[Please, note the Newsgroups.]

Recent discussion about XV's problems were held in some newsgroup.
Here is some text users of XV might find interesting.
I have added more to text to this collection article, so read on, even
you so my articles a while ago.

I hope author of XV corrects those problems as best he can, so fine
program XV is that it is worth of improving.
(I have also minor ideas for 24bit XV, e-mail me for them.)

Any misundertanding of mine is understandable.


Juhana Kouhia


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Note that 'xv' saves only 8bit/rasterized images; that means that
the saved jpegs are just like jpeg-to-gif-to-jpeg quality.
Also, there's three kind of 8bit quantizers; your final image quality
depends on them too.
 
This were the situation when I read jpeg FAQ a while ago.
 
IMHO, it is design error of 'xv'; there should not be such confusing
errors in programs.
There's two errors:
  -xv allows the saving of 8bit/rasterized image as jpeg even the
   original is 24bit -- saving 8bit/rasterized image instead of
   original 24bit should be a special case
  -xv allows saving the 8bit/rasterized image made with any quantizer
   -- the main case should be that 'xv' quantizes the image with the
   best quantizer available before saving the image to a file; lousier
   quantizers should be just for viewing purposes (and a special cases
   in saving the image, if at all)
 
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It is limit of *XV*, but not limit of design.
It is error in design.
It is error that 8bit/quantized/rasterized images are stored as jpegs;
jpeg is not designed to that.

As matter of fact, I'm sure when XV were designed 24bit displays were
known. It is not bad error to program a program for 8bit images only
at that time, but when 24bit image formats are included to program the
whole design should be changed to support 24bit images.
That were not done and now we have
 -the program violate jpeg design (and any 24bit image format)
 -the program has human interface errors.

Otherway is to drop saving images as jpegs or any 24bit format without
clearly saying that it is special case and not expected in normal use.

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Some new items follows.

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I have seen that XV quantizes the image sometimes poorly with -best24
option than with default option we have.
The reason surely is the quantizer used as -best24; it is (surprise)
the same than used in ppmquant.

If you remember, I have tested some quantizers. In that test I found
that rlequant (with default) is best, then comes djpeg, fbmquant, xv
(our default) in that order. In my test ppmquant suggeeded very poorly
-- it actually gave image with bad artifacts.

I don't know is ppmquant improved any, but I expect no.
So, use of XV's -best24 option is not very good idea.

I suggest that author of XV changes the quantizer to the one used in
rlequant -- I'm sure rle-people gives permission.
(Another could be one used in ImageMagick; I have not tested it, so I
can say nothing about it.)

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Some minor bugs in human interface are:

Key pressings and cursor clicks goes to a buffer; Often it happens
that I make click errors or press keyboard when cursor is in the wrong
place. It is very annoying when you have waited image to come about
five minutes and then it is gone away immediately.
The buffer should be cleaned when the image is complete.

Also, good idea is to wait few seconds before activating keyboard
and mouse for XV after the image is completed.
Often it happens that image pops to the screen quickly, just when
I'm writing something with editor or such. Those key pressings
then go to XV and image has gone or something weird.

In the color editor, when I turn a color meter and release it, XV
updates the images. It is impossible to change all RGB values first
and then get the updated image. It is annoying wait image to be
updated when the setting are not ready yet.
I suggest of adding an 'apply' button to update the exchanges done.