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- Path: sparky!uunet!utcsri!eecg.toronto.edu!lemieux
- Newsgroups: comp.os.os2.misc
- From: lemieux@eecg.toronto.edu (Guy Gerard Lemieux)
- Subject: Re: "Bug" in Joel Armungaud's 800x600x256 driver - update
- Message-ID: <1992Jul31.100408.1501@jarvis.csri.toronto.edu>
- References: <1992Jul30.172933.24073@njitgw.njit.edu>
- Date: 31 Jul 92 14:04:08 GMT
- Lines: 49
-
- dic5340@hertz.njit.edu (David Charlap) writes:
- >You've all heard the bug about dotted vertical and horizontal lines
- >appearing (and not always clearing) when popping up menus on the WPS
- >desktop. Well, I've noticed that after installing a background bitmap
- >for the desktop, these lines don't appear.
-
- I have a background bitmap, and the lines still appear.
- (I am using argyle.bmp from Windows 3.1 :)
-
- I think the algorithm simply inverts the pixel index in order to draw
- the dotted lines. If you are using specialized video drivers, perhaps
- the colour table has two complementary indexes which have the same
- colour (unlikely), or:
-
- perhaps your background bitmap is a dithered pattern of two
- complementary indexes, and so drawing the dotted lines merely shifts the
- dither pixels a bit along the line and you can't notice the difference.
- For example, simplify things by saying the background bitmap uses only
- two colours: black (0) or white (1), and the indexes of these colours
- are such that ~black == white. If your background is dithered:
- 010101010101010101
- 101010101010101010
- 010101010101010101
- 101010101010101010
- 010101010101010101
- 101010101010101010
- and you draw a border around the background by inverting (~):
- 010101010101010101
- 110101010101010100
- 000101010101010111
- 111010101010101000
- 001010101010101011
- 101010101010101010
- then you can hardly tell the difference (when the pixels are small enough).
-
- >PS: Anyone with Windows background bitmaps can use them unmodified
- > with WPS. Apparantly, you don't have to convert them to OS/2
- > bitmaps for Lockup and the background to read them. I've
- > currently got the Windows 3.1 "Arcade" backdrop tiled across my
- > desktop with no ill effects (although it's kind of hard to read
- > icon text)
-
- I can confirm this, I've cycled through them all...
-
- >--
- > |) David Charlap "I don't even represent myself
- > /|_ dic5340@hertz.njit.edu sometimes so NJIT is right out!.
- > ((|,)
- > ~|~ Hi! I am a .signature virus, copy me into your .signature file.
-