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