HarmonyOS 鸿蒙Next readPixelsToBuffer

可以参考如下代码：

import componentSnapshot from '[@ohos](/user/ohos).arkui.componentSnapshot'
import image from '[@ohos](/user/ohos).multimedia.image'
import { promptAction } from '[@kit](/user/kit).ArkUI'
import { BusinessError } from '[@kit](/user/kit).BasicServicesKit';
import dataSharePredicates from '[@ohos](/user/ohos).data.dataSharePredicates';
import { abilityAccessCtrl, PermissionRequestResult, Permissions, bundleManager, common } from '[@kit](/user/kit).AbilityKit';
import fs from '[@ohos](/user/ohos).file.fs';
// import { photoAccessHelper } from '[@kit](/user/kit).MediaLibraryKit';
import PhotoAccessHelper from '[@ohos](/user/ohos).file.photoAccessHelper';

[@Entry](/user/Entry)
[@Component](/user/Component)
export struct SnapshotExample {
 [@State](/user/State) pixmap: image.PixelMap | undefined = undefined

 build() {
   Column() {
     Row() {
       Image(this.pixmap).width(200).height(200).border({ color: Color.Black, width: 2 }).margin(5)
       Image($r('app.media.ic_internet'))
         .autoResize(true)
         .width(200)
         .height(200)
         .margin(5)
         .id("root")
     }

     Button("click to generate UI snapshot")
       .onClick(() => {
         componentSnapshot.get("root", (error: Error, pixmap: image.PixelMap) => {
           if (error) {
             console.log("error: " + JSON.stringify(error))
             return;
           }
           this.pixmap = pixmap
           const readBuffer: ArrayBuffer = new ArrayBuffer(96); // 96为需要创建的像素buffer大小，取值为：height * width *4

           grantPermission().then((status: boolean) => {
             if (status) {

               let packOpts: image.PackingOption = { format: "image/jpeg", quality: 100 }
               const imagePacker = image.createImagePacker();
               imagePacker.packing(this.pixmap, packOpts)
                 .then(async (data: ArrayBuffer) => {
                   console.log('packing succeeded.');
                   this.savePicture(data)
                 }).catch((error: BusinessError) => {
                 console.log('packing failed.');
               })
               
             }
           })

      
         })
       }).margin(10)
   }
   .width('100%')
   .height('100%')
   .alignItems(HorizontalAlign.Center)
 }

 async savePicture(buffer: ArrayBuffer): Promise<void> {
   let photoAccessHelper: PhotoAccessHelper.PhotoAccessHelper =
     PhotoAccessHelper.getPhotoAccessHelper(getContext(this) as common.UIAbilityContext);
   let options: PhotoAccessHelper.CreateOptions = {
     title: Date.now().toString()
   };
   let photoUri: string = await photoAccessHelper.createAsset(PhotoAccessHelper.PhotoType.IMAGE, 'jpg', options);
   console.info(photoUri)
   //createAsset的调用需要ohos.permission.READ_IMAGEVIDEO和ohos.permission.WRITE_IMAGEVIDEO的权限
   let file: fs.File = fs.openSync(photoUri, fs.OpenMode.READ_WRITE | fs.OpenMode.CREATE);
   await fs.write(file.fd, buffer);
   fs.closeSync(file);
 }
}


const TAG: string = '[Permission]';

const PERMISSIONS: Array<Permissions> = [
 'ohos.permission.CAMERA',
 "ohos.permission.READ_IMAGEVIDEO",
 "ohos.permission.WRITE_IMAGEVIDEO"
];

const context = getContext(this) as common.UIAbilityContext;

export default async function grantPermission(): Promise<boolean> {
 try {
   let bundleInfo: bundleManager.BundleInfo =
     await bundleManager.getBundleInfoForSelf(
       bundleManager.BundleFlag.GET_BUNDLE_INFO_WITH_APPLICATION
     );
   let appInfo: bundleManager.ApplicationInfo = bundleInfo.appInfo;
   let tokenId = appInfo.accessTokenId;
   let atManager = abilityAccessCtrl.createAtManager();
   let pems: Array<Permissions> = [];
   for (let i = 0; i < PERMISSIONS.length; i++) {
     let state = await atManager.checkAccessToken(tokenId, PERMISSIONS[i]);
     if (state !== abilityAccessCtrl.GrantStatus.PERMISSION_GRANTED) {
       pems.push(PERMISSIONS[i]);
     }
   }
   if (pems.length > 0) {
     let ctx = context
     let result: PermissionRequestResult = await atManager.requestPermissionsFromUser(ctx, pems);
     let grantStatus: Array<number> = result.authResults;
     let length: number = grantStatus.length;
     for (let i = 0; i < length; i++) {
       if (grantStatus[i] !== 0) {
         return false;
       }
     }
   }
   return true;
 } catch (error) {
   return false;
 }
}