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指南媒体Camera Kit（相机服务）开发相机应用基础能力(C/C++)分段式拍照(C/C++)

分段式拍照(C/C++)

更新时间: 2026-07-09 02:26
本文导读

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。

  1. 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。

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    1. #include <cstdint>
    2. #include <unistd.h>
    3. #include <string>
    4. #include <thread>
    5. #include <cstdio>
    6. #include <fcntl.h>
    7. #include <map>
    8. #include <string>
    9. #include <vector>
    10. #include <native_buffer/native_buffer.h>
    11. #include "iostream"
    12. #include "mutex"
    13. 

    14. #include "hilog/log.h"
    15. #include "ohcamera/camera.h"
    16. #include "ohcamera/camera_input.h"
    17. #include "ohcamera/capture_session.h"
    18. #include "ohcamera/photo_output.h"
    19. #include "ohcamera/preview_output.h"
    20. #include "ohcamera/video_output.h"
    21. #include "napi/native_api.h"
    22. #include "ohcamera/camera_manager.h"
    23. #include "common/log_common.h"
    24. 

    25. #include "multimedia/image_framework/image/image_native.h"
    26. #include "multimedia/image_framework/image/image_source_native.h"
    27. #include "multimedia/image_framework/image/image_packer_native.h"
    28. #include "multimedia/media_library/media_access_helper_capi.h"
    29. #include "multimedia/media_library/media_asset_base_capi.h"
    30. #include "multimedia/media_library/media_asset_capi.h"
    31. #include "multimedia/media_library/media_asset_change_request_capi.h"
    32. #include "multimedia/media_library/media_asset_manager_capi.h"
    33. #include "multimedia/media_library/moving_photo_capi.h"
    34. #include "ohcamera/photo_native.h"
    35. #include <window_manager/oh_display_info.h>
    36. #include <window_manager/oh_display_manager.h>
    camera_manager.h

  2. 在CMake脚本中链接相关动态库。

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    1. target_link_libraries(entry PUBLIC
    2.     libace_napi.z.so
    3.     libhilog_ndk.z.so
    4.     libohcamera.so
    5.     libimage_source.so
    6.     libmedia_asset_manager.so
    7.     libimage_packer.so
    8. )

  3. 相机初始化及拍照触发参考拍照(C/C++)。

  4. 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。

    注意

    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。
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    1. // 分段式拍照回调函数。
    2. void onPhotoAssetAvailable(Camera_PhotoOutput *photoOutput, OH_MediaAsset *mediaAsset)
    3. {
    4.     if (mediaAsset == nullptr) {
    5.         DRAWING_LOGI("onPhotoAssetAvailable mediaAsset is nullptr !");
    6.         return;
    7.     }
    8.     DRAWING_LOGD("onPhotoAssetAvailable start!");
    9.     NDKCamera::MediaAssetRelease();
    10.     g_mediaAsset = mediaAsset;
    11.     NDKCamera::MediaAssetGetUri(mediaAsset);
    12.     NDKCamera::MediaAssetGetDisplayName(mediaAsset);
    13.     NDKCamera::MediaAssetGetSize(mediaAsset);
    14.     NDKCamera::MediaAssetGetDateModifiedMs(mediaAsset);
    15.     NDKCamera::MediaAssetGetWidth(mediaAsset);
    16.     NDKCamera::MediaAssetGetHeight(mediaAsset);
    17.     NDKCamera::MediaAssetGetOrientation(mediaAsset);
    18.     NDKCamera::MediaAssetManagerCreate();
    19.     NDKCamera::MediaAssetChangeRequest(mediaAsset);
    20.     DRAWING_LOGD("onPhotoAssetAvailable finish!");
    21.     return;
    22. }
    23. 

    24. // 注册分段式拍照回调。
    25. Camera_ErrorCode NDKCamera::PhotoOutputRegisterPhotoAssetAvailableCallback(void)
    26. {
    27.     DRAWING_LOGD("NDKCamera::PhotoOutputRegisterPhotoAssetAvailableCallback start!");
    28.     MediaAssetManagerCreate();
    29.     ret_ = OH_PhotoOutput_RegisterPhotoAssetAvailableCallback(photoOutput_, onPhotoAssetAvailable);
    30.     if (ret_ != CAMERA_OK) {
    31.         DRAWING_LOGD("NDKCamera::PhotoOutputRegisterPhotoAssetAvailableCallback failed.");
    32.     }
    33.     DRAWING_LOGD(
    34.         "NDKCamera::PhotoOutputRegisterPhotoAssetAvailableCallback return with ret code: %{public}d!",
    35.         ret_);
    36.     return ret_;
    37. }
    38. 

    39. MediaLibrary_ErrorCode NDKCamera::MediaAssetChangeRequest(OH_MediaAsset *mediaAsset)
    40. {
    41.     DRAWING_LOGD("NDKCamera::MediaAssetChangeRequest start!");
    42.     MediaAssetChangeRequestCreate(mediaAsset);
    43.     MediaAssetManagerRequestImage(mediaAsset);
    44.     DRAWING_LOGD("NDKCamera::MediaAssetChangeRequest finish!");
    45.     return MEDIA_LIBRARY_OK;
    46. }
    47. 

    48. MediaLibrary_ErrorCode NDKCamera::MediaAssetChangeRequestCreate(OH_MediaAsset *mediaAsset)
    49. {
    50.     DRAWING_LOGD("NDKCamera::MediaAssetChangeRequestCreate start!");
    51.     g_changeRequest = OH_MediaAssetChangeRequest_Create(mediaAsset);
    52.     if (g_changeRequest == nullptr) {
    53.         DRAWING_LOGD("NDKCamera::MediaAssetChangeRequestCreate failed.");
    54.     }
    55.     return MEDIA_LIBRARY_OK;
    56. }
    57. 

    58. MediaLibrary_ErrorCode NDKCamera::MediaAssetManagerCreate(void)
    59. {
    60.     DRAWING_LOGD("NDKCamera::MediaAssetManagerCreate start!");
    61.     mediaAssetManager = OH_MediaAssetManager_Create();
    62.     if (mediaAssetManager == nullptr) {
    63.         DRAWING_LOGD("NDKCamera::MediaAssetManagerCreate failed.");
    64.     }
    65.     return MEDIA_LIBRARY_OK;
    66. }
    67. 

    68. void OnRequestImageDataPreparedWithDetails(MediaLibrary_ErrorCode result, MediaLibrary_RequestId requestId,
    69.     MediaLibrary_MediaQuality mediaQuality, MediaLibrary_MediaContentType type, OH_ImageSourceNative *imageSourceNative)
    70. {
    71.     auto cb = (void (*)(char *))(g_requestImageCallback);
    72.     auto qCb = (void (*)(char *))(g_requestImageQualityCallback);
    73.     DRAWING_LOGD("OnRequestImageDataPreparedWithDetails start!");
    74.     if (mediaQuality == MediaLibrary_MediaQuality::MEDIA_LIBRARY_QUALITY_FAST) {
    75.         DRAWING_LOGD("OnRequestImageDataPreparedWithDetails into fast quality mode!");
    76.         g_mediaQualityCb = "fast";
    77.         qCb(g_mediaQualityCb);
    78.     } else {
    79.         DRAWING_LOGD("OnRequestImageDataPreparedWithDetails into high quality mode!");
    80.         g_mediaQualityCb = "high";
    81.         qCb(g_mediaQualityCb);
    82.     }
    83.     DRAWING_LOGD("OnRequestImageDataPreparedWithDetails GetUri uri_ = %{public}s", URI);
    84.     cb(const_cast<char *>(URI));
    85.     NDKCamera::ChangeRequestAddResourceWithBuffer(imageSourceNative);
    86.     return;
    87. }
    88. 

    89. // 请求图片数据：deliveryMode/quality等通过requestOptions控制，完成后进回调OnRequestImageDataPreparedWithDetails。
    90. MediaLibrary_ErrorCode NDKCamera::MediaAssetManagerRequestImage(OH_MediaAsset *mediaAsset)
    91. {
    92.     DRAWING_LOGD("NDKCamera::MediaAssetManagerRequestImage start! g_deliveryMode = %{public}d",
    93.         g_deliveryMode);
    94.     requestOptions.deliveryMode = g_deliveryMode;
    95.     result = OH_MediaAssetManager_RequestImage(mediaAssetManager, mediaAsset, requestOptions, &g_requestId,
    96.         OnRequestImageDataPreparedWithDetails);
    97.     if (result != MEDIA_LIBRARY_OK) {
    98.         DRAWING_LOGD("NDKCamera::MediaAssetManagerRequestImage failed.");
    99.     }
    100.     DRAWING_LOGD("NDKCamera::MediaAssetManagerRequestImage return with ret code: %{public}d!", result);
    101.     return result;
    102. }
    103. 

    104. MediaLibrary_ErrorCode NDKCamera::ChangeRequestAddResourceWithBuffer(OH_ImageSourceNative *imageSourceNative)
    105. {
    106.     DRAWING_LOGD("NDKCamera::ChangeRequestAddResourceWithBuffer start!");
    107.     size_t bufferSize = BUFFER_SIZE;
    108.     char buffer[BUFFER_SIZE];
    109.     int fd = open("/data/storage/el2/base/haps/test.jpg", O_RDONLY);
    110.     int fr = read(fd, buffer, bufferSize);
    111.     if (fr == -1) {
    112.         DRAWING_LOGD("NDKCamera::ChangeRequestAddResourceWithBuffer read failed.");
    113.         return MEDIA_LIBRARY_OK;
    114.     }
    115.     if (fr == BUFFER_SIZE) {
    116.         DRAWING_LOGD("NDKCamera::ChangeRequestAddResourceWithBuffer read not complete.");
    117.         return MEDIA_LIBRARY_OK;
    118.     }
    119.     result = OH_MediaAssetChangeRequest_AddResourceWithBuffer(g_changeRequest,
    120.         MediaLibrary_ResourceType::MEDIA_LIBRARY_IMAGE_RESOURCE, (uint8_t *)buffer, (uint32_t)bufferSize);
    121.     if (result != MEDIA_LIBRARY_OK) {
    122.         DRAWING_LOGD("NDKCamera::ChangeRequestAddResourceWithBuffer failed.");
    123.         DRAWING_LOGD("NDKCamera::ChangeRequestAddResourceWithBuffer failed %{public}d.", result);
    124.         return MEDIA_LIBRARY_OK;
    125.     }
    126.     result = OH_MediaAccessHelper_ApplyChanges(g_changeRequest);
    127.     if (result != MEDIA_LIBRARY_OK) {
    128.         DRAWING_LOGD(
    129.             "NDKCamera::ChangeRequestAddResourceWithBuffer OH_MediaAccessHelper_ApplyChanges failed.");
    130.         return MEDIA_LIBRARY_OK;
    131.     }
    132.     DRAWING_LOGD("NDKCamera::ChangeRequestAddResourceWithBuffer OH_MediaAccessHelper_ApplyChanges return "
    133.                  "with ret code: %{public}d!",
    134.         result);
    135.     return result;
    136. }
    137. 

    138. MediaLibrary_ErrorCode NDKCamera::ChangeRequestSaveCameraPhoto(void)
    139. {
    140.     DRAWING_LOGD("NDKCamera::ChangeRequestSaveCameraPhoto start!");
    141.     result = OH_MediaAssetChangeRequest_SaveCameraPhoto(g_changeRequest,
    142.         MediaLibrary_ImageFileType::MEDIA_LIBRARY_IMAGE_JPEG);
    143.     if (result != MEDIA_LIBRARY_OK) {
    144.         DRAWING_LOGD(
    145.             "NDKCamera::ChangeRequestSaveCameraPhoto OH_MediaAssetChangeRequest_SaveCameraPhoto failed.");
    146.     }
    147.     DRAWING_LOGD("NDKCamera::ChangeRequestSaveCameraPhoto OH_MediaAssetChangeRequest_SaveCameraPhoto "
    148.                  "return with ret code: %{public}d!",
    149.         result);
    150.     result = OH_MediaAccessHelper_ApplyChanges(g_changeRequest);
    151.     if (result != MEDIA_LIBRARY_OK) {
    152.         DRAWING_LOGD("NDKCamera::ChangeRequestSaveCameraPhoto OH_MediaAccessHelper_ApplyChanges failed.");
    153.     }
    154.     DRAWING_LOGD("NDKCamera::ChangeRequestSaveCameraPhoto OH_MediaAccessHelper_ApplyChanges return with "
    155.                  "ret code: %{public}d!",
    156.         result);
    157.     return result;
    158. }
    159. 

    160. MediaLibrary_ErrorCode NDKCamera::ChangeRequestDiscardCameraPhoto(void)
    161. {
    162.     DRAWING_LOGD("NDKCamera::ChangeRequestDiscardCameraPhoto start!");
    163.     result = OH_MediaAssetChangeRequest_DiscardCameraPhoto(g_changeRequest);
    164.     if (result != MEDIA_LIBRARY_OK) {
    165.         DRAWING_LOGD("NDKCamera::ChangeRequestDiscardCameraPhoto "
    166.                      "OH_MediaAssetChangeRequest_DiscardCameraPhoto failed.");
    167.     }
    168.     DRAWING_LOGD("NDKCamera::ChangeRequestDiscardCameraPhoto OH_MediaAssetChangeRequest_DiscardCameraPhoto "
    169.                  "return with ret code: %{public}d!",
    170.         result);
    171.     result = OH_MediaAccessHelper_ApplyChanges(g_changeRequest);
    172.     if (result != MEDIA_LIBRARY_OK) {
    173.         DRAWING_LOGD(
    174.             "NDKCamera::ChangeRequestDiscardCameraPhoto OH_MediaAccessHelper_ApplyChanges failed.");
    175.     }
    176.     DRAWING_LOGD("NDKCamera::ChangeRequestDiscardCameraPhoto OH_MediaAccessHelper_ApplyChanges return with "
    177.                  "ret code: %{public}d!",
    178.         result);
    179.     return result;
    180. }
    181. 

    182. MediaLibrary_ErrorCode NDKCamera::ChangeRequestRelease(void)
    183. {
    184.     DRAWING_LOGD("NDKCamera::ChangeRequestRelease start!");
    185.     result = OH_MediaAssetChangeRequest_Release(g_changeRequest);
    186.     if (result != MEDIA_LIBRARY_OK) {
    187.         DRAWING_LOGD("NDKCamera::ChangeRequestRelease failed.");
    188.     }
    189.     g_changeRequest = nullptr;
    190.     DRAWING_LOGD("NDKCamera::ChangeRequestRelease return with ret code: %{public}d!", result);
    191.     return result;
    192. }
    camera_manager.cpp
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