# Using ImagePacker to Encode Pictures

Image encoding refers to the process of encoding a picture into an archived image in different formats (only in JPEG and HEIF currently) for subsequent processing, such as storage and transmission.

## How to Develop

Read [Image API Reference](../../reference/apis-image-kit/js-apis-image.md#imagepacker) for APIs related to image encoding.

### Encoding Images into File Streams

1. Create an **ImagePacker** object.

   ```ts
   // Import the required module.
   import { image } from '@kit.ImageKit';
   
   const imagePackerApi = image.createImagePacker();
   ```

2. Set the encoding output stream and encoding parameters.

   **format** indicates the image encoding format, and **quality** indicates the image quality. The value ranges from 0 to 100, and the value 100 indicates the optimal quality.

      > **NOTE**
      >
      > According to the MIME protocol, the standard encoding format is image/jpeg. When the APIs provided by the image module are used for encoding, **PackingOption.format** must be set to **image/jpeg**. The file name extension of the encoded image file can be .jpg or .jpeg, and the file can be used on platforms that support image/jpeg decoding.

      ```ts
      let packOpts: image.PackingOption = {
        format: "image/jpeg",
        quality: 98,
        bufferSize: 10,
        desiredDynamicRange: image.PackingDynamicRange.AUTO,
        needsPackProperties: true
      };
      ```

3. Encode the image and save the encoded image.

   ```ts
   import { BusinessError } from '@kit.BasicServicesKit';
   imagePackerApi.packing(picture, packOpts).then( (data : ArrayBuffer) => {
     console.info('Succeeded in packing the image.'+ data);
   }).catch((error : BusinessError) => { 
     console.error('Failed to pack the image. And the error is: ' + error); 
   })
   ```

### Encoding Images into Files

During encoding, you can pass in a file path so that the encoded memory data is directly written to the file.

   ```ts
  const context : Context = getContext(this);
  const path : string = context.cacheDir + "/picture.jpg";
  let file = fileIo.openSync(path, fileIo.OpenMode.CREATE | fileIo.OpenMode.READ_WRITE);
  imagePackerApi.packToFile(picture, file.fd, packOpts).then(() => {
    console.info('Succeeded in packing the image to file.');
  }).catch((error : BusinessError) => {
    console.error('Failed to pack the image. And the error is: ' + error);
  })
   ```