#鸿蒙通关秘籍#如何使用PixelMap深拷贝实现图片裁剪？

async function copyPixelMap(pm: PixelMap): Promise<PixelMap> {
  const imageInfo: image.ImageInfo = await pm.getImageInfo();
  const buffer: ArrayBuffer = new ArrayBuffer(pm.getPixelBytesNumber());
  await pm.readPixelsToBuffer(buffer);
  const opts: image.InitializationOptions = {
    editable: true,
    pixelFormat: image.PixelMapFormat.RGBA_8888,
    size: { height: imageInfo.size.height, width: imageInfo.size.width }
  };
  return await image.createPixelMap(buffer, opts);
}

async function aboutToAppear(): Promise<void> {
  const context: Context = getContext(this);
  const resourceMgr: resourceManager.ResourceManager = context.resourceManager;
  const fileData: Uint8Array = await resourceMgr.getRawFileContent(ImageCropConstants.RAWFILE_PICPATH);
  const buffer = fileData.buffer.slice(fileData.byteOffset, fileData.byteLength + fileData.byteOffset);
  this.imageSource = image.createImageSource(buffer);
  const decodingOptions: image.DecodingOptions = {
    editable: false,
    desiredPixelFormat: image.PixelMapFormat.BGRA_8888,
  }
  this.pixelMapSrc = await this.imageSource.createPixelMap(decodingOptions);
  this.pixelMapDst = await copyPixelMap(this.pixelMapSrc!);
}

async function cropImage(proportion: number): Promise<void> {
  const pixelMapTemp = await copyPixelMap(this.pixelMapSrc);
  const imageInfo: image.ImageInfo = await pixelMapTemp.getImageInfo();
  let imageHeight: number = imageInfo.size.height;
  let imageWith: number = imageInfo.size.width;
  if (proportion === ImageCropConstants.ONE_ONE) {
    if (imageHeight > imageWith) {
      imageHeight = imageWith;
    } else {
      imageWith = imageHeight;
    }
  }
  await pixelMapTemp.crop({ size: { height: imageHeight / proportion, width: imageWith }, x: 0, y: 0 });
  this.pixelMapDst = pixelMapTemp;
}
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