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--- cs:pdf_to_pictures [2019/02/07 15:16]
paolo_bolzoni Add border parameter
+++ cs:pdf_to_pictures [2019/02/11 16:30] (current)
paolo_bolzoni Trim paper horizontally
@@ Line 1: / Line 1: @@
 ======= Convert PDF to pictures =======
-Seldom printers fail to print a PDF file, a is converting the file to a sequence of pictures; basically doing the whole process to decide where the inks should go in your computer before sending the result to the printer.
+Seldom printers fail to print a PDF file, a possible solution is to convert the file to a sequence of pictures; basically this means to do the whole process that decides where the inks should go in your computer; before sending the result to the printer.
-Ghostscript does most of the hard work creating the pictures, however it does not apply any kind of antialiasing so when creating a picture in the printing resolution (usually 300 DPI) the result will be poor.
+Ghostscript does most of the hard work creating the pictures, however it does not apply any kind of smoothing to the curves so when creating a picture in the printing resolution (usually 300 DPI) the result will be poor.
 To workaround this problem we use a trick similar to videogames antialiasing. We create the picture 4 times larger and we resize it later to the correct size applying smoothing algorithms.
-Finally we losslessy put all the pictures in a new PDF. The resulting PDF will have no text, no fonts or anything a part of pictures. So it lost much of its convenience and the resulting file will be much larger, however printers will not fail to print it.
+Finally we losslessy put all the pictures in a new PDF. The resulting PDF will have no text, no fonts or anything a part of pictures. So it loses much of its convenience and the resulting file will be much larger, however printers will not fail to print it.
 Software used:
@@ Line 18: / Line 18: @@
   $ gs -sDEVICE=pngalpha -o output-%04d.png -r1200 input.pdf
-Please note that 1200 is four time the wanted resolution, we want to print to 300DPI.
+Please note that 1200 is four times the wanted resolution, we want to print to 300DPI.
@@ Line 31: / Line 31: @@
+====== Excessive memory usage ======
+It is possible to use greater resolutions to print for example with 600DPI, just use ''-r2400''. But the ''convert'' step may require too much memory to resize the output ''.png'' files. It is the case, it is possible to limit the amount of memory using environment variables:
+  MAGICK_TEMPORARY_PATH=. MAGICK_AREA_LIMIT=1024mb  convert ...
+''convert'' will store its temporary files in the current directory and avoid using more than 1Gb of memory. The process might be slower, but it will end correctly.
+Here is [[https://www.imagemagick.org/script/resources.php#environment|the list of environment variables that ImageMagick understands]].
+====== Change paper size ======
+''img2pdf'' creates a ''.pdf'' file with the requested page size. But if the original ''.pdf'' was in another format the pages might have weird borders as the result will be squeezed, but not deformed. To print a letter size ''.pdf'' in A4 for example will result in very tall top and bottom borders; this happens because the letter paper size is wider and shorter, when squeezed in the A4 the horizontal borders will be almost the same (because the picture is just a bit smaller), but the vertical ones will be much taller.
+It is worth a try to trim the pictures to have the new paper size. To do so you need to know the correct size of the picture and ''convert''. For example, if you want to print 300DPI, the picture size will be the paper size **in inches** times 300.
+The command, for a 300DPI A4 will be:
+  $ convert input.png -gravity Center -crop 2481x3507+0+0 +repage output.png
+It is also possible to add ''-gravity Center -crop 2481x3507+0+0 +repage'' directly in Step two just before the output filename.

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