图片上传主要有两种方式，一种是转成Base64，另外一种是二进制流上传

1.二进制流上传

用PPNetworkHelp第三方上传时可以同时上传多张图片，但如果缺点是无法确认哪张照片上传失败，所以简单做了修改，每次上传一张图片，迭代调用。

//加入SSS毫秒图片名称更长，但能更好的避免文件重名。

   for (NSUInteger i = 0; i < images.count; i++) {
            // 图片经过等比压缩后得到的二进制文件
            NSData *imageData = UIImageJPEGRepresentation(images[i], imageScale ?: 1.f);
            // 默认图片的文件名, 若fileNames为nil就使用
            NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
            formatter.dateFormat = @"yyyyMMddHHmmssSSS";
            NSString *str = [formatter stringFromDate:[NSDate date]];
            //NSLog(@"===%@",str);
            NSString *imageFileName = NSStringFormat(@"%@%ld.%@",str,i,imageType?:@"jpg");
            [formData appendPartWithFileData:imageData
                                        name:name
                                    fileName:fileNames ? NSStringFormat(@"%@.%@",fileNames[i],imageType?:@"jpg") : imageFileName
                                    mimeType:NSStringFormat(@"image/%@",imageType ?: @"jpg")];
        }

[PPNetworkHelper  uploadImagesWithURL: @"http://192.168.0.117/device/ImgDemo/getImageDemo"
                               parameters:@{}
                                     name:@"photo[]"
                                   images: @[self.photoArr[_currentIndex]]
                                fileNames:nil
                               imageScale:0.3
                                imageType:@"jpg"
                                 progress:^(NSProgress *progress) {
                                     //1. png后缀的图片也可以jpg形式上传成功
                                     //2. 回调方法中加入了自动释放池
                                     //3. 递归调用可以显示每张图片的上传情况
                                     //进度
                                     //NSLog(@"==%@",progress);
                                     //NSLog(@"%lld",progress.completedUnitCount);
                                     //NSLog(@"%lld",progress.totalUnitCount);
                                     NSLog(@"%.2f",progress.fractionCompleted);
                                   

                                 }
                                  success:^(id responseObject) {
                                      [self continueUpLoadImageWithisSuccess:YES];
                                
                                  }
                                  failure:^(NSError *error) {
                                      [self continueUpLoadImageWithisSuccess:NO];
                                  }];
}

递代调用

- (void)continueUpLoadImageWithisSuccess:(BOOL)isSuccess{
    
    //如果上传失败,并且没有超过最大上传次数,重新上传
    if (!isSuccess) {
        self.onceFailedCount++;
        if (self.onceFailedCount < kMaxUploadCount) {
            [self upLoadImage];
            return;
        }else{
            [self.failedIndexs addObject:[NSString stringWithFormat:@"%ld", self.currentIndex]];
        }
    }
    [SVProgressHUD showProgress:(CGFloat)self.currentIndex/self.photoArr.count];
    //清空失败次数
    self.onceFailedCount = 0;
    //记录新的下标index++
    self.currentIndex++;
    //判断是否上传完毕
    if (self.currentIndex == self.photoArr.count) {
        //如果是已经上传完了,结束
        if (self.failedIndexs.count != 0) {
            NSMutableString *mutableString = [NSMutableString string];
            for (NSString *index in self.failedIndexs) {
                [mutableString appendFormat:@"第%@张",index];
            }
            [SVProgressHUD showErrorWithStatus:[NSString stringWithFormat:@"%@上传失败",mutableString]];
        }else{
            [SVProgressHUD showSuccessWithStatus:@"图片全部上传成功"];
        }

    }else{
        //如果还没上传完成,继续下一次上传
        [self upLoadImage];
    }
}

2. Base64方式

图片转成Base64字符串
- (NSString*)imageToString:(UIImage*)image{
    
    if (!image) {
        return @"";
    }
    NSString *mineType = nil;
    if (UIImageJPEGRepresentation(image, 1)) {
        mineType =  @"image/jpg";
    }else{
        mineType = @"image/png";
    }
    
    NSData *data = [self resetSizeOfImageData:image maxSize:100];
    NSString *encodedImageStr =  [data base64EncodedStringWithOptions:NSDataBase64Encoding64CharacterLineLength];
    NSString *headString =[NSString stringWithFormat:@"data:%@;base64,",mineType];
    
    return  [headString stringByAppendingString:encodedImageStr];
    
}

如果对图片压缩效果不满意，可以进行再次压缩

//对图片再次压缩
- (NSData *)resetSizeOfImageData:(UIImage *)source_image maxSize:(NSInteger)maxSize
{
    //先调整分辨率
    CGSize newSize = CGSizeMake(source_image.size.width, source_image.size.height);
    
    CGFloat tempHeight = newSize.height / 1024;
    CGFloat tempWidth = newSize.width / 1024;
    
    if (tempWidth > 1.0 && tempWidth > tempHeight) {
        newSize = CGSizeMake(source_image.size.width / tempWidth, source_image.size.height / tempWidth);
    }
    else if (tempHeight > 1.0 && tempWidth < tempHeight){
        newSize = CGSizeMake(source_image.size.width / tempHeight, source_image.size.height / tempHeight);
    }
    
    UIGraphicsBeginImageContext(newSize);
    [source_image drawInRect:CGRectMake(0,0,newSize.width,newSize.height)];
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    
    //调整大小
    NSData *imageData;
    if (UIImagePNGRepresentation(newImage)) {
        imageData = UIImagePNGRepresentation(newImage);
    }else{
        imageData = UIImageJPEGRepresentation(newImage, 0.001);
    }
    
    NSUInteger sizeOrigin = [imageData length];//字节长度Byte
    NSUInteger sizeOriginKB = sizeOrigin / 1024;
    NSLog(@"%ld",sizeOriginKB);
    if (sizeOriginKB > maxSize) {
        //如果 压缩后还不满意，则再度压缩
        NSData *finallImageData ;
        
        if (UIImageJPEGRepresentation(newImage, 0.0001)) {
            finallImageData = UIImageJPEGRepresentation(newImage, 0.0001);
        }else{
            finallImageData = UIImagePNGRepresentation(newImage);
            
        }
        NSLog(@"%ld",finallImageData.length/1024);
        return finallImageData;
    }
    
    return imageData;
}