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canvas-toBlob.js
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canvas-toBlob.js
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/* canvas-toBlob.js
* A canvas.toBlob() implementation.
* 2011-07-13
*
* By Eli Grey, http://eligrey.com and Devin Samarin, https://github.com/eboyjr
* License: X11/MIT
* See LICENSE.md
*/
/*global self */
/*jslint bitwise: true, regexp: true, confusion: true, es5: true, vars: true, white: true,
plusplus: true */
/*! @source http://purl.eligrey.com/github/canvas-toBlob.js/blob/master/canvas-toBlob.js */
(function(view) {
"use strict";
var
Uint8Array = view.Uint8Array
, HTMLCanvasElement = view.HTMLCanvasElement
, is_base64_regex = /\s*;\s*base64\s*(?:;|$)/i
, base64_ranks
, decode_base64 = function(base64) {
var
len = base64.length
, buffer = new Uint8Array(len / 4 * 3 | 0)
, i = 0
, outptr = 0
, last = [0, 0]
, state = 0
, save = 0
, rank
, code
, undef
;
while (len--) {
code = base64.charCodeAt(i++);
rank = base64_ranks[code-43];
if (rank !== 255 && rank !== undef) {
last[1] = last[0];
last[0] = code;
save = (save << 6) | rank;
state++;
if (state === 4) {
buffer[outptr++] = save >>> 16;
if (last[1] !== 61 /* padding character */) {
buffer[outptr++] = save >>> 8;
}
if (last[0] !== 61 /* padding character */) {
buffer[outptr++] = save;
}
state = 0;
}
}
}
// 2/3 chance there's going to be some null bytes at the end, but that
// doesn't really matter with most image formats.
// If it somehow matters for you, truncate the buffer up outptr.
return buffer.buffer;
}
;
if (Uint8Array) {
base64_ranks = new Uint8Array([
62, -1, -1, -1, 63, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1
, -1, -1, 0, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9
, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25
, -1, -1, -1, -1, -1, -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35
, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51
]);
}
if (HTMLCanvasElement && !HTMLCanvasElement.prototype.toBlob) {
HTMLCanvasElement.prototype.toBlob = function(callback, type /*, ...args*/) {
if (!type) {
type = "image/png";
} if (this.mozGetAsFile) {
callback(this.mozGetAsFile("canvas", type));
return;
}
var
args = Array.prototype.slice.call(arguments, 1)
, dataURI = this.toDataURL.apply(this, args)
, header_end = dataURI.indexOf(",")
, data = dataURI.substring(header_end + 1)
, is_base64 = is_base64_regex.test(dataURI.substring(0, header_end))
, BlobBuilder = view.BlobBuilder || view.WebKitBlobBuilder || view.MozBlobBuilder
, bb = new BlobBuilder
, blob
;
if (BlobBuilder.fake) {
// no reason to decode a data: URI that's just going to become a data URI again
blob = bb.getBlob(type);
if (is_base64) {
blob.encoding = "base64";
} else {
blob.encoding = "URI";
}
blob.data = data;
blob.size = data.length;
} else if (Uint8Array) {
if (is_base64) {
bb.append(decode_base64(data));
} else {
bb.append(decodeURIComponent(data));
}
blob = bb.getBlob(type);
}
callback(blob);
};
}
}(self));