游程编码源代码

这个...........楼上的诸位说的都是什么啊。今天刚好看到这个问题，把基纤蔽你的E-mail给我把，我有纯c的源码（RLC）。

算了，直接贴关键部分吧搏州。这个有一点竖锋C++成分，很容易改的。

bool CompressRunLength(BYTE *pSrc, int nSrcLen, BYTE *&pDes, int &nDesLen, int nBitsPerSample, void* nRuns, int nRunCount, int nRunSize)

bool DecompressRunLength(BYTE *pSrc, int nSrcLen, BYTE *&pDes, int &nDesLen)

#define GetDWORD(buf,bit,mask) ((*(DWORD*)(((BYTE*)buf)+((bit)>>3)))>>((bit)&7)&(mask))

#define GetWORD(buf,bit,mask) ((*(WORD*)(((BYTE*)buf)+((bit)>>3)))>>((bit)&7)&(mask))

int GetBitCount(int n)

{

int nBitCount = 0

while(n)

n >>= 1, nBitCount++

return nBitCount

}

int BinarySearch(void* pValue, int nVlaueSize, void* pArray, int nCount)

{

int nIndex, nResult, nStart = 0, nEnd = nCount-1

while(nStart <= nEnd)

{

nIndex = (nEnd+nStart)/2

if((nResult = memcmp((BYTE*)pArray+nIndex*nVlaueSize, pValue, nVlaueSize)) == 0)

return nIndex

if(nResult >0)

nEnd = nIndex-1

else

nStart = nIndex+1

}

return -1

}

bool CompressRunLength(BYTE *pSrc, int nSrcLen, BYTE *&pDes, int &nDesLen, int nBitsPerSample, void* nRuns, int nRunCount, int nRunSize)

{

pDes = (BYTE*)malloc(nSrcLen*2)

memset(pDes, 0, nSrcLen*2)

nDesLen = sizeof(DWORD)

*(DWORD*)pDes = nSrcLen // save source length

*(pDes+nDesLen++) = nBitsPerSample// save bits per sample

*(pDes+nDesLen++) = nRunCount // save runs count

*(pDes+nDesLen++) = nRunSize // save run bytes

memcpy(pDes+nDesLen, nRuns, nRunCount*nRunSize)// save runs

nDesLen += nRunCount*nRunSize

nDesLen <<= 3// bytes to bits

if(nRunCount == 0)

nRunCount = 256, nRunSize = 1, nRuns = NULL

int nBitsPerTypeIndex = GetBitCount(nRunCount-1)

int nMaxRunLength = (1 <<nBitsPerSample)-1, nRunLength, nRunIndex, nByte = 0

// loop in the source buffer

while(nByte <nSrcLen)

if((nRuns &&(nRunIndex = BinarySearch(pSrc+nByte, nRunSize, nRuns, nRunCount)) != -1 &&

memcmp(pSrc+nByte+nRunSize, (BYTE*)nRuns+nRunIndex*nRunSize, nRunSize) == 0) ||

(!nRuns &&(nRunIndex = *(pSrc+nByte)) == *(pSrc+nByte+1)))

{ // set bit to 1 to indicate type found

*(pDes+(nDesLen>>3)) |= 1 <<(nDesLen&7)

*(DWORD*)(pDes+(++nDesLen>>3)) |= nRunIndex <<(nDesLen&7)

nDesLen += nBitsPerTypeIndex

// skip the two repeated runs

nByte += nRunSize*2

// get run length - 2 (without the two repeated runs)

nRunLength = 0

while(nRunLength <nMaxRunLength &&nByte <nSrcLen &&

((nRuns &&memcmp(pSrc+nByte, (BYTE*)nRuns+nRunIndex*nRunSize, nRunSize) == 0) || (!nRuns &&(BYTE)nRunIndex == *(pSrc+nByte))))

nRunLength++, nByte += nRunSize

// save run length and increment destination length by bits per sample

*(DWORD*)(pDes+(nDesLen>>3)) |= nRunLength <<(nDesLen&7)

nDesLen += nBitsPerSample

}

else // copy one byte

*(WORD*)(pDes+(++nDesLen>>3)) |= *(pSrc+nByte++) <<(nDesLen&7), nDesLen += 8

nDesLen = (nDesLen+7)/8// bits to bytes

pDes = (BYTE*)realloc(pDes, nDesLen)

return true

}

bool DecompressRunLength(BYTE *pSrc, int nSrcLen, BYTE *&pDes, int &nDesLen)

{

if(nSrcLen == 0)

return true

// allocate destination buffer

nDesLen = *(DWORD*)pSrc

pDes = (BYTE*)malloc(nDesLen)

memset(pDes, 0, nDesLen)

// copy compression information

int nSrcIndex = sizeof(DWORD)

int nBitsPerSample = *(pSrc+nSrcIndex++)

int nRunCount = *(pSrc+nSrcIndex++)

int nRunSize = *(pSrc+nSrcIndex++)

void* nRuns = pSrc+nSrcIndex

nSrcIndex += nRunSize*nRunCount

nSrcIndex <<= 3// bytes to bits

if(nRunCount == 0)

nRunCount = 256, nRunSize = 1, nRuns = NULL

int nBitsPerTypeIndex = GetBitCount(nRunCount-1)

int nMaxTypeIndex = (1 <<nBitsPerTypeIndex)-1

int nMaxRunLength = (1 <<nBitsPerSample)-1

int nDesIndex = 0, nRunLength, nRunIndex, nRun, nByte

nSrcLen <<= 3// bytes to bits

while(nSrcIndex <nSrcLen-8)

if((*(pSrc+(nSrcIndex>>3)) >>(nSrcIndex++&7)) &1)

{

nRunIndex = GetDWORD(pSrc, nSrcIndex, nMaxTypeIndex), nSrcIndex += nBitsPerTypeIndex

nRunLength = GetDWORD(pSrc, nSrcIndex, nMaxRunLength)+2, nSrcIndex += nBitsPerSample

for(nRun = 0nRun <nRunLengthnRun++)

for(nByte = 0nByte <nRunSizenByte++, nDesIndex += 8)

*(WORD*)(pDes+(nDesIndex>>3)) |= nRuns ? GetWORD(nRuns+nRunSize*nRunIndex, nByte<<3, 0xff) : (BYTE)nRunIndex

}

else // copy one byte

*(WORD*)(pDes+(nDesIndex>>3)) |= GetWORD(pSrc, nSrcIndex, 0xff), nDesIndex += 8, nSrcIndex += 8

return true

}

游程编码又称“运行长度编码”或“行程编码”，是一种统计编码，该编码属于无损压缩编码，是栅格数据压缩的重要编码方法。对于二值图有效。

行程编码的基本原理是：用一罩族个符号值或串长代替具有相同值的连续符号（连续符号构成了一段连续的“行程”。行程编码因此而得名），使符号长度少于原始数据的长度。只在各行或者各列数据的代码发生变化时，一次记录该代码及相同代码重复的个数，从而实现数据的压缩。

常见的游程编码格式包括TGA，Packbits，PCX以及ILBM。

行程编码是连续精确的编码，在传输过程中，如果其中一位符号发生错误，即可影响整个编码序列，使行程编码无法还原回原始数据。

游程长度在栅格加密时，做闷祥数据量没有明显增加，压缩效率纯搏较高，且易于检索、叠加合并等 *** 作，运算简单，适用于机器存储容量小，数据需大量压缩，而又要避免复杂的编码和解码运算，增加处理和 *** 作时间的情况。

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