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1# 图片接收器(C/C++)
2
3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。
4
5## 开发步骤
6
7### 添加依赖
8
9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。
10
11```txt
12target_link_libraries(entry PUBLIC libace_napi.z.so libhilog_ndk.z.so libimage_ndk.z.so libimage_receiver_ndk.z.so libnative_image.so)
13```
14
15### 添加接口映射
16
17打开src/main/cpp/hello.cpp文件，在Init函数中添加接口映射如下：
18
19```c++
20EXTERN_C_START
21static napi_value Init(napi_env env, napi_value exports)
22{
23    napi_property_descriptor desc[] = {
24        { "createFromReceiver", nullptr, createFromReceiver, nullptr, nullptr, nullptr, napi_default, nullptr },
25    };
26
27    napi_define_properties(env, exports, sizeof(desc) / sizeof(desc[0]), desc);
28    return exports;
29}
30EXTERN_C_END
31```
32
33### 添加权限申请
34
35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](../../quick-start/module-configuration-file.md)：
36
37   ```
38   "requestPermissions":[
39      {
40        "name" : "ohos.permission.CAMERA"
41      }
42    ]
43   ```
44
45### JS侧调用
46
471. 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:
48
49    ```js
50    import image from '@ohos.multimedia.image'
51
52    export const createFromReceiver: (a: image.ImageReceiver) => image.Image;
53    ```
54
552. 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:
56
57    ```js
58    import testNapi from 'libentry.so'
59    import image from '@ohos.multimedia.image'
60    import abilityAccessCtrl from '@ohos.abilityAccessCtrl'
61    import camera from '@ohos.multimedia.camera'
62
63    @Entry
64    @Component
65    struct Index {
66      private receiver: image.ImageReceiver | undefined = undefined;
67      func (){
68         let context = getContext()
69         abilityAccessCtrl.createAtManager().requestPermissionsFromUser(context,['ohos.permission.CAMERA']).then(async () => {
70            let cameraManager = await camera.getCameraManager(context);
71            // 获取支持的相机设备对象
72            let cameraDevices: Array<camera.CameraDevice> = cameraManager.getSupportedCameras();
73            if (cameraDevices.length <= 0) {
74            return;
75            }
76            // 获取对应相机设备的profiles
77            let profiles: camera.CameraOutputCapability = cameraManager.getSupportedOutputCapability(cameraDevices[0])
78            let previewProfiles: Array<camera.Profile> = profiles.previewProfiles;
79            if (previewProfiles.length <= 0) {
80            return;
81            }
82            let profileObj = previewProfiles[0];
83            this.receiver = image.createImageReceiver(profileObj.size.width, profileObj.size.height, image.ImageFormat.JPEG, 8);
84            let receiverSurfaceId: string = await this.receiver.getReceivingSurfaceId();
85            // 创建预览流输出对象
86            let previewOutput: camera.PreviewOutput = cameraManager.createPreviewOutput(profileObj,receiverSurfaceId);
87            let cameraInput : camera.CameraInput = cameraManager.createCameraInput(cameraDevices[0]);
88            // 打开相机
89            await cameraInput.open();
90            // 会话流程
91            let captureSession : camera.CaptureSession = cameraManager.createCaptureSession();
92            // 配置会话
93            captureSession.beginConfig();
94            // 把cameraInput加入到会话
95            captureSession.addInput(cameraInput);
96            // 吧预览流加入到会话
97            captureSession.addOutput(previewOutput);
98            // 提交配置信息
99            await captureSession.commitConfig();
100            // 会话开始
101            await captureSession.start();
102
103            this.receiver.on('imageArrival', () => {
104               let img : image.Image = testNapi.createFromReceiver(this.receiver);
105               img.release();
106            })
107
108         });
109      }
110
111      build() {
112         Row() {
113            Column() {
114            Button("start")
115               .width(100)
116               .height(100)
117               .onClick(() => {
118                  console.log("button click in");
119                  if (this.receiver == undefined) {
120                     this.func();
121                  }
122               })
123            }
124            .width('100%')
125         }
126         .height('100%')
127      }
128   }
129    ```
130
131
132### Native接口调用
133
134具体接口说明请参考[API文档](../../reference/apis-image-kit/image.md)
135
136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：
137
138**添加引用文件**
139
140   ```c++
141
142      #include <multimedia/image_framework/image_mdk.h>
143      #include <multimedia/image_framework/image_receiver_mdk.h>
144      #include <malloc.h>
145      #include <hilog/log.h>
146
147      static napi_value createFromReceiver(napi_env env, napi_callback_info info)
148      {
149         size_t argc = 1;
150         napi_value args[2] = {nullptr};
151         napi_get_cb_info(env, info, &argc, args , nullptr, nullptr);
152         napi_valuetype valuetype0;
153         napi_typeof(env, args[0], &valuetype0);
154         napi_ref reference;
155         napi_create_reference(env, args[0], 1 ,&reference);
156         napi_value imgReceiver_js;
157         napi_get_reference_value(env, reference, &imgReceiver_js);
158
159         ImageReceiverNative * imgReceiver_c = OH_Image_Receiver_InitImageReceiverNative(env, imgReceiver_js);
160
161         int32_t capacity;
162         OH_Image_Receiver_GetCapacity(imgReceiver_c, &capacity);
163         OH_LOG_Print(LOG_APP, LOG_INFO, 0xFF00, "[receiver]", "capacity: %{public}d", capacity);
164         int32_t format;
165         OH_Image_Receiver_GetFormat(imgReceiver_c, &format);
166         OH_LOG_Print(LOG_APP, LOG_INFO, 0xFF00, "[receiver]", "format: %{public}d", format);
167         char * surfaceId = static_cast<char *>(malloc(sizeof(char)));
168         OH_Image_Receiver_GetReceivingSurfaceId(imgReceiver_c, surfaceId, sizeof(char));
169         OH_LOG_Print(LOG_APP, LOG_INFO, 0xFF00, "[receiver]", "surfaceId: %{public}c", surfaceId[0]);
170         OhosImageSize size;
171         OH_Image_Receiver_GetSize(imgReceiver_c, &size);
172         OH_LOG_Print(LOG_APP, LOG_INFO, 0xFF00, "[receiver]", "OH_Image_Receiver_GetSize  width: %{public}d, height:%{public}d", size.width, size.height);
173
174         int32_t ret;
175         napi_value nextImage;
176         // 或调用 OH_Image_Receiver_ReadNextImage(imgReceiver_c, &nextImage);
177         ret = OH_Image_Receiver_ReadLatestImage(imgReceiver_c, &nextImage);
178
179         ImageNative * nextImage_native = OH_Image_InitImageNative(env, nextImage);
180
181         OhosImageSize imageSize;
182         OH_Image_Size(nextImage_native, &imageSize);
183         OH_LOG_Print(LOG_APP, LOG_INFO, 0xFF00, "[receiver]", "OH_Image_Size  width: %{public}d, height:%{public}d", imageSize.width, imageSize.height);
184
185         OhosImageComponent imgComponent;
186         ret = OH_Image_GetComponent(nextImage_native, 4, &imgComponent); // 4=jpeg
187
188         uint8_t *img_buffer = imgComponent.byteBuffer;
189
190         ret = OH_Image_Release(nextImage_native);
191         ret = OH_Image_Receiver_Release(imgReceiver_c);
192         return nextImage;
193      }
194   ```
195