# 使用Image_NativeModule完成多图对象编码

图像编码类，用于创建以及释放ImagePacker实例，并编码多图对象。

#### 开发步骤

#### 添加链接库

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libimage\_packer.so 以及日志依赖libhilog\_ndk.z.so。

```
target_link_libraries(entry PUBLIC libhilog_ndk.z.so libimage_source.so libimage_packer.so libpixelmap.so)
```

#### Native接口调用

具体接口说明请参考Image\_NativeModule。

在DevEco Studio新建Native C++应用，默认生成的项目中包含index.ets文件，在entry\\src\\main\\cpp目录下会自动生成一个cpp文件（hello.cpp或napi\_init.cpp，本示例以hello.cpp文件名为例）。在hello.cpp中实现C API接口调用逻辑，示例代码如下：

**编码接口使用示例**

根据MIME标准，标准编码格式为image/jpeg。当使用image编码时，编码参数中的编码格式image\_MimeType设置为image/jpeg，image编码后的文件扩展名可设为.jpg或.jpeg，可在支持image/jpeg解码的平台上使用。

部分接口在API version 20以后才支持，需要开发者在进行开发时选择合适的API版本。

1.  导入相关头文件。
    
    ```
    #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>
    ```
    
2.  日志宏定义可参考下述代码按实际需求自行修改。
    
    ```
    #undef LOG_DOMAIN
    #undef LOG_TAG
    #define LOG_DOMAIN 0x3200
    #define LOG_TAG "IMAGE_SAMPLE"
    ```
    
3.  定义用于图像处理的常量。
    
    ```
    #define AUTO 0
    #define SDR 1
    const int MAX_SIZE = 1024;
    const int MAX_FORMAT_LENGTH = 20;
    ```
    
4.  定义ImagePictureNative类。
    
    ```
    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() {}
    };
    ```
    
5.  创建ImagePictureNative的一个实例。
    
    ```
    static ImagePictureNative *g_thisPicture = new ImagePictureNative();
    ```
    
6.  创建GetJsResult函数处理napi返回值。
    
    ```
    // 处理napi返回值。
    napi_value GetJsResult(napi_env env, int result)
    {
        napi_value resultNapi = nullptr;
        napi_create_int32(env, result, &resultNapi);
        return resultNapi;
    }
    ```
    
7.  创建ImagePacker实例，指定编码参数后，将Picture多图对象编码至文件或缓冲区。
    
    ```
    // 设置编码参数。
    void SetPackOptions(OH_PackingOptions *packerOptions,
                        Image_MimeType format,
                        uint32_t quality,
                        bool needsPackProperties,
                        int32_t desiredDynamicRange)
    {
        OH_PackingOptions_SetMimeType(packerOptions, &format);
        OH_PackingOptions_SetQuality(packerOptions, quality);
        OH_PackingOptions_SetNeedsPackProperties(packerOptions, needsPackProperties);
        OH_PackingOptions_SetDesiredDynamicRange(packerOptions, desiredDynamicRange);
    }
    
    // PackToData。
    napi_value PackToDataFromPicture(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) {
            OH_LOG_ERROR(LOG_APP, "napi_get_cb_info failed!");
            return GetJsResult(env, g_thisPicture->errorCode);
        }
        
        size_t outDataSize = 10000 * 10000;
        uint8_t *outData = new uint8_t[outDataSize];
    
        if (g_thisPicture->packerOptions == nullptr) {
            g_thisPicture->errorCode = OH_PackingOptions_Create(&g_thisPicture->packerOptions);
        }
        if (g_thisPicture->imagePacker == nullptr) {
            g_thisPicture->errorCode = OH_ImagePackerNative_Create(&g_thisPicture->imagePacker);
        }
        
        char strFormat[MAX_FORMAT_LENGTH];
        size_t strFormatSize;
        napi_get_value_string_utf8(env, args[0], strFormat, MAX_FORMAT_LENGTH, &strFormatSize);
        OH_LOG_DEBUG(LOG_APP, "PackToDataFromPicture format: %{public}s", strFormat);
    
        Image_MimeType format;
        format.size = strFormatSize;
        format.data = const_cast<char *>(strFormat);
        uint32_t quality = 95;
        bool needsPackProperties = true;
        int32_t desiredDynamicRange = AUTO;
        SetPackOptions(g_thisPicture->packerOptions, format, quality, needsPackProperties, desiredDynamicRange);
        // 确保picture对象已被创建。
        g_thisPicture->errorCode = OH_ImagePackerNative_PackToDataFromPicture(
            g_thisPicture->imagePacker, g_thisPicture->packerOptions, g_thisPicture->picture, outData, &outDataSize);
        
        // 释放imagePacker和packerOptions。
        OH_PackingOptions_Release(g_thisPicture->packerOptions);
        g_thisPicture->packerOptions = nullptr;
        OH_ImagePackerNative_Release(g_thisPicture->imagePacker);
        g_thisPicture->imagePacker = nullptr;
        
        if (g_thisPicture->errorCode != IMAGE_SUCCESS) {
            OH_LOG_ERROR(LOG_APP, "OH_ImagePackerNative_PackToDataFromPicture failed, errCode: %{public}d.",
                         g_thisPicture->errorCode);
            delete[] outData;
            return GetJsResult(env, g_thisPicture->errorCode);
        } else {
            OH_LOG_DEBUG(LOG_APP, "OH_ImagePackerNative_PackToDataFromPicture success !");
        }
        delete[] outData;
        return GetJsResult(env, g_thisPicture->errorCode);
    }
    
    // PackToFile。
    napi_value PackToFileFromPicture(napi_env env, napi_callback_info info)
    {
        size_t argc = 2;
        napi_value args[2] = {nullptr};
        if (napi_get_cb_info(env, info, &argc, args, nullptr, nullptr) != napi_ok) {
        OH_LOG_ERROR(LOG_APP, "napi_get_cb_info failed!");
            return GetJsResult(env, g_thisPicture->errorCode);
        }
        uint32_t fd = 0;
        napi_get_value_uint32(env, args[0], &fd);
    
        if (g_thisPicture->packerOptions == nullptr) {
            g_thisPicture->errorCode = OH_PackingOptions_Create(&g_thisPicture->packerOptions);
        }
        if (g_thisPicture->imagePacker == nullptr) {
            g_thisPicture->errorCode = OH_ImagePackerNative_Create(&g_thisPicture->imagePacker);
        }
        
        char strFormat[MAX_FORMAT_LENGTH];
        size_t strFormatSize;
        napi_get_value_string_utf8(env, args[1], strFormat, MAX_FORMAT_LENGTH, &strFormatSize);
        OH_LOG_INFO(LOG_APP, "PackToFileFromPicture format: %{public}s", strFormat);
    
        Image_MimeType format;
        format.size = strFormatSize;
        format.data = const_cast<char *>(strFormat);
        uint32_t quality = 95;
        bool needsPackProperties = false;
        int32_t desiredDynamicRange = SDR;
        SetPackOptions(g_thisPicture->packerOptions, format, quality, needsPackProperties, desiredDynamicRange);
        // 确保picture对象已被创建。
        g_thisPicture->errorCode = OH_ImagePackerNative_PackToFileFromPicture(
            g_thisPicture->imagePacker, g_thisPicture->packerOptions, g_thisPicture->picture, fd);
        
        // 释放imagePacker和packerOptions。
        OH_PackingOptions_Release(g_thisPicture->packerOptions);
        g_thisPicture->packerOptions = nullptr;
        OH_ImagePackerNative_Release(g_thisPicture->imagePacker);
        g_thisPicture->imagePacker = nullptr;
        
        if (g_thisPicture->errorCode != IMAGE_SUCCESS) {
            OH_LOG_ERROR(LOG_APP, "OH_ImagePackerNative_PackToFileFromPicture failed,"
                         "errCode: %{public}d.", g_thisPicture->errorCode);
            return GetJsResult(env, g_thisPicture->errorCode);
        } else {
            OH_LOG_DEBUG(LOG_APP, "OH_ImagePackerNative_PackToFileFromPicture success !");
        }
    
        return GetJsResult(env, g_thisPicture->errorCode);
    }
    ```