دوست عزیز اینو تست کنید
عکس مورد نظر رو داخل PictureBox1 بذارید.
به متغیر x اندازه طول و y اندازه ارتفاع جدید عکس رو بدید
Dim bm As New Bitmap(PictureBox1.Image)
Dim x As Int32
Dim y As Int32
Dim width As Integer = Val(x)
Dim height As Integer = Val(y)
Dim thumb As New Bitmap(width, height)
Dim g As Graphics = Graphics.FromImage(thumb)
g.InterpolationMode = Drawing2D.InterpolationMode.HighQualityBicubic
g.DrawImage(bm, New Rectangle(0, 0, width, height), New Rectangle(0, 0, bm.Width, _
bm.Height), GraphicsUnit.Pixel)
g.Dispose()
thumb.Save("C:\newimage.bmp", _
System.Drawing.Imaging.ImageFormat.Bmp) 'can use any image format
bm.Dispose()
thumb.Dispose()