保存到沙盒只要先把沙盒路徑寫好，直接存入就行了
/*保存到沙盒
UIImage * imgsave =self.img.image;
NSString * path =NSHomeDirectory();
NSString * Pathimg =[path stringByAppendingString:@"/Documents/111.png"];
[UIImagePNGRepresentation(imgsave) writeToFile:Pathimg atomically:YES];
NSLog(@"%@",path);//這是沙盒路徑
*/
/*
NSString * PATH =[NSString stringWithFormat:@"%@/Documents/%@.png",NSHomeDirectory(),@"text"];
image.image=[[UIImage alloc]initWithContentsOfFile:PATH];
*/
