Correct way to save map in PDF format

[monje314]

Hi.

I'm trying to save maps generated with Starplot as PDFs so I can print them on A4 paper (8.27 x 11.69 inches).

According to the documentation at https://starplot.dev/reference-mapplot/#starplot.MapPlot.export, I can pass additional variables that the savefig function in matplotlib accepts. I've been trying to save a map as a PDF on the paper size A4 as showed in this in this snippet (Note that using the papertype parameter to specify paper size is not available for the PDF format) :

....
from matplotlib.transforms import Bbox
....
bbox=Bbox([[0.0, 0.0], [8.27, 11.69]]) #paper size
mymap.export("file_name.pdf", format='pdf', padding=0.3, transparent=True, metadata={'Creator': 'Me', 'Title': 'Awesome'},  bbox_inches=bbox, orientation='landscape')

But I'm getting the following error:

TypeError: matplotlib.figure.Figure.savefig() got multiple values for keyword argument 'bbox_inches'

So, is it impossible to specify the paper size? If this isn't the correct way to save a map as a PDF on a specific paper size, what would be the correct way?

Thanks in advance for the help.

[steveberardi]

That error is getting raised because starplot hardcodes the value for bbox_inches to "tight" -- I think using the paper size here though would produce unexpected results, i.e. I'm guessing it'll just crop the plot at that size.

Although Starplot can export to PDF, I'd recommend exporting to PNG or SVG and then importing the result into some desktop publishing software (e.g. MS Word, Pages, InDesign, Affinity Publisher, etc) to create the PDF exactly how you'd like.

[monje314]

Thanks a lot for the reply.

I wrote a quick and dirty bash script to transform SVG to PDF
It assumes a portrait A4 paper. Try to use all height printable area (paper height minus top and bottom margis), calculate the size of the width and centre it. It shouldn't be difficult to adapt it to other scenarios.

#!/bin/bash

## A4 size (asume mm)
PAGE_WIDTH=297
PAGE_HEIGHT=210

## Margins (asume mm)
MARGIN_TOP=4
MARGIN_BOTTOM=6
MARGIN_LEFT=6
MARGIN_RIGHT=6

# Number of decimals to use.
# If not set, RATIO shall have no decimals, (which makes it not work)
SCALE=8

svg2pdf(){

        FILE_IN=$1
        EXTENSION="${FILE_IN##*.}"
        FILENAME="${FILE_IN%.*}"
        if [ "$EXTENSION" != "svg" ]; then
                echo "ABORTING: input file $FILE_IN has no extension \"svg\"."
                exit
        fi

        ## May be this is not the best way for get image size.
        SVG_WIDTH=$(grep -Po 'width="\K[^"]+pt' $FILE_IN |sed 's/pt$//')
        SVG_HEIGHT=$(grep -Po 'height="\K[^"]+pt' $FILE_IN |sed 's/pt$//')

        ## We choose HEIGHT to fill PAGE_HEIGHT (minus MARGIN_TOP and MARGIN_BOTTOM)
        HEIGHT=$(echo "scale=$SCALE; $PAGE_HEIGHT-$MARGIN_TOP-$MARGIN_BOTTOM" |bc)

        ## Calculate aspect ratio
        RATIO=$(echo "scale=$SCALE; $SVG_WIDTH/$SVG_HEIGHT" |bc)

        ## Calculate WIDTH
        WIDTH=$(echo "scale=$SCALE; $RATIO*$HEIGHT" |bc)

        LIMIT_WIDTH=$(echo "scale=$SCALE; $PAGE_WIDTH-$MARGIN_LEFT-$MARGIN_RIGHT" |bc)

        if [ $(echo "$WIDTH > $LIMIT_WIDTH"| bc) -eq 1 ]; then
                echo "WARNING: Paper width too small"
                echo "         Width: $WIDTH"
                echo "         Limit: $LIMIT_WIDTH"
        fi

        TOP=$MARGIN_TOP
        LEFT=$(echo "scale=$SCALE; ($PAGE_WIDTH-$WIDTH-$MARGIN_RIGHT+$MARGIN_LEFT)/2"| bc)

        ## rsvg-convert command is provided by package librsvg2-bin
        rsvg-convert --format=pdf --page-width=${PAGE_WIDTH}mm --width=${WIDTH}mm --page-height=${PAGE_HEIGHT}mm --height=${HEIGHT}mm --keep-aspect-ratio --top=${TOP}mm --left=${LEFT}mm --dpi-x=600 --dpi-y=600 $FILE_IN >${FILENAME}.pdf

}


if [ -z "$1" ]; then
        echo ABORTING: You must provide SVG filename as parameter
        exit
fi

svg2pdf $1

Just in case it's useful to anyone.

Regards.

[steveberardi]

thanks for sharing that script!

btw, there's also a good Python library WeasyPrint that lets you create PDFs from HTML/CSS. I've been using it for Sky Atlas.

[monje314]

I take note regarding the WeasyPrint library. Probably I shall use it in my next Startplot project.

Cheers.