grade-js

2018-06-13 admin

grade-js是什么

什么是grade-js,This JavaScript library produces complimentary gradients generated from the top 2 dominant colours in supplied images

grade-js介绍、grade-js使用

<div class=“gradient-wrap”> <img src="./samples/finding-dory.jpg" alt="" /> </div> <div class=“gradient-wrap”> <img src="./samples/good-dinosaur.jpg" alt="" /> </div>


If you have the `grade.js` in your project, you can include it with a script tag and initialise it like so:

```text-html-basic
<script src="path/to/grade.js"></script>
<script type="text/javascript">
    window.addEventListener('load', function(){
        /*
            A NodeList of all your image containers (Or a single Node).
            The library will locate an <img /> within each
            container to create the gradient from.
         */
        Grade(document.querySelectorAll('.gradient-wrap'))
    })
</script>

If you pass in a 3rd parameter and it’s a function, the HTML element(s) you passed in as the 1st parameter will not be manipulated, but an array will be returned to you, for you to do as you please with, ie.

Grade(document.querySelectorAll('.gradient-wrap'), null, function(gradientData){
    // sample contents of `gradientData` can be inspected here https://jsonblob.com/57c4601ee4b0dc55a4f180f1
})

If you’ve installed from npm, you can use the library like so:

import Grade from 'grade-js'
// initialise as above

The module this imports will be using ES2015 syntax, so it will need to be transpiled by a build tool, like Babel, and if you are importing the module in this fashion (and using npm), I imagine you’re already using a bundling tool, like Webpack or Browserify!

Running locally

If you want to run this locally, just to test it, you need to serve index.html via a webserver, not just by opening it in a browser, else the browser will throw a security error. I would recommend either live-server (requires Node.js installed on your machine) or if you have Python installed, just run python -m SimpleHTTPServer inside the project root. If you’re on Windows, I believe WAMP/Apache is the best way to go.

Remote images

This plugin utilises the <canvas> element and the ImageData object, and due to cross-site security limitations, the script will fail if one tries to extract the colors from an image not hosted on the current domain, unless the image allows for Cross Origin Resource Sharing.

Enabling CORS on S3

To enable CORS for images hosted on S3 buckets, follow the Amazon guide here; adding the following to the bucket’s CORS configuration:

<CORSRule>
 <AllowedOrigin>*</AllowedOrigin>
 <AllowedMethod>GET</AllowedMethod>
</CORSRule>

For all images, you can optionally also include a cross-origin attribute in your image.


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