npm package: @inventivetalent/image-hash
Description: Create a hash from an image
Author: Daniel Morrison
Latest version: 4.1.3

# image-hash
A wrapper around [block-hash](https://github.com/commonsmachinery/blockhash-js) to easily hash a local or remote file with Node.

Supports JPG and PNG

## Install
```bash
npm i -S image-hash
```

## Use
```javascript
const { imageHash }= require('image-hash');

// remote file simple
imageHash('https://ichef-1.bbci.co.uk/news/660/cpsprodpb/7F76/production/_95703623_mediaitem95703620.jpg', 16, true, (error, data) => {
  if (error) throw error;
  console.log(data);
  // 0773063f063f36070e070a070f378e7f1f000fff0fff020103f00ffb0f810ff0
});

// remote file with requestjs config object
const config = {
  uri: 'https://ichef-1.bbci.co.uk/news/660/cpsprodpb/7F76/production/_95703623_mediaitem95703620.jpg'
};

imageHash(config, 16, true, (error, data) => {
  if (error) throw error;
  console.log(data);
  // 0773063f063f36070e070a070f378e7f1f000fff0fff020103f00ffb0f810ff0
});

//local file
imageHash('./_95695590_tv039055678.jpg', 16, true, (error, data) => {
  if (error) throw error;
  console.log(data);
  // 0773063f063f36070e070a070f378e7f1f000fff0fff020103f00ffb0f810ff0
});

//Buffer
const fBuffer = fs.readFileSync(__dirname + '/example/_95695591_tv039055678.jpeg');
imageHash({
  ext: 'image/jpeg',
  data: fBuffer
}, 16, true, (error, data) => {
  if(error) throw error;
  console.log(data);
  // 0773063f063f36070e070a070f378e7f1f000fff0fff020103f00ffb0f810ff0
});

//Buffer, without ext arg
const fBuffer = fs.readFileSync(__dirname + '/example/_95695591_tv039055678.jpeg');
imageHash({
  data: fBuffer
}, 16, true, (error, data) => {
  if(error) throw error;
  console.log(data);
  // 0773063f063f36070e070a070f378e7f1f000fff0fff020103f00ffb0f810ff0
});
```

## API
```
// name
imageHash(location, bits, precise, callback)

// types
imageHash(string|object, int, bool, function)
```

### Image-Hash Arguments

| Argument | Type                 | Description                                                                                                                                                                                                                                                                                                                                                  | Mandatory | Example   |
| -------- | -------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | --------- | --------- |
| location | `object` or `string` | A [RequestJS Object](https://github.com/request/request#requestoptions-callback), `Buffer` object (See input types below for more details), or `String` with a valid url or file location                                                                                                                                                                                                                               | Yes       | see above |
| bits     | `int`                | The number of bits in a row. The more bits, the more unique the hash.                                                                                                                                                                                                                                                                                        | Yes       | 8         |
| precise  | `bool`               | Whether a precision algorithm is used. `true` Precise but slower, non-overlapping blocks. `false` Quick and crude, non-overlapping blocks. Method 2 is recommended as a good tradeoff between speed and good matches on any image size. The quick ones are only advisable when the image width and height are an even multiple of the number of blocks used. | Yes       | `true`    |
| callback | `function`           | A function with `error` and `data` arguments - see below                                                                                                                                                                                                                                                                                                     |

#### Location Object Types

```typescript
// Url Request Object
interface UrlRequestObject {
  encoding?: string | null,
  url: string | null,
};
// Buffer Object
interface BufferObject {
  ext?: string, // mime type of buffered file
  data: Buffer,
  name?: string // file name for buffered file
};
```

### Callback Arguments

| Argument | Type                     | Description                                                                         |
| -------- | ------------------------ | ----------------------------------------------------------------------------------- |  |  |
| error    | `Error Object` or `null` | If a run time error is detected this will be an `Error Object`, otherwise `null`    |
| data     | `string` or `null`       | If there is no run time error, this be will be your hashed result, otherwise `null` |

## Development
I have made this with Typescript, ESLint, Jest, Babel and VSCode. All config files and global binaries are included. For developers using VS Code, make sure you have ESLint extension installed.

## Testing
`npm test`

## Credit

The hard bit of this comes with thanks from [commonsmachinery](https://github.com/commonsmachinery) for [blockhash-js](https://github.com/commonsmachinery/blockhash-js)

## License

Distributed under an MIT license