Re: [Groff] Background Image

[Ted Harding]

On 16-Sep-06 Miklos Somogyi wrote:
> Hello!
> 
> Is it possible to insert a graphic as the background
> for a page? Sort of similar to the `epsf' special escape
> in enscript.
> 
> Even better would be a way to define a PostScript `form'
> to be inserted on each page of output.
> 
> This could be useful for letterhead or emulating pre-printed forms.
> 
> Any advice is most appreciated. Thanks!
> 
> Louis

If you want a background on just one page, then the best way
is to place it there as the first action before defining any
other printing on the page.

In the following examples I'm assuming A4 paper, and PS output..

Example 1: A background "Draft" in large grey type, diagonal:

a) To use this on just one page, have the following as the
first thing in your source file:

\X'ps: exec gsave 0.7 setgray \
196 720 moveto \
-60 rotate 1 -1 scale \
/Helvetica-Bold findfont 180 scalefont setfont \
(D r a f t) show \
grestore'

Then continue with the rest of your input. This will be overprinted
on the "Draft" background.

b) To have this on every page, locate the part of your macro
package which prints any page headers. For example, in the ms
macros these are the stringa "LH", "CH", "RH". So, in ms macros,
start with

.ds LH \X'ps: exec gsave 0.7 setgray \
196 720 moveto \
-60 rotate 1 -1 scale \
/Helvetica-Bold findfont 180 scalefont setfont \
(D r a f t) show \
grestore'
\*[LH]


The string definition ".ds LH" ensures that the background
is printed on every subsequent page, but (at least in ms
macros) the headers are not printed on page 1; so that is
why there is an explicit "\*[LH]" before you do anything else.

Example 2: A background image on a single page

Suppose that this image is an EPS file bkg.eps, and its
proportions (height by width) are correct for your paper,
though perhaps its BoundingBox may be of a different overall
size. For A4, height/width = 1.414 ... so let's suppose that
the BoundingBox in the EPS file is 20 100 120 241
[ i.e. (241 - 100) = 1.4*(120 - 20) ] so that it's in the
same proportions as A4 (not essential of course, depending
on your image; just for illustration).

Then, using the BoundingBox information, which you have to read
from the EPS file, suppose you want this image to be 6in wide
(432 points = 432000 groff PS units), and therefore 8.4in tall
(604.8 points = 604800 units), with its lefthand side 1in
(72 points) from the left and the bottom of the image to
be 10in (720p) from the top. This will (roughly) centre the
image on the page. Then start your file with

\Z'\
\h'1i'\v'10i'\
\X'ps: import bkg.eps 20 100 120 241 43200'
\'

and continue with the rest of your input for the document.

Similarly to (b) for (1) above, if you want this image on every
page then you can

.ds LH \Z'\
\h'1i'\v'10i'\
\X'ps: import bkg.eps 20 100 120 241 43200'
\'
\*[LH]

However, this will have the effect that for every page in the
output, the entire PostScript code of the image will be put
into every page in the ouput, which could give a large file
for a long document!

You can work round this by using "\X'ps: def ... " to define
a graphics object in the PostScript once and for all.

See my mail to the groff list on 17 October 2005 with subject

  Re: [Groff] PS and "page background"

for a more extended discussion of the issues.

Best wishes,
Ted.

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E-Mail: (Ted Harding) <address@hidden>
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Date: 16-Sep-06                                       Time: 20:54:06
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