DrawImage resized image too small
The issue happens when scaling to 2x or larger.
Looks like the whole problem is caused by the wrong default PixelOffsetMode.
By offsetting pixels during rendering, you can improve render quality at the cost of render speed.
Setting it to
g.PixelOffsetMode = PixelOffsetMode.Half;
makes it go away for me.
Setting it to
g.PixelOffsetMode = PixelOffsetMode.HighQuality;
also works fine.
Default, None and HighSpeed cause the image to be rendered a little to the left and up.
Often you will also want to set InterpolationMode.NearestNeighbor.