sharp-bmp/README.md

Bmp encoder and decoder for sharp base on bmp-js.

# sharp-bmp

Bmp encoder and decoder for [sharp](https://www.npmjs.com/package/sharp) base on [bmp-js](https://www.npmjs.com/package/bmp-js).

## Install

```bash
npm install sharp-bmp
```

## Usage

### Create an instance of sharp from a BMP image

```js
const bmp = require("sharp-bmp");

bmp.sharpFromBmp("input.bmp", {
  // sharp constructor options
}) // returns an instance of sharp
  .toFile("output.png");
```

### Write output image data to a BMP file

```js
const sharp = require("sharp");
const bmp = require("sharp-bmp");

const image = sharp("input.jpg");

bmp.sharpToBmp(image, "output.bmp")
  .then((info) => {
    console.log(info); // { size, width, height }
  })
  .catch((err) => {
    console.error(err);
  });
```

### Decode BMP

```js
const fs = require("fs");
const sharp = require("sharp");
const bmp = require("sharp-bmp");

const buffer = fs.readFileSync("input.bmp");
const bitmap = bmp.decode(buffer);

sharp(bitmap.data, {
  raw: {
    width: bitmap.width,
    height: bitmap.height,
    channels: 4,
  },
})
  .toFile("output.png");
```

### Encode BMP

```js
const fs = require("fs");
const sharp = require("sharp");
const bmp = require("sharp-bmp");

(async () => {
  const image = sharp("input.jpg");
  const { data, info } = await image
    // If the image has alpha transparency channel
    .flatten({ background: "#ffffff" })
    // If the image has no alpha transparency channel
    .ensureAlpha()
    .raw()
    .toBuffer({ resolveWithObject: true });
  const bitmap = {
    data,
    width: info.width,
    height: info.height,
  };
  const rawData = bmp.encode(bitmap);
  fs.writeFileSync("output.bmp", rawData.data);

  console.log(rawData.data.length); // size of output.bmp
})();
```

## Change Log

### 0.1.3

- Merge alpha transparency channel with a white background

### 0.1.4

- `sharpFromBmp(input, options)` support `Buffer` input.

### 0.1.5

- `sharpFromBmp(input, options, resolveWithObject)` add the third option, if `true`, will return an object with decoding info, default by `false`
- Update index.d.ts