How to set the output be generated in a cell different from "Output"

Question

I would have some functions, for instance Plot, to generate their output using a different Cell's style rather than "Output". The reason is that I'm producing some documents with many images and, for editing reasons, I need to adjust some options of their cell's style.

Unfortunately, I cannot change the "Output" style, because other kind of outputs don't have the same formatting as images. Just to make and example, suppose I want all graphics centered in the cell, while other output left aligned. So, I would assign a custom style to the output generate by Plot. Is there any suggestion?

Answer 1

For Graphics output specifically there is a nice approach using $DisplayFunction:

(* create a new output style -- overwrites existing custom style sheet *)
SetOptions[EvaluationNotebook[],
 StyleDefinitions -> 
  Notebook[{Cell[StyleData[StyleDefinitions -> "Default.nb"]], 
    Cell[StyleData["altOutput"], TextAlignment -> Center]}, 
   StyleDefinitions -> "PrivateStylesheetFormatting.nb"]
 ]

(* define a display function *)
altOutput[expr_] := CellPrint @ ExpressionCell[expr, "altOutput"]

$DisplayFunction = altOutput;

Graphics output in this Notebook will now be centered. You could also set the DisplayFunction option for individual plot types independently rather than using the global $DisplayFunction parameter.

Answer 2

It is possible to change the style used for output with this Front End option:

"GeneratedCellStyles" -> {"Output" -> (* style *)}

One can change this style as part of the output formatting routine using $PrePrint, like this:

defaultOut[] := SetOptions[EvaluationNotebook[],
  "GeneratedCellStyles" -> {"Output" -> "Output"}]

altOut[] := SetOptions[EvaluationNotebook[],
  "GeneratedCellStyles" -> {"Output" -> "altOutput"}]

output[gr_Graphics] := (altOut[]; gr)
output[other_] := (defaultOut[]; other)

$PrePrint = output;

Now (bare) Graphics objects will be output with a Cell style of "altOutput" rather than "Output" yet other expressions will be handled normally. One could extend output to handle an arbitrary number of heads as needed. (Graphics is merely an example here.)

Answer 3

If you want to do it all programmatically you could import the notebook containing the cells with graphics and change the cell style for cells containing graphics:

changeStyle[file_String, newStyle_String] := 
  Module[{nb = NotebookOpen[file], nb1},
   nb1 = NotebookGet[nb];
   NotebookClose[nb];
   nb = nb1 /. (p1 : Cell[BoxData[GraphicsBox[_, ___]], "Output", ___] :> (p1 /. 
         "Output" -> newStyle) );
   NotebookSave[nb, file];
   ];

changeStyle["/pathTo/Untitled.nb", "Text"]

To address @MichaelE2 concerns:

changeStyle[file_String, newStyle_String] := 
  Module[{nb = NotebookOpen[file], nb1, newfile},
   nb1 = NotebookGet[nb];
   NotebookClose[nb];
   nb = nb1 /. (p1 : 
        Cell[BoxData[GraphicsBox[_, ___]], "Output", ___] :> (p1 /. 
         "Output" -> newStyle));
   newfile = 
    SystemDialogInput[
     "FileSave", {NotebookDirectory[], {"New File \"*.nb\"" -> {"*.nb"}}}, WindowTitle -> "Saved New Notebook"];
   If[newfile =!= $Canceled && newfile =!= $Failed,
    NotebookSave[nb, newfile]
    ]
   ];

Answer 4

An alternative is to use $Post to post-process output automatically as it is generated.

For instance, the following outputs anything with the head Graphics in a style "centeredOutput", which could be defined in whatever manner one wants.

centerGraphics[g_Graphics | g_Graphics3D] := CellPrint@ExpressionCell[g, "centeredOutput"];
centerGraphics[x_] := x;

$Post = centerGraphics

One could center the graphics also by wrapping it in Pane:

centerGraphics[g_Graphics | g_Graphics3D] := Pane[g, Alignment -> Center, ImageSize -> Full];

Update: From a suggestion by Mr.Wizard, with this definition, formatting the graphics could be handled more gracefully by setting $PrePrint = centerGraphics and $Post =. (or leave $Post unset). Then the value of Out will be the graphics instead of the Pane.

Notes (updated) --

Any existing graphics would have to be reevaluated.

One should be aware that $Post affects the output value. For example, after executing Plot, the head of % would be Cell, if using the first definition of centerGraphics.

One can circumvent $Post by wrapping the graphics in a head that does not affect typesetting. For instance, Defer@Evaluate@Plot[Sin[x], {x, 0, 10}] would be printed in a normal "Output" cell but the graphics will still be centered.

Because of this, if one wishes to Deploy graphics, one might want to add a rule to centerGraphics to handle Deploy. For example, centerGraphics[g : Deploy[Graphics[__]] | ...] := ...

One need not create a special style. One can set options directly in ExpressionCell, such as with this body for the definition of centerGraphics:

CellPrint@ExpressionCell[g, "Output", TextAlignment -> Center]