#####+ (UIImage *)imageNamed:(NSString *)fileName
If displaying a bundle image only once, it is recommended to use + (UIImage *)imageWithContentsOfFile:(NSString *)path instead so as not to have the system cache the image. Per Apple documentation:
If you have an image file that will only be displayed once and wish to ensure that it does not get added to the system’s cache, you should instead create your image using imageWithContentsOfFile:. This will keep your single-use image out of the system image cache, potentially improving the memory use characteristics of your app.
#####@property(nonatomic) BOOL clearsContextBeforeDrawing
Setting a UIView's clearsContextBeforeDrawing to NO can in many cases improve drawing performance, particularly if you are implementing the drawing code of a custom view.
If you set the value of this property to NO, you are responsible for ensuring the contents of the view are drawn properly in your drawRect: method. If your drawing code is already heavily optimized, setting this property is NO can improve performance, especially during scrolling when only a portion of the view might need to be redrawn.
By default, UIKit clears a view’s current context buffer prior to calling its drawRect: method to update that same area. If you are responding to scrolling events in your view, clearing this region repeatedly during scrolling updates can be expensive. To disable the behavior, you can change the value in the clearsContextBeforeDrawing property to NO.
#####@property(nonatomic) CGRect frame
When setting the frame property of a UIView item, it is valuable to ensure that the coordinates correspond to pixel locations, otherwise anti-aliasing will occur, reducing performance and potentially causing blurry edges in your interface. One straightforward solution is to use CGRectIntegral() to automatically round the CGRect values to the nearest point. For screens with a higher pixel density than 1 pixel per point, the coordinates only need to be rounded to the nearest 1.0f / screen.scale