Image Encoding (ArkTS)

Image encoding refers to the process of encoding a pixel map into an archived image in different formats (only in JPEG, WebP, and PNG 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 '@ohos.multimedia.image';
   
   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.

   let packOpts : image.PackingOption = { format:"image/jpeg", quality:98 };
   

3. Create a PixelMap object or an ImageSource object.

4. Encode the image and save the encoded image.

   Method 1: Use PixelMap for encoding.

   import {BusinessError} from '@ohos.base'
   imagePackerApi.packing(pixelMap, packOpts).then( (data : ArrayBuffer) => {
     // data is the file stream obtained after packing. You can write the file and save it to obtain an image.
   }).catch((error : BusinessError) => { 
     console.error('Failed to pack the image. And the error is: ' + error); 
   })
   

   Method 2: Use ImageSource for encoding.

   import {BusinessError} from '@ohos.base'
   imagePackerApi.packing(imageSource, packOpts).then( (data : ArrayBuffer) => {
       // data is the file stream obtained after packing. You can write the file and save it to obtain an image.
   }).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.

Method 1: Use PixelMap to encode the image and pack it into a file.

import {BusinessError} from '@ohos.base'
import fs from '@ohos.file.fs'
const context : Context = getContext(this);
const path : string = context.cacheDir + "/pixel_map.jpg";
let file = fs.openSync(path, fs.OpenMode.CREATE | fs.OpenMode.READ_WRITE);
imagePackerApi.packToFile(pixelMap, file.fd, packOpts).then(() => {
    // Pack the image into the file.
}).catch((error : BusinessError) => { 
  console.error('Failed to pack the image. And the error is: ' + error); 
})

Method 2: Use ImageSource to encode the image and pack it into a file.

import {BusinessError} from '@ohos.base'
import fs from '@ohos.file.fs'
const context : Context = getContext(this);
const filePath : string = context.cacheDir + "/image_source.jpg";
let file = fs.openSync(filePath, fs.OpenMode.CREATE | fs.OpenMode.READ_WRITE);
imagePackerApi.packToFile(imageSource, file.fd, packOpts).then(() => {
    // Pack the image into the file.
}).catch((error : BusinessError) => { 
  console.error('Failed to pack the image. And the error is: ' + error); 
})