On 08/05/12 09:56, Albert Astals Cid wrote: > El Dilluns, 7 de maig de 2012, a les 19:14:54, Carlos Fernandez va escriure: >> Albert, >> >> Thanks for the quick reply. > > Please don't answer me, answer to the list, there's no reason to keep the > discussion "hidden" to the rest of the world. > >> I am reading the DPI and image dimensions from Preview on OS X. It >> reports the fractions DPI for the 2040x2640 image. Is the DPI >> information baked into the image as metadata? > > No idea to be honest.
Yes, the DPI is stored in the image file. In the case of PNG it is stored as a integer specifying the number of pixels per metre. The difference you are seeing is the rounding error due to the conversion from dots/inch to pixels/metre rounded to an integer. Your viewer is then converting the rounded value back to dpi. As pixels/metre is the only unit supported by the PNG standard there is nothing poppler can do to avoid the rounding problem. > >>>> using "-r 150" (or just relying on the default value of 150) to create >>>> an image on a 8.5x11 inch pdf generates an image that is 1275 × 1651 >>>> pixels at 150dpi. >> >> Should this image be 1275x1650? > > That might make sense. > > Anyway this is a development list, if you are not planning to develop a fix > what you should do is open a bug in bugzilla, it is much easier to keep track > of the bugs in there. > > Cheers, > Albert > >> >> Carlos >> >> On Mon, May 7, 2012 at 5:17 PM, Albert Astals Cid <[email protected]> wrote: >>> El Dilluns, 7 de maig de 2012, a les 16:58:27, Carlos Fernandez va > escriure: >>>> trying to split a pdf into page images using pdftoppm. I would like >>>> the resulting images to maintain the same size and scale as the source >>>> PDF. unfortunately the images being generated are somewhat >>>> unexpected. >>>> >>>> using "-r 150" (or just relying on the default value of 150) to create >>>> an image on a 8.5x11 inch pdf generates an image that is 1275 × 1651 >>>> pixels at 150dpi. >>>> >>>> using "-r 240" to create an image on the same 8.5x11 inch pdf >>>> generates an image that is 2040 x 2640 pixels at 239.97 dpi. >>> >>> Hmmm, really? >>> 2040/8.5 = 240 not 239.97 >>> 2640/11 = 240 not 239.97 >>> >>>> these results were consistent for png or tiff output. I got similar >>>> results for other dpi settings across a few different PDFs. >>>> >>>> What can i do to get more consistent results? >>> >>> What's inconsistent? >>> >>> Albert >>> >>>> Carlos >>>> _______________________________________________ >>>> poppler mailing list >>>> [email protected] >>>> http://lists.freedesktop.org/mailman/listinfo/poppler >>> >>> _______________________________________________ >>> poppler mailing list >>> [email protected] >>> http://lists.freedesktop.org/mailman/listinfo/poppler > _______________________________________________ > poppler mailing list > [email protected] > http://lists.freedesktop.org/mailman/listinfo/poppler _______________________________________________ poppler mailing list [email protected] http://lists.freedesktop.org/mailman/listinfo/poppler
