PNG decoding and splash screen...

[fxRichard]

I am a big Java developer with C experience, everything I do OO is in Java and use C with JNI for anything I cannot do in Java. (Just a heads up on where I am coming from). In one of my applications I need to show a splash screen in C prior to running the Java stuff. I have found/copied/pasted/modified etc the code to do transparent splash screens based off a PNG file using the Windows Imaging Component. The problem is this is only available on Vista and up, I know you can install WIC on XP but is there an easier way to decode PNG's in XP without WIC so I can use them in my application. Here are my two main methods that do the work:

// Loads a PNG image from the specified stream (using Windows Imaging Component).
IWICBitmapSource * LoadBitmapFromStream(IStream * ipImageStream)
{
    // initialize return value
    IWICBitmapSource * ipBitmap = NULL;
 
    // load WIC's PNG decoder
    IWICBitmapDecoder * ipDecoder = NULL;
    if (FAILED(CoCreateInstance(CLSID_WICPngDecoder, NULL, CLSCTX_INPROC_SERVER, __uuidof(ipDecoder), reinterpret_cast<void**>(&ipDecoder))))
        goto Return;

	// load the PNG
    if (FAILED(ipDecoder->Initialize(ipImageStream, WICDecodeMetadataCacheOnLoad)))
        goto ReleaseDecoder;
 
    // check for the presence of the first frame in the bitmap
    UINT nFrameCount = 0;
    if (FAILED(ipDecoder->GetFrameCount(&nFrameCount)) || nFrameCount != 1)
        goto ReleaseDecoder;
 
    // load the first frame (i.e., the image)
    IWICBitmapFrameDecode * ipFrame = NULL;
    if (FAILED(ipDecoder->GetFrame(0, &ipFrame)))
        goto ReleaseDecoder;
 
    // convert the image to 32bpp BGRA format with pre-multiplied alpha
    //   (it may not be stored in that format natively in the PNG resource,
    //   but we need this format to create the DIB to use on-screen)
    WICConvertBitmapSource(GUID_WICPixelFormat32bppPBGRA, ipFrame, &ipBitmap);
    ipFrame->Release();
 
ReleaseDecoder:
    ipDecoder->Release();
Return:
    return ipBitmap;
}

// Creates a 32-bit DIB from the specified WIC bitmap.
HBITMAP CreateHBITMAP(IWICBitmapSource * ipBitmap)
{
    // initialize return value
    HBITMAP hbmp = NULL;
 
    // get image attributes and check for valid image
    UINT width = 0;
    UINT height = 0;
    if (FAILED(ipBitmap->GetSize(&width, &height)) || width == 0 || height == 0)
        goto Return;
 
    // prepare structure giving bitmap information (negative height indicates a top-down DIB)
    BITMAPINFO bminfo;
    ZeroMemory(&bminfo, sizeof(bminfo));
    bminfo.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
    bminfo.bmiHeader.biWidth = width;
    bminfo.bmiHeader.biHeight = -((LONG) height);
    bminfo.bmiHeader.biPlanes = 1;
    bminfo.bmiHeader.biBitCount = 32;
    bminfo.bmiHeader.biCompression = BI_RGB;
 
    // create a DIB section that can hold the image
    void * pvImageBits = NULL;
    HDC hdcScreen = GetDC(NULL);
    hbmp = CreateDIBSection(hdcScreen, &bminfo, DIB_RGB_COLORS, &pvImageBits, NULL, 0);
    ReleaseDC(NULL, hdcScreen);
    if (hbmp == NULL)
        goto Return;
 
    // extract the image into the HBITMAP
    const UINT cbStride = width * 4;
    const UINT cbImage = cbStride * height;
    if (FAILED(ipBitmap->CopyPixels(NULL, cbStride, cbImage, static_cast<BYTE *>(pvImageBits))))
    {
        // couldn't extract image; delete HBITMAP
        DeleteObject(hbmp);
        hbmp = NULL;
    }
 
Return:
    return hbmp;
}

[hoxsiew]

So I'm not sure what the problem is here. Is it decoding the PNG? Why not use a BMP instead?

[fxRichard]

Well as it sits it works fine in Windows Vista and 7 as I am using the Windows Imaging Component (WIC), and this comes standard on Vista and up however in XP is where the problem is. I need to show be able to create an HBITMAP from a PNG file in XP without using WIC thus this example works fine just not in XP, I am looking for an alternative. Thanks.

[hoxsiew]

I thought maybe you could just convert your PNG to BMP and use that from a resource (MS invented BMP after all). There's CImage if you're using MFC/ATL. It handles PNG just fine.