Image Processing Operations
 
The AVT system offers a number of specialized image processing operations
the are optimized for use with slow scan images; These are generally
available in the RoboSynth window, and when you press the "Lcor" button
that is actually IN the RoboSynth window - that opens yet another
process window with some very, VERY nice goodies in it.

Let's stick to the RoboSynth window for the moment, however.

In here you will find Four transmit convert buttons (discussed in the
file headed RobotColor.doc, along with the post-receive tint
control). You will also find a button headed "Luma". This button takes the
contents of the Red, Green, and Blue buffers and creates a Black and white
image according to the forumla used for NTSC composite images: 59% from the
green buffer, 30% from the red buffer, and 11% from the blue buffer. This
has two effects; One obvious (it makes it black and white) and the other
not so obvious: it makes a smoothed image from a color one that may have
been quite rough.

You will also notice two sets of arrow buttons. One pair has small "b"'s in
them, and the other has small "c"'s. In the center of these four arrows
are three small square buttons labled "H", "N" and "Z".

The Arrows are for stepping the brightness and contrast up and down,
the "H" button generates a histogram, the "Z" button allows you to
"zoom in" on an image, and the "N" creates the color or B&W negative
of the image. For all of these operations, you MUST be in the correct
resolution and color/bw setting, or you may get a surprise!

Like most functions in the AVT system, if you are in B&W, then the contrast
and brightness functions, the histogram, image negative, and the zoom only
affect that particular buffer - red, green OR blue. If you are in color,
all three of the red, green and blue are affected, and the color image
is redrawn for you when the operation is completed.

As a reminder, if any of the following buttons are "lit", you are in
color:

CMP   AVT   111   25.5    51     102

Otherwise, you are in black and white. If you WANT to be in black and white,
then make sure that the correct button of the RED, GREEN, and BLUE buttons
is selected BEFORE you attempt one of these operations.

If any of these buttons are lit, you are in HIGH resolution:

36/24   72/36  90/17a   34   *94/17b   51   102

Otherwise, you are in low resolution.

Tinting

Another control available in the RoboSynth window is the "Post-receive
tint control". This control is for adjusting the effective receive
frequency after you have received a Robot color image.

For instance, let's say you receive a Robot color (12,24, 36, or 72)
image, and it's a little bit too red. Open this window, and press the
left mouse button with the pointer positioned to the right of the knob
in the tint control - this is the side marked "green". Click the left
button once. Now wait a few moments... watch for the process cursor
to travel down the left side of the screen. When the knob "snaps"
back to the center, it's done - and you can do it again, of you like.
Until the knob snaps back, you should NOT touch it again - it can be
quite confusing if you ask it to queue up several tint operations.

You can also drag the knob a fair distance in either direction, and
then release it - that will heavily tint the image.

What about other types of images, like AVT images?

You can use the tint control on them, too, but first you'll need
to do a synthesize on them. We suggest, for tint purposes, that you
only use the 24 second synthesis for lo-res (24 sec AVT, etc) and the
72 second synthesis for hi-res (90 sec AVT). You can not use the
tint control on 94 second AVT images - the format is incompatible
with the robot x:y formats.

Once synthesized, the image can be treated as if it was a newly
received Robot-format image - which, in effect, it is. You'll notice
the loss of resolution that is the Robot's virtual signature on
an image. The composite format reduces by at least 1/2 the amount
of color information in an image - and that's in the 24 and 72
second modes. In the 12 and 36 second modes, color information is
a mere 1/4 of that contained in an AVT image. But, if you want to
tint, this is the way to accomplish it within the program.

Line Correction

If you press the "Lcor" button, a new window opens and you have a number
of Image processing tools available to you that have to do with single
line error correction (hence the name - Lcor = Line CORection).

The first thing to notice is the small "keypad" of arrow keys, with
the square button in the center. The up and down arrows (and the up and
down cursor keys on the kbd, if you prefer) move a small cursor up and
down along side the image you are working on. If you press the square
button in the center of the keypad, then this action is multiplied - the
small white cursor moves in ten line steps instead of 1 line steps.

The right and left arrows (and the right and left on the keyboard) actually
shift the line you are on to the right or left - you can correct many of the
positioning errors that are inherent in the old, error-prone protocols
like Robot composite color, and 8 second B&W.

In addition, the action of the center shift button is duplicated by the
ENTER key on the numeric keypad - note that this is NOT the "RETURN" key
on the main keyboard.

That does something else, of course, as you will see in a moment.

Look at the right edge of the window. You will see three small buttons.
Two have small 'c's adjacent to arrows in them, and one has a line with
two arrows pointing at it.

The 'c' buttons are line-copy buttons. They cause the line below or above
the line that the cursor is on to be copied into the current line.

The line with the two arrows pointing at the line in the center is a
line synthsize initiator. This causes the line that the cursor is
positioned upon to be completely replaced with a line that was
created from the average of the line above it and the line below it.
Try each of these three options on each line you want to be working on,
see which works best for you.

You'll also see a button labled "Shft". This is for use with the 
Line-sequential modes such as Volker-Wrasse or WA7WOD's line sequential
modes (25.5, 50,102). If you receive an image that seems to go to some
wild (and WRONG) color combination in the middle of the image, bring up
the window, move the cursor to the scan line where the problem occurs,
and press the Shft button once or twice. That should clear it up.

You may find that you might have to do that multiple times in order to
completely clean up the image, but it's quite easy to do.

The RETURN key on the keyboard does this too, when this window is open.

There are three pairs of arrows, red green and blue. These move the
red, green or blue memories contents down or up on scan line each time
they are pressed. This is useful after receiving an RGB image which has
lost a line, that is, it's one line shorter due to QRM or whatever.

These functions are available from the keyboard also, on the numeric
pad - the 7-8 are red-up and red-down, the 4-5 are green-up and green-down,
and the 1-2 are the blue-up and the blue-down.

In addition, the two copy and the synthesize options are available from
the three keys at the top right of the numeric keypad. The 9 is copy
down, the 6 is copy up, and the 3 is synthsize.

Remember that you can use the Amiga programs "Butcher" and PixMate" to
do REALLY heavy-duty image processiing work for you; But these operations
are specific to SSTV, and are unlikely to be included in a standard
image processing suite.