docs: Add 'Make PDF files smaller' post

source/_posts/make-pdf-files-smaller.md

@@ -0,0 +1,81 @@
+---
+title: Make PDF files smaller
+date: 2019-01-05 00:00:00
+tags:
+---
+
+The most effective ways of reducing the file size of a PDF is by converting to grayscale and reduce the resolution.
+
+<!-- more -->
+
+Requirement: ghostscript (installed by default in Ubuntu)
+
+Save the following script as "pdfcompress.sh".
+
+Usage: `sh pdfcompress.sh input.pdf`
+
+The output compressed file is named as "input.compressed.pdf"
+
+```bash
+#!/bin/sh
+
+filename=$(basename "$1")
+dir=$(dirname "$1")
+
+gs \
+	-sOutputFile="$dir/${filename%.*}.compressed.pdf" \
+	-sDEVICE=pdfwrite \
+	-dPDFSETTINGS=/ebook \
+	-sColorConversionStrategy=Gray \
+	-sColorConversionStrategyForImages=/Gray \
+	-dProcessColorModel=/DeviceGray \
+	-dCompatibilityLevel=1.4 \
+	-dNOPAUSE -dBATCH -dQUIET \
+	"$1"
+```
+
+
+Options ([more info](https://ghostscript.com/doc/current/Ps2pdf.htm#Options)):
+
+- Remove **ColorConversionStrategy**, **ColorConversionStrategyForImages** and **ProcessColorModel** lines to retain colour.
+- **PDFSETTINGS**:
+	- */default* selects output intended to be useful across a wide variety of uses. 72 DPI.
+	- */screen* selects low-resolution output similar to the Acrobat Distiller "Screen Optimized" setting. 72 DPI.
+	- */ebook* selects medium-resolution output similar to the Acrobat Distiller "eBook" setting. 150 DPI.
+	- */printer* selects output similar to the Acrobat Distiller "Print Optimized" setting. 300 DPI.
+	- */prepress* selects output similar to Acrobat Distiller "Prepress Optimized" setting. 300 DPI.
+
+</br>
+Use the following script to compress all PDFs in a folder.
+
+Usage: `sh pdfcompress.sh 'target folder'`
+
+```bash
+#!/bin/sh
+
+cd "$1"
+
+for i in *.pdf; do
+    [ -f "$i" ] || break
+
+	# Skip compressed PDFs
+	echo "$i" | grep --quiet ".compressed.pdf"
+
+	if [ $? = 1 ]
+	then
+		gs \
+			-sOutputFile="${i%.*}.compressed.pdf" \
+			-sDEVICE=pdfwrite \
+			-dPDFSETTINGS=/ebook \
+			-sColorConversionStrategy=Gray \
+			-sColorConversionStrategyForImages=/Gray \
+			-dProcessColorModel=/DeviceGray \
+			-dCompatibilityLevel=1.4 \
+			-dNOPAUSE -dBATCH -dQUIET \
+			"$i"
+	fi
+done
+```
+
+Source: [Internal Pointers](https://www.internalpointers.com/post/compress-pdf-file-ghostscript-linux), [firstdoit](https://gist.github.com/firstdoit/6390547), [ahmed-musallam](https://gist.github.com/ahmed-musallam/27de7d7c5ac68ecbd1ed65b6b48416f9), [Ghostscript Docs](https://ghostscript.com/doc/current/Ps2pdf.htm)
+