Legacy ImageMagick Discussions Archive

In Windows, If I put a number after "-units", I get an error: The error is reasonable, as the documentation http://www.imagemagick.org/script/comma ... .php#units doesn't give numbers as options.

snibgo wrote: ↑2017-01-23T13:17:44-07:00 In Windows, If I put a number after "-units", I get an error:

Code: Select all

f:\web\im>%IM%convert rose: -density 300 -units 1 x.png

convert.exe: unrecognized units type `1' @ error/convert.c/ConvertImageCommand/3116.

The error is reasonable, as the documentation http://www.imagemagick.org/script/comma ... .php#units doesn't give numbers as options.

That's interesting. It never gave me an error. What version of windows are you running and what version of ImageMagick are you on?

IM v6.9.5-3, Windows 8.1. The Windows version should make no difference.

If you specify a density and not a unit, then some printers may not interpret the correct units and the print page size will be wrong.

fmw42 wrote: ↑2017-01-23T14:10:51-07:00 If you specify a density and not a unit, then some printers may not interpret the correct units and the print page size will be wrong.

If I am converting a pdf where all pages are 8.5x11 to tiff files and then writing on them digitally using a tablet and then afterwards converting the modified tiff files back to pdf, what unit size should I be using? When I am converting the original pdf document I am using 300 dpi setting.

Where do the PDF files originate? Are they from a scanner as raster images in a PDF shell or as vector data from some PDF writer such as Acrobat?

PDF files have no density and so no size in inches. All that is defined by specifying the density (resolution) and units when printing or converting to non-PDF raster data such as PNG or JPG.

Once you have converted your PDFs to TIF, there is no point in converting the TIFF back to PDF. If you start with a vector PDF and convert to raster TIF and then back to PDF, you will get a much enlarged PDF than the original and about the same as the TIFF file, since the conversion of the TIFF to PDF does not vectorize the data, but simply puts a vector shell about the raster tif image.

See http://www.imagemagick.org/Usage/formats/#vector

If your PDF is not vector in the beginning, but is already a raster image in a vector shell, such as from a scanner. The you already have a large PDF. I am not sure what point there is to converting back to PDF after modifying the raster TIFF.

fmw42 wrote: ↑2017-01-23T16:57:27-07:00 Where do the PDF files originate? Are they from a scanner as raster images in a PDF shell or as vector data from some PDF writer such as Acrobat?

PDF files have no density and so no size in inches. All that is defined by specifying the density (resolution) and units when printing or converting to non-PDF raster data such as PNG or JPG.

Once you have converted your PDFs to TIF, there is no point in converting the TIFF back to PDF. If you start with a vector PDF and convert to raster TIF and then back to PDF, you will get a much enlarged PDF than the original and about the same as the TIFF file, since the conversion of the TIFF to PDF does not vectorize the data, but simply puts a vector shell about the raster tif image.

See http://www.imagemagick.org/Usage/formats/#vector

If your PDF is not vector in the beginning, but is already a raster image in a vector shell, such as from a scanner. The you already have a large PDF. I am not sure what point there is to converting back to PDF after modifying the raster TIFF.

I teach high school mathematics and I write notes in Microsoft Word and sometimes LaTeX. Once my notes are completed, I compile them and create a PDF coursepack for myself and other members of my department. I am creating the PDFs just using the option in Microsoft word and use smallpdf as an online resource to compile all the pdf files into one large file. In class, rater than writing on a board, I convert my PDF into TIFF files (layers are extremely helpful) and write notes with my students digitally and often paste images from Geogebra examples that I do in class. I just use Autodesk Sketchbook for this. Afterwards, If I have students who are away for an event or if they are ill, I will often take the Tiff files that have completed class notes, convert them back into a pdf document and then put them onto a class website. I also share completed notes packages of my notes for new students coming into the country and also other teachers in my department and other schools. I just want to make sure that when they go to print the document, it prints properly.

Thank you for all of the help you have been providing me.

I would recommend that you specify both -density and -unit. If you do not specify the right units rather than dpi (inches), you will get dpc (centimeters) or the printer may not interpret your density value correctly. So if you want the printer to print your density in inches, then be sure to specify -units pixelsperinch along with whatever density you need to make 8x11 prints.