https://www.drought.gov/modules/custom/external_libs/libs/canvasToBlob/canvasToBlob.js?tlrx84

1/* canvas-toBlob.js
2 * A canvas.toBlob() implementation.
3 * 2016-05-26
4 *
5 * By Eli Grey, http://eligrey.com and Devin Samarin, https://github.com/eboyjr
6 * License: MIT
7 *   See https://github.com/eligrey/canvas-toBlob.js/blob/master/LICENSE.md
8 */
9
10/*global self */
11/*jslint bitwise: true, regexp: true, confusion: true, es5: true, vars: true, white: true,
12  plusplus: true */
13
14/*! @source http://purl.eligrey.com/github/canvas-toBlob.js/blob/master/canvas-toBlob.js */
15
16(function(view) {
17  "use strict";
18  var
19    Uint8Array = view.Uint8Array
20    , HTMLCanvasElement = view.HTMLCanvasElement
21    , canvas_proto = HTMLCanvasElement && HTMLCanvasElement.prototype
22    , is_base64_regex = /\s*;\s*base64\s*(?:;|$)/i
23    , to_data_url = "toDataURL"
24    , base64_ranks
25    , decode_base64 = function(base64) {
26      var
27        len = base64.length
28        , buffer = new Uint8Array(len / 4 * 3 | 0)
29        , i = 0
30        , outptr = 0
31        , last = [0, 0]
32        , state = 0
33        , save = 0
34        , rank
35        , code
36        , undef
37      ;
38      while (len--) {
39        code = base64.charCodeAt(i++);
40        rank = base64_ranks[code-43];
41        if (rank !== 255 && rank !== undef) {
42          last[1] = last[0];
43          last[0] = code;
44          save = (save << 6) | rank;
45          state++;
46          if (state === 4) {
47            buffer[outptr++] = save >>> 16;
48            if (last[1] !== 61 /* padding character */) {
49              buffer[outptr++] = save >>> 8;
50            }
51            if (last[0] !== 61 /* padding character */) {
52              buffer[outptr++] = save;
53            }
54            state = 0;
55          }
56        }
57      }
58      // 2/3 chance there's going to be some null bytes at the end, but that
59      // doesn't really matter with most image formats.
60      // If it somehow matters for you, truncate the buffer up outptr.
61      return buffer;
62    }
63  ;
64  if (Uint8Array) {
65    base64_ranks = new Uint8Array([
66      62, -1, -1, -1, 63, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1
67      , -1, -1,  0, -1, -1, -1,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9
68      , 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25
69      , -1, -1, -1, -1, -1, -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35
70      , 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51
71    ]);
72  }
73  if (HTMLCanvasElement && (!canvas_proto.toBlob || !canvas_proto.toBlobHD)) {
74    if (!canvas_proto.toBlob)
75      canvas_proto.toBlob = function(callback, type /*, ...args*/) {
76        if (!type) {
77          type = "image/png";
78        } if (this.mozGetAsFile) {
79          callback(this.mozGetAsFile("canvas", type));
80          return;
81        } if (this.msToBlob && /^\s*image\/png\s*(?:$|;)/i.test(type)) {
82          callback(this.msToBlob());
83          return;
84        }
85
86        var
87          args = Array.prototype.slice.call(arguments, 1)
88          , dataURI = this[to_data_url].apply(this, args)
89          , header_end = dataURI.indexOf(",")
90          , data = dataURI.substring(header_end + 1)
91          , is_base64 = is_base64_regex.test(dataURI.substring(0, header_end))
92          , blob
93        ;
94        if (Blob.fake) {
95          // no reason to decode a data: URI that's just going to become a data URI again
96          blob = new Blob
97          if (is_base64) {
98            blob.encoding = "base64";
99          } else {
100            blob.encoding = "URI";
101          }
102          blob.data = data;
103          blob.size = data.length;
104        } else if (Uint8Array) {
105          if (is_base64) {
106            blob = new Blob([decode_base64(data)], {type: type});
107          } else {
108            blob = new Blob([decodeURIComponent(data)], {type: type});
109          }
110        }
111        callback(blob);
112      };
113
114    if (!canvas_proto.toBlobHD && canvas_proto.toDataURLHD) {
115      canvas_proto.toBlobHD = function() {
116        to_data_url = "toDataURLHD";
117        var blob = this.toBlob();
118        to_data_url = "toDataURL";
119        return blob;
120      }
121    } else {
122      canvas_proto.toBlobHD = canvas_proto.toBlob;
123    }
124  }
125}(typeof self !== "undefined" && self || typeof window !== "undefined" && window || this.content || this));