Merge 2 images

I am trying to merge 2 images and able to perform the activity. But always the 2nd image not sitting completely or some issues.

Here is the code I have used.

Dim Result, g, Name, Layer
Set Result = DotNetFactory.CreateInstance("System.Drawing.Bitmap", "System.Drawing", 1920, 1080)  'My monitor resolution
Set g = DotNetFactory.CreateInstance("System.Drawing.Graphics").FromImage(Result)

Set Layer = DotNetFactory.CreateInstance("System.Drawing.Bitmap", "System.Drawing", "C:\1.png")
g.DrawImage Layer, 0, 0, 600, 500

Set Layer = DotNetFactory.CreateInstance("System.Drawing.Bitmap", "System.Drawing", "C:\2.png")
g.DrawImage Layer, 0, 500, 600, 1100

Result.Save str & "3.png"

Code is working without any errors but always some mismatch in x,y DPIs. Also I tried DrawImageUnScaled but no luck.

Could anyone tell me what exactly I am doing wrong with DPI positions.