SetDIBitsToDevice和stretchBlt 函数显示JPG PNG图片

[www2t]

MSDN代码
//
// pvJpgImage points to a buffer containing the JPEG image
// nJpgImageSize is the size of the buffer
// ulJpgWidth is the width of the JPEG image
// ulJpgHeight is the height of the JPEG image
//

//
// Check if CHECKJPEGFORMAT is supported (device has JPEG support)
// and use it to verify that device can handle the JPEG image.
//

ul = CHECKJPEGFORMAT;

if (
// Check if CHECKJPEGFORMAT exists:

(ExtEscape(hdc, QUERYESCSUPPORT,
sizeof(ul), &ul, 0, 0) > 0) &&

// Check if CHECKJPEGFORMAT executed without error:

(ExtEscape(hdc, CHECKJPEGFORMAT,
pvJpgImage, nJpgImageSize, sizeof(ul), &ul) > 0) &&

// Check status code returned by CHECKJPEGFORMAT:

(ul == 1)
)
{
//
// Initialize the BITMAPINFO.
//

memset(&bmi, 0, sizeof(bmi));
bmi.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
bmi.bmiHeader.biWidth = ulJpgWidth;
bmi.bmiHeader.biHeight = -ulJpgHeight; // top-down image
bmi.bmiHeader.biPlanes = 1;
bmi.bmiHeader.biBitCount = 0;
bmi.bmiHeader.biCompression = BI_JPEG;
bmi.bmiHeader.biSizeImage = nJpgImageSize;

//
// Do the SetDIBitsToDevice.
//

iRet = SetDIBitsToDevice(hdc,
ulDstX, ulDstY,
ulDstWidth, ulDstHeight,
0, 0,
0, ulJpgHeight,
pvJpgImage,
&bmi,
DIB_RGB_COLORS);

if (iRet == GDI_ERROR)
return FALSE;
}
else
{
//
// Decompress image into a DIB and call SetDIBitsToDevice
// with the DIB instead.
//
}

这里的 ulJpgHeight ulJpgWidth pvJpgImage nJpgImageSize 初值从哪里来 ul又是个什么类型
那位大哥能不能给详细解释一下
最好能给个完整的代码

[fandh]

ul估计是UINT类型吧！
ulJpgHeight ulJpgWidth pvJpgImage nJpgImageSize 应该是你要显示的JPG的一些信息，高度、宽度等

[dzq138]

初值可以从IImage *pImage = NULL;中得动
先打开一个文件.

CFile file;
	CFileException fe;
	CString FileName ;
	DWORD dwFileLength;
	BYTE* pBuff;
	
	FileName=L"\\Storage Card\\读取内存jpgg\\0-1-10.jpg";
	if(0 == file.Open(FileName, CFile::modeRead | CFile::shareDenyWrite, &fe))  //打开文件
	{
		AfxMessageBox(L"打开文件失败");
		return ;
	}
	dwFileLength = file.GetLength();  //取得文件总长度
	pBuff=new BYTE[dwFileLength];  
	file.Seek(0 ,CFile::begin);  //定位
	file.Read((BYTE*)(pBuff) , dwFileLength); //读字节
	file.Close(); 
IImagingFactory   *pImgFactory   =   NULL;
	IImage   *pImage   =   NULL;
	HRESULT hrCoInit;
    HDC hdcCont=NULL,hdcMem=NULL;
	ImageInfo pimageinfo;//= new  sizeof(ImageInfo);
	RECT rect;

hrCoInit=CoInitializeEx(NULL, COINIT_MULTITHREADED);
	CoCreateInstance(CLSID_ImagingFactory,NULL,1,IID_IImagingFactory,(void**) &pImgFactory);
	pImgFactory->CreateImageFromBuffer(pBuff,dwFileLength,BufferDisposalFlag::BufferDisposalFlagNone ,&pImage);
	pImage->GetImageInfo( &pimageinfo);
	rect.top =0;
	rect.left =0;
	rect.right =pimageinfo.Width ; //这里可以得到宽
	rect.bottom =pimageinfo.Height ;//这里可以得到高

pImage->Draw(m_dcCompatible,&rect,NULL);  //m_dcCompatible 是一个CDC....

[crjwlaq]

vs2008 中使用 CImage

vc6使用ole吧