From 60af8a33c2972b5a0cc56555d37c86dc0bb1ea4a Mon Sep 17 00:00:00 2001 From: Jonas Smedegaard Date: Sun, 11 Dec 2022 19:36:56 +0100 Subject: expand to document dimensions and marks, and provide resize method using CropMark --- USE.md | 101 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++--- 1 file changed, 97 insertions(+), 4 deletions(-) diff --git a/USE.md b/USE.md index d65fbeb..f03aa3c 100644 --- a/USE.md +++ b/USE.md @@ -17,7 +17,76 @@ or look at underlying scripts `pdftops`and `pstopdf13`. pdftops %f ps2pdf13 infile outfile -## Resize PDF with crop marks +## PDF resizing and/or scaling + +PDF **resizing** is changing *media* size, +either together with or independent of content. + +PDF **scaling** (a.k.a. "zooming") is changing *content* size, +relative to size of media size. + +Both resizing and scaling at once can be confusing. +A suggested approach is to first media+content together, +then scale content relative to this new target media size. + +### PDF dimensions + +Resizing and/or scaling PDF files +is tied to input and output dimensions. +Simple measures are standard page formats like A4, A3, or letter, +but more reliable are internal "box" dimensions measured in "pt": + +In addition to page sizes, +PDF files technically annotate content using several "boxes": + + * MediaBox: full printable area + * Required + * CropBox: area displayed in a PDF viewer + * Optional, defaults to MediaBox + * BleedBox: area including TrimBox/ArtBox and bleed + * Optional, defaults to MediaBox + * Must be larger than TrimBox/ArtBox, and smaller than MediaBox + * TrimBox: subset of printable area without bleed, cropmarks etc. + * Optional + * ArtBox: essential subset of printable area + * Optional + +(Technically a "BoundingBox" is not a PDF hint +but the equivalent of ArtBox in EPS and DSC-compliant Postscript.) + +E.g. an A4 sized PDF page +is technically a page with a /MediaBox of approx. [595 x 842 pt][page_dimensions]. + +### Extracting PDF box hints + +Resolve all boxes (computing from defaults any omitted ones): + + pdfinfo -box -l -1 input.pdf + +Extract MediaBox: + + gs -dQUIET -dNODISPLAY -dNOSAFER -sFileName=input.pdf \ + -c "FileName (r) file runpdfbegin 1 1 pdfpagecount {pdfgetpage /MediaBox get {=print ( ) print} forall (\n) print} for quit" + +To check if other boxes exist, +replace `/MediaBox` with e.g. `/CropBox` in above command, +and test if running the command succeeds. + +### Computing PDF dimensions + +Ghostscript can virtually render each page and compute the area used, +useful e.g. for cropping a PDF. + +Compute BoundingBox for each page individually (*not* across them all): + + gs -q -dBATCH -dNOPAUSE -sDEVICE=bbox -dLastPage=1 input.pdf 2>&1 | grep %%BoundingBox + +Source: + +[page_dimensions]: + "Postscript page dimensions as defined in Ghostscript" + +### Resize PDF with crop marks Simple resizing to fit target paper size can often be done on-the-fly at the print dialog. @@ -47,7 +116,7 @@ one of its features is easy scaling by area. plakativ --factor=0.5 --size=250mmx337mm --output=output.pdf input.pdf -### using Ghostscript +### using Ghostscript with fitPage Ghostscript resizing is done by first defining target size and then tell to resize content to fit that target with `FitPage`. @@ -59,7 +128,31 @@ and explicitly set those values scaled down by 21/29.7 (the ratio between A3 and A4 page formats). Example command, -for a PDF document with width 910.24 and height 1258.9 -(as reported by `pdfinfo`): +resizing from A3+ to A4 +(source width 910.24 and height 1258.9 as reported by `pdfinfo`): gs -o output.pdf -sDEVICE=pdfwrite -dDEVICEWIDTHPOINTS=643.60333 -dDEVICEHEIGHTPOINTS=890.131 -dFIXEDMEDIA -dFitPage -dCompatibilityLevel=1.4 input.pdf + +TODO: maybe options `-dDEVICEWIDTHPOINTS` and `-dDEVICEHEIGHTPOINTS` can be shortened as `-dDEVICEWIDTH` and `-dDEVICEHEIGHT` + +### using Ghostscript with setpagedevice + +Some PDF documents embeds `/CropBox` marks +which is not handled by the `-dfitPage` option. +For effectively resizing such documents, +each page need to have applied a `/CropBox` mark matching the new size. + +Example command, +resizing from A4 to printable-area-A4 +(i.e. a dumb printer always auto-resizing to fit): + + gs -o output.pdf -sDEVICE=pdfwrite -dDEVICEWIDTHPOINTS=595 -dDEVICEHEIGHTPOINTS=842 -dFIXEDMEDIA -dCompatibilityLevel=1.4 \ + -c "<> setpagedevice" -f input.pdf + +TODO: maybe options `-dDEVICEWIDTHPOINTS` and `-dDEVICEHEIGHTPOINTS` are superfluous + +TODO: maybe options `-dDEVICEWIDTHPOINTS` and `-dDEVICEHEIGHTPOINTS` can be shortened as `-dDEVICEWIDTH` and `-dDEVICEHEIGHT` + +TODO: maybe works only with `CropMark` applied for whole PDF file (and when none are applied?) but fails when input file already contain per-page `CropMark` hints + +Source: -- cgit v1.2.3