How to split single pdf page in half vertically using ghostscript - pdf

Question

I have a pdf in landscape orientation and is a "Page Spread".
I need to split the page in half vertically in the middle.
I used this setting to cut the pdf in half: this one gets the left part of the page
"C:\Program Files (x86)\gs\gs9.10\bin\gswin32c.exe" -o output.pdf
-sDEVICE=pdfwrite -dNOPAUSE -dBATCH -dSAFER -dSubsetFonts=true -dEmbedAllFonts=true -g 750x1085 -c
"<</BeginPage{0.95 0.96 scale 20 22 translate}>> setpagedevice" "<</PageOffset [0 0]>> setpagedevice" -f input.pdf
The above command works fine. My problem now is I need to set the Mediabox, Cropbox, Bleedbox, Trimbox, and artbox similar to the size of the splitted page. In the instance above; it should be 750x1085.
What should be the correct command/settings to run on GS so that the Mediabox, Cropbox, Bleedbox, Trimbox and artbox has the same sizes?
UPDATE
This is a sample of the PDF file I'm trying to cut in half:
PDF FILE TO SPLIT
I am now using /PAGE pdfmark and this is the command I'm trying to use:
"C:\Program Files (x86)\gs\gs9.10\bin\gswin32c.exe" -o output.pdf -sDEVICE=pdfwrite -dNOPAUSE -dBATCH
-dSAFER -dUseCropbox -dSubsetFonts=true -dEmbedAllFonts=true -g7500x10850
-c "[/CropBox [0 0 750 1085] /PAGES pdfmark"
"[/MediaBox [0 0 750 1085] /PAGES pdfmark"
"[/TrimBox [0 0 750 1085] /PAGES pdfmark"
"[/BleedBox [0 0 750 1085] /PAGES pdfmark"
"[/ArtBox [0 0 750 1085] /PAGES pdfmark"
"<</BeginPage{0.95 0.96 scale 20 22 translate}>> setpagedevice"
"<</PageOffset [0 0]>> setpagedevice"
-f input.pdf
I still can't achieve setting the Cropbox, MediaBox, TrimBox, BleedBox, ArtBox with the same size.
What should be the correct settings for the command?

Answer 1

Moving to an answer here, comments are too small.
Your basic problem is that the original PDF file already contains all of the Box parameters you are trying to modify. The Ghostscript PDF interpreter will, for certain classes of output device, preserve those boxes by writing its own version of a pdfmark to the device. Because this happens after your pdfmark, it replaces yours.
There is, unfortunately, no mechanism in place to disable this. Additionally, since you are using Windows, you have the resources built into the ROM file system, so you can't readily modify them.
So at this point there isn't really anything you can do about this. If you are comfortable downloading the source and meddling with some PostScript let me know and I think I can give you a solution (you don't need to rebuild GS, but the PostScript resources aren't available separately).
EDIT to include some suggested work-arounds
In pdf_main.ps:
% Test whether the current output device handles pdfmark.
/.writepdfmarkdict 1 dict dup /pdfmark //null put readonly def
/.writepdfmarks { % - .writepdfmarks <bool>
currentdevice //.writepdfmarkdict .getdeviceparams
mark eq { //false } { pop pop //true } ifelse
systemdict /DOPDFMARKS known or
} bind def
You could alter /.writepdmarks to be:
/.writepdfmarks { % - .writepdfmarks <bool>
false
} bind def
But note that a number of other things will stop being emitted in the output PDF file.
Instead you could look at the code in pdf_showpage_finish:
/pdfshowpage_finish { % <pagedict> pdfshowpage_finish -
save /PDFSave exch store
...
...
.writepdfmarks {
% Copy the boxes.
{ /CropBox /BleedBox /TrimBox /ArtBox } {
2 copy pget {
% .pdfshowpage_Install transforms the user space do same here with the boxes
oforce_elems
2 { Page pdf_cached_PDF2PS_matrix transform 4 2 roll } repeat
normrect_elems 4 index 5 1 roll fix_empty_rect_elems 4 array astore
mark 3 1 roll {/PAGE pdfmark} stopped {cleartomark} if
} {
pop
} ifelse
} forall
You can modify the line '{ /CropBox /BleedBox /TrimBox /ArtBox }', any Boxes you don't want to preserve you can remove from that line.
If you want to prevent any of them overriding your specifications, then remove the lines from '% Copy the boxes' up to '% Copy annotations and links'
Please note this only works on a system where the resources are not built into a ROM file system, or where the resources are at least available on disk, and the path to the Resource files is specified using the -I switch.