海康工业相机镜头阴影矫正LSC

前言

• 镜头阴影校正（Lens Shading Correction）是为了解决由于lens的光学特性，由于镜头对于光学折射不均匀导致的镜头周围出现阴影的情况。
• 由于Lens的光学特性，Sensor影像区的边缘区域接收的光强比中心小，所造成的中心和四角亮度不一致的现象。镜头本身就是一个凸透镜，由于凸透镜原理，中心的感光必然比周边多。如图所示：
  
  实际成像效果如图：
  
  中间区域发亮，四角发黑

海康工业相机SDK LSC算法矫正接口

SDK下载获取

海康机器视觉sdk简介，下载链接：机器视觉下载中心，下载安装MVS即可

示例程序demo，参考“C:\Program Files (x86)\MVS\Development\Samples\VC\VS\SimpleSamples*LensShadingCorrection*”

代码流程简介

LSC矫正主要分为标定文件生成、lsc矫正使用

LSC标定文件生成

核心思想是在取流接口中，或者到一张待标定的图片，调用标定接口进行标定文件生成
如下代码，再回调函数中，调用MV_CC_LSCCalib接口，生成LSCCalib.bin标定文件

void __stdcall ImageCallBackEx(unsigned char * pData, MV_FRAME_OUT_INFO_EX* pFrameInfo, void* pUser)
{
    printf("Get One Frame: Width[%d], Height[%d], nFrameNum[%d]\n", pFrameInfo->nWidth, pFrameInfo->nHeight, pFrameInfo->nFrameNum);
    int nRet = MV_OK;
    //判断是否需要标定
    if (true == g_IsNeedCalib)
    {
        // LSC标定
        MV_CC_LSC_CALIB_PARAM stLSCCalib = {0};
        stLSCCalib.nWidth = pFrameInfo->nWidth;
        stLSCCalib.nHeight = pFrameInfo->nHeight;
        stLSCCalib.enPixelType = pFrameInfo->enPixelType;
        stLSCCalib.pSrcBuf = pData;
        stLSCCalib.nSrcBufLen = pFrameInfo->nFrameLen;
        if (g_pCalibBuf == NULL || g_nCalibBufSize < (pFrameInfo->nWidth*pFrameInfo->nHeight*sizeof(unsigned short)))
        {
            if (g_pCalibBuf)
            {
                free(g_pCalibBuf);
                g_pCalibBuf = NULL;
                g_nCalibBufSize = 0;
            }
            g_pCalibBuf = (unsigned char *)malloc(pFrameInfo->nWidth*pFrameInfo->nHeight*sizeof(unsigned short));
            if (g_pCalibBuf == NULL)
            {
                printf("malloc pCalibBuf fail !\n");
                return;
            }
            g_nCalibBufSize = pFrameInfo->nWidth*pFrameInfo->nHeight*sizeof(unsigned short);
        }
        stLSCCalib.pCalibBuf = g_pCalibBuf;
        stLSCCalib.nCalibBufSize = g_nCalibBufSize;
        stLSCCalib.nSecNumW = 689;
        stLSCCalib.nSecNumH = 249;
        stLSCCalib.nPadCoef = 2;
        stLSCCalib.nCalibMethod = 2;
        stLSCCalib.nTargetGray = 100;
        //同一个相机，在场景、算法参数和图像参数都不变情况下，理论上只需要进行一次标定，可将标定表保存下来。
        //不同相机图片标定出来的标定表不可复用，当场景改变或算法参数改变或图像参数改变时，需要重新标定。
        nRet = MV_CC_LSCCalib(pUser, &stLSCCalib);
        if (MV_OK != nRet)
        {
            printf("LSC Calib fail! nRet [0x%x]\n", nRet);
            return;
        }

        //保存标定表到本地
        FILE* fp_out = fopen("./LSCCalib.bin", "wb");
        if (NULL == fp_out)
        {
            return ;
        }
        fwrite(stLSCCalib.pCalibBuf, 1, stLSCCalib.nCalibBufLen, fp_out);
        fclose(fp_out);
        g_IsNeedCalib = false;
    }
}

MV_CC_LSCCalib接口中，需要传入算法参数，来看一下这个结构体MV_CC_LSC_CALIB_PARAM的构成
除了常规的图像宽、高、像素格式之外的参数，部分算法参数如下解释：

typedef struct _MV_CC_LSC_CALIB_PARAM_T_
{
    unsigned int            nWidth;                                 ///< [IN]  \~chinese 图像宽度[16,65535]     \~english Image Width
    unsigned int            nHeight;                                ///< [IN]  \~chinese 图像高度[16-65535]     \~english Image Height
    enum MvGvspPixelType    enPixelType;                            ///< [IN]  \~chinese 像素格式               \~english Pixel format
    unsigned char*          pSrcBuf;                                ///< [IN]  \~chinese 输入数据缓存           \~english Input data buffer
    unsigned int            nSrcBufLen;                             ///< [IN]  \~chinese 输入数据长度           \~english Input data length
    unsigned char*          pCalibBuf;                              ///< [OUT] \~chinese 输出标定表缓存         \~english Output calib buffer
    unsigned int            nCalibBufSize;                          ///< [IN]  \~chinese 提供的标定表缓冲大小(nWidth*nHeight*sizeof(unsigned short))    \~english Provided output buffer size
    unsigned int            nCalibBufLen;                           ///< [OUT] \~chinese 输出标定表缓存长度     \~english Output calib buffer length
    unsigned int            nSecNumW;                               ///< [IN]  \~chinese 宽度分块数             \~english Width Sec num
    unsigned int            nSecNumH;                               ///< [IN]  \~chinese 高度分块数             \~english Height Sec num
    unsigned int            nPadCoef;                               ///< [IN]  \~chinese 边缘填充系数[1,5]      \~english Pad Coef[1,5]
    unsigned int            nCalibMethod;                           ///< [IN]  \~chinese 标定方式(0-中心为基准;1-最亮区域为基准;2-目标亮度为基准) \~english Calib method
    unsigned int            nTargetGray;                            ///< [IN]  \~chinese 目标亮度(标定方式为2时有效)    \~english Target Gray
                                                                    ///< \~chinese 8位,范围：[0,255]            \~english 8bit,range:[0,255]
                                                                    ///< \~chinese 10位,范围：[0,1023]          \~english 10bit,range:[0,1023]
                                                                    ///< \~chinese 12位,范围：[0,4095]          \~english 12bit,range:[0,4095]
    unsigned int            nRes[8];                                ///<       \~chinese 预留                   \~english Reserved
}MV_CC_LSC_CALIB_PARAM;

标定过程，需要特定场景的，按照如下步骤进行
1、相机对准均匀场景（均匀光源、白纸、白板等），通过调节曝光、增益等，使得图像灰度在120-160之间（镜头光圈保持与实际使用场景一致）

2、运行标定程序，生成标定文件；可直接运行LensShadingCorrection示例demo，exe路径下会有当前标定文件生成
3、拍摄实际物体，运行矫正程序，观察效果；可直接运行LensShadingCorrection示例demo观察
如果标定矫正效果不佳，那么就需要重新调整标定场景，重新生成标定文件
同理，如遇到多种光源切换场景，可以生成不同的标定文件，进行动态切换矫正

LSC矫正

拿到标定文件后，矫正过程相对简单，获取一张图像后，再调用MV_CC_LSCCorrect接口即可完成（每一张图片都需要调用，一张一张矫正）

void __stdcall ImageCallBackEx(unsigned char * pData, MV_FRAME_OUT_INFO_EX* pFrameInfo, void* pUser)
{
    printf("Get One Frame: Width[%d], Height[%d], nFrameNum[%d]\n", pFrameInfo->nWidth, pFrameInfo->nHeight, pFrameInfo->nFrameNum);
    int nRet = MV_OK;
    // LSC校正
    if (g_pDstData == NULL || g_nDstDataSize < pFrameInfo->nFrameLen)
    {
        if (g_pDstData)
        {
            free(g_pDstData);
            g_pDstData = NULL;
            g_nDstDataSize = 0;
        }

        g_pDstData = (unsigned char *)malloc(pFrameInfo->nFrameLen);
        if (g_pDstData == NULL)
        {
            printf("malloc pDstData fail !\n");
            return;
        }
        g_nDstDataSize = pFrameInfo->nFrameLen;
    }
    MV_CC_LSC_CORRECT_PARAM stLSCCorrectParam = {0};
    stLSCCorrectParam.nWidth = pFrameInfo->nWidth;
    stLSCCorrectParam.nHeight = pFrameInfo->nHeight;
    stLSCCorrectParam.enPixelType = pFrameInfo->enPixelType;
    stLSCCorrectParam.pSrcBuf = pData;
    stLSCCorrectParam.nSrcBufLen = pFrameInfo->nFrameLen;
    stLSCCorrectParam.pDstBuf = g_pDstData;
    stLSCCorrectParam.nDstBufSize = g_nDstDataSize;
    stLSCCorrectParam.pCalibBuf = g_pCalibBuf;
    stLSCCorrectParam.nCalibBufLen = g_nCalibBufSize;
    nRet = MV_CC_LSCCorrect(pUser, &stLSCCorrectParam);
    if (MV_OK != nRet)
    {
        printf("LSC Correct fail! nRet [0x%x]\n", nRet);
        return;
    }
    //矫正完成，其他图像处理
}

矫正耗时测试

测试1：不同分辨率图像，不同版本算法，耗时情况

• 算法耗时取决于图像分辨率大小，分辨率越大，耗时越大
  测试2：不同算法参数，矫正模块耗时情况

图像效果对比

测试参数：

LensShadingCorrection完整示例程序

#include <stdio.h>
#include <Windows.h>
#include <conio.h>
#include <io.h>
#include "MvCameraControl.h"
// ch:等待按键输入 | en:Wait for key press
void WaitForKeyPress(void)
{
    while(!_kbhit())
    {
        Sleep(10);
    }
    _getch();
}
bool PrintDeviceInfo(MV_CC_DEVICE_INFO* pstMVDevInfo)
{
    if (NULL == pstMVDevInfo)
    {
        printf("The Pointer of pstMVDevInfo is NULL!\n");
        return false;
    }
    if (pstMVDevInfo->nTLayerType == MV_GIGE_DEVICE)
    {
        int nIp1 = ((pstMVDevInfo->SpecialInfo.stGigEInfo.nCurrentIp & 0xff000000) >> 24);
        int nIp2 = ((pstMVDevInfo->SpecialInfo.stGigEInfo.nCurrentIp & 0x00ff0000) >> 16);
        int nIp3 = ((pstMVDevInfo->SpecialInfo.stGigEInfo.nCurrentIp & 0x0000ff00) >> 8);
        int nIp4 = (pstMVDevInfo->SpecialInfo.stGigEInfo.nCurrentIp & 0x000000ff);
        // ch:打印当前相机ip和用户自定义名字 | en:print current ip and user defined name
        printf("CurrentIp: %d.%d.%d.%d\n" , nIp1, nIp2, nIp3, nIp4);
        printf("UserDefinedName: %s\n\n" , pstMVDevInfo->SpecialInfo.stGigEInfo.chUserDefinedName);
    }
    else if (pstMVDevInfo->nTLayerType == MV_USB_DEVICE)
    {
        printf("UserDefinedName: %s\n", pstMVDevInfo->SpecialInfo.stUsb3VInfo.chUserDefinedName);
        printf("Serial Number: %s\n", pstMVDevInfo->SpecialInfo.stUsb3VInfo.chSerialNumber);
        printf("Device Number: %d\n\n", pstMVDevInfo->SpecialInfo.stUsb3VInfo.nDeviceNumber);
    }
    else
    {
        printf("Not support.\n");
    }
    return true;
}
unsigned char * g_pDstData = NULL;
unsigned int g_nDstDataSize = 0;
unsigned char * g_pCalibBuf = NULL;
unsigned int g_nCalibBufSize = 0;
bool g_IsNeedCalib = true;
void __stdcall ImageCallBackEx(unsigned char * pData, MV_FRAME_OUT_INFO_EX* pFrameInfo, void* pUser)
{
    printf("Get One Frame: Width[%d], Height[%d], nFrameNum[%d]\n", pFrameInfo->nWidth, pFrameInfo->nHeight, pFrameInfo->nFrameNum);

    int nRet = MV_OK;
    //判断是否需要标定
    if (true == g_IsNeedCalib)
    {
        // LSC标定
        MV_CC_LSC_CALIB_PARAM stLSCCalib = {0};
        stLSCCalib.nWidth = pFrameInfo->nWidth;
        stLSCCalib.nHeight = pFrameInfo->nHeight;
        stLSCCalib.enPixelType = pFrameInfo->enPixelType;
        stLSCCalib.pSrcBuf = pData;
        stLSCCalib.nSrcBufLen = pFrameInfo->nFrameLen;
        if (g_pCalibBuf == NULL || g_nCalibBufSize < (pFrameInfo->nWidth*pFrameInfo->nHeight*sizeof(unsigned short)))
        {
            if (g_pCalibBuf)
            {
                free(g_pCalibBuf);
                g_pCalibBuf = NULL;
                g_nCalibBufSize = 0;
            }

            g_pCalibBuf = (unsigned char *)malloc(pFrameInfo->nWidth*pFrameInfo->nHeight*sizeof(unsigned short));
            if (g_pCalibBuf == NULL)
            {
                printf("malloc pCalibBuf fail !\n");
                return;
            }
            g_nCalibBufSize = pFrameInfo->nWidth*pFrameInfo->nHeight*sizeof(unsigned short);
        }
        stLSCCalib.pCalibBuf = g_pCalibBuf;
        stLSCCalib.nCalibBufSize = g_nCalibBufSize;
        stLSCCalib.nSecNumW = 689;
        stLSCCalib.nSecNumH = 249;
        stLSCCalib.nPadCoef = 2;
        stLSCCalib.nCalibMethod = 2;
        stLSCCalib.nTargetGray = 100;
        //同一个相机，在场景、算法参数和图像参数都不变情况下，理论上只需要进行一次标定，可将标定表保存下来。
        //不同相机图片标定出来的标定表不可复用，当场景改变或算法参数改变或图像参数改变时，需要重新标定。
        nRet = MV_CC_LSCCalib(pUser, &stLSCCalib);
        if (MV_OK != nRet)
        {
            printf("LSC Calib fail! nRet [0x%x]\n", nRet);
            return;
        }
        //保存标定表到本地
        FILE* fp_out = fopen("./LSCCalib.bin", "wb");
        if (NULL == fp_out)
        {
            return ;
        }
        fwrite(stLSCCalib.pCalibBuf, 1, stLSCCalib.nCalibBufLen, fp_out);
        fclose(fp_out);

        g_IsNeedCalib = false;
    }
    // LSC校正
    if (g_pDstData == NULL || g_nDstDataSize < pFrameInfo->nFrameLen)
    {
        if (g_pDstData)
        {
            free(g_pDstData);
            g_pDstData = NULL;
            g_nDstDataSize = 0;
        }
        g_pDstData = (unsigned char *)malloc(pFrameInfo->nFrameLen);
        if (g_pDstData == NULL)
        {
            printf("malloc pDstData fail !\n");
            return;
        }
        g_nDstDataSize = pFrameInfo->nFrameLen;
    }
    MV_CC_LSC_CORRECT_PARAM stLSCCorrectParam = {0};
    stLSCCorrectParam.nWidth = pFrameInfo->nWidth;
    stLSCCorrectParam.nHeight = pFrameInfo->nHeight;
    stLSCCorrectParam.enPixelType = pFrameInfo->enPixelType;
    stLSCCorrectParam.pSrcBuf = pData;
    stLSCCorrectParam.nSrcBufLen = pFrameInfo->nFrameLen;
    stLSCCorrectParam.pDstBuf = g_pDstData;
    stLSCCorrectParam.nDstBufSize = g_nDstDataSize;
    stLSCCorrectParam.pCalibBuf = g_pCalibBuf;
    stLSCCorrectParam.nCalibBufLen = g_nCalibBufSize;
    nRet = MV_CC_LSCCorrect(pUser, &stLSCCorrectParam);
    if (MV_OK != nRet)
    {
        printf("LSC Correct fail! nRet [0x%x]\n", nRet);
        return;
    }
    if (pFrameInfo->nFrameNum < 10)
    {
        //保存图像到文件
        MV_SAVE_IMG_TO_FILE_PARAM stSaveFileParam;
        memset(&stSaveFileParam, 0, sizeof(MV_SAVE_IMG_TO_FILE_PARAM));
        stSaveFileParam.enImageType = MV_Image_Bmp;
        stSaveFileParam.enPixelType = pFrameInfo->enPixelType;
        stSaveFileParam.nWidth      = pFrameInfo->nWidth;
        stSaveFileParam.nHeight     = pFrameInfo->nHeight;
        stSaveFileParam.nDataLen    = pFrameInfo->nFrameLen;
        stSaveFileParam.pData       = pData;
        sprintf_s(stSaveFileParam.pImagePath, 256, "BeforeImage_w%d_h%d_fn%03d.bmp", stSaveFileParam.nWidth, stSaveFileParam.nHeight, pFrameInfo->nFrameNum);
        nRet = MV_CC_SaveImageToFile(pUser, &stSaveFileParam);
        if (MV_OK != nRet)
        {
            printf("SaveImageToFile failed[%x]!\n", nRet);
            return;
        }
        stSaveFileParam.pData       = g_pDstData;
        sprintf_s(stSaveFileParam.pImagePath, 256, "AfterImage_w%d_h%d_fn%03d.bmp", stSaveFileParam.nWidth, stSaveFileParam.nHeight, pFrameInfo->nFrameNum);
        nRet = MV_CC_SaveImageToFile(pUser, &stSaveFileParam);
        if (MV_OK != nRet)
        {
            printf("SaveImageToFile failed[%x]!\n", nRet);
            return;
        }
    }
}
int main()
{
    int nRet = MV_OK;
    void* handle = NULL;
    do 
    {
        // ch:枚举设备 | en:Enum device
        MV_CC_DEVICE_INFO_LIST stDeviceList;
        memset(&stDeviceList, 0, sizeof(MV_CC_DEVICE_INFO_LIST));
        nRet = MV_CC_EnumDevices(MV_GIGE_DEVICE | MV_USB_DEVICE, &stDeviceList);
        if (MV_OK != nRet)
        {
            printf("Enum Devices fail! nRet [0x%x]\n", nRet);
            break;
        }
        if (stDeviceList.nDeviceNum > 0)
        {
            for (unsigned int i = 0; i < stDeviceList.nDeviceNum; i++)
            {
                printf("[device %d]:\n", i);
                MV_CC_DEVICE_INFO* pDeviceInfo = stDeviceList.pDeviceInfo[i];
                if (NULL == pDeviceInfo)
                {
                    break;
                } 
                PrintDeviceInfo(pDeviceInfo);            
            }  
        } 
        else
        {
            printf("Find No Devices!\n");
            break;
        }
        printf("Please Input camera index(0-%d):", stDeviceList.nDeviceNum-1);
        unsigned int nIndex = 0;
        scanf_s("%d", &nIndex);
        if (nIndex >= stDeviceList.nDeviceNum)
        {
            printf("Input error!\n");
            break;
        }
        // ch:选择设备并创建句柄 | en:Select device and create handle
        nRet = MV_CC_CreateHandle(&handle, stDeviceList.pDeviceInfo[nIndex]);
        if (MV_OK != nRet)
        {
            printf("Create Handle fail! nRet [0x%x]\n", nRet);
            break;
        }
        // ch:打开设备 | en:Open device
        nRet = MV_CC_OpenDevice(handle);
        if (MV_OK != nRet)
        {
            printf("Open Device fail! nRet [0x%x]\n", nRet);
            break;
        }
        // ch:探测网络最佳包大小(只对GigE相机有效) | en:Detection network optimal package size(It only works for the GigE camera)
        if (stDeviceList.pDeviceInfo[nIndex]->nTLayerType == MV_GIGE_DEVICE)
        {
            int nPacketSize = MV_CC_GetOptimalPacketSize(handle);
            if (nPacketSize > 0)
            {
                nRet = MV_CC_SetIntValue(handle,"GevSCPSPacketSize",nPacketSize);
                if(nRet != MV_OK)
                {
                    printf("Warning: Set Packet Size fail nRet [0x%x]!", nRet);
                }
            }
            else
            {
                printf("Warning: Get Packet Size fail nRet [0x%x]!", nPacketSize);
            }
        }
        // ch:设置触发模式为off | eb:Set trigger mode as off
        nRet = MV_CC_SetEnumValue(handle, "TriggerMode", MV_TRIGGER_MODE_OFF);
        if (MV_OK != nRet)
        {
            printf("Set Trigger Mode fail! nRet [0x%x]\n", nRet);
            break;
        }
        //判断是否可以本地导入
        FILE* fp = fopen("./LSCCalib.bin", "rb");
        if (fp)
        {
            int nFileLen = filelength(fileno(fp));
            if (g_pCalibBuf == NULL || g_nCalibBufSize < nFileLen)
            {
                if (g_pCalibBuf)
                {
                    free(g_pCalibBuf);
                    g_pCalibBuf = NULL;
                    g_nCalibBufSize = 0;
                }
                g_pCalibBuf = (unsigned char *)malloc(nFileLen);
                if (g_pCalibBuf == NULL)
                {
                    printf("malloc pCalibBuf fail !\n");
                    break;
                }
                g_nCalibBufSize = nFileLen;
            }
            fread(g_pCalibBuf, 1, g_nCalibBufSize, fp);
            fclose(fp);
            g_IsNeedCalib = false;
        }
        // ch:注册抓图回调 | en:Register image callback
        nRet = MV_CC_RegisterImageCallBackEx(handle, ImageCallBackEx, handle);
        if (MV_OK != nRet)
        {
            printf("Register Image CallBack fail! nRet [0x%x]\n", nRet);
            break;
        }
        // ch:开始取流 | en:Start grab image
        nRet = MV_CC_StartGrabbing(handle);
        if (MV_OK != nRet)
        {
            printf("Start Grabbing fail! nRet [0x%x]\n", nRet);
            break;
        }
        printf("Press a key to stop grabbing.\n");
        WaitForKeyPress();
        Sleep(1000);
        // ch:停止取流 | en:Stop grab image
        nRet = MV_CC_StopGrabbing(handle);
        if (MV_OK != nRet)
        {
            printf("Stop Grabbing fail! nRet [0x%x]\n", nRet);
            break;
        }

        // ch:关闭设备 | en:Close device
        nRet = MV_CC_CloseDevice(handle);
        if (MV_OK != nRet)
        {
            printf("Close Device fail! nRet [0x%x]\n", nRet);
            break;
        }
        // ch:销毁句柄 | en:Destroy handle
        nRet = MV_CC_DestroyHandle(handle);
        if (MV_OK != nRet)
        {
            printf("Destroy Handle fail! nRet [0x%x]\n", nRet);
            break;
        }
    } while (0);
    if (g_pCalibBuf)
    {
        free(g_pCalibBuf);
        g_pCalibBuf = NULL;
        g_nCalibBufSize = 0;
    }
    if (g_pDstData)
    {
        free(g_pDstData);
        g_pDstData = NULL;
        g_nDstDataSize = 0;
    }
    if (nRet != MV_OK)
    {
        if (handle != NULL)
        {
            MV_CC_DestroyHandle(handle);
            handle = NULL;
        }
    }
    printf("Press a key to exit.\n");
    WaitForKeyPress();
    return 0;
}