b4415e2d创建于 2025年12月20日历史提交

Using Image_NativeModule to Edit Exif Data

Image Kit provides the capabilities of reading and editing Exchangeable Image File Format (Exif) data.

Exif is a file format dedicated for photos taken by digital cameras and is used to record attributes and shooting data of the photos. Currently, JPEG, PNG, HEIF, and WEBP²³⁺ images that contain Exif data are supported.

Users may need to view or modify the Exif data of photos in the Gallery application. When the manual lens parameters of the camera are not automatically written as part of the Exif data or the shooting time is incorrect due to camera power-off, you can manually correct the Exif data.

Currently, OpenHarmony allows you to view and modify part of Exif data. For details, see OHOS_IMAGE_PROPERTY_XXX.

How to Develop

Adding a Link Library

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

target_link_libraries(entry PUBLIC libhilog_ndk.z.so libimage_source.so)

Calling the Native APIs

For details about the C APIs for reading and editing Exif data, see OH_ImageSource_GetImageProperty and OH_ImageSource_ModifyImageProperty.

Create a native C++ application in DevEco Studio. The project created by default contains the index.ets file, and a hello.cpp or napi_init.cpp file is generated in the entry\src\main\cpp directory. In this example, the generated file is hello.cpp. Implement the C APIs in hello.cpp. Refer to the sample code below.

Example for Reading and Editing Exif Data

NOTE

Certain APIs are supported only in API version 20 or later. You should select an appropriate API version during development.

Import the required header files.

#include <string>
#include <hilog/log.h>
#include <multimedia/image_framework/image/image_source_native.h>
#include "napi/native_api.h"

loadImageSource.cpp

Modify the log macro definition as required.

#undef LOG_DOMAIN
#undef LOG_TAG
#define LOG_DOMAIN 0x3200
#define LOG_TAG "IMAGE_SAMPLE"

loadImageSource.cpp

Define the ImageSourceNative class.

class ImageSourceNative {
public:
    OH_ImageSource_Info *imageInfo;
    OH_ImageSourceNative *source = nullptr;
    OH_PixelmapNative *resPixMap = nullptr;
    OH_Pixelmap_ImageInfo *pixelmapImageInfo = nullptr;
    uint32_t frameCnt = 0;
    ImageSourceNative() {}
    ~ImageSourceNative() {}
};

imageKits.h

Create an instance of ImageSourceNative.

static ImageSourceNative *g_thisImageSource = new ImageSourceNative();

loadImageSource.cpp

Create the GetJsResult function to process the NAPI return value.

// Process the NAPI return value.
napi_value GetJsResult(napi_env env, int result)
{
    napi_value resultNapi = nullptr;
    napi_create_int32(env, result, &resultNapi);
    return resultNapi;
}

napi_init.cpp

After an ImageSource object is created, read and edit its Exif data.

NOTE

For details about how to create an ImageSource object, see Image Decoding.

// Obtain the value of a specified property.
napi_value GetImageProperty(napi_env env, napi_callback_info info)
{
    napi_value argValue[1] = {nullptr};
    size_t argCount = 1;
    if (napi_get_cb_info(env, info, &argCount, argValue, nullptr, nullptr) != napi_ok || argCount < 1 ||
        argValue[0] == nullptr) {
        OH_LOG_ERROR(LOG_APP, "GetImageProperty napi_get_cb_info failed!");
        return GetJsResult(env, IMAGE_BAD_PARAMETER);
    }
    // Modify the value of a specified property key.
    char key[MAX_STRING_LENGTH];
    size_t keySize = MAX_STRING_LENGTH;
    napi_get_value_string_utf8(env, argValue[0], (char *)key, sizeof(key), &keySize);
    Image_String getKey;
    getKey.data = key;
    getKey.size = keySize;
    Image_String getValue;
    OH_LOG_INFO(LOG_APP, "OH_ImageSourceNative_GetImageProperty key: %{public}s.", getKey.data);
    Image_ErrorCode errCode = OH_ImageSourceNative_GetImagePropertyWithNull(g_thisImageSource->source,
                                                                            &getKey, &getValue);
    if (errCode != IMAGE_SUCCESS) {
        OH_LOG_ERROR(LOG_APP, "OH_ImageSourceNative_GetImageProperty failed, errCode: %{public}d.", errCode);
        return GetJsResult(env, errCode);
    }
    napi_value resultNapi = nullptr;
    napi_create_string_utf8(env, getValue.data, getValue.size, &resultNapi);
    free(getValue.data);
    getValue.data = nullptr;
    return resultNapi;
}

// Modify the value of a specified property.
napi_value ModifyImageProperty(napi_env env, napi_callback_info info)
{
    napi_value argValue[2] = {nullptr};
    size_t argCount = 2;
    const size_t minCount = 2;
    if (napi_get_cb_info(env, info, &argCount, argValue, nullptr, nullptr) != napi_ok || argCount < minCount ||
        argValue[0] == nullptr || argValue[1] == nullptr) {
        OH_LOG_ERROR(LOG_APP, "ModifyImageProperty napi_get_cb_info failed!");
        return GetJsResult(env, IMAGE_BAD_PARAMETER);
    }

    // Obtain the key to be modified.
    char key[MAX_STRING_LENGTH];
    size_t keySize = MAX_STRING_LENGTH;
    napi_get_value_string_utf8(env, argValue[0], (char *)key, sizeof(key), &keySize);
    Image_String setKey;
    setKey.data = key;
    setKey.size = keySize;
    OH_LOG_INFO(LOG_APP, "ModifyImageProperty key: %{public}s.", setKey.data);
    
    // Obtain the value to be modified.
    char value[MAX_STRING_LENGTH];
    size_t valueSize;
    napi_get_value_string_utf8(env, argValue[1], (char *)value, MAX_STRING_LENGTH, &valueSize);
    Image_String setValue;
    setValue.data = value;
    setValue.size = valueSize;
    OH_LOG_INFO(LOG_APP, "ModifyImageProperty value: %{public}s.", setValue.data);

    Image_ErrorCode errCode = OH_ImageSourceNative_ModifyImageProperty(g_thisImageSource->source, &setKey, &setValue);
    return ReturnErrorCode(env, errCode, "OH_ImageSourceNative_ModifyImageProperty");
}

loadImageSource.cpp