Great, Ian, thanks a lot. You have boiled down the problem to its kernel.

The inclusion of ticks, tick labels, axis/frame/plot-labels, insets, etc. is another problem. PlotRange does not help. Probably PlotRangePadding, ImagePadding, ImageMargins with some calculations would solve it.

Actually, what is missing, is a PlotSize-Option or the like that tells the size of the plotted axes, leaving out all adornments around the plotted graphics primitives. Other graphics applications have something like a drawing area for that which can be directly sized.

Hi Werner,

No problem. The stuff I posted was chopped out of a bigger stylesheet I use and contains elements that aren't strictly necessary. All you really need is...

   Cell[StyleData[All, "Printout"], Magnification -> 1.0]

and possibly...

  Cell[StyleData[All, "Working"] , Magnification -> 1.0 ]

if you want your graphics to line up with the ruler in the working environment. The easiest way to add these lines is via the stylesheet editor menu. I chosen not to use Mathematica's Quantity functions for this straightforward application as the conversions are very simple.

Hope this helps,

Ian

Thanks, Ian, for your help.

I think your program is exactly the same as mine. As I told in my previous reply to you some minutes ago, the problem does not ly within the program coding, but within the style sheet only.

We can forget about that draw-mm-paper program. Your small draw-a-rectangle is much better suited to isolate my problem.

Best regards, Werner

Thanks very much, Ian. This helped although I don't understand it.

1. The rulers don't help. They show sizes as defined in the program but not in real-world measures when printed. Of course, your program shows the correct size. So does my draw-mm-Paper program from above. The problem starts when it comes to printing.

2. If I just copy your 4-liner-program without your style options into my notebook and run it, it shows a rectangle of width 100 according to the ruler. But when printed it becomes 72 mm x 36 mm only! Hence it is too small by a factor of 72/100. This is my problem.

3. If I run your complete RealWorldSize program including the style options, it shows the same but prints correctly 100 mm x 50 mm!

4. If I copy your style options into my notebook everything shows as before but prints correctly!

5. Hence all our programs are correct. The secret lies within that style options only. Those style options tell:

   Module[
    {
     mm = 72.0/25.4,   (* Factor to express mm in dpi - e.g. 
     25.4\[Times]mm gives 72dpi, or 1 inch *)
     mm2em = 30/127      (* Factor to convert from mm to em - 
     WL tabs are measured in ems *)
     },
    SetOptions[
     EvaluationNotebook[],
     (* Display options *)
     AutoOpenPalettes -> {},
     (*EvaluationCompletionAction \[Rule]"ShowTiming",*)
     PrintingOptions -> {"PrintingMargins" -> {{0, 0}, {20, 20}}*mm},
     WindowToolbars -> {"RulerBar"},
     StyleDefinitions -> Notebook[
       {
        (*Inherit default stylesheet*)
        Cell[StyleData[StyleDefinitions -> "Default.nb"]],
        (*Style Environment Names*)
        Cell[StyleData[All, "Working"] , Magnification -> 1.0 ],
        Cell[StyleData[All, "Printout"], Magnification -> 1.0],
        Cell[StyleData["Input"]
         , CellMargins -> {{30 mm, 30 mm}, {Inherited, Inherited}} 
         ],
        Cell[
         StyleData["Input", "Printout"]
         , CellMargins -> {{30 mm, 30 mm}, {Inherited, Inherited}} 
         ],
        (*Output*)
        Cell[
         StyleData["Output"]
         , CellMargins -> 
          CurrentValue[{StyleDefinitions, {"Input", "Working"}, 
            CellMargins}]
         ],
        Cell[
         StyleData["Output", "Printout"]
         , CellMargins -> 
          CurrentValue[{StyleDefinitions, {"Input", "Printout"}, 
            CellMargins}]
         , ShowCellLabel -> False
         ]
        }
       ]
     ]
    ]
   

   Until now, I have never bothered with style sheets. I suppose most of the definitions are probably not relevant for sizing since they are standard or just change margins. But I have no idea which are the options I really need for correct printout. And why do I need them?

6. BTW: Your mm2em at the top of the module is never used. And I think that your comment - not the value - for mm = 72.0 / 25.4 is easily misunderstood since you talk about dpi (dots per inch) which is a printer hardware feature of the resolution, but not some sizing measure. It should read: "Factor to express mm in pt (points) - e.g. 25.4 mm gives 72 pt, or 1 inch".

   WL mostly takes sizes in points. 1 pt is defined as 1/72 inch = 25.4/72 mm = 127/360 mm. With, for example, "ImageSize->w" w is meant to be in pt. If you want to have a width of b mm you have to write: "ImageSize->360/127 b". See:

   UnitConvert[Quantity[b, "millimeter"], "point"]
   Quantity[(360 b)/127, "DesktopPublishingPoints"]
   

I do not know how the printers dpi-feature should affect print sizes. This is just a hardware-related resolution feature. If I tell any printer to draw something one inch long it is internally rendered into say, 600 dots/pixels but in the end, it is one inch long on printed paper.

I'm afraid that you are right with historic roots of Mathematica and that at the moment it's just a mess.

Hi Gianluca, I did not try that and wonder about it. What I mean is running the program and then having the output cell with the graphics within my notebook. Select that cell and print it with Ctrl+P

Since I do not know how to show direct output cells within that forum, I inserted another statement in my program as the very last line:

Export["\users\Werner\Desktop\mm.png", g]

And then moved that png-picture from my desktop into the forum editor.

Probably the Export brings even more things concerning sizes into the game