On approximately 7/13/2009 10:59 AM, came the following characters from the keyboard of John Culleton: > On Friday 10 July 2009 05:00:58 pm Glenn Linderman wrote: > >> On approximately 6/29/2009 4:05 PM, came the following characters >> from >> >> the keyboard of Ross Presser: >> >>> In fact, the single image contained on the page is 2236x3025 >>> pixels and 8.89"x12.1", giving a resolution of 250 dpi, not 300 >>> dpi. >>> >>> ImageMagick won't know this, of course; I dug it out using >>> Acrobat 9.0 Pro's measurement and preflight tools. >>> >> Hmm. So if Acrobat 9.0 Pro can figure out the "native" dpi, why >> can't other tools do it? I suppose it is "hard" or >> "undocumented"? It seems that mostly it is Ghostscript that is >> used to look at .ps and .pdf files... if it could learn how to >> report on the dpi, it seems the world would be a better place.... >> Guessing random dpi values until it "looks good" (and bigger dpi >> values don't look "better") is a poor way of proceeding.... >> >> I suppose different images contained within a .pdf or .ps file >> might have different resolutions. >> >> I'd like to know if there is a tool that exists that can do >> either or both of the following: >> >> 1) extract embedded image characteristics from .ps and .pdf >> files, so that an appropriate dpi setting can be used to convert >> the whole file to raster. >> >> 2) extract the embedded images to .tif or .png format, retaining >> the exact pixels, and setting the dpi to achieve the scale at >> which it was embedded. >> >> Do tools like these exist? How much do they cost, or where can >> they be obtained? >> > > I sometimes import files into Gimp and do these kind of > manipulations. The major manipulation occurs at the front end. If > the PDF/PS file is in vector format then you can set a healthy dpi > figure up front when you open it. Then the function > image>scale image > lets you do what you need. I just did that with a pdf created from > a Gimp Manual html file. I set it at 600 dpi. Detail of the text is > just fine even at magnified views. >
Right... one can always overspecify the DPI and then reduce to what you need, and hope the result is reasonable, and often it is. One can do that with GIMP, PhotoShop, IrfanView, and even ImageMagick! But it would be nicer to be able to extract the image pixels that actually exist, to obtain an unscaled version of the image. _______________________________________________ Magick-users mailing list [email protected] http://studio.imagemagick.org/mailman/listinfo/magick-users
