[Android system] Tracking the camera direction

background:

          System code tracking of camera preview direction and picture direction after taking pictures

See blog:

             https://blog.csdn.net/liwei16611/article/details/52206894?locationNum=5&fps=1 camera process

             https://www.e-learn.cn/topic/58947 camera2 framework

            

 

1. android framework/下各目录作用：

                    https://blog.csdn.net/yui_hatano/article/details/89517165

framework/av下是多媒体框架，camera在这个里面

2.预览角度流程
      public native final void setDisplayOrientation(int degrees);
                     |                                //Camera.java
                     |                            
      android_hardware_Camera_setDisplayOrientation(JNIEnv *env, jobject thiz,jint value))
                     |                               //android_hardware_Camera.cpp
                     |
        Camera::sendCommand(int32_t cmd, int32_t arg1, int32_t arg2)
                     |                              //Camera.cpp
                     |
        Camera2Client::sendCommand(int32_t cmd, int32_t arg1, int32_t arg2) 
        {                                          //Camera2Client.cpp
            ...    //省略
            case CAMERA_CMD_SET_DISPLAY_ORIENTATION:
                return commandSetDisplayOrientationL(arg1);
            ...   //省略
        }
                     |                            
                     |
       int transform = 
              Parameters::degToTransform(degrees,mCameraFacing==CAMERA_FACING_FRONT);
                     |
                     |
        int Parameters::degToTransform(int degrees, bool mirror)
        {                                            //Parameters.cpp

                //前摄镜像，后摄不镜像
        }

2813 int Parameters::degToTransform(int degrees, bool mirror) {
2814     if (!mirror) {
2815         if (degrees == 0) return 0;
2816         else if (degrees == 90) return HAL_TRANSFORM_ROT_90;
2817         else if (degrees == 180) return HAL_TRANSFORM_ROT_180;
2818         else if (degrees == 270) return HAL_TRANSFORM_ROT_270;
2819     } else {  // Do mirror (horizontal flip)
2820         if (degrees == 0) {           // FLIP_H and ROT_0
2821             return HAL_TRANSFORM_FLIP_H;
2822         } else if (degrees == 90) {   // FLIP_H and ROT_90
2823             return HAL_TRANSFORM_FLIP_H | HAL_TRANSFORM_ROT_90;
2824         } else if (degrees == 180) {  // FLIP_H and ROT_180
2825             return HAL_TRANSFORM_FLIP_V;
2826         } else if (degrees == 270) {  // FLIP_H and ROT_270
2827             return HAL_TRANSFORM_FLIP_V | HAL_TRANSFORM_ROT_90;
2828         }
2829     }
2830     ALOGE("%s: Bad input: %d", __FUNCTION__, degrees);
2831     return -1;
2832 }

 

打印的一些log:
    打开后摄时，degToTransform会调用两次，默认第一次传入的degToTransform的degree第一次是0，第二次是90，如果app
不修改预览方向，在这里可以根据传入的角度进行调整预览方向。

 

先写到这里吧...