[Wylug-help] Set PDF background to transparent without quality loss

[Dan Walker]

Hmm.

Editing scanned bitmaps might well reduce quality - you won't get 
decent-looking lines if the scan goes through a .JPG stage.

Ideally, you'd get / recreate the invoice paper in a vector package - 
You could try asking whoever created it in the first place, or maybe try 
converting your scan to vector with Inkscape, then output it as a PDF 
after clean-up?

Failing that—and cleaning up vectors traced from a bitmap can be 
tiresome—you could try setting your scanner to produce non-compressed 
(or lossless) images such and PNG or GIF, and then convert the white to 
transparent with Imagemagick (e.g. see 
http://www.imagemagick.org/discourse-server/viewtopic.php?t=12619 - I 
haven't tried it though )

There's no ideal solution from a scanned image, scanned bitmaps are hard 
to make look "clean" when they're actually artwork rather than photographs.

Yrs,

Dan

(Gosh, it's been a while since I posted here ;)

On 18/09/15 12:47, Gary Stainburn wrote:
> Hi all,
>
> As part of my virtual Printer -> invoice paper -> PDF project I'm struggling.
>
> I've got everything working except merging the invoice paper and the invoice.
>
> I have a single page PDF with the invoice stationery from a scanned original.
> I have the invoice as produced by our business management software
>
> I then ran
>
> pdftk invoice.pdf background  invoice_paper.pdf output output.pdf.
>
> Unfortunately this didn't work because our business software splatted all over
> the company logo.
>
> I then tried
>
> pdftk invoice.pdf background  invoice_paper.pdf output output.pdf.
>
> which priority to the invoice paper, effectively putting it over the invoice
> instead of behind it.  This of course means that the blank background of the
> paper splats over the invoice.
>
> The answer is to make the white background of the invoice_paper.pdf
> transparent.  I've tried doing this using PDFedit, convert, and gimp but the
> end result is a significant reduction of the quality of the
> invoice_paper.pdf.
>
> Can anyone suggest al alternative method, preferrably also removing the
> blemishes on the scanned paper.
>
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