vc++ mfc 里保存缩放的bmp图片 不失真

在此感谢http://topic.csdn.net/t/20061013/18/5081010.html

贴主： zsllrtx

void CSaveView::OnFileSave()

{

BITMAP info;//原始图片

m_bitmap.GetBitmap(&info);

CDC DC1;

DC1.CreateCompatibleDC(NULL);

DC1.SelectObject(&m_bitmap);

DC1.MoveTo(0,0);

DC1.LineTo(info.bmWidth,info.bmHeight);

CDC DC2;

CBitmap bmp;//缩放后的图片

bmp.CreateCompatibleBitmap(&DC1,200,200);

DC2.CreateCompatibleDC(NULL);

DC2.SelectObject(&bmp);

int mode = SetStretchBltMode(DC2, COLORONCOLOR); //设置不失真缩放

DC2.StretchBlt(0,0,200,200,&DC1,0,0,info.bmWidth,info.bmHeight,SRCCOPY);

SetStretchBltMode(DC2, mode);

CFileDialog dlg(false,"bmp",NULL,OFN_HIDEREADONLY | OFN_OVERWRITEPROMPT,NULL,this);

if(IDOK == dlg.DoModal())

{

CString bmpfile = dlg.GetPathName();

CFile file(bmpfile,CFile::modeCreate|CFile::modeWrite);

BITMAP bInfo;

bmp.GetBitmap(&bInfo);

//计算调色板大小

int panelsize = 0;

if (bInfo.bmBitsPixel<24) //非真彩色

{

panelsize = int(pow((double)2,bInfo.bmBitsPixel)*sizeof(RGBQUAD));

}

//定义位图信息

BITMAPINFO* bMapInfo = (BITMAPINFO*)LocalAlloc(LPTR,sizeof(BITMAPINFOHEADER)+panelsize);

bMapInfo->bmiHeader.biBitCount = bInfo.bmBitsPixel;

bMapInfo->bmiHeader.biClrImportant = 0;

bMapInfo->bmiHeader.biCompression = 0;

bMapInfo->bmiHeader.biHeight = bInfo.bmHeight;

bMapInfo->bmiHeader.biPlanes = bInfo.bmPlanes;

bMapInfo->bmiHeader.biSize = sizeof(BITMAPINFO);

bMapInfo->bmiHeader.biSizeImage = bInfo.bmHeight*bInfo.bmWidthBytes;

bMapInfo->bmiHeader.biWidth = bInfo.bmWidth;

bMapInfo->bmiHeader.biXPelsPerMeter = 0;

bMapInfo->bmiHeader.biYPelsPerMeter = 0;

//获取位图的实际数据

char* pData = new char[bMapInfo->bmiHeader.biSizeImage];

int len = GetDIBits(DC2.m_hDC,bmp,0,bInfo.bmHeight,pData,bMapInfo,DIB_RGB_COLORS);

BITMAPFILEHEADER bFileHeader;

bFileHeader.bfType = 0x4D42;

bFileHeader.bfReserved1 = 0;

bFileHeader.bfReserved2 = 0;

bFileHeader.bfSize = sizeof(BITMAPFILEHEADER);

bFileHeader.bfOffBits = sizeof(BITMAPFILEHEADER)+sizeof(BITMAPINFOHEADER)+panelsize;

//向文件中写入位图数据

file.Write(&bFileHeader,sizeof(BITMAPFILEHEADER));

file.Write(&bMapInfo->bmiHeader,sizeof(BITMAPINFOHEADER));

file.Write(pData,bMapInfo->bmiHeader.biSizeImage+panelsize);

file.Close();

delete pData;

LocalFree(bMapInfo);

}

}