.. _image_encoding_jpeg:

图像编码（JPEG）
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

.. _functional_constraints_of_jpeg_encoding:

功能约束
"""""""""""""""""""""""""""""""""""""""""""""""""""""

KA200提供的图像编码器只支持JPEG图像编码，编码的功能约束参见下表。

.. _table_14_jpeg_encoding_constraints:

表 JPEG编码功能约束
"""""""""""""""""""""""""""""""""""""""""""""""""""""

+----------+-----------+------------------------------------------------------------------------------+
| 约束项   | 属性      | 参数                                                                         |
+==========+===========+==============================================================================+
| 输入     | 分辨率    | - 最大：3840×2160                                                            |
|          |           | - 最小：16×16                                                                |
|          +-----------+------------------------------------------------------------------------------+
|          | 格式      | - 支持YUV420SP/YUVJ420P NV12 8bit                                            |
|          |           | - 不支持算术编码                                                             |
|          |           | - 不支持渐进JPEG格式                                                         |
|          |           | - 不支持JPEG2000格式                                                         |
|          +-----------+------------------------------------------------------------------------------+
|          | 输入内存  | 只能调用lynMalloc和lynFree进行图像编码输入的内存申请和释放                   |
+----------+-----------+------------------------------------------------------------------------------+
| 输出     | 输出格式  | JPEG压缩格式（YUVJ420P）的图片文件，输出像素色域是JPEG色域，即范围为[0, 255] |
|          +-----------+------------------------------------------------------------------------------+
|          | 输出内存  | 只能调用lynMalloc和lynFree进行图像编码输出的内存申请和释放                   |
+----------+-----------+------------------------------------------------------------------------------+

.. _image_encoding_process:

图像编码
"""""""""""""""""""""""""""""""""""""""""""""""""""""

用户可以从LynSDK提供的示例代码中查看完整样例，在示例代码中，调用各接口后都添加了异常判断和处理，以下是关键步骤代码示例，仅供参考，不可以直接拷贝编译。

.. code-block:: c++

    std::string srcFileName = "../source/test.yuv";
    std::string dstFileName = "./output/encoded_jpg.jpg";
    
    // 删除已有文件
    FileManager::deleteFile(dstFileName);

    lynCodecBuf_t inDataLocal = GetInputFromFile(srcFileName);

    lynContext_t context = nullptr;
    int ret = lynCreateContext(&context, 0);
    EXPECT_EQ(ret, 0);

    lynStream_t jpegStream = nullptr;
    ret = lynCreateStream(&jpegStream);
    EXPECT_NE(jpegStream, nullptr);

    // 把图像数据copy到Device侧
    lynJencInfo_t attr;
    attr.params.inputFormat = LYN_PIX_FMT_NV12;
    attr.params.width = 620;
    attr.params.height = 478;
    attr.params.jpegQuality = 80;

    attr.input.size = inDataLocal.size;
    ret = lynMalloc((void **)&attr.input.data, attr.input.size);
    EXPECT_EQ(ret, 0);

    ret = lynMemcpyAsync(jpegStream, attr.input.data, inDataLocal.data, inDataLocal.size, ClientToServer);
    EXPECT_EQ(ret, 0);

    attr.output.size = inDataLocal.size;
    ret = lynMalloc((void **)&attr.output.data, attr.output.size);
    EXPECT_EQ(ret, 0);

    // 异步编码
    ret = lynJpegEncodeAsync(jpegStream, &attr);
    EXPECT_EQ(ret, 0);

    lynCodecBuf_t *outbuf = new lynCodecBuf_t;
    outbuf->data = (uint8_t *)malloc(inDataLocal.size);
    outbuf->size = inDataLocal.size;

    rcvData *out_data = new rcvData;
    out_data->pQueue = nullptr;
    out_data->packet = &attr.output;
    out_data->localBuf = outbuf;
    out_data->dstFile = dstFileName;
    lynStreamAddAsyncCallback(jpegStream, RecvPacketCallback, out_data);
    lynSynchronizeStream(jpegStream);

    lynDestroyStream(jpegStream);
    lynFree(attr.input.data);
    lynFree(attr.output.data);
    free(inDataLocal.data);
    free(outbuf->data);
    delete outbuf;

    lynDestroyContext(context);