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Old 03-28-2013, 11:26 PM   #371
willus
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Quote:
Originally Posted by dgvirtual View Post
Thanks for explanation. Native mode does not work here, since the file is scanned. It might well be jpeg-based... Now, if the original pdf is composed of jpeg images, would the k2pdfopt convert it to a png based pdf in any step of the three below?

But then I tried to repeat the steps by which I got the pdf with quality loss and I got stuck I do not know how I succeeded the first time...
...
Could you tell me what is it that goes wrong here? I am attaching the original image... Attachment 103604
It took a little tinkering, but the commands I used are:

k2pdfopt -ui- -mode copy -cmax -1 -g 1 -bpc 8 -grid 2x1x0 -n- -w 1t -h 1t -dr 2 page01.pdf -o temp.pdf

k2pdfopt -ui- -as -ml 0.4 -mr 0.4 -w 758 -h 942 -odpi 213 -om 0.04 temp.pdf -o out.pdf

The 'e-14' issue is a bug in my code. Apparently scientific notation is not allowed for move commands in PDF files, and since I use %g as a formatter and your document has a /Rotate 90 directive in the page objects, there end up being some very small scientifically formatted values in the move commands (e.g. 1.00234e-14), which aren't allowed in PDF. So I'll fix that, but for now I've provided a work around. Note that if k2pdfopt didn't have this bug, native mode would have worked fine in the first command--it doesn't matter whether the source document is scanned or not. Native mode conversion is the best way to preserve the fidelity of the original file.

Anyway, because of the bug, I had to use bitmap mode in the first conversion command. And yes, k2pdfopt, in bitmap mode, will effectively convert the scanned JPEG images to PNG (4-bit grayscale by default).

Here are what the less obvious options do:

-mode copy sets the output to be a copy of the input, with the output in bitmap mode.

-cmax -1 -g 1 -bpc 8 preserves the source contrast, gamma, bits per pixel (none of this would have been necessary if I could have done a native mode conversion) so that you don't get dithering artifacts.

-grid 2x1x0 breaks each page into 2 output pages (2 x 1 grid, no overlap)

-n- turns off native mode (-grid turns it on, so you have to turn it back off--again, not necessary if native mode had worked)

-w 1t -h 1t sets the output page size to mirror the gridded pieces of the source

-dr 2 doubles the output resolution so that we don't lose fidelity (not necessary if native mode had worked)

The other options are pretty straightforward and can be reviewed in my command-line options page.

Last edited by willus; 03-29-2013 at 08:53 AM. Reason: Found reason for 'e-14' error.
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