Objective-C修改图片尺寸/生成缩略图
+(UIImage *)imageResize :(UIImage*)img andResizeTo:(CGSize)newSize { CGFloat scale = [[UIScreen mainScreen]scale]; //UIGraphicsBeginImageContext(newSize); UIGraphicsBeginImageContextWithOptions(newSize, NO, scale); [img drawInRect:CGRectMake(0,0,newSize.width,newSize.height)]; UIImage* newImage = UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext(); return newImage; }