Chrome: How to print PDF with original size (100%, no scaling/shrinking)

问题

Today I encountered one weird bug in Chrome's printing behavior. When I try to print a dynamically created PDF using Chrome (also in Firefox), every image inside the PDF gets a little bit smaller (8mm). This doesn't happen neither in Adobe Reader/Acrobat/MacOSX Default Printer Dialog.

Let me explain more about my code so far:

dynamic PDF:

I use prawn to dynamically create a PDF A4 (landscape format) using this code:

require 'prawn'
require "prawn/measurement_extensions"

class CustomPdf < Prawn::Document

  def initialize(label) # A4
    super({
       :page_size =>  "A4", 
       :page_layout => :landscape, 
       :margin => 0, 
       :print_scaling => :none})

    image "my_image.png", :width => 213.mm, :at => [3.mm, 3.mm]
  end
end

nested image inside the PDF:

The Image nested inside the PDF has a size of 213mm x 70mm with 300 DPI. In Pixel: 2515x827.

I create the Image using RMagick but the size, dpi and everything so far seems to be alright. So no further explanation at the moment.

Expected result:

The printed PDF will show an image with 213cm width.

Actual result:

The printed PDF will show an image with 205mm width.

What I tried so far

• Setting the prawn page_size to something lower than A4 (since the Image isn't bigger as A4 as well...).
• Playing around with print_scaling(there are 3 modes, :none, :AppDefault, :something_except_the_other_ones (Read more about it here)
• Giving the image a fixed height (70mm)
• Playing around with various settings provided by the Chrome Printer Dialog
• Tested under Windows Chrome (it's 213mm there, weird), maybe it's related to MacOSX Chrome?
• Tested under IE11 (205mm) unfortunately.

Neither of these did anything. I looked through the Bugreporters of Chromium and found 2 people who might share the same problem as I do:

• https://code.google.com/p/chromium/issues/detail?id=97972
• https://code.google.com/p/chromium/issues/detail?id=67091

The last one was touched 2013 but no one said anything that actually worked for my case.

---

Examples

Here is an example 300 DPI image which width is 2515 px: If Imgur changes the resolution to 72, you can pull the example image from the repository (link: https://github.com/posixpascal/chrome-printing-bug/blob/master/example.png)

Here is an example PDF

Direct Link: Direct Link

GitHub PDF Viewer: https://github.com/posixpascal/chrome-printing-bug/blob/master/output.pdf

---

Github Repository with example image & pdf generator script https://github.com/posixpascal/chrome-printing-bug

Unfortunately I can't change the width of the image (not even a pixel). Someone experienced the same problem?

Any ideas? It's an interesting puzzle I guess... :x

---

When I print a plain image or a website with Chrome there is a 'Use Original Size' or '100% size' option which I don't have when printing the PDF.

I also tried making a webpage instead of a PDF and set the image width to 213mm which didn't work either...

回答1:

This is my test results from what i have seen by using a windows system and a Mac ( Yosemite )

Windows :

Printed the PDF in Chome : Perfect - 213 mm

Printed in IE : Perfect - 213 mm. This was less before ( around 205-210ish ). So changed the default print settings :

Selected the Print option -> Used Print Dialog -> Selected the printer -> Print Preferences -> Advanced -> Paper Size -> Changed scaling manually -> tested A4, A5 and so on.-> A5 ( for some reason gave me 213 )

So i moved onto the Mac.

Mac Findings:

Changed Paper Size and tested the same : Size was 213 mm.

This was done like this : Apple Print

So naturally, i tested printing it through Chrome directly instead of opening the PDF through OSX -> Printed at 205 mm.

Tested with printscaling on prawn at :appdefault -> Printed at 213 mm.

Tested the same on Firefox -> lower than 205 - 210 mm.

So i dont really know if its a Chrome issue because its acting weird on Firefox for me.

So ultimately, these are my findings after testing out the code on my end.

回答2:

I experienced a similar 8 mm shrinkage using Chrome on Windows. Checked all my printer properties and settings and couldn't find what could be doing it. Turns out, I had the option "fit to page" ticked in the Chrome printing (ctrl+p) screen. Un-ticked it and reprinted a page, compared their widths and they were 8 mm off. Sometimes it's the simple things...

回答3:

In my experience, Chrome prints html usually smaller. It may have to do with WebKit engine having "smart shrinking" feature. I have come across to it here (text search shrinkage). Or, it might be just that, Chrome developers gave it a little tweak since people in the past complained that the stuff does not fit the print.

来源：https://stackoverflow.com/questions/32849271/chrome-how-to-print-pdf-with-original-size-100-no-scaling-shrinking