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L_AutoBinarizeBitmap

#include "l_bitmap.h"

L_LTIMGCOR_API L_INT EXT_FUNCTION L_AutoBinarizeBitmap(pBitmap, uFactor, uFlags)

Applies binary segmentation to a bitmap automatically.

This feature is available in version 16 or higher.

Parameters

pBITMAPHANDLE pBitmap

Pointer to the bitmap handle referencing the bitmap having binary segmentation applied automatically.

L_UINT uFactor

Threshold Factor. The meaning of this factor depends on which type of thresholding is being used. For more information see the description of the uFlags parameter.

L_UINT uFlags

Flags that indicate the type of pre-processing to perform on the bitmap and the type of thresholding to use. You can use a bitwise OR (|) to specify one flag from each group.

Value	Meaning
Type of pre-processing to perform on the bitmap:
AUTO_BINARIZE_PRE_AUTO	[0x00000000] Perform automatic pre-processing. This is the default value.
AUTO_BINARIZE_NO_PRE	[0x00000001] Do not perform pre-processing.
AUTO_BINARIZE_PRE_BG_ELIMINATION	[0x00000002] Eliminate the background of the bitmap but keep the key features, such as text.
AUTO_BINARIZE_PRE_LEVELING	[0x00000004] Perform automatic color leveling.
Type of threshold to use:
AUTO_BINARIZE_THRESHOLD_AUTO	[0x00000000] Perform automatic thresholding. This is the default value.
AUTO_BINARIZE_THRESHOLD_USER	[0x00000010] Let the user choose the threshold value, to be passed in `uFactor`. Valid values range from 0 to 255.
AUTO_BINARIZE_THRESHOLD_PERCENTILE	[0x00000020] Perform percentile thresholding. In this case uFactor is the percentage of black pixels at which to perform thresholding, expressed in hundredths of a percent. For example, 500 means 5 percent. Valid values range from 0 to 10000.
AUTO_BINARIZE_THRESHOLD_MEDIAN	[0x00000040] Perform median thresholding.

Returns

Value	Meaning
SUCCESS	The function was successful.
< 1	An error occurred. Refer to Return Codes.

Comments

AutoBinarize converts a colored image into a binary image automatically, without losing important image features such as text. This function uses several pre-processing and threshold operations which enable the user to extract the key features of any colored image. It can be adjusted to be suitable for a specific input device, such as a scanner or camera. It is ideal for making unclear document images more readable. This function is especially useful for improving recognition results (OCR, Barcode, OMR, ICR).

L_AutoBinarizeBitmap options:

Automatic pre-processing
Pre-processing using background elimination
Pre-processing using color leveling
Perform automatic, percentile or median threshold
Manually specify a threshold value

To update a status bar or detect a user interrupt during execution of this function, refer to L_SetStatusCallback.

This function does not support 12 and 16-bit grayscale and 48 and 64-bit color images. If the image is 12 and 16-bit grayscale and 48 and 64-bit color, the function will not return an error.

This function does not support signed data images. It returns the error code ERROR_SIGNED_DATA_NOT_SUPPORTED if a signed data image is passed to this function.

This function does not support 32-bit grayscale images. It returns the error code ERROR_GRAY32_UNSUPPORTED if a 32-bit grayscale image is passed to this function.

Required DLLs and Libraries

LTIMGCOR
For a listing of the exact DLLs and Libraries needed, based on the toolkit version, refer to Files To Be Included With Your Application.

Platforms

Win32, x64, Linux.

Functions

Topics

Example

L_INT AutoBinarizeBitmapExample(L_VOID) 
{ 
   L_INT nRet; 
   BITMAPHANDLE LeadBitmap;   /* Bitmap handle to hold the loaded image. */ 
   /* Load the bitmap, keeping the bits per pixel of the file */ 
   nRet = L_LoadBitmap (MAKE_IMAGE_PATH(TEXT("cannon.jpg")), &LeadBitmap, sizeof(BITMAPHANDLE), 0, ORDER_BGR, NULL, NULL); 
   if(nRet !=SUCCESS) 
      return nRet; 
  
   nRet = L_AutoBinarizeBitmap(&LeadBitmap, 0, AUTO_BINARIZE_PRE_AUTO | AUTO_BINARIZE_THRESHOLD_AUTO); 
   if(nRet !=SUCCESS) 
      return nRet; 
   nRet = L_SaveBitmap(MAKE_IMAGE_PATH(TEXT("Result.BMP")), &LeadBitmap, FILE_BMP, 24, 0, NULL); 
   if(nRet !=SUCCESS) 
      return nRet; 
   //free bitmap  
   if(LeadBitmap.Flags.Allocated)   
      L_FreeBitmap(&LeadBitmap);   
   return SUCCESS; 
}

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