[Tex/LaTex] What should be the right width of an image for each document-classes

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I would like to print good images in A4 document (300 or 600 dpi). Using an external software,I have to merge differents big images to create a bigger one so I have to resize it with the same software (e.g. Gimp). I would like to know the best width (for example, for use them in a A4 report or a book class) so I can directly resize this big image to the proper size with the external software.

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I wanted to post this as a comment, but I ran out of space.

There is always some confusion on the resolution of graphics. Usually the smaller the print gets the higher resolution is required. The dpi actually stands for dots per inch an is a printer specific detail. Graphic programs usually use ppi pixels per inch. It is often referred to as the same, but it is not.

Resizing in the source document is only a good option if you are using vector graphics, which will be directly rendered by the printer.

In all bitmap graphics you schould try to resize it with an actual graphic programm. Usually there is a connection between dots and pixels. Many common printers use 1dot(per colour) = 1 pixel, some can do more.

For an optimal result you just need to know how large your picture shall be in the document. I it is 15 inches width and your printer can do 300 dpi, and you say 1 dot = 1 px, then 4500 pixels is the desired width.

You can then include your graphic without resizing it. However, if you are not printing on a high quality printer, this is fairly unnecessary.

Related Solutions

[Tex/LaTex] Scale (resize) large images (graphics) that exceed page margins

Using the adjustbox package with the export option which extends graphicx with several new keys you can now simply use the max width key which scales the image down to that width if it is larger but doesn't scale it at all if it is smaller the equal to it. There are also the related keys max height, max size (for both width and height) as well as min width, min height and min size.

In your case simply use the following code:

\includegraphics[max width=\linewidth]{<image file name>}

Note that you can't set max width etc. in a global way using \setkeys{Gin}{max width=...}. It is implemented in a different way as width. However, I'm planning to add a possibility for this as well.

[Tex/LaTex] Can pdflatex (or any tex package) automatically rescale included images which have been reduced in size

I've tried a little black magic with LaTeX, and found out how to do it without external scripts ─ though it still is somewhat dirty and not that easy to use. Basically, you would need to call ImageMagick from inside LaTeX.

To do this, you need to call it with --shell-escape parameter. This allows for using a command named \write18, that executes a parameter passed to it. Then you could add the following code to the preamble:

\newcommand{\doConvert}[2]{\immediate\write18{convert #1 -resample %
  300x300 -resize #2 #1.rs}}
\newcommand{\imgRs}[4]{\doConvert{#1.#2}{#3x#4}%
  \includegraphics[width=#3, height=#4, type=#2, ext=.#2.rs, read=.#2.rs]{#1}%
}

This enables you to call \imgRs{file}{extension}{width_in_pts}{height_in_pts} in order to convert the image to 300 dpi and include it in the document.

Of course you could always specify the dimensions in inches or any other units: you would just have to change the call to \doConvert in imgRs to account for scaling from unit used to points -- and you would have to use the dimensions consistently. It could be possible to actually find out what were the units used, or make some parameters optional, but it's independent of this solution.

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Related Solutions

[Tex/LaTex] Scale (resize) large images (graphics) that exceed page margins

[Tex/LaTex] Can pdflatex (or any tex package) automatically rescale included images which have been reduced in size

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