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 <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 OnRequestImageDataPreparedWithDetails(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("OnRequestImageDataPreparedWithDetails start!"); if (mediaQuality == MediaLibrary_MediaQuality::MEDIA_LIBRARY_QUALITY_FAST) { DRAWING_LOGD("OnRequestImageDataPreparedWithDetails into fast quality mode!"); g_mediaQualityCb = "fast"; qCb(g_mediaQualityCb); } else { DRAWING_LOGD("OnRequestImageDataPreparedWithDetails into high quality mode!"); g_mediaQualityCb = "high"; qCb(g_mediaQualityCb); } DRAWING_LOGD("OnRequestImageDataPreparedWithDetails 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OnRequestImageDataPreparedWithDetails。 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, OnRequestImageDataPreparedWithDetails); 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; }