docpad-plugin-thumbnails

DocPad plugin to generate thumbnails from your associated image files

npm install docpad-plugin-thumbnails
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Thumbnails Plugin for DocPad

Adds support for thumbnail generation to DocPad using the gm library.

Install

Install either GraphicsMagick or ImageMagick, and then:

npm install --save docpad-plugin-thumbnails

ImageMagick

To specify the use of ImageMagick, rather than GraphicsMagick, you need to add the following configuration setting in your docpad configuration:

plugins:
    thumbnails:
        imageMagick: true

Usage

Basic Usage

Use the @getThumbnail(path, [options...]) function in your templates.

path is the path of your image file, relative to the files directory.

options... are optional parameters, discussed below.

The @getThumbnail() call will return the url to the thumbnail image.

Basic Example

We could create the document mydocument.html.eco containing the following:

<img src="<%= @getThumbnail("images/image1.jpg", { w: 100, h: 100 }) %>"  alt="my image">

Where image1.jpg is in the src/files/images/ directory.

This will run the default resize operation which will fit the image into the given maximum boundaries, in this case 100x100 pixels.

On site generation, the file out/images/image1.thumb_default_w100h100q85.jpg will be created. It will also be updated whenever the source image src/files/images/image1.jpg changes.

AssociatedFiles Example

The Thumbnails plugin works well with the AssociatedFiles plugin. The example below (this time in coffeekup) will display 100x100 thumbnails of all images associated with the document using the AssociatedFiles plugin, with a link to the full-size image:

image_exts = ['jpg', 'JPG', 'jpeg', 'JPEG', 'png', 'PNG']
images = @getDocument().getAssociatedFiles().findAll({extension: $in: image_exts}).toJSON()
for image in images
    a href: image.url, -> img src: @getThumbnail(image.url, w: 100, h: 100), alt: image.name

Configuration

Options

The optional arguments to @getThumbnail can be one or more of the following:

  • an object containing parameters to pass to the target.
  • a string to specify a preset
  • a string to specify a target

Image Parameters

There are 3 different image parameters you can specify:

  • w for the width of the image
  • h for the height of the image
  • q for the JPEG quality setting

Parameters can be set using the object form shown in the examples above, or via presets, discussed below.

Presets

Presets are basically aliases for a set of image parameters that you can define in your docpad configuration. Using presets can be more convenient than specifying parameters for each image individually, and helps your site stay consistent. For example, in your docpad.coffee file you might define the following:

plugins:
    thumbnails:
        presets:
            'default':
                w: 200
                h: 200
                q: 90
            'small':
                w: 100
                h: 100
            'medium':
                w: 300
                h: 300
            'large':
                w: 500
                h: 500

If no parameters (or preset names) are passed to the @getThumbnail() function, then the default parameters will be used. Given the above configuration, the example below will resize the image to 200x200 at 90% quality.

<img src="<%= @getThumbnail("images/image1.jpg") %>"  alt="my image">

You can pass multiple parameters to the @getThumbnails() call, and they will be applied from left to right. For example, you could use the default height and quality parameters and just override the width as follows:

<img src="<%= @getThumbnail("images/image1.jpg", { w: 250 }) %>"  alt="my image">

You can also mix presets with inline parameters, such as:

<img src="<%= @getThumbnail("images/image1.jpg", { q: 80 }, 'medium', { h: 50 }) %>"  alt="my image">

The right-most parameters will take precedence over those specified earlier. So the above example uses w: 300, h: 50, and q: 80.

There are a whole bunch of default presets defined in the plugin, but you will probably want to define your own instead.

Targets

A thumbnail target defines the set of operations to be performed by the plugin. If no target is specified then the default target is executed, which specifies a basic resize operation. Given that, the following example:

<img src="<%= @getThumbnail("images/image1.jpg", { w: 100, h: 100 }) %>"  alt="my image">

Is equivalent to:

<img src="<%= @getThumbnail("images/image1.jpg", "default", { w: 100, h: 100 }) %>"  alt="my image">

The plugin includes another target, zoomcrop, which center-crops the image to the exact width and height supplied, rather than just fitting the image into those boundaries. To specify the zoomcrop target, just change the example to:

<img src="<%= @getThumbnail("images/image1.jpg", "zoomcrop", { w: 100, h: 100 }) %>"  alt="my image">

Creating your own targets

You can overide the default or zoomcrop targets if you wish, or specify completely new ones via the plugin configuration. For example, lets define a couple more to play with:

plugins:
    thumbnails:
        targets:
            'sepia': (img, args) ->
                return img.sepia()
            'rotateleft': (img, args) ->
                return img.rotate('black', -90)

img is a reference to a gm image object. The target function must also return a gm image object.

The args argument is just an object containing the w, h, q parameters passed to @getThumbnail()

You can use any GraphicsMagick/ImageMagick operation supported by the gm module. You can find the details of those in the gm docs.

To run one of our new targets, we can do the following:

<img src="<%= @getThumbnail("images/image1.jpg", 'medium', 'sepia' %>"  alt="my image">

Note that targets and presets can be passed to @getThumbnail in any order, and intermixed as you like. The only caveat is that a target and preset cannot have the same name, otherwise the plugin won't know which one you're talking about.

Note however that in contrast to the presets, the default target is only run if no other targets are specified. So for the above example, the image is not resized at all.

Running multiple targets

You can pass in more than one target to @getThumbnail() and they will be executed in order.

For example, you could do the following to get a small zoom-cropped, sepia'd and rotated image:

<img src="<%= @getThumbnail("images/image1.jpg", 'small', 'zoomcrop', 'sepia', 'rotateleft' %>"  alt="my image">

Of course if this was a common occurence on your site, you would be much better off building a target to do it all in one go, like so:

plugins:
    thumbnails:
        targets:
            'doitall': (img, args) ->
                return img
                    .quality(args.q)
                    .gravity('Center')
                    .resize(args.w, args.h, '^')
                    .crop(args.w, args.h)
                    .sepia()
                    .rotate('black', -90)

Overriding the default target

You can assign a target name to default in the plugin configuration to make that target the new default action. For example, to make zoomcrop the new default:

plugins:
    thumbnails:
        targets:
            'default': 'zoomcrop'

Adding different file formats

By default the plugin supports jpeg and png files. If you wish to use other formats that are supported by ImageMagick/GraphicsMagick you can override the extensions option. This limits the file extensions that are allowed to be passed through the plugin.

extensions: ['jpg', 'JPG', 'jpeg', 'JPEG', 'png', 'PNG', 'gif', 'GIF']

History

You can discover the history inside the History.md file

License

Licensed under the incredibly permissive MIT License
Copyright © 2013 Richard Antecki

Contributors

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