ossimPackedBits Class Reference

This class will allow access to individual packed pixels given an offset and return as an ossim_uint32 type. More...

#include <ossimPackedBits.h>

Public Member Functions
	ossimPackedBits (const ossim_uint8 *packedBits, ossim_uint16 bits)
	Constructor that takes packed bits array and word size in bits. More...
ossim_uint32	getValueAsUint32 (ossim_uint32 idx) const
	Extract out the value at offset indicated by idx and convert the the vale to an ossim_uint32. More...

Protected Attributes
const ossim_uint8 *	thePackedBits
ossim_uint16	theBits
ossim_uint16	theBytes
ossim_uint16	theBitsLeft

Detailed Description

This class will allow access to individual packed pixels given an offset and return as an ossim_uint32 type.

Definition at line 22 of file ossimPackedBits.h.

Constructor & Destructor Documentation

ossimPackedBits()

ossimPackedBits::ossimPackedBits	(	const ossim_uint8 *	packedBits,
		ossim_uint16	bits
	)

Constructor that takes packed bits array and word size in bits.

Parameters

packedBits	The unsigned eight bit array of packed bits. This pointer is not owned by this class, only used.
bits	The number of bits in the packed bits word.

Definition at line 16 of file ossimPackedBits.cpp.

References theBits, theBitsLeft, and theBytes.

      :thePackedBits(packedBits),
       theBits(bits)
{
   theBytes    = theBits>>3;
   theBitsLeft = theBits%8;
}

Member Function Documentation

getValueAsUint32()

ossim_uint32 ossimPackedBits::getValueAsUint32

(

ossim_uint32

idx

)

const

Extract out the value at offset indicated by idx and convert the the vale to an ossim_uint32.

This class only supports packed bits less than 32.

Parameters

idx	The packed bit word index to grab and stuff into an unsigned 32 bit integer.

Definition at line 25 of file ossimPackedBits.cpp.

References theBits, theBitsLeft, theBytes, and thePackedBits.

Referenced by ossimNitfTileSource::explodePackedBits().

{
   ossim_uint32 value        = 0;
   ossim_uint32 tempBits     = (theBitsLeft*idx);
   ossim_uint32 tempBitShift = tempBits%8;
   ossim_uint32 byteOffset   = ( (idx*theBytes) + (tempBits>>3) );
   ossim_uint32 bitCount     = 0;
   ossim_uint32 bitsSeen     = tempBitShift;
   ossim_uint8 bitmask       = 1 << (7-tempBitShift);
   
   while(bitCount < theBits)
   {
      value |= (ossim_uint8)((bool)(thePackedBits[byteOffset]&bitmask));
      ++bitCount;
      ++bitsSeen;
      if(bitsSeen >= 8)
      {
         bitsSeen = 0;
         bitmask = 0x80; // binary pattern 10000000
         ++byteOffset;
      }
      else
      {
         bitmask>>=1;
      }
      if(bitCount < theBits)
      {
         value <<=1;
      }
   }
   
   return value;
}

Member Data Documentation

theBits

ossim_uint16 ossimPackedBits::theBits

protected

Definition at line 47 of file ossimPackedBits.h.

Referenced by getValueAsUint32(), and ossimPackedBits().

theBitsLeft

ossim_uint16 ossimPackedBits::theBitsLeft

protected

Definition at line 49 of file ossimPackedBits.h.

Referenced by getValueAsUint32(), and ossimPackedBits().

theBytes

ossim_uint16 ossimPackedBits::theBytes

protected

Definition at line 48 of file ossimPackedBits.h.

Referenced by getValueAsUint32(), and ossimPackedBits().

thePackedBits

const ossim_uint8* ossimPackedBits::thePackedBits

protected

Definition at line 46 of file ossimPackedBits.h.

Referenced by getValueAsUint32().

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The documentation for this class was generated from the following files:

• ossimPackedBits.h
• ossimPackedBits.cpp