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 for APIs related to image encoding.

Encoding Images into File Streams

1. Create an ImagePacker object.

   // 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.

   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.

   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.

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);
})