图片处理,调节图片的,对比度和亮度

[zsylizard]

1,如何调整一张图片的对比度和亮度
2,对图片中每个像素的只取Green色,我的代码如下

For i = 1 To GreenImage.Height - 2
For j = 1 To GreenImage.Width - 2
Green = CInt(GreenImage.GetPixel(j, i).G)
GreenImage.SetPixel(j, i, Color.FromArgb(Green, Green, Green))
Next
Next
用这样的方法处理一张520*520的图片,即然要8秒种,如何进行优化.

[AprilSong]

１的原理：
http://blog.gameres.com/thread.asp?BlogID=332&threadid=20894


２的优化：
Dim bmp As New Drawing.Bitmap("1.jpg")

Dim cm As New Drawing.Imaging.ColorMatrix
Dim ia As New Drawing.Imaging.ImageAttributes

cm.Matrix00 = 0
cm.Matrix22 = 0

cm.Matrix10 = 1
cm.Matrix12 = 1

ia.SetColorMatrix(cm, Imaging.ColorMatrixFlag.Default, Imaging.ColorAdjustType.Bitmap)

Dim g As Graphics = Drawing.Graphics.FromImage(bmp)
g.DrawImage(bmp0, New Rectangle(0, 0, bmp.Width, bmp.Height), 0, 0, bmp.Width, bmp.Height, GraphicsUnit.Pixel, ia)

PictureBox1.Image = bmp

[AprilSong]

DrawImage 那句的 bmp0 应该是 bmp ……