Using Image_NativeModule to Decode Pictures

This topic describes how to create an ImageSource instance, decode it to obtain Picture object, and release the ImageSource instance.

How to Develop

Adding a Link Library

Open the src/main/cpp/CMakeLists.txt file of the native project, add libimage_source.so and libhilog_ndk.z.so (on which the log APIs depend) to the target_link_libraries dependency.

target_link_libraries(entry PUBLIC libhilog_ndk.z.so libimage_source.so)

Calling the Native APIs

For details about the APIs, see Image_NativeModule.

Create a native C++ application in DevEco Studio. The project created by default contains the index.ets file, and a hello.cpp or napi_init.cpp file is generated in the entry\src\main\cpp directory. In this example, the generated file is hello.cpp. Implement the C APIs in hello.cpp. Refer to the sample code below.

Example of Using the Decoding APIs

NOTE

Certain APIs are supported only in API version 20 or later. You should select an appropriate API version during development.

1. Import the required header files.

   #include <hilog/log.h>
   #include <multimedia/image_framework/image/image_native.h>
   #include <multimedia/image_framework/image/image_packer_native.h>
   #include <multimedia/image_framework/image/image_source_native.h>
   #include <multimedia/image_framework/image/picture_native.h>
   #include <multimedia/image_framework/image/pixelmap_native.h>
   

   loadPicture.cpp

2. Modify the log macro definition as required.

   #undef LOG_DOMAIN
   #undef LOG_TAG
   #define LOG_DOMAIN 0x3200
   #define LOG_TAG "IMAGE_SAMPLE"
   

   loadImageSource.cpp

3. Define the ImagePictureNative class.

   class ImagePictureNative {
   public:
       Image_ErrorCode errorCode = IMAGE_SUCCESS;
       OH_DecodingOptionsForPicture *options = nullptr;
       OH_ImagePackerNative *imagePacker = nullptr;
       OH_PackingOptions *packerOptions = nullptr;
       OH_PictureNative *picture = nullptr;
       OH_ImageSourceNative *source = nullptr;
       ImagePictureNative() {}
       ~ImagePictureNative() {}
   };
   

   imageKits.h

4. Create an ImagePictureNative instance.

   static ImagePictureNative *g_thisPicture = new ImagePictureNative();
   

   loadPicture.cpp

5. Define the ImageAuxiliaryPictureNative class.

   class ImageAuxiliaryPictureNative {
   public:
       Image_ErrorCode errorCode = IMAGE_SUCCESS;
       Image_AuxiliaryPictureType type = AUXILIARY_PICTURE_TYPE_GAINMAP;
       OH_AuxiliaryPictureNative *auxiliaryPicture = nullptr;
       size_t buffSize = 640 * 480 * 4; // Size of the auxiliary picture (width * height * number of bytes per pixel).
       ImageAuxiliaryPictureNative() {}
       ~ImageAuxiliaryPictureNative() {}
   };
   

   imageKits.h

6. Create an ImageAuxiliaryPictureNative instance.

   static ImageAuxiliaryPictureNative *g_thisAuxiliaryPicture  = new ImageAuxiliaryPictureNative();
   

   loadPicture.cpp

7. Create the GetJsResult function to process the NAPI return value.

   // Process the NAPI return value.
   napi_value GetJsResult(napi_env env, int result)
   {
       napi_value resultNapi = nullptr;
       napi_create_int32(env, result, &resultNapi);
       return resultNapi;
   }
   

   napi_init.cpp

8. Create and configure decoding options, and call the decoding API to decode the image and obtain an auxiliary image.

   // Release the image source.
   napi_value ReleasePictureSource(napi_env env, napi_callback_info info)
   {
       if (g_thisPicture->source != nullptr) {
           g_thisPicture->errorCode = OH_ImageSourceNative_Release(g_thisPicture->source);
           g_thisPicture->source = nullptr;
           return GetJsResult(env, g_thisPicture->errorCode);
       }
       
       if (g_thisPicture->picture != nullptr) {
           g_thisPicture->errorCode = OH_PictureNative_Release(g_thisPicture->picture);
           g_thisPicture->picture = nullptr;
           return GetJsResult(env, g_thisPicture->errorCode);
       }
       
       OH_LOG_DEBUG(LOG_APP, "ReleasePictureSource source is null !");
       return GetJsResult(env, g_thisPicture->errorCode);
   }
   
   // Create decoding parameters.
   napi_value CreateDecodingOptions(napi_env env, napi_callback_info info)
   {
       g_thisPicture->errorCode = OH_DecodingOptionsForPicture_Create(&g_thisPicture->options);
   
       if (g_thisPicture->errorCode != IMAGE_SUCCESS) {
           OH_LOG_ERROR(LOG_APP, "OH_DecodingOptionsForPicture_Create failed, errCode: %{public}d.",
                        g_thisPicture->errorCode);
           return GetJsResult(env, g_thisPicture->errorCode);
       } else {
           OH_LOG_DEBUG(LOG_APP, "OH_DecodingOptionsForPicture_Create success !");
       }
   
       return GetJsResult(env, g_thisPicture->errorCode);
   }
   
   // Configure decoding parameters, which are passed from the application layer.
   napi_value SetDesiredAuxiliaryPictures(napi_env env, napi_callback_info info)
   {
       size_t argc = 1;
       napi_value args[1] = {nullptr};
       if (napi_get_cb_info(env, info, &argc, args, nullptr, nullptr) != napi_ok || argc < 1 || args[0] == nullptr) {
           OH_LOG_ERROR(LOG_APP, "napi_get_cb_info failed !");
           return GetJsResult(env, IMAGE_BAD_PARAMETER);
       }
   
       uint32_t length = 0;
       napi_get_array_length(env, args[0], &length);
       if (length <= 0) {
           OH_LOG_ERROR(LOG_APP, "napi_get_array_length failed !");
           return GetJsResult(env, IMAGE_UNKNOWN_ERROR);
       }
       Image_AuxiliaryPictureType typeList[length];
       for (int index = 0; index < length; index++) {
           napi_value element;
           uint32_t ulType = 0;
           napi_get_element(env, args[0], index, &element);
           napi_get_value_uint32(env, element, &ulType);
           typeList[index] = static_cast<Image_AuxiliaryPictureType>(ulType);
           OH_LOG_DEBUG(LOG_APP, "ulType is :%{public}d", ulType);
       }
       
       // Call OH_DecodingOptionsForPicture_Create to create DecodingOptions.
       CreateDecodingOptions(env, info);
       g_thisPicture->errorCode =
           OH_DecodingOptionsForPicture_SetDesiredAuxiliaryPictures(g_thisPicture->options, typeList, length);
       if (g_thisPicture->errorCode != IMAGE_SUCCESS) {
           OH_LOG_ERROR(LOG_APP, "OH_DecodingOptionsForPicture_SetDesiredAuxiliaryPictures failed,errCode: %{public}d.",
                        g_thisPicture->errorCode);
           return GetJsResult(env, g_thisPicture->errorCode);
       } else {
           OH_LOG_DEBUG(LOG_APP, "OH_DecodingOptionsForPicture_SetDesiredAuxiliaryPictures success !");
       }
   
       return GetJsResult(env, g_thisPicture->errorCode);
   }
   
   // Decode data.
   napi_value CreatePictureByImageSource(napi_env env, napi_callback_info info)
   {
       size_t argc = 1;
       napi_value args[1] = {nullptr};
   
       if (napi_get_cb_info(env, info, &argc, args, nullptr, nullptr) != napi_ok || argc < 1 || args[0] == nullptr) {
           OH_LOG_ERROR(LOG_APP, "CreatePicture_ napi_get_cb_info failed !");
           return GetJsResult(env, IMAGE_BAD_PARAMETER);
       }
       
       char filePath[MAX_SIZE];
       size_t pathSize;
       napi_get_value_string_utf8(env, args[0], filePath, MAX_SIZE, &pathSize);
   
       g_thisPicture->errorCode = OH_ImageSourceNative_CreateFromUri(filePath, pathSize, &g_thisPicture->source);
       if (g_thisPicture->errorCode != IMAGE_SUCCESS) {
           OH_LOG_ERROR(LOG_APP, "OH_ImageSourceNative_CreateFromUri failed, errCode: %{public}d.",
                        g_thisPicture->errorCode);
           return GetJsResult(env, g_thisPicture->errorCode);
       } else {
           OH_LOG_DEBUG(LOG_APP, "OH_ImageSourceNative_CreateFromUri success !");
       }
       
       // Create decoding options and then decode the video. The API for creating the decoding options is implemented in SetDesiredAuxiliaryPictures.
       g_thisPicture->errorCode =
           OH_ImageSourceNative_CreatePicture(g_thisPicture->source, g_thisPicture->options, &g_thisPicture->picture);
       
       // Release the decoding options.
       OH_DecodingOptionsForPicture_Release(g_thisPicture->options);
       g_thisPicture->options = nullptr;
       
       g_thisAuxiliaryPicture ->errorCode = OH_PictureNative_GetAuxiliaryPicture(g_thisPicture->picture,
           g_thisAuxiliaryPicture ->type, &g_thisAuxiliaryPicture ->auxiliaryPicture);
       if (g_thisAuxiliaryPicture ->errorCode == IMAGE_SUCCESS) {
           uint8_t* buff = new uint8_t[g_thisAuxiliaryPicture ->buffSize];
           OH_AuxiliaryPictureNative_ReadPixels(g_thisAuxiliaryPicture ->auxiliaryPicture, buff,
               &g_thisAuxiliaryPicture ->buffSize);
           OH_AuxiliaryPictureNative_Release(g_thisAuxiliaryPicture ->auxiliaryPicture);
           g_thisAuxiliaryPicture ->auxiliaryPicture = nullptr;
           delete []buff;
       }
       
       if (g_thisPicture->errorCode != IMAGE_SUCCESS) {
           OH_LOG_ERROR(LOG_APP, "ImageSourceNative_CreatePicture failed, errCode: %{public}d.",
                        g_thisPicture->errorCode);
           return GetJsResult(env, g_thisPicture->errorCode);
       } else {
           OH_LOG_DEBUG(LOG_APP, "ImageSourceNative_CreatePicture success !");
       }
       
       return GetJsResult(env, g_thisPicture->errorCode);
   }
   

   loadPicture.cpp