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Im a bit new to latex, I thought when adding images they were scaled according to some universal default dpi--today I learned this isn't really the case. So I have a few questions regarding images and dpi:

Is there a default dpi value for document classes or for file types?

Does latex's 'dpi' resolution setting affect anything if no images are present?

Does it matter if images have different dpi settings? (is there some convention or something)

Shouldn't it be called ppi instead of dpi?

Jayvl
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  • You should probably differentiate between latex and pdflatex - as far as I know, the two programs handle this differently. As far as ppi and dpi, (also as far as I know) they're the same thing for onscreen purposes. – Sean Allred Apr 13 '13 at 14:44

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LaTeX does not have a dpi setting so your question is rather unclear. LaTeX itself doesn't handle images at all, In classic TeX it just puts a request to include an image into the dvi file and a separate program (eg dvips) selects an image. In pdftex the pdftex engine does handle both aspects but again it doesn't have any setting called dpi the nearest it has its its register \pdfimageresolution but that almost never needs to be set by normal users, LaTeX/pdftex almost always just do the right thing given any image in a format it can handle.

David Carlisle
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    So how does the software decide how large an image of 432x123 pixels is? Assuming I don't specify a width or height option in the insertgraphics command. Perhaps \pdfimageresolution is used? – Jayvl Apr 14 '13 at 01:11
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    @Jayvl well it obviously needs to get a resolution from somewhere, preferably in the image itself or a fallback if not, but my main point is that you seemed to be asking about some setting called dpi and querying its name as well as its function, but if you see such a setting it isn't latex (perhaps a IDE setting a default resolution for print drivers or...) – David Carlisle Apr 14 '13 at 01:18
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    Apparently the setting I was querying was \pdfimageresolution. It defaults to 72 and is overridden if the image contains ppi information or an option such as width= or resolution= is specified. – Jayvl Apr 14 '13 at 12:28