检测扫描图像所属的相机
Detecting the camera that scanned image belongs to
我正在使用 Leadtools 20 API 来控制扫描仪并扫描一些文档。我有 2 个问题。
1 - 当 L_TwainAcquire
与回调函数一起使用时,回调函数从扫描仪接收图像并不断返回 SUCCESS
以获取下一张图像。回调函数中是否有判断图像是来自前置摄像头还是来自后置摄像头?
2 - 有没有办法强制扫描仪仅使用后置摄像头进行扫描?
谢谢你
山姆
如果您指的是使用双面扫描仪时扫描文档的两个面,答案如下:
- 要在位图回调中知道当前正在处理纸张的哪一面,可以在回调函数中使用以下代码:
L_INT EXT_CALLBACK LTwainBitmapCallback(HTWAINSESSION hSession, pBITMAPHANDLE pBitmap, L_VOID * pUserData)
{
L_INT nRet = SUCCESS;
TW_EXTIMAGEINFO* pExtImg = NULL;
int nExtraInfoAftreZero = 0; // we have only one info, so no extra needed
pExtImg = (TW_EXTIMAGEINFO *)malloc(sizeof TW_EXTIMAGEINFO + nExtraInfoAftreZero * sizeof TW_INFO);
if (pExtImg)
{
pExtImg->NumInfos = 1;
pExtImg->Info[0].InfoID = TWEI_PAGESIDE;
pExtImg->Info[0].ItemType = TWTY_UINT16;
nRet = L_TwainGetExtendedImageInfo (hSession, pExtImg);
if (nRet == SUCCESS)
{
// Do processing to returned values
if(pExtImg->Info[0].Item == TWCS_TOP)
OutputDebugString("Front of sheet.\n");
else if (pExtImg->Info[0].Item == TWCS_BOTTOM)
OutputDebugString("Rear of sheet.\n");
else
OutputDebugString("Unexpected!\n");
nRet = L_TwainFreeExtendedImageInfoStructure (&pExtImg);
if(nRet != SUCCESS)
return nRet;
}
free(pExtImg);
}
return SUCCESS;
}
- 可以使用 CAP_CAMERASIDE 和 CAP_CAMERAENABLED 功能的组合来强制扫描特定面,如 Twain Spec 中所述。
引用该文档:
To enable bottom only scanning, set CAP_CAMERASIDE to TWCS_BOTTOM and
set CAP_CAMERAENABLED to TRUE, then set CAP_CAMERASIDE to TWCS_TOP and
set CAP_CAMERAENABLED to FALSE.
如果你的意思是你的电脑有 2 个 Twain 相机源(前后),答案如下:
- 要知道调用
L_TwainAcquire()
时哪个 Twain 源(例如相机)触发了 Twain 位图回调,您可以使用
L_TwainGetSources()
函数与 LTWAIN_SOURCE_ENUMERATE_DEFAULT
标志一起获取当前选择的 Twain 设备。这可以在 inside Bitmap Callback 中完成,如以下代码所示:
// Source Info Callback
L_INT EXT_CALLBACK TwainSourceInfoCallbackCurrent(HTWAINSESSION hSession, pLTWAINSOURCEINFO pSourceInfo, L_VOID * pUserData)
{
strcpy((L_CHAR *)pUserData, pSourceInfo->pszTwnSourceName);
return SUCCESS;
}
// Twain Bitmap Callback
L_INT EXT_CALLBACK LTwainBitmapCallback(HTWAINSESSION hSession, pBITMAPHANDLE pBitmap, L_VOID * pUserData)
{
char szSourceName[1024];
L_TwainGetSources(hSession, TwainSourceInfoCallbackCurrent, sizeof LTWAINSOURCEINFO, LTWAIN_SOURCE_ENUMERATE_DEFAULT, szSourceName);
// Now szSourceName contains name of Twain Source.
return SUCCESS;
}
- 是的,您可以通过在扫描前将其名称发送到
L_TwainSelectSource()
函数来强制从特定设备(扫描仪、相机等)进行扫描,如下所示:
LTWAINSOURCE TwainSource;
TwainSource.uStructSize = sizeof LTWAINSOURCE;
TwainSource.pszTwainSourceName = pszRearCameraTwainSourceName;
L_TwainSelectSource(twainSession, &TwainSource);
// Now L_TwainAcquire() will capture from Rear Camera
要查找所有设备的名称,您可以使用此代码:
L_TwainGetSources(twainSession, TwainSourceInfoCallback, sizeof LTWAINSOURCEINFO, LTWAIN_SOURCE_ENUMERATE_ALL, NULL);
源信息回调将为每个 Twain 源触发一次。可以这样实现:
L_INT EXT_CALLBACK TwainSourceInfoCallback(HTWAINSESSION hSession, pLTWAINSOURCEINFO pSourceInfo, L_VOID * pUserData)
{
OutputDebugString(pSourceInfo->pszTwnSourceName); // You can save the names of Twain Sources into global variables if you like
OutputDebugString("\n");
return SUCCESS;
}
我正在使用 Leadtools 20 API 来控制扫描仪并扫描一些文档。我有 2 个问题。
1 - 当 L_TwainAcquire
与回调函数一起使用时,回调函数从扫描仪接收图像并不断返回 SUCCESS
以获取下一张图像。回调函数中是否有判断图像是来自前置摄像头还是来自后置摄像头?
2 - 有没有办法强制扫描仪仅使用后置摄像头进行扫描?
谢谢你
山姆
如果您指的是使用双面扫描仪时扫描文档的两个面,答案如下:
- 要在位图回调中知道当前正在处理纸张的哪一面,可以在回调函数中使用以下代码:
L_INT EXT_CALLBACK LTwainBitmapCallback(HTWAINSESSION hSession, pBITMAPHANDLE pBitmap, L_VOID * pUserData)
{
L_INT nRet = SUCCESS;
TW_EXTIMAGEINFO* pExtImg = NULL;
int nExtraInfoAftreZero = 0; // we have only one info, so no extra needed
pExtImg = (TW_EXTIMAGEINFO *)malloc(sizeof TW_EXTIMAGEINFO + nExtraInfoAftreZero * sizeof TW_INFO);
if (pExtImg)
{
pExtImg->NumInfos = 1;
pExtImg->Info[0].InfoID = TWEI_PAGESIDE;
pExtImg->Info[0].ItemType = TWTY_UINT16;
nRet = L_TwainGetExtendedImageInfo (hSession, pExtImg);
if (nRet == SUCCESS)
{
// Do processing to returned values
if(pExtImg->Info[0].Item == TWCS_TOP)
OutputDebugString("Front of sheet.\n");
else if (pExtImg->Info[0].Item == TWCS_BOTTOM)
OutputDebugString("Rear of sheet.\n");
else
OutputDebugString("Unexpected!\n");
nRet = L_TwainFreeExtendedImageInfoStructure (&pExtImg);
if(nRet != SUCCESS)
return nRet;
}
free(pExtImg);
}
return SUCCESS;
}
- 可以使用 CAP_CAMERASIDE 和 CAP_CAMERAENABLED 功能的组合来强制扫描特定面,如 Twain Spec 中所述。
引用该文档:
To enable bottom only scanning, set CAP_CAMERASIDE to TWCS_BOTTOM and set CAP_CAMERAENABLED to TRUE, then set CAP_CAMERASIDE to TWCS_TOP and set CAP_CAMERAENABLED to FALSE.
如果你的意思是你的电脑有 2 个 Twain 相机源(前后),答案如下:
- 要知道调用
L_TwainAcquire()
时哪个 Twain 源(例如相机)触发了 Twain 位图回调,您可以使用L_TwainGetSources()
函数与LTWAIN_SOURCE_ENUMERATE_DEFAULT
标志一起获取当前选择的 Twain 设备。这可以在 inside Bitmap Callback 中完成,如以下代码所示:
// Source Info Callback
L_INT EXT_CALLBACK TwainSourceInfoCallbackCurrent(HTWAINSESSION hSession, pLTWAINSOURCEINFO pSourceInfo, L_VOID * pUserData)
{
strcpy((L_CHAR *)pUserData, pSourceInfo->pszTwnSourceName);
return SUCCESS;
}
// Twain Bitmap Callback
L_INT EXT_CALLBACK LTwainBitmapCallback(HTWAINSESSION hSession, pBITMAPHANDLE pBitmap, L_VOID * pUserData)
{
char szSourceName[1024];
L_TwainGetSources(hSession, TwainSourceInfoCallbackCurrent, sizeof LTWAINSOURCEINFO, LTWAIN_SOURCE_ENUMERATE_DEFAULT, szSourceName);
// Now szSourceName contains name of Twain Source.
return SUCCESS;
}
- 是的,您可以通过在扫描前将其名称发送到
L_TwainSelectSource()
函数来强制从特定设备(扫描仪、相机等)进行扫描,如下所示:
LTWAINSOURCE TwainSource;
TwainSource.uStructSize = sizeof LTWAINSOURCE;
TwainSource.pszTwainSourceName = pszRearCameraTwainSourceName;
L_TwainSelectSource(twainSession, &TwainSource);
// Now L_TwainAcquire() will capture from Rear Camera
要查找所有设备的名称,您可以使用此代码:
L_TwainGetSources(twainSession, TwainSourceInfoCallback, sizeof LTWAINSOURCEINFO, LTWAIN_SOURCE_ENUMERATE_ALL, NULL);
源信息回调将为每个 Twain 源触发一次。可以这样实现:
L_INT EXT_CALLBACK TwainSourceInfoCallback(HTWAINSESSION hSession, pLTWAINSOURCEINFO pSourceInfo, L_VOID * pUserData)
{
OutputDebugString(pSourceInfo->pszTwnSourceName); // You can save the names of Twain Sources into global variables if you like
OutputDebugString("\n");
return SUCCESS;
}