update zh-cn/application-dev/media/image-pixelmap-operation.md.

Signed-off-by: N刘关鹏 <liuguanpeng1@huawei.com>

zh-cn/application-dev/media/image-pixelmap-operation.md

@@ -31,7 +31,7 @@
    const readBuffer = new ArrayBuffer(pixelBytesNumber);
    pixelMap.readPixelsToBuffer(readBuffer).then(() => {
      console.info('Succeeded in reading image pixel data.');
-   }).catch(error => {
+   }).catch((error : BusinessError) => {
      console.error('Failed to read image pixel data. And the error is: ' + error);
    })
    
@@ -44,7 +44,7 @@
    }
    pixelMap.readPixels(area).then(() => {
      console.info('Succeeded in reading the image data in the area.');
-   }).catch(error => {
+   }).catch((error : BusinessError) => {
      console.error('Failed to read the image data in the area. And the error is: ' + error);
    })