AVCaptureMetadataOutput rectOfInterest

AVCaptureMetadataOutput rectOfInterest参数文档：

 @abstract

Specifies a rectangle of interest for limiting the search area for visual metadata.

 

 @discussion

The value of this property is a CGRect that determines the receiver's rectangle of interest for each frame of video.  

The rectangle's origin is top left and is relative to the coordinate space of the device providing the metadata.  Specifying 

a rectOfInterest may improve detection performance for certain types of metadata. The default value of this property is the 

value CGRectMake(0, 0, 1, 1).  Metadata objects whose bounds do not intersect with the rectOfInterest will not be returned.

文档上说该坐标范围为(0,0,1,1)，且原点为左上方；

实际应用可得：原点为右上方，范围为(0,0,1,1)