# image-conversion


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> [image-conversion](https://github.com/WangYuLue/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](https://demo.wangyulue.com/image-conversion/)).


## Methods Map

![Alt text](https://raw.githubusercontent.com/WangYuLue/image-conversion/master/image/xmind.png)

## Getting started

### Install

```bash
npm i image-conversion --save

# or 

yarn add image-conversion
```
### Include the library

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

in CommonJS:
```js
const imageConversion = require("image-conversion");
```

in ES6:

```js
import * as imageConversion from 'image-conversion';
```

or 

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

### Use examples

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

1. Compress image to 200kb:
```js
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);
}
```

2. Compress images at a quality of 0.9
```js
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:
```js
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;<br> 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; <br> if object type,you can pass parameters to the `imagetoCanvas` and `dataURLtoFile` method;<br> Reference is as follow: |

#### Tips:

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

#### Example:
```js
// 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); <br> if object type,you can pass parameters to the `imagetoCanvas` and `dataURLtoFile` method;<br> Reference is as follow: |

#### Tips:

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

#### Example:
```js
// 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;<br> 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;<br> 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](https://caniuse.com/#search=Promise) and [fetch](https://caniuse.com/#search=fetch) support.

## License

[MIT](http://opensource.org/licenses/MIT)