Dim b As New Bitmap(Me.PictureBox1.Image)
Dim i, j As Int32
Dim c As New Color
For i = 0 To b.Width - 1
For j = 0 To b.Height - 1
c = b.GetPixel(i, j) '得到像素顔色信息
b.SetPixel(i, j, Color.FromArgb(255, c.R, c.G, c.B * 0.5)) '重新設置顔色
Next
Next
Me.PictureBox1.Image = b