LBitmap::ShiftData

#include "ltwrappr.h"

virtual L_INT LBitmap::ShiftData (pSrcBitmap, uSrcLowBit, uSrcHighBit, uDstLowBit, uDstBitsPerPixel)

virtual L_INT LBitmap::ShiftData (plSrcBitmap, uSrcLowBit, uSrcHighBit, uDstLowBit, uDstBitsPerPixel)

Selects a specified number of bits from an 8, 12 or 16-bit grayscale bitmap into a mask and places the mask in a new 8, 12 or 16-bit grayscale bitmap. This function is available in the Medical toolkits.

Returns

Comments

The function is used mainly as a visualization aid. You can select certain bits of the supported type bitmap and display them in another bitmap.

You can use this function for other purposes than visualization. For example, lets say you loaded a 16-bit file that has the pixels in Motorola format (where the high and low bytes are swapped). You can swap the high and low 8 bits for each pixel by calling this function twice and OR-ing the results.

The pDstBitmap should not be allocated when calling this function. You should free the allocated bitmap before calling this function. When the function returns successfully the pDstBitmap will be an 8, 12 or 16-bit grayscale.

For 8, 12 and 16-bit grayscale bitmaps, the uSrcLowBit can range from 0 to 7, 0 to 11, and 0 to 15 respectively. However if this value exceeded the range then the function will not return an error, and the pDstBitmap will be a pure black bitmap.

The uSrcHighBit must be greater than or equal to uSrcLowBit. The function will return an invalid parameter error if uSrcHighBit < uSrcLowBit.

The uDstLowBit can range from 0 to uDstBitsPerPixel 1. If you pass greater values for uDstLowBit, the function will not return an error, but pDstBitmap will become a pure black bitmap.

The following example shows you how to treat a 16-bit grayscale bitmap:

In a16-bit grayscale bitmap, the bits are ordered as b15 b14 b13 ... b2 b1 b0. You can choose the bit from where to start moving the bits.

For example, if the mask starts at the fourth bit (b3), with a length equal to 6 bits, the destination starting position is 4 and we want to create an 8-bit destination bitmap:

uSrcLowBit = 3

uSrcHighBit = 8

uDstLowBit = 4

uDstBitsPerPixel = 8

Source bitmap (pSrcBitmap):

------------------- 

b15 b14 b13 b12 b11 b10 b9 |b8 b7 b6 b5 b4 b3| b2 b1 b0

-------------------  

0 1 1 0 1 1 1 0 1 0 0 1 1 1 0 1 

Destination bitmap (pDstBitmap):

-------------  

   |b7 b6 b5 b4| b3 b2 b1 b0 

    ------------- 

   0 0 1 1 0 0 0 0 

You can notice that b7 and b8 of pSrcBitmap are truncated in the bitmap object since there is no space for them.

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

This function supports 8, 12 and 16-bit grayscale bitmaps only. Support for 12 and 16-bit grayscale images are available only in the Document/Medical toolkits. It also can process the whole image or a region of the image. If a bitmap has a region, the effect is applied only to the region.

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

See Also

Example

L_INT LBitmap__ShiftDataExample(LBitmap *pLeadBitmap, LBitmap *pSrcBitmap) 
{
   L_INT nRet;
   /* This example applies Shifing. */
   /* Move 5 bits starting from bit 2 into the high 8-bits of the destination bitmap */
   nRet =pLeadBitmap->ShiftData (pSrcBitmap, 
                                 2 /* uSrcLowBit */, 
                                 6 /* uSrcHighBit*/, 
                                 3 /* uDstLowBit */, 
                                 8 /* uDstBitsPerPixel */ );
   if(nRet !=SUCCESS)
      return nRet;
   pLeadBitmap->Free ();
   // Now we have the resulting image in pLeadBitmap
   
   return SUCCESS;
}