[Lowfer] Watering hole lowfers

[JD]

>>> What is your technique of getting those HUGE capture graphics down to 
>>> the 30 Kb ?

Magic!  :-)

Actually, it's a combination of techniques along with a helpful graphics 
program called LView.  LView Pro 2006 is one I bought to be able to process 
images better in 32-bit Windows, but the older 1995 shareware version, LView 
Pro 1.B/16, is actually easier to use for compressing graphics of this sort.

The first thing I do to keep final file sizes down is something you might 
not expect: I let Argo save everything in Windows BMP format.  If you save a 
picture in JPG, then process it in some way and run it through JPEG 
compression again, the artifacts arising from the first compression show up 
as added "detail" (really, noise) in the image, and each subsequent 
compression tries to account for them as if they were legitimate detail. 
This runs the size up a little, and degrades image quality as well. 
Therefore, I keep everything in uncompressed form until the very end.

When prepping a capture for posting, my next step is usually to crop heavily 
to get rid of any detail on screen that isn't needed to tell the story. 
Once in a while, you may have seen some images where I omitted large parts 
of the frequency scale of an Argo capture, for instance.  Solid blocks of 
color or white space don't count so badly against you in JPEG compression, 
but lots of adjacent high-contrast pixels do, so I generally eliminate as 
many extraneous details as I safely can.

(Sometimes I even do a separate version of the image in which I can soften 
the focus, then use MS Paint to help me replace less important areas of the 
waterfall with the softened version, while leaving the portion containing 
the trace at its original sharpness.  It helps to double the image sizes 
first, do the replacement, then shrink back to the original size.  The 
resulting reduction of spatial frequency response means a lot of the 
Discrete Cosine Transform coefficients become insignificant and don't have 
to be accounted for, enabling the compressed file to be smaller.  This 
softening and replacement can be a time consuming process, though, so I 
don't do it very often.)

The final trick is to set the JPEG I/O quality option of the LView software 
for greater compression/lower image fidelity.  Doesn't sound pleasant, but 
if you do it only one time as the very last step, the damage is minimized. 
LView uses a scale of 20 to 95 for image quality, in steps of one unit, with 
a default of 75.  (Many JPEG graphics programs have such a setting, though 
some may use different scales for degree of compression; while others only 
offer a few quality grades.)  I keep the original bitmap open, and re-save 
it in JPG format with progressively lower quality settings until I achieve 
the desired result.  Depending on the size of the image and the amount of 
detail in it, I generally only have to go down to 50-60 units to make a 
typical capture end up at 32 kB or less.  Sometimes I have to go much 
farther, and other times (very small images) I can leave it at the default 
setting.

The latest image is one where I wanted to show large areas around the 
desired traces, including spurious signals, to illustrate the effect the 
increasing static levels had on everything simultaneously.  That precluded 
doing much more cropping, or any softening of detail at all.  The only 
helpful manipulation was a bit of gamma correction to darken the background, 
as I had left Argo's sensitivity relatively high in AGC mode.  That not only 
normalized the appearance, it also reduced the difference between adjoining 
pixels in less bright areas of the image, enhancing compression efficiency 
slightly.  However, that still didn't allow a whole lot of reduction, so 
this time it was mainly brute force--the first time I've ever had to go all 
the way down to 20 units on the compression quality setting.  But since the 
image had remained uncompressed in all steps prior to the end, I think it 
didn't turn out too badly.

Hope that helps answer the question without being too boring.

John