Re: pdfcairo terminal; seams between bars in the colorbox

[Dima K. <gn...@di...>]

Ethan A Merritt <me...@uw...> writes:

>> The patches I'm proposing are here:
>> 
>>   https://github.com/dkogan/gnuplot/tree/colorbox_smooth
>
> I do not know how to generate the relevant patches via github. It
> says: "master and colorbox_smooth are entirely different commit
> histories" Could you please send me the relevant patch series as
> generated by "git format-patch"?

I'm only two patches out-of-date:

  dima@shorty:~/projects/gnuplot$ git show-branch HEAD origin/master
  ! [HEAD] smooth colorbox: render as a bitmap if the terminal supports it
   ! [origin/master] Do not report terminal type to user until after initialization is complete
  --
  +  [HEAD] smooth colorbox: render as a bitmap if the terminal supports it
  +  [HEAD^] no-op cleanup: consolidated next-colorbox-slice logic
  +  [HEAD~2] no-op cleanup: consolidated draw-colorbox-slice logic
  +  [HEAD~3] no-op cleanup: consolidated colorbox bounds logic
  +  [HEAD~4] no-op cleanup: consolidated steps-in-colorbox logic
   + [origin/master] Do not report terminal type to user until after initialization is complete
   + [origin/master^] VMS cleanup
  ++ [HEAD~5] qt:  qt4 was apparently weak at int->double promotion

I'm attaching the patches to this email.


> OK. The other alternative is to make this specific to cairopdf. Unless
> you know of other terminals that suffer from the same problem?

Actually.... You're right. It's only semi-related to THIS discussion,
but let me bring that up.

The svg terminal currently produces images with no image-rendering
annotations. And most browsers render images with bilinear interpolation
by default, which makes low-res images look very wrong. I looked at this
a while back, and, there was no browser-independent way to turn that
off. And I think there still isn't. I'm attaching an svg of this gnuplot
script made WITH the new patches AND by manually adding
image-rendering="crisp-edges" to it:

  set output "/tmp/tst-colorbox-log.svg"
  set terminal svg
  set palette maxcolors 5
  set logscale cb
  set cbrange [1:10]
  plot 5 with points palette

If you open that in firefox, it should look good, but if you open it in
chrome, it won't. To make it work in chrome, "crisp-edges" needs to
become "pixelated". I don't know how to make it work with both. So if we
can fix this, I'd say we should do the colorbox-image thing whenever
available. But if we can't, maybe limiting it to only cairopdf (or NOT
svg) is the answer.

Let me ask a web-dev friend about how to make svg work right in all
browsers. There's probably a way.

The current set of attached patches does NOT limit itself to cairopdf


>> I don't see this. I'm looking at
>> 
>>   https://gnuplot.sourceforge.net/demo/heatmaps.html
>
> That is the png version; it doesn't show the effect I'm talking about.
> Have a look at the svg version
>     https://gnuplot.sourceforge.net/demo_svg/heatmaps.html
>
> In particular the plot with title
>     Compare "image" and "image pixels"

Ah yes. This is exactly what I mentioned above. I don't remember any
terminal other than svg having this problem. But I certainly haven't
touched all of them.