UIImage * testImg = [UIImage imageNamed:@"goods_5"];
UIImageWriteToSavedPhotosAlbum(testImg, nil, nil, nil);//写入相册
NSData * data = UIImageJPEGRepresentation(testImg, 0.4);//转成jpg格式图片
NSData * data2 = UIImagePNGRepresentation(testImg);//转成png格式照片
UIImage * testImg2 = [UIImage imageWithData:data];//jpg格式的图片
UIImage * testImg3 = [UIImage imageWithData:data2];//png格式的图片
