【转载】 Windows Mobile下画透明PNG图片的解决方案

转载：http://blog.csdn.net/hhygcy/archive/2009/04/29/4138195.aspx

最近一直看到有人在问这个PNG的东西,正好在工作的时候也用得到,就找了几个图片试了一下.从wince开始引入了IImage的支持,这样我们可以用IImage来load 这些图片. 大致的流程很多地方都有:

CoCreateInstance创建IImagingFactory, 然后用CreateImageFromFile创建IImage的接口,最后把这个IImage用draw的接口画到DC.但是问题在于这个Draw是没有设置transparent属性的? 这个东西应该如何操作呢? 在网上看到了一个解决方案. 就是把这个png图片转化成一张32位的bitmap,然后再透明的画到DC上.这里有一段调试成功的代码:

HBITMAP LoadPngImage2 (HDC hdc, LPCTSTR filename)
{
    IImagingFactory* pImageFactory = 0;
    IImage* pImage = 0;
    ImageInfo imageInfo;
    CoInitializeEx(0, COINIT_MULTITHREADED);
    HBITMAP hBitmap = 0;
    LPBYTE lpByte;
    if (SUCCEEDED(CoCreateInstance(CLSID_ImagingFactory, 0, CLSCTX_INPROC_SERVER, IID_IImagingFactory, (void**)&pImageFactory)))
    {
        if (SUCCEEDED(pImageFactory->CreateImageFromFile(filename, &pImage))&& SUCCEEDED(pImage->GetImageInfo(&imageInfo)))
        {
            HDC bmpDC = CreateCompatibleDC(hdc);
            //LPBYTE lpByte;
            BITMAPINFO *pbinfo ;
            pbinfo = (BITMAPINFO *)calloc(1, sizeof(BITMAPINFO) + 4 * sizeof(INT)) ;
            if(!pbinfo)
                return FALSE ;
            pbinfo->bmiHeader.biSize = sizeof (BITMAPINFOHEADER);
            pbinfo->bmiHeader.biWidth = imageInfo.Width ;
            pbinfo->bmiHeader.biHeight = imageInfo.Height ;
            pbinfo->bmiHeader.biPlanes = 1;
            pbinfo->bmiHeader.biBitCount = 32;
            pbinfo->bmiHeader.biCompression = BI_ALPHABITFIELDS;
            pbinfo->bmiHeader.biSizeImage = 0 ;
            pbinfo->bmiHeader.biXPelsPerMeter = 11811;
            pbinfo->bmiHeader.biYPelsPerMeter = 11811;
            pbinfo->bmiHeader.biClrUsed = 0;
            pbinfo->bmiHeader.biClrImportant = 0;
            int *pMask = (int*)&(pbinfo->bmiColors[0]) ;
            *pMask++ = 0x00FF0000 ;
            *pMask++ = 0x0000FF00 ;
            *pMask++ = 0x000000FF ;
            *pMask++ = 0xFF000000 ;
            hBitmap = CreateDIBSection(NULL, pbinfo, DIB_RGB_COLORS, (void **)&lpByte, NULL, 0) ;
            free(pbinfo) ;
            if(!hBitmap || !lpByte)
                return FALSE ;
            RECT rect = {0, 0, imageInfo.Width, imageInfo.Height};
            IBitmapImage *pBitmapImage;
            BitmapData bitmapData;
            bitmapData.Width = imageInfo.Width;
            bitmapData.Height = imageInfo.Height;
            bitmapData.PixelFormat = imageInfo.PixelFormat;
            pBitmapImage = NULL;
            pImageFactory->CreateBitmapFromImage(pImage, imageInfo.Width, imageInfo.Height, PIXFMT_32BPP_ARGB,
                InterpolationHintDefault, &pBitmapImage);
            pBitmapImage->LockBits(&rect, ImageLockModeRead,PIXFMT_32BPP_ARGB, &bitmapData);
            //transferring the pixels
            memcpy(lpByte, bitmapData.Scan0, imageInfo.Width * imageInfo.Height * 4);
            pBitmapImage->UnlockBits(&bitmapData);
            pBitmapImage->Release();
            pImage->Release();
            DeleteDC(bmpDC);
        }
        pImageFactory->Release();
    }
    CoUninitialize();
    //ProcessThePixelsWithAlphaChannel Here
    // vertical flip and ProcessThePixelsWithAlphaChannel here
    for (UINT y=0; y<imageInfo.Height/2; y++)
    {
        BYTE * pPixel = (BYTE *) lpByte + imageInfo.Width * 4 * y;
        BYTE * pDstPixel = (BYTE*) lpByte + imageInfo.Width * 4 * (imageInfo.Height-y-1);
        for (UINT x=0; x<imageInfo.Width; x++)
        {
            pPixel[0] = pPixel[0] * pPixel[3] / 255;
            pPixel[1] = pPixel[1] * pPixel[3] / 255;
            pPixel[2] = pPixel[2] * pPixel[3] / 255;
            pDstPixel[0] = pDstPixel[0] * pDstPixel[3] / 255;
            pDstPixel[1] = pDstPixel[1] * pDstPixel[3] / 255;
            pDstPixel[2] = pDstPixel[2] * pDstPixel[3] / 255;
            INT* pOrigin = (INT*)pPixel;
            INT* pDst    = (INT*)pDstPixel;
            INT temp = *pOrigin;
            *pOrigin = *pDst;
            *pDst = temp;
            pPixel += 4;
            pDstPixel += 4;
        }
    }
    return hBitmap;
}

 

类似的源码可以在MSDN论坛的某一个帖子中找到.但是不是非常完整且正确. 这里做了一些修正. 略去之前的那些过程,但看最后的这个for循环, 实际上做了一个垂直方向的180度翻转. 这就是说这里的接口memcpy拷贝过去的图片像素信息实际上是被翻转过的, 这个在很多camera的帧里面都有体现.