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85 lines
2.6 KiB
Markdown
85 lines
2.6 KiB
Markdown
# JavaScript Canvas to Blob
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## Description
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Canvas to Blob is a polyfill for the standard JavaScript
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[canvas.toBlob](http://www.w3.org/TR/html5/scripting-1.html#dom-canvas-toblob)
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method.
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It can be used to create
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[Blob](https://developer.mozilla.org/en-US/docs/Web/API/Blob)
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objects from an HTML
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[canvas](https://developer.mozilla.org/en-US/docs/HTML/Canvas) element.
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## Usage
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Include the (minified) JavaScript Canvas to Blob script in your HTML markup:
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```html
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<script src="js/canvas-to-blob.min.js"></script>
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```
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Then use the *canvas.toBlob()* method in the same way as the native
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implementation:
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```js
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var canvas = document.createElement('canvas');
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/* ... your canvas manipulations ... */
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if (canvas.toBlob) {
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canvas.toBlob(
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function (blob) {
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// Do something with the blob object,
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// e.g. creating a multipart form for file uploads:
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var formData = new FormData();
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formData.append('file', blob, fileName);
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/* ... */
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},
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'image/jpeg'
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);
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}
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```
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## Requirements
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The JavaScript Canvas to Blob function has zero dependencies.
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However, Canvas to Blob is a very suitable complement to the
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[JavaScript Load Image](https://github.com/blueimp/JavaScript-Load-Image)
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function.
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## API
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In addition to the **canvas.toBlob** polyfill, the JavaScript Canvas to Blob
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script provides one additional function called **dataURLtoBlob**, which is added
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to the global window object, unless the library is loaded via a module loader
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like RequireJS, Browserify or webpack:
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```js
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// 80x60px GIF image (color black, base64 data):
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var b64Data = 'R0lGODdhUAA8AIABAAAAAP///ywAAAAAUAA8AAACS4SPqcvtD6' +
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'OctNqLs968+w+G4kiW5omm6sq27gvH8kzX9o3n+s73/g8MCofE' +
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'ovGITCqXzKbzCY1Kp9Sq9YrNarfcrvcLDovH5PKsAAA7',
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imageUrl = 'data:image/gif;base64,' + b64Data,
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blob = window.dataURLtoBlob && window.dataURLtoBlob(imageUrl);
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```
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## Browsers
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The following browsers support either the native or the polyfill
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*canvas.toBlob()* method:
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### Desktop browsers
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* Google Chrome (see [Chromium issue #67587](https://code.google.com/p/chromium/issues/detail?id=67587))
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* Apple Safari 6.0+ (see [Mozilla issue #648610](https://bugzilla.mozilla.org/show_bug.cgi?id=648610))
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* Mozilla Firefox 4.0+
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* Microsoft Internet Explorer 10.0+
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### Mobile browsers
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* Apple Safari Mobile on iOS 6.0+
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* Google Chrome on iOS 6.0+
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* Google Chrome on Android 4.0+
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## Test
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[JavaScript Canvas to Blob Test](https://blueimp.github.io/JavaScript-Canvas-to-Blob/test/)
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## License
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The JavaScript Canvas to Blob script is released under the
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[MIT license](http://www.opensource.org/licenses/MIT).
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