There are several ways you can convert a PDF to an image format such as PNG or JPEG. However if you want to batch process / automate the conversion of several PDF files then the most efficient tool for this purpose is the Ghostscript.
Ghostscript is an interpreter for PDF and PostScript and is available on Windows, Unix, Linux and OpenVMS platforms. Click here to download Ghostscript.
Basic Ghostscript command
In its very simple form Ghostscript can be executed as below:
gs -sDevice=png16m -sOutputFile="pic-1.png" input.pdf
This command will convert a single page pdf file named input.pdf and saves the output to pic-1.png
sDevice option specifies the output device. It can be any available device such as jpeg, tiff32nc, pngmono, etc., For a list of all available devices check help using the command gs -h
Convert multi page PDF to PNG files
To convert a multi-page pdf file and generate separate png file for each page the command is:
gs -dNOPAUSE -dBATCH -sDEVICE=png16m -sOutputFile="Pic-%d.png" input.pdf
The above command will generate a separate PNG file for each page in the pdf file input.pdf. The %din the output file name is replaced by the page number hence the PNG files are named pic-1, pic-2, pic3, and so on., for pages 1, 2, 3, respectively.
-dNOPAUSE option disables the prompt and pause after each page is processed.
-dBATCH option causes Ghostscript to exit when processing of the file specified in the command has finished.
Convert specific page(s) of multi-page PDF to PNG
You could use the options –dFirstPage and –dLastPage to convert specific pages of a multi-page PDF document. For example, to convert that pages 3 and 4 of a pdf document named input.pdf, the command is:
gs -dNOPAUSE -dBATCH -sDEVICE=png16m –dFirstPage=3 –dLastPage=4 -sOutputFile="Pic-%d.png" input.pdf
Other Uses of Ghostscript
Ghostscript can do many more things other than just converting PDF and Postscript files to images such as viewing files, printing, changing the resolution of the images, rasterize a document, rendering a file in grayscale etc., There are also a number of utility scripts the invokes Ghostscript with appropriate options for converting PDF to Postscript and vice versa. Most popular among them are ps2pdf and pdf2ps.
