Gets the segments contained in the region for a particular row.


#include "l_bitmap.h"

L_LTDIS_API L_INT L_GetBitmapClipSegments(pBitmap, nRow, pSegmentBuffer, puSegmentCount)



Pointer to the bitmap handle referencing the bitmap.

L_INT nRow

The number of the row for which to get the segments. The first row is 0, and the last row is 1 less than the bitmap height.

L_UINT * pSegmentBuffer

Pointer to the buffer to be updated with the segments from row nRow contained in the region. This buffer should be large enough to contain twice as many values as indicated in *puSegmentCount.

L_UINT * puSegmentCount

Address of a variable to be updated with the number of segments from row nRow that are contained in the region.


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


To use this function, first call L_GetBitmapRgnBounds with pXForm set to NULL, to get the bitmap boundaries. The bounding rectangle will indicate which rows are contained in the region. Go through all the rows contained in the region to get the segments contained in the region.

The segments are returned as an array of pairs of horizontal offsets. The first point in the pair is the beginning of the segment (it is contained in the region). The last point in the pair is the end of the segment. To follow the Windows rules, the end of the segment is the first point NOT CONTAINED in the region.

In most regions, there will be one segment per row. However, some regions can have 0, 1, 2 or more segments.

For example, assume that for a particular row there are two segments. pSegmentBuffer will be filled with 4 values. Lets call them x0, x1, x2, x3. In this case:

It is recommended that you allocate a buffer large enough to hold all the possible segments. To get the maximum number of segments, call L_GetBitmapClipSegmentsMax. Allocate an array of unsigned values that can contain the largest number of segments. See the example for more details.

Required DLLs and Libraries


Win32, x64, Linux.

See Also




This example will set the pixels from the first row inside the region to black.

L_INT GetBitmapClipSegmentsExample(pBITMAPHANDLE pBitmap) 
   L_INT    nRet; 
   L_UINT   uSegments, uMaxSegments; 
   L_UINT*  pSegments; 
   RECT     rcClip; 
   L_UINT   i, nRow, nColumn; 
   // get the maximum number of elements in a row, so I know how big the array of segments should be 
   nRet = L_GetBitmapClipSegmentsMax(pBitmap, &uMaxSegments); 
   if (nRet != SUCCESS) 
      return nRet; 
   // allocate an array large enough to store the maximum number of segments. Note that 
   // L_GetBitmapClipSegmentsMax took into account that each segment has two extremities. 
   pSegments = (L_UINT*)GlobalAlloc(GPTR, uMaxSegments * sizeof(L_UINT)); 
   if (!pSegments) 
      return ERROR_NO_MEMORY;  // not enough memory!! 
   // get the region bounds, so I know which is the first row 
   nRet = L_GetBitmapRgnBounds(pBitmap, NULL, &rcClip); 
   if (nRet != SUCCESS) 
      return nRet; 
   // Set all pixels in the segments within the region to black 
   L_BOOL bInRegion; 
   for (nRow = rcClip.top; (LONG)nRow < rcClip.bottom; nRow++) 
      // get the segments for the current row  
      nRet = L_GetBitmapClipSegments(pBitmap, nRow, pSegments, &uSegments); 
      if (nRet != SUCCESS) 
         return nRet; 
      for (i = 0; (uSegments > 0) && (i < uSegments - 1); i++) 
         for (nColumn = pSegments[i]; nColumn < pSegments[i + 1]; nColumn++) 
            if ((LONG)nColumn < pBitmap->Width) 
               bInRegion = L_IsPtInBitmapRgn(pBitmap, nRow, nColumn); 
               if (bInRegion) 
                  nRet = L_PutPixelColor(pBitmap, nRow, nColumn, 0); 
                  if (nRet != SUCCESS) 
                     return nRet; 
   // free the segments array 
   return SUCCESS; 

Help Version 22.0.2023.7.11
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LEADTOOLS Raster Imaging C API Help

Products | Support | Contact Us | Intellectual Property Notices
© 1991-2023 LEAD Technologies, Inc. All Rights Reserved.