分段式拍照(C/C++)

分段式拍照是相机的最重要功能之一，相机输出低质量图用作快速显示，提升用户感知拍照速度，同时使用高质量图保证最后的成图质量达到系统相机的水平，既满足了后处理算法的需求，又不阻塞前台的拍照速度，构筑相机性能竞争力，提升了用户的体验。

在第一阶段，系统快速上报轻量处理的图片，轻量处理的图片比全质量图低，出图速度快。应用通过回调会收到一个PhotoAsset对象，通过该对象可调用媒体库接口，读取图片或落盘图片。
在第二阶段，相机框架会根据应用的请求图片诉求或者在系统闲时，进行图像增强处理得到全质量图，将处理好的图片传回给媒体库，替换轻量处理的图片。

开发步骤

详细的API说明请参考OH_Camera。

导入NDK接口，接口中提供了相机相关的属性和方法，导入方法如下。

#include <cstdint>
#include <unistd.h>
#include <string>
#include <thread>
#include <cstdio>
#include <fcntl.h>
#include <map>
#include <string>
#include <vector>
#include <native_buffer/native_buffer.h>
#include "iostream"
#include "mutex"

#include "hilog/log.h"
#include "ohcamera/camera.h"
#include "ohcamera/camera_input.h"
#include "ohcamera/capture_session.h"
#include "ohcamera/photo_output.h"
#include "ohcamera/preview_output.h"
#include "ohcamera/video_output.h"
#include "napi/native_api.h"
#include "ohcamera/camera_manager.h"
#include "common/log_common.h"

#include "multimedia/image_framework/image/image_native.h"
#include "multimedia/image_framework/image/image_source_native.h"
#include "multimedia/image_framework/image/image_packer_native.h"
#include "multimedia/media_library/media_access_helper_capi.h"
#include "multimedia/media_library/media_asset_base_capi.h"
#include "multimedia/media_library/media_asset_capi.h"
#include "multimedia/media_library/media_asset_change_request_capi.h"
#include "multimedia/media_library/media_asset_manager_capi.h"
#include "multimedia/media_library/moving_photo_capi.h"
#include "ohcamera/photo_native.h"
#include <window_manager/oh_display_info.h>
#include <window_manager/oh_display_manager.h>

在CMake脚本中链接相关动态库。

target_link_libraries(entry PUBLIC
    libace_napi.z.so
    libhilog_ndk.z.so
    libohcamera.so
    libimage_source.so
    libmedia_asset_manager.so
    libimage_packer.so
)

相机初始化及拍照触发参考拍照(C/C++)。

注册分段式（PhotoAssetAvailable）拍照回调，对比单段式拍照，仅注册的拍照回调接口不同。

如果已经注册了PhotoAssetAvailable回调，并且在Session开始之后又注册了PhotoAvailable回调，PhotoAssetAvailable和PhotoAvailable同时注册，会导致流被重启，仅PhotoAssetAvailable生效。

不建议开发者同时注册PhotoAssetAvailable和PhotoAvailable。

注册PhotoAssetAvailableCallback回调，接收分段式拍照回图示例：

分段式拍照开发流程（PhotoAssetAvailableCallback）：

在会话commitConfig前注册分段式拍照回调。
通过分段式拍照回调，获取媒体库资源mediaAsset。
通过mediaAsset直接落盘图片或者通过mediaAsset配置策略模式请求图像资源，业务处理后通过buffer保存图片，或显示图片(参考拍照(C/C++)步骤5)。
使用完后解注册分段式拍照回调函数。

// 分段式拍照回调函数。
void onPhotoAssetAvailable(Camera_PhotoOutput *photoOutput, OH_MediaAsset *mediaAsset)
{
    if (mediaAsset == nullptr) {
        DRAWING_LOGI("onPhotoAssetAvailable mediaAsset is nullptr !");
        return;
    }
    DRAWING_LOGD("onPhotoAssetAvailable start!");
    NDKCamera::MediaAssetRelease();
    g_mediaAsset = mediaAsset;
    NDKCamera::MediaAssetGetUri(mediaAsset);
    NDKCamera::MediaAssetGetDisplayName(mediaAsset);
    NDKCamera::MediaAssetGetSize(mediaAsset);
    NDKCamera::MediaAssetGetDateModifiedMs(mediaAsset);
    NDKCamera::MediaAssetGetWidth(mediaAsset);
    NDKCamera::MediaAssetGetHeight(mediaAsset);
    NDKCamera::MediaAssetGetOrientation(mediaAsset);
    NDKCamera::MediaAssetManagerCreate();
    NDKCamera::MediaAssetChangeRequest(mediaAsset);
    DRAWING_LOGD("onPhotoAssetAvailable finish!");
    return;
}

// 注册分段式拍照回调。
Camera_ErrorCode NDKCamera::PhotoOutputRegisterPhotoAssetAvailableCallback(void)
{
    DRAWING_LOGD("NDKCamera::PhotoOutputRegisterPhotoAssetAvailableCallback start!");
    MediaAssetManagerCreate();
    ret_ = OH_PhotoOutput_RegisterPhotoAssetAvailableCallback(photoOutput_, onPhotoAssetAvailable);
    if (ret_ != CAMERA_OK) {
        DRAWING_LOGD("NDKCamera::PhotoOutputRegisterPhotoAssetAvailableCallback failed.");
    }
    DRAWING_LOGD(
        "NDKCamera::PhotoOutputRegisterPhotoAssetAvailableCallback return with ret code: %{public}d!",
        ret_);
    return ret_;
}

MediaLibrary_ErrorCode NDKCamera::MediaAssetChangeRequest(OH_MediaAsset *mediaAsset)
{
    DRAWING_LOGD("NDKCamera::MediaAssetChangeRequest start!");
    MediaAssetChangeRequestCreate(mediaAsset);
    MediaAssetManagerRequestImage(mediaAsset);
    DRAWING_LOGD("NDKCamera::MediaAssetChangeRequest finish!");
    return MEDIA_LIBRARY_OK;
}

MediaLibrary_ErrorCode NDKCamera::MediaAssetChangeRequestCreate(OH_MediaAsset *mediaAsset)
{
    DRAWING_LOGD("NDKCamera::MediaAssetChangeRequestCreate start!");
    g_changeRequest = OH_MediaAssetChangeRequest_Create(mediaAsset);
    if (g_changeRequest == nullptr) {
        DRAWING_LOGD("NDKCamera::MediaAssetChangeRequestCreate failed.");
    }
    return MEDIA_LIBRARY_OK;
}

MediaLibrary_ErrorCode NDKCamera::MediaAssetManagerCreate(void)
{
    DRAWING_LOGD("NDKCamera::MediaAssetManagerCreate start!");
    mediaAssetManager = OH_MediaAssetManager_Create();
    if (mediaAssetManager == nullptr) {
        DRAWING_LOGD("NDKCamera::MediaAssetManagerCreate failed.");
    }
    return MEDIA_LIBRARY_OK;
}

void OnRequsetImageDataPreparedWithDetails(MediaLibrary_ErrorCode result, MediaLibrary_RequestId requestId,
    MediaLibrary_MediaQuality mediaQuality, MediaLibrary_MediaContentType type, OH_ImageSourceNative *imageSourceNative)
{
    auto cb = (void (*)(char *))(g_requestImageCallback);
    auto qCb = (void (*)(char *))(g_requestImageQualityCallback);
    DRAWING_LOGD("OnRequsetImageDataPreparedWithDetails start!");
    if (mediaQuality == MediaLibrary_MediaQuality::MEDIA_LIBRARY_QUALITY_FAST) {
        DRAWING_LOGD("OnRequsetImageDataPreparedWithDetails into fast quality mode!");
        g_mediaQualityCb = "fast";
        qCb(g_mediaQualityCb);
    } else {
        DRAWING_LOGD("OnRequsetImageDataPreparedWithDetails into high quality mode!");
        g_mediaQualityCb = "high";
        qCb(g_mediaQualityCb);
    }
    DRAWING_LOGD("OnRequsetImageDataPreparedWithDetails GetUri uri_ = %{public}s", URI);
    cb(const_cast<char *>(URI));
    NDKCamera::ChangeRequestAddResourceWithBuffer(imageSourceNative);
    return;
}

// 请求图片数据：deliveryMode/quality等通过requestOptions控制，完成后进回调OnRequsetImageDataPreparedWithDetails。
MediaLibrary_ErrorCode NDKCamera::MediaAssetManagerRequestImage(OH_MediaAsset *mediaAsset)
{
    DRAWING_LOGD("NDKCamera::MediaAssetManagerRequestImage start! g_deliveryMode = %{public}d",
        g_deliveryMode);
    requestOptions.deliveryMode = g_deliveryMode;
    result = OH_MediaAssetManager_RequestImage(mediaAssetManager, mediaAsset, requestOptions, &g_requestId,
        OnRequsetImageDataPreparedWithDetails);
    if (result != MEDIA_LIBRARY_OK) {
        DRAWING_LOGD("NDKCamera::MediaAssetManagerRequestImage failed.");
    }
    DRAWING_LOGD("NDKCamera::MediaAssetManagerRequestImage return with ret code: %{public}d!", result);
    return result;
}

MediaLibrary_ErrorCode NDKCamera::ChangeRequestAddResourceWithBuffer(OH_ImageSourceNative *imageSourceNative)
{
    DRAWING_LOGD("NDKCamera::ChangeRequestAddResourceWithBuffer start!");
    size_t bufferSize = BUFFER_SIZE;
    char buffer[BUFFER_SIZE];
    int fd = open("/data/storage/el2/base/haps/test.jpg", O_RDONLY);
    int fr = read(fd, buffer, bufferSize);
    if (fr == -1) {
        DRAWING_LOGD("NDKCamera::ChangeRequestAddResourceWithBuffer read failed.");
        return MEDIA_LIBRARY_OK;
    }
    if (fr == BUFFER_SIZE) {
        DRAWING_LOGD("NDKCamera::ChangeRequestAddResourceWithBuffer read not complete.");
        return MEDIA_LIBRARY_OK;
    }
    result = OH_MediaAssetChangeRequest_AddResourceWithBuffer(g_changeRequest,
        MediaLibrary_ResourceType::MEDIA_LIBRARY_IMAGE_RESOURCE, (uint8_t *)buffer, (uint32_t)bufferSize);
    if (result != MEDIA_LIBRARY_OK) {
        DRAWING_LOGD("NDKCamera::ChangeRequestAddResourceWithBuffer failed.");
        DRAWING_LOGD("NDKCamera::ChangeRequestAddResourceWithBuffer failed %{public}d.", result);
        return MEDIA_LIBRARY_OK;
    }
    result = OH_MediaAccessHelper_ApplyChanges(g_changeRequest);
    if (result != MEDIA_LIBRARY_OK) {
        DRAWING_LOGD(
            "NDKCamera::ChangeRequestAddResourceWithBuffer OH_MediaAccessHelper_ApplyChanges failed.");
        return MEDIA_LIBRARY_OK;
    }
    DRAWING_LOGD("NDKCamera::ChangeRequestAddResourceWithBuffer OH_MediaAccessHelper_ApplyChanges return "
                 "with ret code: %{public}d!",
        result);
    return result;
}

MediaLibrary_ErrorCode NDKCamera::ChangeRequestSaveCameraPhoto(void)
{
    DRAWING_LOGD("NDKCamera::ChangeRequestSaveCameraPhoto start!");
    result = OH_MediaAssetChangeRequest_SaveCameraPhoto(g_changeRequest,
        MediaLibrary_ImageFileType::MEDIA_LIBRARY_IMAGE_JPEG);
    if (result != MEDIA_LIBRARY_OK) {
        DRAWING_LOGD(
            "NDKCamera::ChangeRequestSaveCameraPhoto OH_MediaAssetChangeRequest_SaveCameraPhoto failed.");
    }
    DRAWING_LOGD("NDKCamera::ChangeRequestSaveCameraPhoto OH_MediaAssetChangeRequest_SaveCameraPhoto "
                 "return with ret code: %{public}d!",
        result);
    result = OH_MediaAccessHelper_ApplyChanges(g_changeRequest);
    if (result != MEDIA_LIBRARY_OK) {
        DRAWING_LOGD("NDKCamera::ChangeRequestSaveCameraPhoto OH_MediaAccessHelper_ApplyChanges failed.");
    }
    DRAWING_LOGD("NDKCamera::ChangeRequestSaveCameraPhoto OH_MediaAccessHelper_ApplyChanges return with "
                 "ret code: %{public}d!",
        result);
    return result;
}

MediaLibrary_ErrorCode NDKCamera::ChangeRequestDiscardCameraPhoto(void)
{
    DRAWING_LOGD("NDKCamera::ChangeRequestDiscardCameraPhoto start!");
    result = OH_MediaAssetChangeRequest_DiscardCameraPhoto(g_changeRequest);
    if (result != MEDIA_LIBRARY_OK) {
        DRAWING_LOGD("NDKCamera::ChangeRequestDiscardCameraPhoto "
                     "OH_MediaAssetChangeRequest_DiscardCameraPhoto failed.");
    }
    DRAWING_LOGD("NDKCamera::ChangeRequestDiscardCameraPhoto OH_MediaAssetChangeRequest_DiscardCameraPhoto "
                 "return with ret code: %{public}d!",
        result);
    result = OH_MediaAccessHelper_ApplyChanges(g_changeRequest);
    if (result != MEDIA_LIBRARY_OK) {
        DRAWING_LOGD(
            "NDKCamera::ChangeRequestDiscardCameraPhoto OH_MediaAccessHelper_ApplyChanges failed.");
    }
    DRAWING_LOGD("NDKCamera::ChangeRequestDiscardCameraPhoto OH_MediaAccessHelper_ApplyChanges return with "
                 "ret code: %{public}d!",
        result);
    return result;
}

MediaLibrary_ErrorCode NDKCamera::ChangeRequestRelease(void)
{
    DRAWING_LOGD("NDKCamera::ChangeRequestRelease start!");
    result = OH_MediaAssetChangeRequest_Release(g_changeRequest);
    if (result != MEDIA_LIBRARY_OK) {
        DRAWING_LOGD("NDKCamera::ChangeRequestRelease failed.");
    }
    g_changeRequest = nullptr;
    DRAWING_LOGD("NDKCamera::ChangeRequestRelease return with ret code: %{public}d!", result);
    return result;
}

开发步骤​

开发步骤