LBitmapRgn::GetClipSegments

#include "ltwrappr.h"

virtual L_INT LBitmapRgn::GetClipSegments(nRow, pSegmentBuffer, puSegmentCount)

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

Returns

Comments

To use this function, first call LBitmapRgn::SetRgnXForm with pXform set to NULL, and then use LBitmapRgn::GetRgnBounds to get the boundaries of the class objects associated bitmap. 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 and puSegmentCount will be filled with the value 4. Lets call them x0, x1, x2, x3. In this case:

• portion from 0 to x0 1 is OUTSIDE the region

• portion from x0 to x1 - 1 is INSIDE the region

• portion from x1 to x2 1 is OUTSIDE the region

• portion from x2 to x3 1 is INSIDE the region

• portion from x3 to pBitmap->Width 1 is OUTSIDE the region

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

Required DLLs and Libraries

Platforms

Win32, x64.

See Also

Example

The following example sets the pixels of the first row inside a region to black.

L_INT LBitmapRgn__GetClipSegmentsExample(LBitmapBase & Bitmap, L_TCHAR * pszFile)
{
   L_INT nRet;
   LBitmapRgn Region;
   L_UINT uSegments;
   L_UINT * pSegments;
   RECT rcRegion, rcClip;
   nRet =Bitmap.Load(pszFile);
   if(nRet !=SUCCESS)
      return nRet;
   Region.SetBitmap(&Bitmap);
   SetRect(&rcRegion,
           Bitmap.GetWidth() / 4,
           Bitmap.GetHeight() / 4,
           3 * Bitmap.GetWidth() / 4,
           3 * Bitmap.GetHeight() / 4);  
   
   nRet =Region.SetRgnRect(&rcRegion);
   if(nRet !=SUCCESS)
      return nRet;
   // Get the maximum number of elements in a row, so we 
   // know how big the array of segments should be.
   nRet =Region.GetClipSegmentsMax(&uSegments);
   if(nRet !=SUCCESS)
      return nRet;
   // Allocate an array large enough to store the maximum 
   // number of segments. Note that LBitmapRgn::GetClipSegmentsMax
   // took into account that each segment has two extremities.
   pSegments = (L_UINT *) GlobalAllocPtr(GMEM_MOVEABLE, 
                                         uSegments * sizeof(L_UINT));
   
   if(!pSegments)
      return -1; // Not enough memory!
   // Get the region bounds, so we know the first row
   nRet =Region.SetRgnXForm(NULL);
   if(nRet !=SUCCESS)
      return nRet;
   nRet =Region.GetRgnBounds(&rcClip);
   if(nRet !=SUCCESS)
      return nRet;
   // Get the segments for the first row
   nRet =Region.GetClipSegments(rcClip.top, pSegments, &uSegments);
   if(nRet !=SUCCESS)
      return nRet;
   // Do something with the segments:
   // To keep this example simple, we will set 
   // the pixels in the segments to 0.
   for (L_UINT i = 0; i < uSegments; i+=2)
      for (L_UINT j = pSegments[i]; j < pSegments[i + 1]; j++)
      {
         nRet =Bitmap.PutPixelColor(rcClip.top, j, 0);
         if(nRet !=SUCCESS)
            return nRet;
      }
   // Free the segments array
   GlobalFreePtr(pSegments);
   return SUCCESS;
}