Hi Peter,
On 30/10/2004, at 1:31 AM, Peter Morling wrote:
*** processing 1 images ***
The script that is being run now is pstoimg :
Debug (syswait): Running "C:\Perl\bin\perl.exe
C:\usr\local\l2h\bin\pstoimg.bat
-type gif -debug -tmp C:\Temp\l2h2116 -discard -scale 1.6 -geometry
26x16 -margi
ns 126,72 -crop abls -transparent -out img1.gif C:\Temp\l2h2116\image001.ps"
at C:\usr\local\l2h\bin/latex2html.bat line 4249
This is a Perl script that comes with LaTeX2HTML. You can read it and follow its logic, to correlate the messages with the program-flow.
Running "C:\usr\local\bin\pnmcrop.exe -verbose < C:\Temp\l2h2116\p1408.pnm > C:\Temp\l2h2116\p1408.t01"
C:\usr\local\bin\pnmcrop.exe: Background color is #0000b3 C:\usr\local\bin\pnmcrop.exe: cropping 2 rows off the top C:\usr\local\bin\pnmcrop.exe: cropping 2 rows off the bottom C:\usr\local\bin\pnmcrop.exe: cropping 1 col off the left C:\usr\local\bin\pnmcrop.exe: cropping 3 cols off the right C:\usr\local\bin\pnmcrop.exe: Background color is #000000
At this point, the image should have been cropped to just snugly include the "cropping-bars" (or justification bars).
This step means that LaTeX2HTML doesn't need to know "exactly" where the ink is on the page, omly that it indeed is within the rectangular graphic produced by dvips and Ghostscript. That way we don't need to worry about variability with software versions, or that different fonts may be being used on different platforms.
Next the cropping-bars are removed:
Running "C:\usr\local\bin\pnmcrop.exe -verbose -bot -sides < C:\Temp\l2h2116\p1408.pnm > C:\Temp\l2h2116\p1408.t02"
C:\usr\local\bin\pnmcrop.exe: Not cropping. No border found. C:\usr\local\bin\pnmcrop.exe: Background color is #000000
Hmm; failure to remove the bottom bar should mean that the bottom row of pixels is not all of the same colour (usually black).
That happens when the font-metrics are not such as to correctly include all of the "ink" within the rectangle described by the metric information.
This sometimes happens at the right-hand end, with math symbols
that are "curvy", such as script letters. Adding an extra \, in the LaTeX
is generally enough to fix it.
Alternatively, it could be that the cropping-bars themselves do not meet exactly at the left-hand end.
Running "C:\usr\local\bin\pnmcrop.exe -verbose -l -sides < C:\Temp\l2h2116\p1408.pnm > C:\Temp\l2h2116\p1408.t03"
Image "C:\Temp\l2h2116\p1408.pnm" is PGM, 46x35 C:\usr\local\bin\pnmcrop.exe: cropping 2 cols off the left C:\usr\local\bin\pnmcrop.exe: Background color is #0000b3
Having used the -debug switch, you should be able to look at the temporary bitmap images: p1408.t01 p1408.t02 p1408.t03 etc. to see what went wrong.
(The process number, 1408 here, will be different each time.)
One final "shaving" crop is done along the bottom edge:
Running "C:\usr\local\bin\pnmcrop.exe -verbose -sides -bot < C:\Temp\l2h2116\p1408.pnm > C:\Temp\l2h2116\p1408.t04" Image "C:\Temp\l2h2116\p1408.t04" is PGM, 46x34
C:\usr\local\bin\pnmcrop.exe: cropping 1 row off the bottom
... just in case there are 1 or 2 rows of all-white pixels there. This is to ensure that text without descenders sit snugly on the baseline, rather than a little above it.
If this "shave" removes too much, then it's assumed that all that white space is required --- the unshaved image is used instead.
Image "C:\Temp\l2h2116\p1408.pnm" is PGM, 46x34
Running "C:\usr\local\bin\ppmquant.exe 256 < C:\Temp\l2h2116\p1408.pnm >
C:\Temp\l2h2116\p1408.t05"
C:\usr\local\bin\ppmquant.exe: making histogram... C:\usr\local\bin\ppmquant.exe: 2 colors found C:\usr\local\bin\ppmquant.exe: choosing 256 colors... C:\usr\local\bin\ppmquant.exe: mapping image to new colors...
Running "C:\usr\local\bin\ppmtogif.exe -trans #ffffff < C:\Temp\l2h2116\p1408.pnm > img1.gif" pstoimg.bat: Written img1.gif
C:\usr\local\bin\ppmtogif.exe: computing colormap... C:\usr\local\bin\ppmtogif.exe: 2 colors found
(img1.gif is attached)
Why is the gif created from p1408.pnm ? And not one of the .pnm files that
are cropped?
There is a renaming of the final temporary file back to the standard .pnm name.
In the pstoimg script, you'll see that the various graphics utilities are
called via:
&do_cmd($in,$tmp,$cmd) || return 0;
The coding in sub do_cmd includes a Rename call, so that the input and output files have the standard .pnm name.
This is done to make it easy to call the various utilities for special effects:
flip, rotate, padding, etc.
If I manually executes:
C:\testtex>C:\usr\local\bin\pnmcrop.exe -black -verbose -bot < C:\Temp\l2h2116\p1408.pnm > C:\Temp\l2h2116\p1408.tmp C:\usr\local\bin\pnmcrop.exe: Background color is #000000 C:\usr\local\bin\pnmcrop.exe: cropping 2 rows off the bottom
I will get the correct image, attached: img1a.gif.
OK; but you aren't working with the same input file that LaTeX2HTML used.
Try it with p1408.t01 or p1408.t02 and you should find that a bottom-crop doesn't work.
I think the cropping-bars are not meeting properly --- just missing by a single pixel; viz
XX XX XX XXXX (bottom of a letter 'O' say) XX XXXX XXXX XX XXXX XXXX XX XXXXXXX XX XX XXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXXXXXXX XX
Here the 1st bottom-crop will fail. The left-crop removes the 2 columns on the left; and now the shaving-crop removes the white row at the bottom. (If the bottom bar had been correctly removed, the shave would have removed the 2 white rows above it!)
I hope this information is detailed enough.
Does this explanation make sense to you.
If there is indeed just 1 pixel causing problems with some images, then it's probably due to a rounding effect, as Ghostscript creates an image at fixed resolution. The bottom edges of the \hrule s for the bars may be just sufficiently different to be on different sides of a pixel boundary.
Try varying the $IMAGE_SCALE factor by small amounts, and force the images to be remade. You should be able to find a suitable value that works well without oversizing the images.
Best,
Hope this helps,
Ross
Peter <img1.gif><img1a.gif>
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