Sets the overlay bitmap of this L_OcrPage.
#include "ltocr.h"
L_LTOCR_API L_INT EXT_FUNCTION L_OcrPage_SetOverlayBitmap(page, bitmapHandle)
Handle to the OCR page.
BITMAPHANDLE to use to update the page overlay bitmap.
| Value | Meaning |
|---|---|
| SUCCESS | The function was successful. |
| < 1 | An error occurred. Refer to Return Codes. |
The overlay image of an L_OcrPage will be used when the image is saved by an L_OcrDocument in the following situations:
By default, the overlay image is the original image used to create the page. It is the same value obtained by calling L_OcrPage_GetBitmap with L_OcrPageBitmapType_Original option.
In some situation, the user might want to use a different bitmap as the overlay. For example, a smaller version is passed to the OCR engine to conserve memory while the original version will only be used on save purposes in a PDF with image/text option. You can call L_OcrPage_SetOverlayBitmap before saving the document (memory-based) or adding the page to the document (file-based) and the engine will use this new bitmap as the overlay value. If auto-preprocessing was performed on the page through L_OcrPage_AutoPreprocess, then the same values might need to be applied to the overlay as well. Use L_OcrPage_GetAutoPreprocessValues to get the accumulative values of any inversion, rotation or deskewing applied by the pre-processor.
To clear the temporarily overlay image, call L_OcrPage_SetOverlayBitmap with a NULL value.
To get the overlay image at any time, call L_OcrPage_GetOverlayBitmap. Note that this property will return the same image reference passed to the last L_OcrPage_SetOverlayBitmap call. It will not return the original image.
The overlay bitmap is not freed by this L_OcrPage.
L_INT L_OcrPage_SetOverlayBitmapExample(){BITMAPHANDLE bitmap = { 0 };L_OcrEngine ocrEngine = NULL;L_OcrPage ocrPage = NULL;L_OcrDocumentManager ocrDocumentManager = NULL;L_OcrDocument ocrDocument = NULL;// Create an instance of the engineL_INT retCode = L_OcrEngineManager_CreateEngine(L_OcrEngineType_LEAD, &ocrEngine);if(retCode == SUCCESS){// Start the engine using default parametersretCode = L_OcrEngine_Startup(ocrEngine, NULL, OCR_LEAD_RUNTIME_DIR);if(retCode != SUCCESS)return retCode;// Load a page to be recognizedretCode = L_LoadBitmap(MAKE_IMAGE_PATH(L_TEXT("Ocr1.tif")), &bitmap, sizeof(BITMAPHANDLE), 0, ORDER_RGB, NULL, NULL);if(retCode != SUCCESS)goto CLEANUP;// Add an image to OCR page. don't transfer ownership of the bitmap to the page we will control this original imageretCode = L_OcrPage_FromBitmap(ocrEngine, &ocrPage, &bitmap, L_OcrBitmapSharingMode_None, NULL, NULL);if(retCode != SUCCESS)goto CLEANUP;// Get OCR page default overlay bitmap and save it to diskBITMAPHANDLE origOverlayBitmap = {0};retCode = L_OcrPage_GetOverlayBitmap(ocrPage, &origOverlayBitmap, sizeof(BITMAPHANDLE));if(retCode != SUCCESS)goto CLEANUP;// if the OCR page has overlay bitmap they save it before we change itif(origOverlayBitmap.Flags.Allocated)L_SaveBitmap(TEXT("OcrPageOrigOverlayBitmap.tif"), &origOverlayBitmap, FILE_CCITT_GROUP4, origOverlayBitmap.BitsPerPixel, 2, NULL);// Apply some auto preprocessing on the imageL_OcrPage_AutoPreprocess(ocrPage, L_OcrAutoPreprocessPageCommands_All, NULL, NULL);// resize down our original bitmap into half and set it as the OCR page overlay bitmap to conserve memory.retCode = L_SizeBitmap(&bitmap, bitmap.Width / 2, bitmap.Height / 2, SIZE_RESAMPLE);if(retCode != SUCCESS)goto CLEANUP;// Now you might want to apply the same auto preprocessing commands applied to the OCR page into the overlay bitmap// before you set it, to do so, you need to call L_OcrPage_GetAutoPreprocessValues function first to determine what// kind of preprocessing values were applied to the OCR pageL_OcrPageAutoPreprocessValues autoPreprocessValues = {0};retCode = L_OcrPage_GetAutoPreprocessValues(ocrPage, &autoPreprocessValues);if(retCode == SUCCESS){if(autoPreprocessValues.IsInverted)L_InvertBitmap(&bitmap, 0);if(autoPreprocessValues.DeskewAngle > 0)L_DeskewBitmap(&bitmap, NULL,RGB(0, 0, 0), DSKW_PROCESS | DSKW_RESAMPLE);if(autoPreprocessValues.RotationAngle > 0)L_RotateBitmap(&bitmap, autoPreprocessValues.RotationAngle, ROTATE_RESAMPLE, RGB(0, 0, 0));}// Now save our updated overlay bitmap to diskL_SaveBitmap(TEXT("OcrPageUpdatedOverlayBitmap.tif"), &bitmap, FILE_CCITT_GROUP4, bitmap.BitsPerPixel, 2, NULL);retCode = L_OcrPage_SetOverlayBitmap(ocrPage, &bitmap);if(retCode != SUCCESS)goto CLEANUP;// Recognize the page// Note: Recognize can be called without calling AutoZone or manually adding zones.// The engine will check and automatically auto-zones the page.retCode = L_OcrPage_Recognize(ocrPage, NULL, NULL);if(retCode != SUCCESS)goto CLEANUP;//Get the document managerretCode = L_OcrEngine_GetDocumentManager(ocrEngine, &ocrDocumentManager);if(retCode != SUCCESS)goto CLEANUP;// Create file-based OCR documentretCode = L_OcrDocumentManager_CreateDocument(ocrDocumentManager, &ocrDocument, L_OcrCreateDocumentOptions_AutoDeleteFile, NULL);if(retCode != SUCCESS)goto CLEANUP;// Add page to the document.retCode = L_OcrDocument_AddPage(ocrDocument, ocrPage);if(retCode != SUCCESS)goto CLEANUP;// Adding the page to a file based document will take a snap shot of the recognition data and store it in the document. At this// point, the page is no longer needed. So destroy it to free up memory not used anymoreL_OcrPage_Destroy(ocrPage);// Set the handle to NULL so we do not free it in our clean-up codeocrPage = NULL;// Save the document we have as PDF Image/Text// Get the format options for PDFDOCWRTPDFOPTIONS pdfOptions;pdfOptions.Options.uStructSize = sizeof(DOCWRTPDFOPTIONS);L_OcrDocumentManager_GetFormatOptions(ocrDocumentManager, DOCUMENTFORMAT_PDF, &pdfOptions.Options);// Set the PDF ImageOverText option to TRUEpdfOptions.bImageOverText = L_TRUE;// Give the engine our updated PDF optionsL_OcrDocumentManager_SetFormatOptions(ocrDocumentManager, DOCUMENTFORMAT_PDF, &pdfOptions.Options);retCode = L_OcrDocument_Save(ocrDocument, MAKE_IMAGE_PATH(L_TEXT("Output.pdf")), DOCUMENTFORMAT_PDF, NULL, NULL);// Now if you opened the saved PDF file you will see our resized image shown as the PDF image over text// instead of the original OCR page bitmap.}CLEANUP:if(bitmap.Flags.Allocated)L_FreeBitmap(&bitmap);if(ocrPage != NULL)L_OcrPage_Destroy(ocrPage);if(ocrDocument != NULL)L_OcrDocument_Destroy(ocrDocument);if(ocrEngine != NULL)L_OcrEngine_Destroy(ocrEngine);return retCode;}