imghdr

imghdr

The imghdr module determines the type of image contained in a file or octet-streams(object of Buffer), inspired by Python's imghdr module.

Installation

npm install imghdr

Usage

var imghdr = require('imghdr');
 
var imgPath = __dirname + '/meituan.jpg';
var ext = 'jpg';
 
var exts = imghdr.what(imghdr);
console.log(exts);
// => ['jpg', 'jpeg']
 
if (exts.indexOf(ext) === -1) {
    console.log('The `' + imgPath + '`\'s extension is not a `' + ext + '`');
} else {
    console.log('OK');
}
// => 'OK'

API

The imghdr module defines the following function:

imghdr.what(imgPath)

Tests the image data contained in the file named by imgPath, and returns an array of strings describing the image type. imgPath can be a object of Buffer.

Value	Image format
"png"	Portable Network Graphics
"jpeg","jpg"	JPEG data in JFIF or Exif formats
"gif"	GIF 87a and 89a Files
"tiff"	Tagged Image File Format
"bmp"	BMP files
"webp"	WebP files

You can extend the list of file types imghdr can recognize by appending to this variable:

imghdr.tests

A list of functions performing the individual tests. Each function takes a argument: the octet-streams(object of Buffer).The test function should return an array of strings describing the image type if the test succeeded, or [] if it failed.

Example:

function testCustom(buf) {
    var sigBuf = new Buffer([0x6c, 0x6f, 0x76, 0x65]);
    var testSigBuf = buf.slice(2, 6);
 
    return (sigBuf.toString() == testSigBuf.toString()) ? ['custom'] : [];
}
 
// add to list of `tests`
imghdr.tests.push(testCustom);
 
var testBuf = new Buffer([0x49, 0x20, 0x6c, 0x6f, 0x76, 0x65, 0x20, 0x79, 0x6f, 0x75]);
imghdr.what(testBuf);
// => ['custom']

Reference

• http://www.filesignatures.net
• http://www.garykessler.net/library/file_sigs.html
• https://docs.python.org/3.4/library/imghdr.html

LICENSE

MIT