C++图像处理 -- PCX格式图像（上）
PCX是一个比较早的图像文件格式，它也有过一段时间的辉煌，但随着计算机硬、软件的发展，该图像格式基本已成过去时，主要是因为早期PCX格式图像是配合当时显卡硬件而设计的，如CGA/EGA/VGA等，现在显然已经过时了，虽然后来的版本增加了对256色和24位真彩色的支持，但仍然因其文件格式的先天不足，导致操作很不方便，如256色图像调色板就是以“补丁”形式追加到文件最后面的，24位真彩色用以前EGA图像卡按行以彩色面形式存放等；另外PCX的RLE编码对6位以下像素格式是比较有效的，对目前8位为主的像素格式压缩也不尽人意，如24位像素格式压缩后，有时比不压缩空间占用还大。
虽然PCX格式图像目前使用不多，但还是有很多软件是支持这种格式的，如Photoshop。在图像处理编程时，偶尔也会遇到这种格式的图像，但不象BMP、JPEG、GIF等图像格式容易找到现存的库函数或组件，所以本文提供了PCX格式图像与GDI+位图的相互转换的代码，本文分上下两篇，上篇将PCX格式图像转换为GDI+位图，下篇将GDI+位图转换为PCX格式图像。下面是转换源码：
typedef struct // pcx文件头
{
BYTE flag; // 标记
BYTE version; // 版本号
BYTE encodeing; // 编码方式
BYTE bitsPrePixel; // 平面像素位数
WORD xMin; // 最小X
WORD yMin; // 最小Y
WORD xMax; // 最大X
WORD yMax; // 最大Y
WORD hRes; // 水平分辨率
WORD vRes; // 垂直分辨率
BYTE palette[48]; // 16色调色板
BYTE reserved; // 保留
BYTE planes; // 平面数
WORD bytesPreLine; // 每行字节数
WORD paletteType; // 调色板类型。1：彩色或黑白，2：灰度
BYTE filler[58];
}PcxFileHeader, *PPcxFileHeader;
//---------------------------------------------------------------------------
FORCEINLINE
LPBYTE UnpackPckLine(LPBYTE dest, LPBYTE source, INT bytes)
{
while (bytes > 0)
{
if (*source > 0xc0)
{
INT count = *source ++ & 0x3f;
BYTE c = *source ++;
bytes -= count;
for (; count > 0; *dest ++ = c, count --);
}
else
{
*dest ++ = *source ++;
bytes --;
}
}
return source;
}
//---------------------------------------------------------------------------
// 单色或256色
VOID UnpackPck(BitmapData *data, LPBYTE bitsMem, INT bytesPreLine)
{
LPBYTE p = (LPBYTE)data->Scan0;
LPBYTE m = bitsMem;
for (UINT y = 0; y < data->Height; y ++, p += data->Stride)
{
m = UnpackPckLine(p, m, bytesPreLine);
}
}
//---------------------------------------------------------------------------
// 16色
VOID UnpackPck4(BitmapData *data, LPBYTE bitsMem, INT bytesPreLine)
{
LPBYTE p = (LPBYTE)data->Scan0;
LPBYTE m = bitsMem;
INT datOffset = data->Stride -
((GetPixelFormatSize(data->PixelFormat) * data->Width + 7) >> 3);
if (data->Width & 1) datOffset ++;
INT bytes1 = bytesPreLine;
INT bytes2 = bytes1 << 1;
INT bytes3 = bytes2 + bytes1;
INT bytes = bytes1 << 2;
LPBYTE buffer = new BYTE[bytes];
for (UINT y = 0; y < data->Height; y ++, p += datOffset)
{
m = UnpackPckLine(buffer, m, bytes);
LPBYTE b = buffer;
BYTE mask = 0x80;
for (UINT x = 0; x < data->Width; x ++)
{
if (*b & mask) *p |= 1;
if (*(b + bytes1) & mask) *p |= 2;
if (*(b + bytes2) & mask) *p |= 4;
if (*(b + bytes3) & mask) *p |= 8;
if (x & 1) p ++;
else *p <<= 4;
mask >>= 1;
if (!mask)
{
mask = 0x80;
b ++;
}
}
}
delete[] buffer;
}
//---------------------------------------------------------------------------
// 24位真彩色
VOID UnpackPck24(BitmapData *data, LPBYTE bitsMem, INT bytesPreLine)
{
INT bytes1 = bytesPreLine;
INT bytes2 = bytes1 << 1;
INT bytes = bytes2 + bytes1;
INT width = (INT)data->Width > bytesPreLine? bytesPreLine : data->Width;
INT datOffset = data->Stride - width * 3;
PRGBTriple p = (PRGBTriple)data->Scan0;
LPBYTE m = bitsMem;
LPBYTE buffer = new BYTE[bytes];
for (INT y = 0; y < (INT)data->Height; y ++, (LPBYTE)p += datOffset)
{
m = UnpackPckLine(buffer, m, bytes);
LPBYTE b = buffer;
for (INT x = 0; x < width; x ++, p ++, b ++)
{
p->rgbtRed = *b;
p->rgbtGreen = *(b + bytes1);
p->rgbtBlue = *(b + bytes2);
}
}
delete[] buffer;
}
//---------------------------------------------------------------------------
Bitmap *UnpackPckImage(LPBYTE imageMem, INT imageBytes)
{
PcxFileHeader *header = (PcxFileHeader*)imageMem;
if (header->flag != 0x0a) return NULL;
PRGBTriple ppal = NULL;
PixelFormat format = PixelFormatUndefined;
if (header->bitsPrePixel == 1)
{
if (header->planes == 4)
{
format = PixelFormat4bppIndexed;
ppal = (PRGBTriple)header->palette;
}
else format = PixelFormat1bppIndexed;
}
else
{
if (header->planes == 3)
format = PixelFormat24bppRGB;
else if (header->planes == 1)
{
ppal = (PRGBTriple)(imageMem + imageBytes - 256 * 3);
if (*((LPBYTE)ppal - 1) == 0x0c)
format = PixelFormat8bppIndexed;
}
}
if (format == PixelFormatUndefined) return NULL;
Bitmap *bmp = new Bitmap(header->xMax - header->xMin + 1,
header->yMax - header->yMin + 1, format);
if (ppal)
{
INT count = 1 << (header->bitsPrePixel * header->planes);
ColorPalette *pal = (ColorPalette*)new BYTE[count * sizeof(ARGB) + sizeof(ColorPalette)];
PRGBQuad pp = (PRGBQuad)pal->Entries;
for (INT i = 0; i < count; i ++)
{
pp[i].rgbBlue = ppal[i].rgbtRed;
pp[i].rgbGreen = ppal[i].rgbtGreen;
pp[i].rgbRed = ppal[i].rgbtBlue;
pp[i].rgbReserved = 255;
}
pal->Flags = 0;
pal->Count = count;
bmp->SetPalette(pal);
delete[] pal;
}
LPBYTE bitsMem = imageMem + sizeof(PcxFileHeader);
BitmapData data;
Gdiplus::Rect r(0, 0, bmp->GetWidth(), bmp->GetHeight());
bmp->LockBits(&r, ImageLockModeRead | ImageLockModeWrite, format, &data);
switch (format)
{
case PixelFormat4bppIndexed:
UnpackPck4(&data, bitsMem, header->bytesPreLine);
break;
case PixelFormat24bppRGB:
UnpackPck24(&data, bitsMem, header->bytesPreLine);
break;
default:
UnpackPck(&data, bitsMem, header->bytesPreLine);
}
bmp->UnlockBits(&data);
return bmp;
}
//---------------------------------------------------------------------------
Bitmap *LoadPcxImageFromStream(IStream *stream)
{
LARGE_INTEGER move;
ULARGE_INTEGER size;
move.QuadPart = 0;
if (stream->Seek(move, STREAM_SEEK_END, &size) != S_OK)
return NULL;
stream->Seek(move, STREAM_SEEK_SET, NULL);
LPBYTE imageMem = new BYTE[size.LowPart];
Bitmap *bmp = NULL;
if (stream->Read(imageMem, size.LowPart, NULL) == S_OK)
bmp = UnpackPckImage(imageMem, size.LowPart);
delete[] imageMem;
return bmp;
}
//---------------------------------------------------------------------------
上面代码中，UnpackPckImage函数是核心代码，负责对PCX格式图像内存映像进行解析并转换。现在版本的PCX格式图像主要是单色、16色、256色和24位真彩色，本文代码能准确的解析这几种图像。但有时也可能有些不规范图像，如16色图像，规范的格式应该是像素位数bitsPrePixel=1，像素平面planes=4，同时调色板数据在文件头的palette中，这是从EGA显示卡遗留下来的格式，但如bitsPrePixel=4，像素平面planes=1的格式描述，也同样是16色格式，而且是符合现代16色格式的，我用Photoshop对这种格式描述做过实验，但会显示文件不完整的错误，既然是“不完整”而不是非法错误，证明这种16色格式描述也应该是正确的，因此我尝试将调色板从文件头移到文件尾，结果Photoshop果然将图像读出来了，但只显示了一半的宽度，由此，我得知这是Photoshop的容错读取，即它忽略了bitsPrePixel=4这个描述，而是把它当256色图像处理的，事实上，在Photoshop中是没法正确保存16色图像的，它总是将16色用256色方式保存的，我在UnpackPckImage函数中也采用了这种容错方式，只要图像尾部有调色板，就可以当256色处理；只要planes=3，就当24位真彩色读取，而不再管其它描述。
LoadPcxImageFromStream函数只是简单的从流读取PCX格式图像到内存映像而已，之所以选择从流读取，主要是考虑通用性。为了能从文件读取PCX图像，我也写了一个不完整的文件流类，只需要前面6个接口函数能用就行了（事实上，只要Read、Write和Seek3个函数能用即可）。下面是这个文件流类和LoadPcxImageFromFile函数代码：
class FileStream : public IStream
{
HANDLE handle;
INT refCount;
public:
HRESULT STDMETHODCALLTYPE QueryInterface(REFIID riid, VOID **ppvObject)
{
if (lstrcmp((LPTSTR)&riid, (LPTSTR)&IID_IStream) == 0 ||
lstrcmp((LPTSTR)&riid, (LPTSTR)&IID_IUnknown) == 0)
{
*ppvObject = this;
AddRef();
return S_OK;
}
*ppvObject = NULL;
return E_NOINTERFACE;
}
ULONG STDMETHODCALLTYPE AddRef(VOID)
{
refCount ++;
return refCount;
}
ULONG STDMETHODCALLTYPE Release(VOID)
{
if (refCount > 0) -- refCount;
if (refCount == 0) delete this;
return refCount;
}
HRESULT STDMETHODCALLTYPE Read(VOID *pv, ULONG cb, ULONG *pcbRead)
{
ULONG readBytes;
if (ReadFile(handle, pv, cb, &readBytes, NULL))
{
if (pcbRead) *pcbRead = readBytes;
return S_OK;
}
return E_FAIL;
}
HRESULT STDMETHODCALLTYPE Write(CONST VOID *pv, ULONG cb, ULONG *pcbWritten)
{
ULONG writeBytes;
if (WriteFile(handle, pv, cb, &writeBytes, NULL))
{
if (pcbWritten) *pcbWritten = writeBytes;
return S_OK;
}
return E_FAIL;
}
HRESULT STDMETHODCALLTYPE Seek(LARGE_INTEGER dlibMove, DWORD dwOrigin, ULARGE_INTEGER *plibNewPosition)
{
ULARGE_INTEGER pos;
dlibMove.LowPart = SetFilePointer(handle, dlibMove.LowPart, &dlibMove.HighPart, dwOrigin);
if (plibNewPosition)
plibNewPosition->QuadPart = dlibMove.QuadPart;
return dlibMove.QuadPart == -1? E_FAIL : S_OK;
}
HRESULT STDMETHODCALLTYPE SetSize(ULARGE_INTEGER libNewSize)
{
return Seek(*(LARGE_INTEGER*)&libNewSize, STREAM_SEEK_END, NULL);
}
HRESULT STDMETHODCALLTYPE CopyTo(IStream *pstm, ULARGE_INTEGER cb, ULARGE_INTEGER *pcbRead, ULARGE_INTEGER *pcbWritten)
{
return S_OK;
}
HRESULT STDMETHODCALLTYPE Commit(DWORD grfCommitFlags)
{
return S_OK;
}
HRESULT STDMETHODCALLTYPE Revert(VOID)
{
return STG_E_REVERTED;
}
HRESULT STDMETHODCALLTYPE LockRegion(ULARGE_INTEGER libOffset, ULARGE_INTEGER cb, DWORD dwLockType)
{
return STG_E_INVALIDFUNCTION;
}
HRESULT STDMETHODCALLTYPE UnlockRegion(ULARGE_INTEGER libOffset, ULARGE_INTEGER cb, DWORD dwLockType)
{
return STG_E_INVALIDFUNCTION;
}
HRESULT STDMETHODCALLTYPE Stat(STATSTG *pstatstg, DWORD grfStatFlag)
{
return S_OK;
}
HRESULT STDMETHODCALLTYPE Clone(IStream **ppstm)
{
return E_NOTIMPL;
}
public:
FileStream(VOID) : refCount(0), handle((HANDLE)(-1)) {}
FileStream(LPTSTR fileName, BOOL isRead) : refCount(0)
{
handle = CreateFile(fileName, GENERIC_READ | GENERIC_WRITE,
FILE_SHARE_READ | FILE_SHARE_WRITE, NULL,
isRead? OPEN_EXISTING : CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL);
}
~FileStream(VOID)
{
if (handle != (HANDLE)(-1))
CloseHandle(handle);
}
};
//---------------------------------------------------------------------------
Bitmap *LoadPcxImageFromFile(LPTSTR fileName)
{
IStream *stream = new FileStream(fileName, TRUE);
stream->AddRef();
Bitmap *bmp = LoadPcxImageFromStream(stream);
stream->Release();
return bmp;
}
//---------------------------------------------------------------------------
下面是个从文件读取并显示的例子代码（BCB2010）：
void __fastcall TForm1::Button2Click(TObject *Sender)
{
Bitmap *bmp;
if ((bmp = LoadPcxImageFromFile("d:\\1-1-8.pcx")) == NULL)
throw new Exception("Load Image fail");
Gdiplus::Graphics *g = new Gdiplus::Graphics(Canvas->Handle);
g->DrawImage(bmp, 0, 0);
delete g;
delete bmp;
}
本文没有对PCX文件格式进行详细讲解，主要原因是这些网上可以搜索得到，虽然并不完全可靠，但参考一下是可行的，而且，我自己也没法比网上讲的更透彻了，毕竟，PCX格式图像太“古老”了，古老的我想找几个以前版本的文件做实验都没法找到，只好靠Photoshop保存，或者自己写这种格式文件。
C++图像处理 -- PCX格式图像（下）
《C++图像处理 -- PCX格式图像（上）》将PCX格式图像转换为GDI+位图，本文则介绍将GDI+位图转换为PCX格式图像。
下面是GDI+位图转换为PCX格式图像代码：
INT PackPcxLine(LPBYTE dest, LPBYTE source, INT bytesPreLine, INT planes)
{
LPBYTE pd = dest;
INT delta = planes --;
LPBYTE ps = source + planes;
INT bytes = bytesPreLine;
while(planes >= 0)
{
INT count = 0;
BYTE c = *ps;
do
{
count ++;
if (-- bytes == 0)
{
if (-- planes < 0) break;
bytes = bytesPreLine;
ps = source + planes;
}
else ps += delta;
} while(c == *ps && count < 0x3f);
if (c >= 0xc0 || count > 1)
*pd ++ = count | 0xc0;
*pd ++ = c;
}
return pd - dest;
}
//---------------------------------------------------------------------------
typedef union
{
WORD value;
struct
{
BYTE low;
BYTE high;
};
}testMask;
INT PackPcx4Line(LPBYTE dest, LPBYTE source, INT bytesPreLine, INT width)
{
INT bytes = bytesPreLine << 2;
LPBYTE buf = dest + bytes;
testMask mask;
mask.value = 0x1001;
width = (width + 1) >> 1;
while(mask.high)
{
BYTE c = 0;
BYTE bit = 0x80;
LPBYTE pb = buf;
for (INT i = 0; i < width; i ++)
{
if (source[i] & mask.high) c |= bit;
bit >>= 1;
if (source[i] & mask.low) c |= bit;
bit >>= 1;
if (bit == 0)
{
*pb ++ = c;
c = 0;
bit = 0x80;
}
}
buf += bytesPreLine;
mask.value <<= 1;
}
return PackPcxLine(dest, dest + bytes, bytes, 1);
}
//---------------------------------------------------------------------------
VOID ARGBQuadToRGBTriple(PRGBTriple dest, PRGBQuad source, INT count)
{
for (INT i = 0; i < count; i++)
{
dest[i].rgbtBlue = source[i].rgbRed;
dest[i].rgbtGreen = source[i].rgbGreen;
dest[i].rgbtRed = source[i].rgbBlue;
}
}
//---------------------------------------------------------------------------
BOOL SavePcxImageToStream(IStream *stream, Bitmap *bmp)
{
PixelFormat format = bmp->GetPixelFormat();
if (format == PixelFormatUndefined)
return FALSE;
PcxFileHeader header;
ColorPalette *pal = NULL;
BYTE palette[256 * 3 + 1];
ZeroMemory(&header, sizeof(PcxFileHeader));
header.bitsPrePixel = GetPixelFormatSize(format);
header.planes = 1;
if (header.bitsPrePixel > 8)
{
format = PixelFormat24bppRGB;
header.planes = 3;
header.bitsPrePixel = 8;
}
else //if (header.bitsPrePixel > 1)
{
pal = (ColorPalette*)new BYTE[256 * sizeof(ARGB) + sizeof(ColorPalette)];
bmp->GetPalette(pal, bmp->GetPaletteSize());
PRGBTriple ppal = (PRGBTriple)&palette[1];
// 如果是16色位图，调色板保存到文件头
if (format == PixelFormat4bppIndexed)
{
header.planes = header.bitsPrePixel;
header.bitsPrePixel = 1;
ppal = (PRGBTriple)header.palette;
}
ARGBQuadToRGBTriple(ppal, (PRGBQuad)pal->Entries, pal->Count);
delete[] pal;
}
Gdiplus::Rect r(0, 0, bmp->GetWidth(), bmp->GetHeight());
header.flag = 0x0A;
header.version = 5;
header.encodeing = 1;
header.xMax = r.Width - 1;
header.yMax = r.Height - 1;
header.hRes = 96;
header.vRes = 96;
header.paletteType = 1;
header.bytesPreLine = (r.Width * header.bitsPrePixel + 7) >> 3;
if (header.bytesPreLine & 1)
header.bytesPreLine ++;
// 保存PCX文件头
if (stream->Write(&header, sizeof(PcxFileHeader), NULL) != S_OK)
return FALSE;
// 获取GDI+位图数据到位图数据结构
BitmapData data;
data.Stride = ((r.Width * GetPixelFormatSize(format) + 31) & -32) >> 3;
INT size = r.Height * data.Stride;
// size为位图数据字节数，header.bytesPreLine*header.planes*2为编码缓冲区字节数
data.Scan0 = (LPVOID)new BYTE[size + header.bytesPreLine * header.planes * 2];
bmp->LockBits(&r, ImageLockModeRead | ImageLockModeUserInputBuf, format, &data);
bmp->UnlockBits(&data);
// 如果单色位图调色板首项不为0，位图数据反向
if (format == PixelFormat1bppIndexed && (*(ARGB*)&palette[1] & 0xffffff))
{
INT count = data.Height * (data.Stride >> 2);
LPDWORD pd = (LPDWORD)data.Scan0;
for (INT i = 0; i < count; pd[i] ^= (DWORD)(-1), i ++);
}
LPBYTE p = (LPBYTE)data.Scan0;
LPBYTE buffer = p + size;
INT bytes;
// 逐行进行RLE编码并保存到流
for (UINT y = 0; y < data.Height; y ++, p += data.Stride)
{
if (format == PixelFormat4bppIndexed)
bytes = PackPcx4Line(buffer, p, header.bytesPreLine, data.Width);
else
bytes = PackPcxLine(buffer, p, header.bytesPreLine, header.planes);
stream->Write(buffer, bytes, NULL);
}
delete[] data.Scan0;
// 如果是256色位图，调色板保存到流的尾部
if (format == PixelFormat8bppIndexed)
{
palette[0] = 0x0c;
stream->Write(palette, 256 * 3 + 1, NULL);
}
return TRUE;
}
//---------------------------------------------------------------------------
BOOL SavePcxImageToFile(LPTSTR fileName, Bitmap *bmp)
{
IStream *stream = new FileStream(fileName, FALSE);
stream->AddRef();
BOOL result = SavePcxImageToStream(stream, bmp);
stream->Release();
return result;
}
//---------------------------------------------------------------------------
代码中SavePcxImageToStream函数已经将大致的转换流程作了注释，本文不再罗嗦，而SavePcxImageToFile函数仍然是利用我写的简易文件流将转换后的PCX格式图像保存到文件，FileStream类在本文上篇《C++图像处理 -- PCX格式图像（上）》中。
下面是个GDI+位图转换为PCX格式图像例子（BCB2010）：
void __fastcall TForm1::Button3Click(TObject *Sender)
{
Gdiplus::Bitmap *bmp = new Gdiplus::Bitmap(L"d:\\1-4.bmp");
if (bmp->GetLastStatus() != Ok)
throw new Exception("Load Image fail");
Gdiplus::Graphics *g = new Gdiplus::Graphics(Canvas->Handle);
g->DrawImage(bmp, 0, 0);
delete g;
SavePcxImageToFile("d:\\1-4.pcx", bmp);
delete bmp;
}
同样，关于PCX文件格式，请网上搜索有关文档。
转自：
https://blog.csdn.net/maozefa/article/details/8547122
https://blog.csdn.net/maozefa/article/details/8550772
