:AssetExtractedColors>
    <span style="width: 20px; height: 20px; display: inline-block;
        background-color: <mt:AssetExtractedColor>">
        <mt:Var name="__counter__">
    </span>
    </mt:AssetExtractedColors>
</p>
</mt:Assets>

The AssetExtractedColor tag can also be used without the AssetExtractedColors tag to output just one color by specifying the index argument, which requires an integer. The following example publishes the second color in the extracted palette:

<mt:Assets>
<p>
    <mt:AssetLabel>:
    <span style="width: 20px; height: 20px; display: inline-block;
        background-color: <mt:AssetExtractedColor index="2">">
        my color
    </span>
</p>
</mt:Assets>

The AssetExtractedColor tag will try to output the requested color. If it's not available, however, it will ourput the previously available color. For example, if a palette of three colors has been found and the template includes <mt:AssetExtractedColor index="5">, the then tag will output the third (last) color in the palette.

Additionally, the AssetExtractedColor tag supports the generate argument. Setting this argument to true (1) will cause the tag to create a Worker to extract colors from the image if not already available. This can be a good way to extract colors from older assets, too.

<mt:Assets>
<p>
    <mt:AssetLabel>:
    <span style="width: 20px; height: 20px; display: inline-block;
        background-color: <mt:AssetExtractedColor index="2" generate="1">">
        my color
    </span>
</p>
</mt:Assets>

License

This plugin is licensed under the same terms as Perl itself.

#Copyright

Copyright 2016, Endevver LLC. All rights reserved.