[l2h] Black bars under integral signs when thelimitsof integration are -\infty and +\infty or analgebraicfraction for each of the upper and lower limits

[Pat Somerville]

Thanks, Professor Ross Moore, for kindly writing to me on the mechanisms for 
the production and elimination of cropping bars.  And thanks for mentioning 
the program MathJax to me.  In an online form I wrote to someone involved 
with MathJax with some questions for him or her to see if MathJax can be 
used for the applications of printing mathematics onto paper and what 
amounts to sending an e-mail letter body with the .html file containing 
mathematics pasted onto it with the images in that letter as attachments to 
it.--Those two activities have been my primary end uses so far of the 
programs LaTeX for printing and LaTeX2HTML with the images as attachments to 
the e-mail letter.  It is good that MathJax can handle LaTeX commands and 
uses open-source code; therefore I assume it would be provided free of 
charge.  Also I think it is very honorable of you, since you have worked so 
much on the program LaTeX2HTML, to mention and suggest another program 
MathJax which performs the similar basic function, although in a somewhat 
different way, of making mathematical symbols capable of being displayed on 
Web pages.  Some people might even consider that surprising.  But I think it 
speaks well of you, Professor Moore.  And thanks for your contributions to 
LaTeX2HTML, which has been a useful, free program for me!  Thanks for your 
kindly provided help, Professor Moore!

Pat

--------------------------------------------------
From: "Ross Moore" <ross.moore at mq.edu.au>
Sent: Friday, April 15, 2011 2:24 AM
To: "Pat Somerville" <l_pat_s at hotmail.com>
Cc: "Latex2Hmtl list" <latex2html at tug.org>
Subject: Re: [l2h] Black bars under integral signs when thelimitsof 
integration are -\infty and +\infty or analgebraicfraction for each of the 
upper and lower limits

> Hello Pat,
>
> On 15/04/2011, at 2:42 PM, Pat Somerville wrote:
>
>
>> In GIMP I could see that the right-hand portion of the upper limit of 
>> positive infinity was either right at the right-hand edge of the 
>> dash-lined box surrounding the image or perhaps was cut off there; I'm 
>> not sure.
>
>> Can you or someone explain to me the mechanisms in detail that cause the 
>> unwanted black line segments to be generated?  So far I know from you, 
>> Dr. Takeno, that if a mathematical expression inside an image would 
>> otherwise extend beyond the right border of the image, somehow the black 
>> line segment was generated underneath the image.  You explained something 
>> about the first step of the cropping procedure which was involved.
>
> The problem that needs to be solved is to align images inline,
> so that they appear to sit nicely on the baseline when viewed
> in a web-browser.
>
> However, HTML only allows vertical alignments of:
>  "top", "bottom" and "middle".
>
> Thus it is "middle" alignment which must be used.
> But to do this, there often needs to be sufficiently much
> white-space below the baseline, to balance what is above it.
> That is, the baseline has to be seen to be exactly in the
> middle of the image.
>
> The image is typeset on a smallish page, but not all of this
> is actually needed, so first some excess white-space must be
> cropped away. But you cannot crop all of it, else the middle
> alignment will not do what is required.
>
> Hence part of the image needs to be (at least part of) a frame,
> that encompasses the full height, depth and width that is required.
> This is the "black bars" that you see, when a step in the process
> does not work as intended.
>
> The TeX coding in  images.tex  is designed to produce those black
> bars at exactly the right place so that they enclose neatly the
> full image plus the correct amount of white-space padding so that
> the final image will align appropriately, after:
>
>  1.  crop away excess whitespace
>  2.  crop away the "black bar" at the bottom
>  3.  crop away the "black bar" at the left side
>
> However, because colours can be used, both for the image content
> and the background, and different scale factors can be chosen,
> achieving the correct amount of cropping is not as easy as you
> might think it should be.
>
> It is done by cropping away whole rows and columns that are all
> of the same colour.
>
> Normally it will be "white" for step 1., leaving behind a rectangle
> including the "black bars" --- "cropping bars" is a better term.
>
> Then for steps 2. & 3. the bottom and left-side cropping bars
> are removed "provided" the whole row (or column) is indeed all
> of the same colour --- usually black.
>
> Mostly this works pretty well, but it relies on the assumption
> that the cropping bars do indeed enclose the full contents
> that are to be shown. It is when this assumption is not actually
> true that the black bars will remain.
>
> Your example failed presumably because the width when TeX typesets
> an \hbox  containing  \int_{-\infty}^{\infty}  has one of the
> limits actually protruding outside the final box dimensions, by more
> than the extra tolerance that LaTeX2HTML allows for the lengths
> of the cropping bars.
>
>>
>> I just guess from what you wrote, Dr. Takeno, that the script eqnfix.sh 
>> obtained from http://www.vyvy.org/main/en/node/102 on the Internet  might 
>> not have been able to eliminate the black line segment under my integral 
>> sign due to a piece of the upper limit that otherwise would have extended 
>> beyond the right border of the .png image.
>
> Yes. Adding that extra \hspace{...} presumably expands the width
> of the typeset \hbox (described above).
>
> You should be able to do it also using a TeX \phantom  :
> viz.
>     $\int_{-\infty}^{\infty} \phantom{dx}$
>
> But this might be too wide, so just adding a bit of extra space
> would probably do:
>                    $\int_{-\infty}^{\infty}\;$
>
> Similarly forcing extra space, either vertically or horizontally,
> can be the best solution in other circumstances too;
> e.g. when using fancy fonts with twirls and swashes, such as
> with Zapf Chancery, or calligraphic styles.
>
>>
>> Thanks, Professor Ross Moore, for suggesting I use the -debug option in a 
>> latex2html command.
>>
>
>
> While LaTeX2HTML is quite good for producing websites based on LaTeX
> content --- I spent many man-hours working on it, along with others,
> back in the 1990s and early this century --- it is now rather dated.
>
> The software that you should be looking at for 21st century websites
> is called MathJAX.
>                    http://www.mathjax.org/
>
> By Googling around, you should be able to find lots of articles
> that decry the use of images of bit of mathematics.
> It is better to get the browser to do proper TeX-based typesetting
> using JavaScript, or other sophisticated scripting language.
> However not all web browser software can support this.  :-(
>
> This has always been the case, since the mid-1990s.
> MathJAX is the best supported solution so far.
>
>
> Hope this helps,
>
> Ross
>
> ------------------------------------------------------------------------
> Ross Moore                                       ross.moore at mq.edu.au
> Mathematics Department                           office: E7A-419
> Macquarie University                             tel: +61 (0)2 9850 8955
> Sydney, Australia  2109                          fax: +61 (0)2 9850 8114
> ------------------------------------------------------------------------
>
>
>
>