鸿蒙（API 12 Beta3版）【使用Image完成图片接收器】图片开发指导依赖JS对象

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依赖中添加libace_napi.z.so，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

此处通过camera图片获取输入数据，需要申请权限ohos.permission.CAMERA，申请方式请参考[向用户申请授权]

JS侧调用

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

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 '@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);// 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profileslet 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);// 把预览流加入到会话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

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=jpeguint8_t *img_buffer = imgComponent.byteBuffer;ret = OH_Image_Release(nextImage_native);ret = OH_Image_Receiver_Release(imgReceiver_c);return nextImage;}

最后呢

很多开发朋友不知道需要学习那些鸿蒙技术？鸿蒙开发岗位需要掌握那些核心技术点？为此鸿蒙的开发学习必须要系统性的进行。

而网上有关鸿蒙的开发资料非常的少，假如你想学好鸿蒙的应用开发与系统底层开发。你可以参考这份资料，少走很多弯路，节省没必要的麻烦。由两位前阿里高级研发工程师联合打造的《鸿蒙NEXT星河版OpenHarmony开发文档》里面内容包含了（ArkTS、ArkUI开发组件、Stage模型、多端部署、分布式应用开发、音频、视频、WebGL、OpenHarmony多媒体技术、Napi组件、OpenHarmony内核、Harmony南向开发、鸿蒙项目实战等等）鸿蒙（Harmony NEXT）技术知识点

如果你是一名Android、Java、前端等等开发人员，想要转入鸿蒙方向发展。可以直接领取这份资料辅助你的学习。下面是鸿蒙开发的学习路线图。

在这里插入图片描述