image-size-stream

Detect the width and height of images in a stream

//       +-----------+
//       |           |
// 300px |  foo.jpg  |
//       |           |
//       +-----------+
//           400px 

var imageSizeStream = createImageSizeStream()
.on('size', function(dimensions) {
  dimensions; //=> {width: 400, height: 300, type: 'jpg'}
  stream.destroy();
});

var stream = fs.createReadStream('path/to/foo.jpg').pipe(imageSizeStream);

Installation

Use npm.

npm install --save image-size-stream

Supported image formats

• BMP
• GIF
• JPEG
• PNG
• PSD
• SVG
• TIFF
• WebP

API

var createImageSizeStream = require('image-size-stream');

createImageSizeStream([option])

option: Object
Return: Object (stream.Transform)

The stream tries to detect the image size and emits size or error event.

var createImageSizeStream = require('image-size-stream');
var imageSizeStream = createImageSizeStream();

option.limit

Type: Number
Default: 128 * 1024

The maximum bytes the stream can reads. It emits an error if it cannot detect the image size though it has reached the limit.

Usually the default value meets the requirements.

Events

size

This event fires when the stream detect the image size. It passes an object in the form {width: [Number], height: [Number], type: [String]} to the callback function.

type will be one of the following strings: bmp gif jpg png psd svg tiff webp

imageSizeStream.on('size', function(dimensions) {
  console.log('size: ' + dimensions.width + ' x ' + dimensions.height);
  console.log('image format: ' + dimensions.type);
});

error

This event fires when the stream failed to detect the image size. It passes an error to the callback function.

Examples

These examples show that you don't need to read the image entirely if you just want to detect its width and height.

Read data from local file system

var fs = require('fs');
var fileStream = fs.createReadStream('path/to/image.jpg');

var createImageSizeStream = require('image-size-stream');
var size = createImageSizeStream();
size
.on('size', function(dimensions) {
  console.log(dimensions);
  fileStream.destroy();
})
.on('error', function(err) {
  throw err;
});

fileStream.pipe(size);

If you want to stop reading the rest of the image file at size event, call fs.ReadStream#destroy() or fs.ReadStream#close().

Read data via HTTP

var http = require('http');

var createImageSizeStream = require('image-size-stream');
var size = createImageSizeStream();
size
.on('size', function(dimensions) {
  console.log(dimensions);
  request.abort();
})
.on('error', function(err) {
  throw err;
});

var request = http.get('url/to/image.png', function(response) {
  response.pipe(size);
});

If you want to stop loading the rest of the image file at size event, call request.abort().

License

Copyright (c) 2014 - 2015 Shinnosuke Watanabe

Licensed under the MIT License.