I'm working on a computer vision project at the moment. Whilst working on it, I've had to resize a few bitmaps due to the webcam library I'm using not being able to properly set the resolution of the camera.

I found this on StackOverflow, and it works quite well. There are a few quality differences, such loss of sharpness due to smoothing, but it's only noticeable when you put the two images side to side.

Bitmap resized = new Bitmap(desiredHeight, desiredWidth);
using (Graphics graphics = Graphics.FromImage(resized))
{
    graphics.SmoothingMode = SmoothingMode.HighQuality;
    graphics.InterpolationMode = InterpolationMode.HighQualityBicubic;
    graphics.PixelOffsetMode = PixelOffsetMode.HighQuality;
    graphics.DrawImage(originalImage,
        new Rectangle(0, 0, desiredHeight, desiredWidth));
}
pictureBox1.Image = resized;

Like I said, works quite well, and definitely one for the snippet bin!