2000＊2000的內存占用是2000＊2000＊4bit

- (UIImage*)imageWithImage:(UIImage*)image       scaledToSize:(CGSize)newSize;{  UIGraphicsBeginImageContext( newSize );  [image drawInRect:CGRectMake(0,0,newSize.width,newSize.height)];  UIImage* newImage = UIGraphicsGetImageFromCurrentImageContext();  UIGraphicsEndImageContext();  return newImage;}-(UIImage*)imageWithImage:(UIImage *)image       resizeFactor:(CGFloat)scale{  CGSize originalSize = image.size;  CGSize newSize = CGSizeMake(originalSize.width * scale, originalSize.height* scale);  UIGraphicsBeginImageContext(newSize);  [image drawInRect:CGRectMake(0,0,newSize.width, newSize.height)];  UIImage * newImage = UIGraphicsGetImageFromCurrentImageContext();  UIGraphicsEndImageContext();  return newImage;}