I -think- what you're talking about is masking.
You need -three- bitmaps: the screen image, the
new image, and the mask. If I remember right, it
should go something like this:
screen[idx] = (screen[index] & mask[index]) | (image[index] &
~mask[index]);
Now bear in mind two things: one, the above
is recreated from scratch -- I might have gotten
the logic wrong (but the concept should work,
even if the equation is wrong); two: I am unfamiliar
w/ the greyscale memory image format in the pilot.
I am assuming a "packed" bitmap, where N adjascent
bits are taken as the value for a single pixel.
If the darned thing works w/ bitplanes, you've
got slightly different math ahead of you.
Screen: 01010101
Mask: 11001100
Image: 10101010
Screen&Mask 01000100
image&~mask 00100010
or the above 01100110
^^||^^||
(|| new, ^^ original)
--
-Richard M. Hartman
[EMAIL PROTECTED]
186,000 mi./sec ... not just a good idea, it's the LAW!
> -----Original Message-----
> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]
> Sent: Thursday, July 08, 1999 11:01 PM
> To: [EMAIL PROTECTED]
> Subject: window/bitmap bits
>
>
> I am looking for some source code which manipulates pixels
> within a bitmap
> or window, preferably greyscale images manipulating either or
> both planes.
>
> My ultimate goal is to quantize a greyscale image down to
> black and white,
> scrANDNOT it off the screen, then scrOR the original
> greyscale image back
> onto the screen.
>
> The way it stands now, if you scrOR a light grey pixel onto a
> dark grey
> pixel, the pixel becomes black on the screen. Icky! I want the pixels
> copied onto the screen to take precedence as to what is already there.
>
>
