├── Readme.md
├── batcat.png
├── example.js
├── index.js
├── macbook.png
└── package.json


/Readme.md:
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 1 | 
 2 | # png-has-alpha
 3 | 
 4 |   Check if a PNG contains any alpha channels.
 5 | 
 6 | ## License
 7 | 
 8 |   MIT
 9 | 
10 | 


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/batcat.png:
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https://raw.githubusercontent.com/tj/node-png-has-alpha/bbc50ae065b0498eac970a986a5d8437a8bbdb14/batcat.png


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/example.js:
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 1 | 
 2 | var hasAlpha = require('./');
 3 | 
 4 | hasAlpha('batcat.png', function(err, yes){
 5 |   if (err) throw err;
 6 |   console.log('batcat: %s', yes ? 'yes' : 'no');
 7 | });
 8 | 
 9 | hasAlpha('macbook.png', function(err, yes){
10 |   if (err) throw err;
11 |   console.log('macbook: %s', yes ? 'yes' : 'no');
12 | });
13 | 
14 | var fs = require('fs');
15 | 
16 | var buf = fs.readFileSync('macbook.png');
17 | console.log('macbook: %s', hasAlpha(buf) ? 'yes' : 'no');
18 | 
19 | var buf = fs.readFileSync('batcat.png');
20 | console.log('batcat: %s', hasAlpha(buf) ? 'yes' : 'no');
21 | 


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/index.js:
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 1 | 
 2 | /**
 3 |  * Module dependencies.
 4 |  */
 5 | 
 6 | var fs = require('fs');
 7 | 
 8 | /**
 9 |  * Expose `hasAlpha`.
10 |  */
11 | 
12 | module.exports = hasAlpha;
13 | 
14 | /**
15 |  * Check if `png` has transparency.
16 |  *
17 |  * @param {String|Buffer} png buffer or filename
18 |  * @param {Function} [fn]
19 |  * @api public
20 |  */
21 | 
22 | function hasAlpha(png, fn) {
23 |   if ('string' == typeof png) return fromFile(png, fn);
24 |   return 6 == png[25];
25 | }
26 | 
27 | /**
28 |  * From file.
29 |  */
30 | 
31 | function fromFile(file, fn) {
32 |   var buf = new Buffer(1);
33 |   fs.open(file, 'r', function(err, fd){
34 |     if (err) return fn(err);
35 |     fs.read(fd, buf, 0, 1, 25, function(err, read, buf){
36 |       if (err) return fn(err);
37 |       fs.close(fd, function(err){
38 |         fn(err, 6 == buf[0]);
39 |       });
40 |     });
41 |   });
42 | }
43 | 


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/macbook.png:
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https://raw.githubusercontent.com/tj/node-png-has-alpha/bbc50ae065b0498eac970a986a5d8437a8bbdb14/macbook.png


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/package.json:
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1 | {
2 |   "name": "png-has-alpha",
3 |   "version": "1.0.0",
4 |   "description": "check if a png has alpha channels",
5 |   "license": "MIT"
6 | }
7 | 


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