Convert your rectangular image into a perfect circle image with transparent bg.

CirclePhoto.m

// @param {UIImage} The rectangle image you want to convert to a round image
// @param {CGSize} The size (width and height) of the resulting round image
// @return {NSData} the PNGRepresentation of the resulting round image
-(NSData *)rectangleImageToTransparentRoundImageFromImage:(UIImage *)image withSize:(CGSize)size {
    
    UIGraphicsBeginImageContextWithOptions(size, NO, 0.0);
    CGContextRef context = UIGraphicsGetCurrentContext();
    
    UIImageView *_imgView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, size.width, size.height)];
    _imgView.image = image;
    _imgView.contentMode = UIViewContentModeScaleAspectFit;
    _imgView.layer.cornerRadius = size.width / 2;
    _imgView.clipsToBounds = YES;
    [_imgView.layer renderInContext:context];
    
    UIImage *img = UIGraphicsGetImageFromCurrentImageContext();
    
    UIGraphicsEndImageContext();
    
    // return NSData
    return UIImagePNGRepresentation(img);
}