Re: What decides the Mono LCD gray scale?
From: voidcoder (voidcoder_at_yahoo.com)
Date: 12/30/04
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Date: Thu, 30 Dec 2004 14:45:54 +0100
Yes, it looks better!!!!
Looks better because 0.299*R + 0.587*G + 0.114*B does not
produce dublicates (eg. RGB(255, 0, 0) != RGB(0, 0, 255) ) as
(R+G+B)/3 does.
Thanks again and Happy New Year!!!! :-)
"cool_harber" <cool_harber@hotmail.com> wrote in message
news:#FYjO0m7EHA.128@TK2MSFTNGP15.phx.gbl...
> 3x,I have tested the palette as you said,but the display is also bad,
> Maybe my lcd just can be used in 4bpp.
> A few days ago,Someone told me another palette in newsgroup,here is the
> code:
> // RGB to YUV conversion is defined by CCIR 601 Standard as
>
> // Y = 0.299*R + 0.587*G + 0.114 B
>
> // Implementation :
>
> // scale= 15
>
> // Gray = (Red*299 + Green*587 + Blue*114)*scale/(1000*255);
>
>
> By the way,I use v_pPaletteBuffer->palette[ 0xFF - i ] to inverted
palette.
>
> "voidcoder" <voidcoder@yahoo.com>
写入消息新闻:ebnNysa7EHA.3820@TK2MSFTNGP11.phx.gbl...
> > Nothing special. Don't really sure that it is right, but
> > I'm using just everage RGB value for grayscale level.
> >
> > eg.
> >
> > for(i=firstEntry;i<end;i++)
> > {
> > v_pPaletteBuffer->palette[ i ] =
> > (((unsigned short)source[i].peBlue + source[i].peGreen +
> > source[i].peRed) / 3);
> > }
> >
> > The better result is using inverted average value, eg
> >
> >
> > v_pPaletteBuffer->palette[ i ] =
> > 0x00FF ^ (((unsigned short)source[i].peBlue +
source[i].peGreen
> > +
> > source[i].peRed) / 3);
> >
> > Please test it and come back with comments (since I think
> > this is not really right way to calculate grayscale palette).
> >
> > May be any1 can share some ideas on "how to calculate right
> > grayscale palette"?
> >
> >
> >
> > "cool_harber" <cool_harber@hotmail.com> wrote in message
> > news:OnQDrka7EHA.2124@TK2MSFTNGP15.phx.gbl...
> >> Thanks,But my lcd display looks so bad,
> >> the text is more clear than the blurred icon or image!~
> >> Can you share me your palette source code?
> >> email:cool_harber@hotmail.com
> >>
> >> "voidcoder" <voidcoder@yahoo.com>
> > 写入消息新闻:eLG5VDP7EHA.2316@TK2MSFTNGP15.phx.gbl...
> >> > If You want to use SA_Lcd driver for that - you are out of luck.
> >> > There are no support for true 4bpp mode. However you can use
> >> > 8bpp mode and turn on monochrome mode in the controller.
> >> > Then just setup your palette with grayscale entries
> >> > (modify DispDrvrSetPalette function). In this case You will have
> >> > 8bpp in frame buffer memory, 4bpp output and 16bit lookup palette
> >> > (where only lower 8bits are grayscale values). And of course
> >> > You have to setup other LCD contoller settings: timings, clocks etc.
> >> >
> >> > At least it works o.k. for me on PXA270.
> >> >
> >> >
> >> >
> >> > "cool_harber" <cool_harber@hotmail.com> wrote in message
> >> > news:eN2ZwbO7EHA.3076@TK2MSFTNGP15.phx.gbl...
> >> >> The mono lcd`s gray scale is decided by lcd controller or lcd
itself?
> >> >> I have a mono lcd with 4 data pins and about 70 Hz frame frequence
,I
> >> >> want to use PXA255 to controll it.Do I get 256 scale gray?
> >> >> Any suggestion is appreciated.
> >> >>
> >> >>
> >> >
> >> >
> >>
> >>
> >
> >
>
>
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