A Few Words About H.A.M.
by Mike Levin
Original source: The Blitter, Journal of the Philadelphia Amiga
Users' Group. 3/92


The problem with H.A.M. mode mostly lies in its name. I mean, who
wants to work in a graphics mode named after pork? I prefer the more
dignified expanded name, Hold-And-Modify. But, the 2 terms will be
used synonymously in this article. The article assumes some basic
experience with the Amiga Computer and graphics programs such as
Deluxe Paint 4 or Digi-Paint 3. 

I will resist the temptation to delve into a full-blown explanation
of Hold-And-Modify. Instead, I will discuss why someone might choose
working with it. But some explanation of this mysterious and under-
utilized graphics mode is in order.

Hold-And-Modify is a graphics mode. It is not necessarily a
resolution. You might refer to a particular resolution as 640x400 or
320x200. H.A.M. mode will expand your capabilities on a 320x200 or a
230x400 resolution screen to be able to use any (or all) of the
Amiga's 4096 colors on-screen simultaneously.

Try not to be overwhelmed or confused with your choices of graphics
resolutions and modes on the Amiga. It is quite imposing at first but
after tackling a few projects, you will start to get a feel for which
modes to use when and how they behave. I have done numerous
professional projects recently and had to make some tough decisions.
I have come out of it with a much higher regard for H.A.M. mode than
I held previously.

Certain features and draw-backs characterize each mode. You must make
the decision which one is appropriate for your task. Further, an
artist or designer can "bring" a great deal to the graphics mode.
Once you have a command over it's properties and nuances, you can
often transcend what you would imagine possible. How many times have
you marvelled at a 32 color 320x200 image by Dave Johnson or Jim
Sachs?

Here, I will deal with H.A.M. mode in the 320x400 resolution. First,
I'll tell you the things which scare most people away (in my
experience). H.A.M. mode can seem strange and unpredictable. It's
plagued with "fringing" problems where undesired colors appear along
the right-most boundaries of graphic elements on your screen. You are
limited to either the Amiga's lowest resolution (i.e. the largest
pixels) or a resolution with pixels having the aspect ratio of bricks
which is also is prone to flicker. This makes dealing with letters on
the screen quite challenging. 

The use of H.A.M. mode has largely been confined to the distribution
and viewing of digitized pictures. It allows the lowest-end of Amigas
to display often startling pictures. This was popularized by our old
friends, NewTek with the Digi-View package. The first popular H.A.M.
paint program was NewTek's Digi-Paint. The idea behind producing
these startling picture files was to digitize in much more
information than the computer could actually display, and have the
software generate the best possible rendering of this information in
H.A.M. mode.

Well, the tools have gone FAR beyond that point. I have settled on 2
decisive tools for working with Hold-And-Modify: Deluxe Paint 4 and
DCTV. Deluxe Paint (DPaint) support is one of the best things to
happen to H.A.M. mode. With all-due respect to the true pioneers of
H.A.M. (NewTek), Deluxe Paint, in my opinion, has made H.A.M. usable.
Some would argue that this is because I have never reached the level
of expertise with Digi-Paint as I have with DPaint. Maybe this is
true and you should take my opinion in that light.

DCTV lets you work with large color palette images in a phenomenal
painting environment without worrying about any of the H.A.M.
limitations. With DCTV, you are working on a composite monitor with
images which - although blurrier than on an RGB monitor or the
Toaster's composite output - seem to defy resolution. You get the
feeling of unbridled creative ability. When you are done working on
the image, DCTV features very respective image processing/conversion
software which will let you convert your DCTV work into Hold-And-
Modify mode.

This is where the all-important color palette must be considered.
This is important because only your first 16 chosen colors can be
used on your H.A.M. screen without fear of unusual "artifacting." All
other colors on your H.A.M. screen will be derived from the first 16.
It is usually good to have a maximum white and a maximum black in
your color palette.

If you already have a color palette, you will usually want to load it
into the DCTV conversion software and use the "keep" option to keep
those colors in the main palette. If you don't do this, there is a
"Remap" feature of Deluxe Paint that can compensate.

When you are working with H.A.M. mode, you are not dealing with
precision. Compromise is the rule. You will sometimes just never get
the exact color in the exact location which you want. H.A.M. mode can
be considered a "painterly" environment where you are dealing with
paint and brushes,and you just can't have the calculated exactness
you might expect with computer graphics.

Why would someone ever willingly choose to work in H.A.M. mode on the
Amiga? Because you can use LOTS of colors! The images you create can
pass for 24 bit images to the untrained eye - especially on a
composite monitor. The files can each be well under 100 kilobytes for
a full-screen color image. This is minuscule compared to the
equivalent 24 bit image. That means quicker disk drive access times,
less space used on the disk, less time on the phone downloading, and
less memory required by the computer.

It means that applications using lots of color images can still be
distributed on a reasonable amount of floppy diskettes. It means that
an Amiga-exclusive image library on CD-ROM can be increased over
other platforms for the comparable images by a (minimum) factor of 4.
This would yield roughly 5000 images on your standard CDTV disk.

It means you can design graphics for the lowest common denominator of
Amigas and you can be sure that your 4096 color image can show on the
entire installed base of over 3 million computers. This is all
because the Amiga with 6 bitplanes can simulate 12 bitplanes with a
sacrifice of the horizontal resolution. 

6 bitplanes should usually yield a maximum of 64 colors. The Amiga
uses it to display 4096 colors! You can call H.A.M. mode a
"discovered" graphics mode. Some of my conversations with the Amiga's
founders indicated that they knew such a graphics mode was possible,
but it was the developers who really established it. This is exactly
the sort of thing which makes the Amiga such an exciting platform.

I will often refer to "equivalent images." It includes full-screen
color images displayed with other systems in 8 bit (and sometimes 24
bit) mode. H.A.M. image files don't have the same usefulness as 24
bit image files for single-frame-recording to film or video. But,
wherever images are intended for direct viewing from the computer,
the comparison of "equivalent" images is valid.

From a designer's point of view (in developing applications such as
kiosks and information retrieval systems), you can work with images
on your Amiga development system and know that any Amiga delivery
system you choose will be capable of displaying those images. It will
look largely the same on the delivery system's monitor as on your's;
no concern about graphics cards, no concern about size of monitor.
Work on an A3000 Tower. Deliver on a CDTV! H.A.M. can often outshine
more expensive alternatives, is available on the tiniest of Amigas,
and can easily be displayed on television monitors.

Since it's so easy to hook televisions to Amigas, you can always
monitor how your images are going to look when displayed on TV
monitors. There are no surprises. You will know when you are
doing things which will create flicker and chroma-crawl. And, your
choices for delivery system display devices are both inexpensive
(normal televisions or RGB monitors) and broad. 

Let's not forget animation! If all other arguments for H.A.M. mode
fail, you can always pull out the fact that your average Amiga can
animate 4096 color images at near 30 frames-per-second with none of
that "tearing" and visible screen redraw other systems demonstrate
when trying to animate equivalent images. 

With H.A.M. mode and data compression, the Amiga can load seemingly
prohibitive amounts of animation data into RAM or stream it off of a
hard drive. Try animating 8 bit full-screen images at 30 fps on other
systems. The solution is usually to frame-record to video, to cut a
lasererdisc, and then to have the computer control the laserdisc!
Yeah - really! The other option is to shrink the animation on the
screen down to about postage-stamp size.

There are few other ways than H.A.M. mode on the Amiga (on such
inexpensive systems) to preview such things as 3D full-screen
animation before rendering 24 bitplane files and single-frame-
recording. How are you going to catch mistakes, get a feel for
continuity, and the subtleties of movement? A H.A.M. mode 30 fps
full-screen animated preview is unique to the Amiga. For some
applications, this "preview" animation is good enough. You can play
it directly off of the hard drive or record it real-time directly to
video without frame-recording!

Many of the H.A.M. related problems can be solved in the planning
stages of a project. Choose your colors carefully (and for reasons).
Decide exactly what your job is. Are you simply displaying digitized
pictures or are you designing the main screen of a kiosk? Are you
going to be doing image-compositing? Are you going to be using text
on the screen?

There are two methods for dealing with text on a H.A.M. screen. The
methods can be used in conjunction. First, select your font
carefully. Some programs such as DCTV Paint will adjust the font
pixel ratio for appropriate appearance in H.A.M. mode. Deluxe Paint
does not do this, so you might (for the sake of ease) want to choose
a font which is normally "condensed" such as the CompuGraphic
Triumvirate Condensed font. When displayed in H.A.M. mode, it will
become expanded and will look like a different, but still correct
font. 

This method still does not solve the "jaggies" caused by low-
resolution graphics. This makes text look unprofessional and leads us
to the second method. You can draw everything much bigger than it is
ultimately intended and then shrink it down with software that can
antialias. This will smooth the text and integrate it into the
background with little H.A.M. fringing. 

To accomplish this in Deluxe Paint 4, you would switch to your spare
screen, choose a big size typeface, type your text, cut it out as a
brush with your background transparent, choose: brush/size/double
vertical, turn antialias level to "high," switch back to your H.A.M.
image screen, turn perspective on, hold the "Ctrl" key down, and move
your mouse to get the appropriate size. You would then let go of the
"Ctrl" key and stamp the brush down. 

It may take several tries to get exactly the clarity you want. A good
idea is to fix the background so that you can rapidly clear your
unsuccessful attempts without the risk of accidentally changing your
image. You may also want to outline your text brush with an
additional color. You can do this by selecting that as your
foreground color and selecting: Brush/Edge/Outline. This will work
even when in perspective mode!

If you know you are going to be using a lot of type and don't want to
give each screen this kind of special attention, I recommend using
the first method. You can design your screens to have a special place
where text will always appear. You would choose one of your basic 16
colors as the background color for this area and another of those
colors for the text itself. This will avoid any H.A.M. fringing
problems on the text. A 3rd color out of your basic 16 can also be
used for text shadows or outlines.

The new Art Department Professional from ASDG also has the ability to
put text onto a H.A.M. image. This may be an option for people not
able to develop the DPaint skills. Also, you may work with text on
your image in DCTV mode before the conversion to Hold-And-Modify.
This can often accomplish nicely antilaliased smooth fonts.
Generally, try not to go much smaller than a 24 point font on a
H.A.M. screen.

When you load brushes into DPaint 4 while working in Hold-And-Modify
mode, they will look incorrect. Fix this by going to the
Colors/Brush/Remap option. Correct the aspect ratio of the brush
(when needed) by going to the Brush/Size/Double Vertical option.
Compositing images may be accomplished in this way.

If you really want to be sold on H.A.M. mode, learn the new color
range functions of Deluxe Paint 4. Try out some of the gradient fill
options. Cut out some brushes on a H.A.M. screen, turn translucency
on, and stamp the brushes down on top of other objects. Everything
is, of course, much nicer on an accelerated machine.

My latest project was demonstrated at the March Philadelphia Amiga
Users' Group meeting. It consisted of 2 full-screen H.A.M. images
(one of them color-cycled), 19 1/4 screen H.A.M. brushes, 4 sizable
animations, and the extended use of animated text (and music, of
course). It was authored and composited with SCALA. The entire
application - images, animations and all - fit onto 2 floppy
diskettes with room to spare. It was one of my most ambitious
projects.

I chose Hold-And-Modify mode early on in the project and was very
happy with my decision. The project was the high-impact demonstration
of CommodoreŽ: The Marketing Plan which was published in the February
issue of the Philadelphia Amiga Users' Group's newsletter, The
Blitter. It is now made to install onto any Amiga with a hard drive.
It is fully interactive, but when left unattended, it's default
automated timing takes over. Even the highlighting of highly detailed
buttons is handled in H.A.M. mode. It will make for excellent user
group demo material when released. Keep an eye out for it.