Using Image to Receive Images

You can use the ImageReceiver APIs to obtain the surface ID of a component, read the latest image or the next image, and release ImageReceiver instances.

How to Develop

Adding Dependencies

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

target_link_libraries(entry PUBLIC libace_napi.z.so libhilog_ndk.z.so libimage_ndk.z.so libimage_receiver_ndk.z.so libnative_image.so)

Adding API Mappings

Open the src/main/cpp/hello.cpp file and add the following API mappings to the Init function:

EXTERN_C_START
static napi_value Init(napi_env env, napi_value exports)
{
    napi_property_descriptor desc[] = {
        { "createFromReceiver", nullptr, createFromReceiver, nullptr, nullptr, nullptr, napi_default, nullptr },
    };

    napi_define_properties(env, exports, sizeof(desc) / sizeof(desc[0]), desc);
    return exports;
}
EXTERN_C_END

Requesting Permissions

To obtain input data of an image from a camera, you must request the ohos.permission.CAMERA permission. For details, see Requesting User Authorization.

Calling APIs on the JS Side

1. Open src\main\cpp\types*libentry\index.d.ts* (where libentry varies according to the project name), and import the following files:

   import { image } from '@kit.ImageKit';
   
   export const createFromReceiver: (a: image.ImageReceiver) => image.Image;
   

2. Open src\main\ets\pages\index.ets, import libentry.so (where libentry varies according to the project name), call the native APIs, and pass in the JS resource object. The following is an example:

   import testNapi from 'libentry.so'
   import { image } from '@kit.ImageKit';
   import { abilityAccessCtrl } from '@kit.AbilityKit';
   import { camera } from '@kit.CameraKit';
   
   @Entry
   @Component
   struct Index {
     private receiver: image.ImageReceiver | undefined = undefined;
     func (){
        let context = getContext()
        abilityAccessCtrl.createAtManager().requestPermissionsFromUser(context,['ohos.permission.CAMERA']).then(async () => {
           let cameraManager = await camera.getCameraManager(context);
           // Obtain the supported camera devices.
           let cameraDevices: Array<camera.CameraDevice> = cameraManager.getSupportedCameras();
           if (cameraDevices.length <= 0) {
           return;
           }
           // Obtain the profiles of the cameras.
           let profiles: camera.CameraOutputCapability = cameraManager.getSupportedOutputCapability(cameraDevices[0], camera.SceneMode.NORMAL_PHOTO);
           let previewProfiles: Array<camera.Profile> = profiles.previewProfiles;
           if (previewProfiles.length <= 0) {
           return;
           }
           let profileObj = previewProfiles[0];
           this.receiver = image.createImageReceiver({width:profileObj.size.width, height:profileObj.size.height}, image.ImageFormat.JPEG, 8);
           let receiverSurfaceId: string = await this.receiver.getReceivingSurfaceId();
           // Create an output object for the preview stream.
           let previewOutput: camera.PreviewOutput = cameraManager.createPreviewOutput(profileObj,receiverSurfaceId);
           let cameraInput : camera.CameraInput = cameraManager.createCameraInput(cameraDevices[0]);
           // Open the camera.
           await cameraInput.open();
           // Create a session.
           let session : camera.PhotoSession = cameraManager.createSession(camera.SceneMode.NORMAL_PHOTO) as camera.PhotoSession;
           // Configure the session.
           session.beginConfig();
           // Add a CameraInput instance to the session.
           session.addInput(cameraInput);
           // Add the preview stream to the session.
           session.addOutput(previewOutput);
           // Commit the configuration.
           await session.commitConfig();
           // Start the session.
           await session.start();
   
           this.receiver.on('imageArrival', () => {
              let img : image.Image = testNapi.createFromReceiver(this.receiver);
              img.release();
           })
   
        });
     }
   
     build() {
        Row() {
           Column() {
           Button("start")
              .width(100)
              .height(100)
              .onClick(() => {
                 console.log("button click in");
                 if (this.receiver == undefined) {
                    this.func();
                 }
              })
           }
           .width('100%')
        }
        .height('100%')
     }
   }
   

Calling the Native APIs

For details about the APIs, see Image.

Obtain the JS resource object from the hello.cpp file and convert it to a native resource object. Then you can call native APIs.

Adding Reference Files

   #include <multimedia/image_framework/image_mdk.h>
   #include <multimedia/image_framework/image_receiver_mdk.h>
   #include <malloc.h>
   #include <hilog/log.h>

   static napi_value createFromReceiver(napi_env env, napi_callback_info info)
   {
      size_t argc = 1;
      napi_value args[2] = {nullptr};
      napi_get_cb_info(env, info, &argc, args , nullptr, nullptr);
      napi_valuetype valuetype0;
      napi_typeof(env, args[0], &valuetype0);
      napi_ref reference;
      napi_create_reference(env, args[0], 1 ,&reference);
      napi_value imgReceiver_js;
      napi_get_reference_value(env, reference, &imgReceiver_js);
      
      ImageReceiverNative * imgReceiver_c = OH_Image_Receiver_InitImageReceiverNative(env, imgReceiver_js);

      int32_t capacity;
      OH_Image_Receiver_GetCapacity(imgReceiver_c, &capacity);
      OH_LOG_Print(LOG_APP, LOG_INFO, 0xFF00, "[receiver]", "capacity: %{public}d", capacity);
      int32_t format;
      OH_Image_Receiver_GetFormat(imgReceiver_c, &format);
      OH_LOG_Print(LOG_APP, LOG_INFO, 0xFF00, "[receiver]", "format: %{public}d", format);
      char * surfaceId = static_cast<char *>(malloc(sizeof(char)));
      OH_Image_Receiver_GetReceivingSurfaceId(imgReceiver_c, surfaceId, sizeof(char));
      OH_LOG_Print(LOG_APP, LOG_INFO, 0xFF00, "[receiver]", "surfaceId: %{public}c", surfaceId[0]);
      OhosImageSize size;
      OH_Image_Receiver_GetSize(imgReceiver_c, &size);
      OH_LOG_Print(LOG_APP, LOG_INFO, 0xFF00, "[receiver]", "OH_Image_Receiver_GetSize  width: %{public}d, height:%{public}d", size.width, size.height);
      
      int32_t ret;
      napi_value nextImage;
      // Alternatively, call OH_Image_Receiver_ReadNextImage(imgReceiver_c, &nextImage).
      ret = OH_Image_Receiver_ReadLatestImage(imgReceiver_c, &nextImage);
      
      ImageNative * nextImage_native = OH_Image_InitImageNative(env, nextImage);

      OhosImageSize imageSize;
      OH_Image_Size(nextImage_native, &imageSize);
      OH_LOG_Print(LOG_APP, LOG_INFO, 0xFF00, "[receiver]", "OH_Image_Size  width: %{public}d, height:%{public}d", imageSize.width, imageSize.height);

      OhosImageComponent imgComponent;
      ret = OH_Image_GetComponent(nextImage_native, 4, &imgComponent); // 4=jpeg
      
      uint8_t *img_buffer = imgComponent.byteBuffer;
      
      ret = OH_Image_Release(nextImage_native);
      ret = OH_Image_Receiver_Release(imgReceiver_c);
      return nextImage;
   }