# [l2h] Math formula background color?

Philipp K. Janert, Ph.D. janert at ieee.org
Mon May 1 07:01:35 CEST 2006

No, there are no black bars on the left/bottom
in this example. I have seen them before though,
in a similar situation.

Is there anything I can/should do to make sure
the image backgrounds are successfully turned
does not help.

Best,

Ph.

On Sunday 30 April 2006 21:47, you wrote:
> On 01/05/2006, at 2:18 PM, Philipp K. Janert, Ph.D. wrote:
> > At the end of this message is a trivial latex file.
> > It contains three display formulas, all essentially
> > the same, except for the specific way the absolute
> > value is designated: once simply using |...|, once
> > using \left|...\right|, and once using \bigl|...\bigr|.
> >
> > The file compiles without problem under pdflatex.
> > I also compiles under latex2html  and images are
> > generated for all three formulas. However, the last
> > one (and only the last one) shows up on a gray
> > background.
>
> Is there not also a black line, remnant of the
> cropping-bar, either along the left or bottom edge ?
>
> What has happened is that the image-processing software
> has not been able to accurately determine that the
> gray background should become transparent.
>
>
> The other images probably have gray backgrounds too,
> but with these, the gray was correctly identified as
> being background, so was made transparent.
>
> > \usepackage{amsmath}
> > to the preamble makes this problem go away, and
> > all generated images are now on white (transparent)
> > background.
>
>   white  is  not the same as  transparent.
> Any colour can be specified to be transparent.
>
> > I wonder why this is?
>
> The difference with  ams-math  could be due to a bit
> of extra space around the | | symbols.
>
> To check for such minute differences, run the job
> with  -debug  after deleting the image files.
>
> Now when they are recreated, the temporary files
> will not be erased. Have a look at these, to see
> how the cropping-bars are used to control the exact
> sizes of the images. Look at them enlarged, to see
> whether you are getting a solid row or column of black
> pixels, before the bars are removed.
>
> Then check whether there is a solid row of gray,
> before the background of the next image becomes
> transparent.
>
> > I could understand that something would fail entirely
> > to compile if a required package (such as amsmat)
> > was not loaded - but everything compiles fine, no
> > matter whether amsmath is loaded or not. But why
> > would the absence of a required package change
> > the background color for a formula image, which is
> > otherwise generated correctly?
>
> It has nothing to do with packages and expansions of
> macros, except insofar as the amount of typesetting
> space around some symbols may vary slightly.
>
> > Best regards,
> >
> > 			Ph.
>
> Hope this helps,
>
> 	Ross Moore
>
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> Ross Moore                                         ross at maths.mq.edu.au
> Mathematics Department                             office: E7A-419
> Macquarie University                               tel: +61 +2 9850 8955
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