Bitmap::FromStream() issues


I’ve been writing some code the last day or so to pull a PNG bitmap out of a resource file and put it into a GDI+ bitmap. You would like to use:


Bitmap::FromResource()


but unfortunately, that only works for BITMAP resources. I found some code internally that uses Bitmap::FromStream() to create GDI+ bitmap – it’s somewhat similar to this code.


That worked fine to draw an image sometimes, but didn’t work other times. Specifically, I couldn’t do something like:


graphics.DrawImage(&bitmap, 0, 0);


while it would work with:


graphics.DrawImage(&bitmap, 0, 0, 32, 32);


It seems that the bitmap you get back from Bitmap::FromStream() doesn’t know how big it is. The first call therefore doesn’t work, nor does trying to draw with transparency using ImageAttributes. If, however, you create a new bitmap:


Bitmap* pGoodBitmap = new Bitmap(width, height, PixelFormat32bppARGB);
Graphics graphics(pGoodBitmap);


Status status = graphics.DrawImage(pLoadedBitmap, 0, 0, width, height);


then that new bitmap (pGoodBitmap here) will be a fully-fledged bitmap that you can then use as you wish.


It might also work work to call Bitmap::Clone()



 

Comments (3)

  1. Mihailik says:

    Eric, why you call this post "FromStream", and at same time you are speaking about "FromResource"?

  2. My Suggestions says:

    Just use the following code. It works with *any* type of image.

    Bitmap bmp;

    using (Stream stream = Assembly.GetExecutingAssembly().GetManifestResourceStream("blah.jpg")

    {

    bmp = Bitmap.FromStream(stream);

    }