UIImage *bgImage = [UIImage imageNamed:@"bg"];        //上下文 : 基于位图(bitmap),所有的东西需要绘制到一张新的图片上去        //1.创建一个基于位图的上下文(开启一个基于位图的上下文)    //size : 新图片的此处    //opaque : 不透明度    //创建一张新的bitmap,也就是新的UIImage对象    UIGraphicsBeginImageContextWithOptions(bgImage.size, NO, 0.0);        //2.画背景    [bgImage drawInRect:CGRectMake(0, 0, bgImage.size.width, bgImage.size.height)];        //3.画右下角水印    UIImage *watermarkImage = [UIImage imageNamed:@"watermark"];    CGFloat scale = 0.2;    CGFloat margin = 5;    CGFloat watermarkW = watermarkImage.size.width * scale;    CGFloat watermarkH = watermarkImage.size.height * scale;    CGFloat watermarkX = bgImage.size.width - watermarkW - margin;    CGFloat watermarkY = bgImage.size.height - watermarkH - margin;        [watermarkImage drawInRect:CGRectMake(watermarkX, watermarkY, watermarkW, watermarkH)];    NSLog(@"%g",watermarkY);        //4.从上下文中取得制作完毕的UIImange对象    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();        //5.结束上下文    UIGraphicsEndImageContext();        //6.将image对象压缩为PNG格式的二进制对象.    NSData *data = UIImagePNGRepresentation(newImage);        //7写入文件    NSString *path = [[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject] stringByAppendingString:@"new.png"];    [data writeToFile:path atomically:YES];    NSLog(@"%@",path);