问一个图片亮度和对比度的有关问题，告知理论即可

问一个图片亮度和对比度的问题，告知理论即可
如何求彩色图片的明亮度和对比度？明亮度和对比度的取值范围是多少？
看了一下，大都是处理亮度和对比度的帖子。

------解决方案--------------------
我一般用的是这些，自己凑出来的式子，和PS的效果差不多

Public Function AdjustBrightnessAndContrast(Brightness As Long, Contrast As Long) As Boolean
Dim i As Long, j As Long
Dim Speed(255) As Byte, Temp As Long
If Contrast > 100 Then Contrast = 100
If Contrast < -100 Then Contrast = -100
For i = 0 To 255
If Contrast > 0 Then
Temp = (i - 127) * Contrast * 0.05 + i
Else
Temp = (i - 127) * Contrast * 0.01 + i
End If
Temp = Temp + Brightness
If Temp < 0 Then Temp = 0
If Temp > 255 Then Temp = 255
Speed(i) = Temp
Next
AdjustBrightnessAndContrast = MapConvert(Speed, R_G_B)
End Function

效果可从http://www.vbgood.com/viewthread.php?tid=53287&extra=page%3D1&page=4下载