图片接收器(C/C++)

图像接收类，用于获取组件surface id，接收最新的图片和读取下一张图片，以及释放ImageReceiver实例。

开发步骤

添加依赖

在进行应用开发之前，开发者需要打开native工程的src/main/cpp/CMakeLists.txt，在target_link_libraries依赖中添libimage_ndk.z.so libimage_receiver_ndk.z.so libnative_image.so 以及日志依赖libhilog_ndk.z.so。

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)

添加接口映射

打开src/main/cpp/hello.cpp文件，在Init函数中添加接口映射如下：

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

添加权限申请

开启调试功能需要在DevEco Studio应用工程的src\main\module.json5文件中增加权限, 配置文件个字段含义详见module.json5配置文件：

"requestPermissions":[
   {
     "name" : "ohos.permission.CAMERA"
   }
 ]

JS侧调用

  1. 打开src\main\cpp\types\libentry\index.d.ts（其中libentry根据工程名生成），导入如下引用文件:

    import image from '@ohos.multimedia.image'

export const createFromReceiver: (a: image.ImageReceiver) => image.Image;

  2. 打开src\main\ets\pages\index.ets，导入"libentry.so（根据工程名生成）"，调用Native接口，传入JS的资源对象。示例如下:

    import testNapi from 'libentry.so'
import image from '@ohos.multimedia.image'
import abilityAccessCtrl from '@ohos.abilityAccessCtrl'
import camera from '@ohos.multimedia.camera'

@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);
        // 获取支持的相机设备对象
        let cameraDevices: Array<camera.CameraDevice> = cameraManager.getSupportedCameras();
        if (cameraDevices.length <= 0) {
        return;
        }
        // 获取对应相机设备的profiles
        let profiles: camera.CameraOutputCapability = cameraManager.getSupportedOutputCapability(cameraDevices[0])
        let previewProfiles: Array<camera.Profile> = profiles.previewProfiles;
        if (previewProfiles.length <= 0) {
        return;
        }
        let profileObj = previewProfiles[0];
        this.receiver = image.createImageReceiver(profileObj.size.width, profileObj.size.height, image.ImageFormat.JPEG, 8);
        let receiverSurfaceId: string = await this.receiver.getReceivingSurfaceId();
        // 创建预览流输出对象
        let previewOutput: camera.PreviewOutput = cameraManager.createPreviewOutput(profileObj,receiverSurfaceId);
        let cameraInput : camera.CameraInput = cameraManager.createCameraInput(cameraDevices[0]);
        // 打开相机
        await cameraInput.open();
        // 会话流程
        let captureSession : camera.CaptureSession = cameraManager.createCaptureSession();
        // 配置会话
        captureSession.beginConfig();
        // 把cameraInput加入到会话
        captureSession.addInput(cameraInput);
        // 吧预览流加入到会话
        captureSession.addOutput(previewOutput);
        // 提交配置信息
        await captureSession.commitConfig();
        // 会话开始
        await captureSession.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%')
  }
}

Native接口调用

具体接口说明请参考API文档

在hello.cpp文件中获取JS的资源对象，并转为Native的资源对象，即可调用Native接口，调用方式示例代码如下：

添加引用文件


   #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;
      // 或调用 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;
   }