真彩色图像变为256色灰度_visualbasic教程

将RGB想成3D之X,Y,Z轴,则BMP的RGB为(r,g,b)与座标(Y,Y,Y)距离最小时的Y即为灰阶值
Y=0.29900*R 0.58700*G 0.11400*B
整数化
Y=(9798*R 19235*G 3735*B)/32768
RGB(Y,Y,Y)就可以了

需一个内有彩色图的PictureBox,CommandBox
OptionExplicit
PrivateDeclareFunctionGetPixelLib”gdi32″_
(ByValhdcAsLong,ByValxAsLong,ByValYAsLong)AsLong
PrivateDeclareFunctionSetPixelVLib”gdi32″_
(ByValhdcAsLong,ByValxAsLong,_
ByValYAsLong,ByValcrColorAsLong)AsLong
PrivatetmpPicAsPicture

PrivateSubForm_Load()
Picture1.ScaleMode=3设为Pixel
Picture1.AutoRedraw=True设定所有Pixel的改变不立即在pictureBox上显示
SettmpPic=Picture1.Picture
EndSub

PrivateSubCommand1_click()
Dimwidth5AsLong,heigh5AsLong,rgb5AsLong
Dimhdc5AsLong,iAsLong,jAsLong
DimbBlueAsLong,bRed->