UIImage NSData转换

-(void)writeButtonAction:(id)sender{
NSString * path = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
NSString * newPath = [NSString stringWithFormat:@"%@/data",path];
UIImage *image = [UIImage imageNamed:@"111.png"];
NSData * data = UIImagePNGRepresentation(image); //如果是PNG的图片用这个，别的就把PNG换成拓展名
[data writeToFile:newPath atomically:YES];
}

-(void)readButtonAction:(id)sender{
NSString * path = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
NSString * newPath = [NSString stringWithFormat:@"%@/data",path];
NSData * data = [NSData dataWithContentsOfFile:newPath];
//将data转换成字符串
UIImage * image = [UIImage imageWithData:data];
[_imageView setImage:image];
}