HarmonyOS 如何读取本地图片的实际长宽

createImageSource并没有必须设置长宽，用的是 image.DecodingOptions；然后通过getImageInfo()获取

import image from '@ohos.multimedia.image';

@Entry
@Component
struct Index {
  @State message: string = 'Hello World';
  @State _pixelMap: image.PixelMap | undefined = undefined;
  @State with: number = 0
  @State hig: number = 0

  async aboutToAppear() {
    console.error("tag aboutToAppear start.");
    let resourceManager = getContext(this).resourceManager;
    let imageArray = await resourceManager.getMediaContent($r('app.media.startIcon'));
    let imageResource = image.createImageSource(imageArray.buffer);
    let opts: image.DecodingOptions = { editable: true }
    this._pixelMap = await imageResource.createPixelMap(opts);
    this._pixelMap.getImageInfo().then((imageInfo : image.ImageInfo) => {
      if (imageInfo == undefined) {
        console.error("Failed to obtain the image pixel map information.");
      }
      this.with = imageInfo.size.width;
      this.hig = imageInfo.size.height;
      console.log("Succeeded in obtaining the image pixel map information.", this.with, this.hig);
    })
    console.error("aboutToAppear end.");
  }

  build() {
    Column() {
      Image($r('app.media.startIcon'))
        .objectFit(ImageFit.None)
        .backgroundColor(Color.Green)
        .borderWidth(2)
        .width(this.with) //设置满足图片需求的宽高
        .height(this.hig)
    }
  }
}