iOS 图片压缩

-(UIImage *)makeThumbnailFromImage:(UIImage *)srcImage scale:(double)imageScale{
    
    UIImage *thumbail = nil;
    CGSize imageSize = CGSizeMake(srcImage.size.width*imageScale, srcImage.size.height*imageScale);
    
    if (srcImage.size.width != imageSize.width || srcImage.size.height != imageSize.height) {
        UIGraphicsBeginImageContext(imageSize);
        CGRect imageRect = CGRectMake(0, 0, imageSize.width, imageSize.height);
        
        [srcImage drawInRect:imageRect];
        thumbail = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();
        
    }
    else{
        thumbail = srcImage;
    }
    return thumbail;
    
}