Re: Converting 24bit image to 16bit

["Mike Main" <anime6@earthlink.net>]

That worked :).  Thank you so much!!!  I sent an email to Andre LaMothe, and
he admitted his error :).  He said each color had 5 bits.


----- Original Message -----
From: <EnderWiggenRules@aol.com>
To: <gameprogrammer@gameprogrammer.com>
Sent: Thursday, October 05, 2000 8:07 PM
Subject: Re: Converting 24bit image to 16bit


> In a message dated 10/5/00 5:58:25 PM Central Daylight Time,
> anime6@earthlink.net writes:
>
> << Someone help me please.  I need to write code to load a 24 bit, bitmap
> into a 16 bit buffer.  How do I do this.  Usually it doesn't work. >>
>
> OK. If I'm remembering right, I think 24-bit images are stored with one
byte
> for Red, Green, and Blue, and 16-bit is just the three attributes split
over
> two bytes. So, if you load a 24-bit image in this order:
>     RRRRRRRR GGGGGGGG BBBBBBBB
> Each color attribute is 8-bit, meaning that it is in the range 0 to 255.
> 16-bit (correct me if I'm wrong) is stored in this fashion:
>     RRRRR GGGGGG BBBBB
> The red and blue color attributes are in the range 0 to 31, and the green
> attribute is in the range 0 to 63, so what you need to do is convert the 0
to
> 255 range to 0 to 31 or 63. This can be done easily by bit shifting.
Here's
> pseudo-code:
>     5BitRed=8BitRed>>3; // 8BitRed/8
>     6BitGreen=8BitGreen>>2; // 8BitGreen/4
>     5BitBlue=8BitBlue>>3;   // 8BitBlue/8
>     Color=5BitBlue+(6BitGreen<<5)+(5BitRed<<11)
> This is the conversion, though depending on the library/video card/driver
you
> are using, the red and blue may be reversed in positioning.
>
> -Ender Wiggin
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