React Image Crop

A responsive image cropping tool for React.

Features

Responsive
Touch enabled
Free-form or fixed aspect crops
Keyboard support for nudging selection
Min/max crop size

Installation

npm i react-image-crop --save

Usage

Include the main js module, e.g.:

var ReactCrop = require('react-image-crop');
// or es6:
import ReactCrop from 'react-image-crop';

Include either dist/ReactCrop.css or ReactCrop.scss.

import 'react-image-crop/dist/ReactCrop.css';
// or scss:
import 'react-image-crop/lib/ReactCrop.scss';

Props

src (required)

<ReactCrop src="path/to/image.jpg" />

You can of course pass a blob path or base64 data.

crop (optional)

All crop values are in percentages, and are relative to the image. All crop params are optional.

var crop = {
  x: 20,
  y: 10,
  width: 30,
  height: 10
}

<ReactCrop src="path/to/image.jpg" crop={crop} />

If you want a fixed aspect can either omit width and height:

var crop = {
 aspect: 16/9
}

Or you need to specify both. As ReactCrop is based on percentages you will need to know the ratio of the image. If you don't see onImageLoaded for how to set your crop in there.

minWidth (optional)

A minimum crop width, as a percentage of the image width.

minHeight (optional)

A minimum crop height, as a percentage of the image height.

maxWidth (optional)

A maximum crop width, as a percentage of the image width.

maxHeight (optional)

A maximum crop height, as a percentage of the image height.

keepSelection (optional)

If true is passed then selection can't be disabled if the user clicks outside the selection area.

disabled (optional)

If true then the user cannot modify or draw a new crop. A class of ReactCrop--disabled is also added to the container for user styling.

onChange(crop, pixelCrop)

A callback which happens for every change of the crop (i.e. many times as you are dragging/resizing). Passes the current crop state object, as well as a pixel-converted crop for your convenience.

Note you must implement this callback and update your crop state, otherwise nothing will change!

onComplete(crop, pixelCrop) (optional)

A callback which happens after a resize, drag, or nudge. Passes the current crop state object, as well as a pixel-converted crop for your convenience.

onImageLoaded(image) (optional)

A callback which happens when the image is loaded. Passes the image DOM element.

Note you should set your crop here if you're using crop.aspect along with a width or height. Since ReactCrop uses percentages we can only infer the correct width and height once we know the image ratio.

import ReactCrop, { makeAspectCrop } from 'react-image-crop';

onImageLoaded = (image) => {
  this.setState({
    crop: makeAspectCrop({
      x: 0,
      y: 0,
      aspect: 16 / 9,
      width: 50,
    }, image.width / image.height),
  });
}

Of course if you already know the image ratio (or just specifying the aspect) you can set the crop earlier!

onDragStart() (optional)

A callback which happens when a user starts dragging or resizing. It is convenient to manipulate elements outside this component.

onDragEnd() (optional)

A callback which happens when a user releases the cursor or touch after dragging or resizing.

crossorigin (optional)

Allows setting the crossorigin attribute on the image.

What about showing the crop on the client?

I wanted to keep this component focused so I didn't provide this. Normally a cropped image will be rendered and cached by a backend. However here are some tips for client-side crop previews:

You can fake a crop in pure CSS, but in order to do this you need to know the maximum width & height of the crop preview and then perform the calc again if the container size changes (since this technique is only possible using pixels). It's advantage is that it's instantaneous:

Example gist

The other technique is to map the cropped image to a canvas, and then get the base64 of the canvas via toDataURL and set this as an image source. The advantage is that the preview behaves like a proper image and is responsive. Now this is important:

toDataURL is synchronous and will block the main thread, for large images this could be for as long as a couple of seconds. Always use toDataURL('image/jpeg') otherwise it will default to image/png and the conversion will be significantly slower.
Keep an eye out for toBlob when this lands on more browsers, as it will be both faster and asynchronous.
Another option to make the conversion faster is to scale the image down before converting it to a base64 (see example in gist).