IImagingFactory IImage

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void DrawImage(HDC hdc)

{

IImagingFactory *pImgFactory = NULL;

IImage *pImage = NULL;

RECT rc = { 0, 0, 110, 88};

// Normally you would only call CoInitialize/CoUninitialize

// once per thread. This sample calls CoInitialize in this

// draw function simply to illustrate that you must call

// CoInitialize before calling CoCreateInstance.

CoInitializeEx(NULL, COINIT_MULTITHREADED);

// Create the imaging factory.

if (SUCCEEDED(CoCreateInstance (CLSID_ImagingFactory,

NULL,

CLSCTX_INPROC_SERVER,

IID_IImagingFactory,

(void **)&pImgFactory)))

{

// Load the image from the JPG file.

if (SUCCEEDED(pImgFactory->CreateImageFromFile(

TEXT("//Program Files//Imaging//flower.jpg"),

&pImage)))

{

// Draw the image.

pImage->Draw(hdc, &rc, NULL);

pImage->Release();

}

pImgFactory->Release();

}

CoUninitialize();

}

IImage::Draw可以绘制透明的PNG图，其原型为：

 
HRESULT Draw(
  HDC                  hdc,
  const RECT*          dstRect,
  OPTIONAL const RECT* srcRect
);

dstRect为显示的区域，如果大小和图片的大小不一样的话，图片会有缩放的效果；

srcRect为源图片的显示区域，比如图片大小320*100，我只需要显示其中一部分时可以指定该参数，否则设为NULL。

注：该参数是以0.01mm为单位的，需要把像素进行转换，可以通过GetImageInfo获取图片dpi参数后进行转换((2.54*1000)/MyImageinfo.Xdpi)*像素。

HRESULT GetImageInfo(
  ImageInfo* imageInfo
);

原图为透明png格式：

调用Draw后效果：