lib-image-conversion

image-conversion

image-conversion is a simple and easy-to-use JS image convert tools, which provides many methods to convert between Image,Canvas,File and dataURL.

In addition，image-conversion can specify size to compress the image (test here).

Methods Map

Getting started

Install

npm i image-conversion --save

# or 

yarn add image-conversion

Include the library

in browser:

<script src="https://cdn.jsdelivr.net/gh/WangYuLue/image-conversion/build/conversion.js"></script>

in CommonJS:

const imageConversion = require("image-conversion");

in ES6:

import * as imageConversion from 'image-conversion';

or

import {compress, compressAccurately} from 'image-conversion';

Use examples

<input id="demo" type="file" onchange="view()">

1. Compress image to 200kb:

function view(){
  const file = document.getElementById('demo').files[0];
  console.log(file);
  imageConversion.compressAccurately(file,200).then(res=>{
    //The res in the promise is a compressed Blob type (which can be treated as a File type) file;
    console.log(res);
  })
}

// or use an async function
async function view() {
  const file = document.getElementById('demo').files[0];
  console.log(file);
  const res = await imageConversion.compressAccurately(file,200)
  console.log(res);
}

1. Compress images at a quality of 0.9

function view(){
  const file = document.getElementById('demo').files[0];
  console.log(file);
  imageConversion.compress(file,0.9).then(res=>{
    console.log(res);
  })
}

Methods list

image-conversion provides many methods to convert between Image,Canvas,File and dataURL,as follow:

imagetoCanvas(image[, config]) → {Promise(Canvas)}

Description:

Convert an image object into a canvas object.

Parameters:

Name	Type	Attributes	Description
image	image		a image object
config	object	optional	with this config you can zoom in, zoom out, and rotate the image

Example:

imageConversion.imagetoCanvas(image);

//or

imageConversion.imagetoCanvas(image,{
  width: 300,   //result image's width
  height: 200,  //result image's height
  orientation:2,//image rotation direction
  scale: 0.5,   //the zoom ratio relative to the original image, range 0-10;
                //Setting config.scale will override the settings of
                //config.width and config.height;
})

config.orientation has many options to choose,as follow:

Options	Orientation
1	0°
2	horizontal flip
3	180°
4	vertical flip
5	clockwise 90° + horizontal flip
6	clockwise 90°
7	clockwise 90° + vertical flip
8	Counterclockwise 90°

Returns:

Promise that contains canvas object.

dataURLtoFile(dataURL[, type]) → {Promise(Blob)}

Description:

Convert a dataURL string to a File(Blob) object. you can determine the type of the File object when transitioning.

Parameters:

Name	Type	Attributes	Description
dataURL	string		a dataURL string
type	string	optional	determine the converted image type; the options are "image/png", "image/jpeg", "image/gif".

Returns:

Promise that contains a Blob object.

compress(file, config) → {Promise(Blob)}

Description:

Compress a File(Blob) object.

Parameters:

Name	Type	Description
file	File(Blob)	a File(Blob) object
config	number | object	if number type, range 0-1, indicate the image quality; if object type,you can pass parameters to the imagetoCanvas and dataURLtoFile method; Reference is as follow:

Tips:

If you compress png transparent images, please select 'image/png' type.

Example:

// number
imageConversion.compress(file,0.8)

//or

// object
imageConversion.compress(file,{
  quality: 0.8,
  type: "image/jpeg",
  width: 300,
  height: 200,
  orientation:2,
  scale: 0.5,
})

Returns:

Promise that contains a Blob object.

compressAccurately(file, config) → {Promise(Blob)}

Description:

Compress a File(Blob) object based on size.

Parameters:

Name	Type	Description
file	File(Blob)	a File(Blob) object
config	number | object	if number type, specify the size of the compressed image(unit KB); if object type,you can pass parameters to the imagetoCanvas and dataURLtoFile method; Reference is as follow:

Tips:

If you compress png transparent images, please select 'image/png' type

Example:

// number
imageConversion.compressAccurately(file,100); //The compressed image size is 100kb
// object
imageConversion.compressAccurately(file,{
  size: 100,    //The compressed image size is 100kb
  accuracy: 0.9,//the accuracy of image compression size,range 0.8-0.99,default 0.95;
                //this means if the picture size is set to 1000Kb and the
                //accuracy is 0.9, the image with the compression result
                //of 900Kb-1100Kb is considered acceptable;
  type: "image/jpeg",
  width: 300,
  height: 200,
  orientation:2,
  scale: 0.5,
})

Returns:

Promise that contains a Blob object.

canvastoDataURL(canvas[, quality, type]) → {Promise(string)}

Description:

Convert a Canvas object into a dataURL string, this method can be compressed.

Parameters:

Name	Type	Attributes	Description
canvas	canvas		a Canvas object
quality	number	optional	range 0-1, indicate the image quality, default 0.92
type	string	optional	determine the converted image type; the options are "image/png", "image/jpeg", "image/gif",default "image/jpeg"

Returns:

Promise that contains a dataURL string.

canvastoFile(canvas[, quality, type]) → {Promise(Blob)}

Description:

Convert a Canvas object into a Blob object, this method can be compressed.

Parameters:

Name	Type	Attributes	Description
canvas	canvas		a Canvas object
quality	number	optional	range 0-1, indicate the image quality, default 0.92
type	string	optional	determine the converted image type; the options are "image/png", "image/jpeg", "image/gif",default "image/jpeg"

Returns:

Promise that contains a Blob object.

dataURLtoImage(dataURL) → {Promise(Image)}

Description:

Convert a dataURL string to a image object.

Parameters:

Name	Type	Description
dataURL	string	a dataURL string

Returns:

Promise that contains a Image object.

downloadFile(file[, fileName])

Description:

Download the image to local.

Parameters:

Name	Type	Attributes	Description
file	File(Blob)		a File(Blob) object
fileName	string	optional	download file name, if none, timestamp named file

filetoDataURL(file) → {Promise(string)}

Description:

Convert a File(Blob) object to a dataURL string.

Parameters:

Name	Type	Description
file	File(Blob)	a File(Blob) object

Returns:

Promise that contains a dataURL string.

urltoBlob(url) → {Promise(Blob)}

Description:

Load the required Blob object through the image url.

Parameters:

Name	Type	Description
url	string	image url

Returns:

Promise that contains a Blob object.

urltoImage(url) → {Promise(Image)}

Description:

Load the required Image object through the image url.

Parameters:

Name	Type	Description
url	string	image url

Returns:

Promise that contains Image object.

Compatibility

image-conversion depend native Promise and Fetch function, Therefore IE 11 is not supported. Other old browser version，check Promise and fetch support.

License

MIT