Question

Basically I’m making an animated UI from scratch. Everything on the UI is derived from a ScreenThing base class which can store a bitmap used to draw that thing, as well as its position. When I want to draw the UI I create a new blank Bitmap of the right size, create a Graphics object from that bitmap, then pass that Graphics object to all of the ScreenThings Draw() method to draw themselves. When that’s done, I print the bitmap to the screen with a PictureBox control.

This all works great, but it’s too slow. I want this to happen at least 30 times per second so the animation is smooth, but it’s taking more than 33 milliseconds for all of this to happen. I’ve seen that the reason for this slowness is the locking and unlocking of the bitmap memory. I’ve tried some code I found online that unlocks the bitmaps and makes a new GetPixel and SetPixel function and tried combining the images pixel by pixel like below, but this took even longer. (code below was just a test, it doesn’t place the image in the right place)

for (int i = 0; i < images.Count; i++)
{
    FastBitmap foreground = new FastBitmap(images[i]);
    foreground.LockImage();

    for (int x = 0; x < images[0].Width; x++)
    {
        for (int y = 0; y < images[0].Height; y++)
        {
            output.SetPixel(x, y, foreground.GetPixel(x, y));
        }
    }

    foreground.UnlockImage();
}

So what’s the best way to do this? Is it possible to use C# to draw a pretty big image (like 1024×768) in real time like this? If all else fails, I guess I could figure out a way to only draw the parts that have changed, but I’d love to avoid doing that if a brute force redraw of everything is possible. Thanks a lot!

Answer 1

Using bitmaps to draw real-time animations is very inefficient. Insted, create a CustomControl, and override its OnPaint method like this:

protected override void OnPaint(PaintEventArgs pe)
{
}

there you can use pe.Graphics to do any drawing you want and no copying to screen is required.
I’ve used it and if you’re drawing routines are reasonably fast, that will be smooth.

Also, remember to call SetStyle(ControlStyles.OptimizedDoubleBuffer, true); in the control constructor to get double buffering