关于BMP文件的读取

最新推荐文章于 2021-12-30 23:07:13 发布

原创最新推荐文章于 2021-12-30 23:07:13 发布 · 1.3k 阅读

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文章标签：

#delete #header #file #数据结构 #struct #buffer

http://hi.youkuaiyun.com/space-289256-do-album-id-85553.html

要使用jpeg图片如上

想必大家对BMP文件的操作并不陌生，只是最近存在的一个问题让我百思不得其解，图片显示的颜色不对，而且出现了明显的倾斜现象，将该JPEG图片转为BMP图片，然后对其进行操作。在VC环境下使用的显示方式是调用DC的SetPixel方法。

如今已经得出了原因，是biSizeImage与图片的大小不一致产生的。现将代码分享如下，得出正确显示。

首先定义了数据结构

typedef struct BITMAP_FILE_TAG
        {
        BITMAPFILEHEADER bitmapfileheader; // this contains the bitmapfile header
        BITMAPINFOHEADER bitmapinfoheader; // this is all the info including the palette
        PALETTEENTRY     palette[256];      // we will store the palette here
        UCHAR            *buffer;           // this is a pointer to the data

} BITMAP_FILE, *BITMAP_FILE_PTR;

读取位图的程序如下：

CString StrFilter = "位图文件(*.bmp)|*.bmp|所有文件(*.*)|*.*||"; //filter file
CFileDialog Dlg(TRUE,   //opendialog
     NULL,   //
     NULL,   //
     NULL,   //
     StrFilter,  //
     this);   //
if (!Dlg.DoModal() == IDOK)  //
{
  return;
}
CString StrFileName;
StrFileName = Dlg.GetFileName();

//BITMAPINFO
BITMAPINFO *pBmpInfo;
//DIB
BYTE* pBmpData;
CFile MyFile;

if (!MyFile.Open(StrFileName,CFile::modeRead|CFile::typeBinary))
{
  return;
}
BITMAPFILEHEADER BmpHeader;   //fileheader
if (MyFile.Read(&BmpHeader, sizeof(BmpHeader)) != sizeof(BmpHeader))
{
  AfxMessageBox("read bimap file header failed");
  return;
}
if (BmpHeader.bfType != 0x4D42)   //'BM'
{
  AfxMessageBox("not bitmap");
  return;
}
BITMAPINFOHEADER BmpInfo;   //infoheader
if (MyFile.Read(&BmpInfo, sizeof(BmpInfo)) != sizeof(BmpInfo))
{
  AfxMessageBox("read bimap info failed");
  return;
}
if (BmpInfo.biBitCount != 24)   //judge 24bit map
{
  AfxMessageBox("not 24bit bitmap,ignored");
  return;
}
pBmpInfo = (BITMAPINFO*)new char[sizeof(BITMAPINFOHEADER)]; //only use the bitmapinfoheader
                //palette not used,
                //cast bitmapinfoheader to bitmapinfo
if (!pBmpInfo)
{
  AfxMessageBox("memory allocate failed");
  return;
}
memcpy(pBmpInfo, &BmpInfo, sizeof(BITMAPINFOHEADER)); //cpy bmpinfo to the point pbmpinfo
DWORD dataBytes = BmpHeader.bfSize - BmpHeader.bfOffBits; //bfsize:size of bimap file
DWORD delta = (dataBytes/BmpInfo.biHeight - BmpInfo.biWidth*3);              //databytes:the pixels size
pBmpData = (BYTE*)new char[dataBytes];
if (!pBmpData)
{
  AfxMessageBox("memory allocate failed");
  delete pBmpInfo;
  return;
}
if (MyFile.Read(pBmpData, dataBytes) != dataBytes)
{
  AfxMessageBox("read bitmap data failed");
  delete pBmpInfo;
  delete pBmpData;
  return;

RGBTRIPLE *rgb;
rgb = new RGBTRIPLE[BmpInfo.biWidth*BmpInfo.biHeight];

MyFile.SeekToBegin();
MyFile.Seek(BmpHeader.bfOffBits, CFile::begin);
if (delta == 0)
{
  MyFile.Read(rgb,BmpInfo.biWidth*BmpInfo.biHeight*3);//read pixels from dataregion
}
else
{
  for (WORD count=0;count<BmpInfo.biHeight;count++)
  {
   MyFile.Read(&rgb[count*BmpInfo.biWidth],BmpInfo.biWidth*3);
   MyFile.Seek(delta,CFile::current);
  }
}
MyFile.Close();
CDC *pDC = GetDC();
CRect rect;
CBrush brush(RGB(255,255,255));
GetClientRect(&rect);
pDC->FillRect(&rect, &brush);
if (BmpInfo.biCompression != BI_RGB)
{
  AfxMessageBox("compressed bmp,no process");
  return;
}

}

for (int i=0;i<BmpInfo.biHeight;i++)

  for (int j=0;j<BmpInfo.biWidth;j++)
  {
    pDC->SetPixel(j, BmpInfo.biHeight-1-i,
    RGB(rgb[i*BmpInfo.biWidth+j].rgbtRed,
                    rgb[i*BmpInfo.biWidth+j].rgbtGreen,
                    rgb[i*BmpInfo.biWidth+j].rgbtBlue));
   for (int k=0; k<1000; k++) ; //延时
  }

  delete pBmpInfo;
  delete pBmpData;
  delete rgb;

}

当然简单的方法也是有的，那就是调用StretchDIBits