截屏存图片到相册或者指定路径

- (BOOL)writeImage:(UIImage*)image toFileAtPath:(NSString*)aPath{    if ((image == nil) || (aPath == nil) || ([aPath isEqualToString:@""]))        return NO;    @try    {                NSData *imageData = nil;        NSString *ext = [aPath pathExtension];        if ([ext isEqualToString:@"png"])        {            imageData = UIImagePNGRepresentation(image);         }        else         {            // the rest, we write to jpeg                        // 0. best, 1. lost. about compress.                        imageData = UIImageJPEGRepresentation(image, 0);                         }             if ((imageData == nil) || ([imageData length] <= 0))            return NO;                [imageData writeToFile:aPath atomically:YES];               return YES;    }    @catch (NSException *e)     {        NSLog(@"create thumbnail exception.");    }    return NO;}