grunt-image-resize
Resizing images made easy - thanks to ImageMagick.
Getting Started
This plugin requires Grunt ^0.4.5
and ImageMagick.
Grunt
If you haven't used Grunt before, be sure to check out the Getting Started guide, as it explains how to create a Gruntfile as well as install and use Grunt plugins. Once you're familiar with that process, you may install this plugin with this command:
npm install grunt-image-resize --save-dev
One the plugin has been installed, it may be enabled inside your Gruntfile with this line of JavaScript:
grunt;
ImageMagick
Make sure ImageMagick is installed on your system and properly set up in your PATH
.
Ubuntu:
$ apt-get install imagemagick
Mac OS X (using Homebrew):
$ brew install imagemagick
Windows & others:
http://www.imagemagick.org/script/binary-releases.php
Confirm that ImageMagick is properly set up by executing convert -help
in a terminal.
The "image_resize" task
Overview
In your project's Gruntfile, add a section named image_resize
to the data object passed into grunt.initConfig()
.
grunt
Options
options.width
Type: Number
Default value: 0
(only if height is defined)
A number value that is passed as pixel or percentage value to imagemagick.
options.height
Type: Number
Default value: 0
(only if width is defined)
A number value that is passed as pixel or percentage value to imagemagick.
options.overwrite
Type: Boolean
Default value: true
Determines whether file that already exist under this destination will be overwritten.
options.upscale
Type: Boolean
Default value: false
Determines whether images will be upscaled. If set to false
(default), image will be copied instead of resized if it would be upscaled by resizing.
options.crop
Type: Boolean
Default value: false
Determines whether images will be cropped after resizing to exactly match options.width
and options.height
.
options.gravity
Type: String
Default value: Center
Possible values: NorthWest
, North
, NorthEast
, West
, Center
, East
, SouthWest
, South
, SouthEast
When cropping images this sets the image gravity. Doesn't have any effect, if options.crop
is false
.
options.concurrency
Type: Number
Default value: Number of CPUs
Determines how many resize operations are executed in parallel.
options.quality
Type: Number
Default value: 1
Determines the output quality of the resized image. Ranges from 0
(really bad) to 1
(almost lossless). Only applies to jpg images.
options.autoOrient
Type: Boolean
Default value: false
Determines if resized image will be rotated according to EXIF information. Only applies to jpg images.
Usage Examples
Default Options
In this example, the default options are used to resize an image to 100px width. So if the test/fixtures/wikipedia.png
file has a width of 500px, the generated result would be a 100px wide tmp/wikipedia.png
.
grunt
Prevent overwriting
In this example, we prevent the destination file from being overwritten if it already exists. It the file tmp/wikipedia.png
already exists, for example because we just ran the task configuration above, this would not overwrite tmp/wikipedia.png
. The file tmp/wikipedia.png
would still be 100px wide.
grunt
Allow upscaling
By default, the task does not resize images which would be upscaled. It only allows downscaling. You can allow upscaling by setting the upscale
option to true
. Otherwise images will copied instead of resized when they would be upscaled by resizing.
grunt
Resize all the images in a directory
grunt
Contributing
In lieu of a formal styleguide, take care to maintain the existing coding style. Add unit tests for any new or changed functionality. Lint and test your code using Grunt.