Real Size Image Printing

Question

I am generating a complicated graphics with Mathematica, but with objects of given sizes (e.g. a line of length 1 inch, between two points). I want to make sure that when I export the graphics, e.g. as pdf, and then when I print it, the line length on paper will be one inch, without additional tweaking (assuming no scaling when printing).

Answer 1

Quite redundant after the other answers and links, but I use something like this for vector-based technical drawings and CNC data (using mm as unit). This is not foolproof as it might e.g. screw up with conflicting options and such, so make sure to check the output.

Important: SetPlotRange for your graphics explicitely:

gfx = Graphics[Line[{{10, 10}, {110, 10}, {110, 110}}], 
  PlotRange -> {{0, 200}, {0, 200}}]

ExportScaled[filename_, gfx_, format_: {210, 297}, opts___?OptionQ] :=
  Module[{mm}, mm = 72/25.4;
  Export[filename, 
   Show[gfx, ImageSize -> format*mm, ImageMargins -> 0, 
    ImagePadding -> None, AspectRatio -> Automatic], opts]]

For proper scaling, your graphics´ PlotRange and the exported ImageSize need to correspond.

ExportScaled["test.pdf", gfx, -Subtract @@@ (PlotRange /. 
     Options[gfx, PlotRange])]

Below: Output measured in Acrobat (Again: It is usually a good idea to test a few cases by measuring them with Ghostview, Acrobat or such. Works just as well for EPS export).

Answer 2

You can specify ImageSize in inches. From docs > ImageSize> MoreInformation:

 Specifications for both width and height can be any of the following: 
     ...
     72di         di inches (before magnification)
     ... 

Examples:

Row[{Plot[{Sin[x], Cos[x]}, {x, -2 Pi, 2 Pi}, Frame -> True, 
AspectRatio -> 1/GoldenRatio, ImageSize -> 72 2], 
Plot[{Sin[x], Cos[x]}, {x, -2 Pi, 2 Pi}, Frame -> True, 
AspectRatio -> 1/GoldenRatio, ImageSize -> 72 3], 
Plot[{Sin[x], Cos[x]}, {x, -2 Pi, 2 Pi}, Frame -> True, 
AspectRatio -> 1/GoldenRatio, ImageSize -> 72 5]}]

EDIT: Per Mr.Wizard's suggestion, adding various Paddings in inches:

inches = 72; 
Panel@ Plot[{Sin[x], Cos[x]}, {x, -2 Pi, 2 Pi}, Frame -> True, 
PlotRangePadding -> {0.001 inches, 0.001 inches}, 
ImagePadding -> 0.3 inches, ImageMargins -> 0.3 inches, 
AspectRatio -> 1/GoldenRatio, ImageSize -> 5 inches]

Answer 3

Your question isn't very specific, so here is a generic example from another question

From the documentation for ImageSize:

The following settings can be given:

72di di inches (before magnification)

Suppose we want to give sizes in centimeters. We establish a scale:

cm = 72/2.54;

And we give the ImageSize in this scale, also making sure to set PlotRangePadding -> None. This gives a 1cm x 1cm orange square on a 19cm x 28cm field.

g = Graphics[{Rectangle[{0, 0}, {19, 28}], Orange, 
    Rectangle[{0, 0}, {1, 1}]}, PlotRangePadding -> None, 
   ImageSize -> {19, 28}*cm];

When exporting you can give a specific resolution to use. For printing 300dpi may be appropriate:

Export["print.tif", g, ImageResolution -> 300]

Answer 4

(I posted a similar answer on MathGroup recently.)

Here's an alternative to the other very good answers you already received.

If you need high accuracy, I recommend exporting to DXF. DXF is a format used by CAD applications requiring precision. Then you can use one of the many DXF-viewers or CAD programs to print to precision. (There seem to be a number of free programs available.)

Please see this answer of mine as well, where I described a little bit how Mathematica treats different units and how one can export figures to size.