Luigi, > So in luatex we have a width of 243pixels at 72dpi, hence 243.91125pt.
> On the other side pdftex takes the other way, so we have 243pixels at 120dpi, hence 146.34676pt. I think that's an unfortunate choice and ask you to at least give a customisation option to take the other choice. latex (far more than context or plain) has an expectation for working over multiple engines. Documented (and documentable) differences are understandable, luatex isn't expected to be fully compatible with pdftex. But this is a difference in internal data in a binary file where luatex is taking a different choice to pdftex (and image magic at least as far as I can see) It is going to be very hard to document to end users when this might occur or what to do if it does. Even if compatibility with pdftex isn't a priority, taking a different choice to common image tools such as image magic convert will cause surprises. as far as I can see most tools that can handle both formats (pdftex, browsers, etc) will treat these two images as the same size https://github.com/latex3/graphics-def/blob/master/testfiles/clip-1-2.jpg https://github.com/latex3/graphics-def/blob/master/testfiles/clip-1-2.png in latex at least the common idiom is to use \includegraphics{clip-1-2} with no extension and leave it to the system to load whichever version it can handle (eg jpg here and .eps for latex/dvips etc. If the different versions (as converted by "convert") come out as different size then this is going to be a recurring cause of support queries. Given that you are anyway poking in the jpeg internals would it at least be possible to give a warning that the image has multiple specified resolutions. If you could give a warning that gave the number 120 the user (or latex on behalf of the user if the warning was trappable) could issue some variant on \pdfvariable imageresolution and force the resolution to be taken into account, or \usejfif data or whatever else makes sense as an interface? That way there would at least be a documentable way of getting the expected size here. Sorry if this sounds ungrateful:-) Thanks for the fix so far I can confirm (after some problems building luatex) that for other images without this resolution ambiguity, luatex now gives the same size as pdftex. David
