gs pdf

brew install ghostscript

# predefined ebook compression
```
gs -sDEVICE=pdfwrite -dPDFSETTINGS=/ebook -dNOPAUSE -dQUIET -dBATCH -sOutputFile="output.pdf" input.pdf
```

compress with resolution:

144 can be replaced to 288 or further, but since 144 is slightly worse than above default, and 288 has good quality but may still too big in some situations

```
gs \
 -q -dNOPAUSE -dBATCH -dSAFER \
 -sDEVICE=pdfwrite \
 -dCompatibilityLevel=1.3 \
 -dPDFSETTINGS=/screen \
 -dEmbedAllFonts=true -dSubsetFonts=true \
 -dColorImageDownsampleType=/Bicubic \
 -dColorImageResolution=144 \
 -dGrayImageDownsampleType=/Bicubic \
 -dGrayImageResolution=144 \
 -dMonoImageDownsampleType=/Bicubic \
 -dMonoImageResolution=144 \
 -sOutputFile=output.pdf \
 input.pdf
```


simpler sh function:

```
pdfcompress() {
  gs -sDEVICE=pdfwrite -dPDFSETTINGS=/ebook -dNOPAUSE -dQUIET -dBATCH -sOutputFile="$1.compressed.pdf" $1
}

# merge pdf
cpdf () {
  gs -q -dNOPAUSE -dBATCH -sDEVICE=pdfwrite -sOutputFile="$1" "${@:2}"
}
```