Re: RGB24 to Apple II color change

["Michael J. Mahon" <mjmahon@aol.com>]

bluebird wrote:
> I want to display RGB 24 bit BMP image on Apple II.
> As you know, RGB888 <-> RGB565 conversion is simple on IBM.
> But in Apple II, I don't know how..
>
> Is there any good conversion source?

You might want to read up on the Apple II and its capabilities.

The original (well, almost original) HGR mode supports only six
fairly saturated colors, and is not a good target for pictures
containing many colors, like gradients, for example.

The Apple //e marked the debut of DHR (double high-res), with
sixteen colors (with a redundant gray).  While this supports
greater variety, it doesn't come close to realism for any but
very contrived "posterized" pictures.

The Apple IIgs introduced SHR (super hi-res) which could support
the display of pictures containing up to 3200 different colors
secected from a 4096 color palette (RGB444) by using considerable
trickery, but even this falls far short of what you would like.

So the short answer is that while arbitrary photos can be converted
to various Apple II formats, the results are far inferior to what
you are no doubt accustomed to.

-michael

NadaNet and AppleCrate II: parallel computing for Apple II computers!
Home page: http://home.comcast.net/~mjmahon

"The wastebasket is our most important design
tool--and it's seriously underused."