Re: Graphics on IIgs?

[spector@vax2.concordia.ca (Mitchell Spector)]

In article area51@earthlink.net (Adam Rumack) writes...
>
>I hear people talking about viewing/editing GIF's on their Apple II's, but
>I dont see how this is possible due to the fact the Apple II screens are
>such low res.  Do you use another monitor?  If so, what kind?  In the

        All Apple II's are capable of viewing GIF graphic images, though
the quality will greatly vary depending on the model your using. When
talking about an 8-bit Apple II (II,II+,IIe,IIc,IIc+ or clone) viewing
is quite limited, and to my knowledge there's only one application that
can even support displaying GIF -- Jason Harper's IIGIF. All you have is
High Resolution and Double-High Resolution to work with and in monochrome
these give you either 240x192 or 560x192. This is fine for viewing 1-bit
B&W images (pixels either on or off), such as those from old monochrome
Macs or line-art that's not of too high a resolution.

        Color, however, is quite a different story. You only have up
to 6 colors (HR) or 16 color (DHR), but the real limitation here is that
due to color placement restrictions, you lose a great deal of resolution
and get color bleeding/fringing affects. In color your resolution in both
modes is 140x192 and you generally get a mess due the glitches with the
way color works. In otherwords, it's virtually worthless unless you have
some _very_ simple low-resolution/color GIF images, such as a cartoon scan.
And even then you shouldn't expect much.

        The Apple IIgs is much better suited for viewing GIF images. It
has a true 320x200 and 640x200 (Super High Resolution) mode. I say "true"
in the sense that none of the above restrictions apply, the resolution
doesn't shift when color is used nor are there any bleeding/fringing
side effects when placing colors next to each other. Also you have a
12-bit color palette (4096 colors) which to work with, giving 256 distinct
colors with 16 shades or hues of each color (256 * 16 = 4096). Where the
limitation comes in is the amount of colors that can be used at once on
screen. In the 320 mode, that is up to 16 colors. There are ways to get
more colors on screen, but you must use scanline interrupts. In otherwords,
you split the screen several times vertically. By spliting it 16 times
you can have 256 colors, while doing it 200 times up to 3200 colors. This
sounds impressive, but in fact all you can have are _no more_ than 16
colors horizontally. Think of it as 16 or 200 separate pictures cut out,
and pasted one under the other. Really all we're doing is creating multiple
16 color images going down the screen. Certainly a great trick, but since 
many GIFs use more than 16 colors across, results will vary. Sometimes 
this can work quite nicely, it all depends how many colors are used 
vertically rather than horizontally. 

	Another solution is to use greyscales to view an image. Take 16 
shades of grey (all the colors inbetween absolute white and absolute black) 
and re-create the image this way. This gives you a near photographic quality 
image, but no color of course. PCs and Macs usually use a wider range of 
colors inbetween white and black, giving 256 greyscales. Finally there's 
the 640 mode, but I won't touch on it too much considering only 4 colors are 
usuable in this mode without any restrictions (it can have 16 pure colors per
line using "mini-palettes" and even split the screen as in the 320 mode, but 
all this can get a tad bit more complex than what I described above). In any 
case, the 640 mode generally isn't used for GIF displays, unless your looking
at line art or 2-bit color images. :) There are countless GIF display programs
for the IIgs, the most popular one being Prism 1.0 and recently Convert 3200.

>comp.sys.apple2 FAQ it said that it is not possible to hook up Mac/PC
>monitors to Apple II's, so any feedback about this would be appreciated.

	That information is outdated. With the Second Sight video board,
not only can a modern PC display be connected to an Apple IIe or IIgs,
but you can use it for displaying GIF and JPEG images in TrueColor at
high resolutions (ie, 640x480x16.7 million colors). A Macintosh display
should work as well with certain PC->Mac video adapters linked to the
video card. I have some negative opinions concerning this add-on board,
although my post is already much too long so I'll leave that for another
post in future... ;-)

>  __     __
>/ __ `_' /        ,,,    Adam Rumack
>|[====|||||||||||[:::}   area51@earthlink.net
>\__.-._\          ```    http://www.earthlink.net/~area51

Mitchell Spector
spector@vax2.concordia.ca