就是在PictureBox里图像的亮度对比度调整，有实例就更好了。网上找到的算法近乎不带注释，没法使啊。

需要颜色数组

Public Class Form1
Function A(Bmp As Bitmap, Offest As Integer) As Bitmap
For i As Integer = 0 To Bmp.Width - 1 *遍历每一列
For j As Integer = 0 To Bmp.Height - 1 *遍历每一行
Dim Color As Color = Bmp.GetPixel(i, j) *获取当前像素点上的颜色
Dim R As Integer = Math.Min(255, Math.Max(0, Color.R + Offest)) *获取颜色的Red
Dim G As Integer = Math.Min(255, Math.Max(0, Color.G + Offest)) *获取颜色的Green
Dim B As Integer = Math.Min(255, Math.Max(0, Color.B + Offest)) *获取颜色的Blue
Bmp.SetPixel(i, j, Color.FromArgb(R, G, B)) *设置颜色
Next
Next
Return Bmp *返回Bmp
End Function
Private Sub TrackBar1_MouseUp(sender As Object, e As MouseEventArgs) Handles TrackBar1.MouseUp
PictureBox1.Image = A(PictureBox1.Image, TrackBar1.Value - 128)
End Sub
End Class

用Marshal类吧 用楼上的双循环那速度真不敢恭维,我敢肯定是动一下卡一下
可以给你看一下效果图,就仅仅是将所有像素点都变成rgb为0,也就是黑色的时间对比