图片中心透明

_imaegView= [[UIImageViewalloc]initWithFrame:[UIScreenmainScreen].bounds];

self.imaegView.image= [selfgetImage];

self.imaegView.alpha=0.5;

[self.viewaddSubview:self.imaegView];

- (UIImage*)getImage {

UIImage*images = [UIImageimageNamed:@"图片"];

UIGraphicsBeginImageContextWithOptions([UIScreenmainScreen].bounds.size,NO,1);

CGContextRefref =UIGraphicsGetCurrentContext();

[imagesdrawInRect:[UIScreenmainScreen].bounds];

CGContextAddEllipseInRect(ref,CGRectMake(50,100,200,200));

CGContextSetBlendMode(ref,kCGBlendModeClear);

CGContextFillPath(ref);

UIImage*image =UIGraphicsGetImageFromCurrentImageContext();

UIGraphicsEndImageContext();

returnimage;

}