Create iOS thumb UIImage

gistfile1.m

- (void)createThumbImageWithImage:(UIImage*)image
{
    float radius = 19.0;
    CGSize originalImageSize = image.size;
    CGRect newRect = CGRectMake(0, 0, radius*2, radius*2);
    float ratio = MAX(newRect.size.width / originalImageSize.width, newRect.size.height / originalImageSize.height);
    
    UIGraphicsBeginImageContextWithOptions(newRect.size, NO, 0.0);
    
    // circular mask
    UIBezierPath *path = [UIBezierPath bezierPathWithArcCenter:CGPointMake(radius, radius)
                                                        radius:radius
                                                    startAngle:0
                                                      endAngle:360
                                                     clockwise:YES];
    [path addClip];
    
    // center crop
    CGRect projectionRect = CGRectMake((newRect.size.width - ratio * originalImageSize.width) / 2,
                                       (newRect.size.height - ratio * originalImageSize.height) / 2,
                                       ratio * originalImageSize.width,
                                       ratio * originalImageSize.height);
    [image drawInRect:projectionRect];
    self.thumbImage = UIGraphicsGetImageFromCurrentImageContext();
    
    UIGraphicsEndImageContext();
}