ImageMagick: convert image to PDF with A4 page size and image fit to page
Solution 1:
If you want to keep the original resolution (lossless) you can try the following command:
convert png.png -background white -page a4 myoutput.pdf
Based on a comment posted before: https://stackoverflow.com/a/24573341/6747994
@m4tx This command only makes sense if the picture has a resolution above 500x800px, it does not zoom in, to avoid pixelated thumbnails.
Solution 2:
You can convert to pdf using ImageMagick
convert png.png myout.pdf
but use pdfjam instead of ImageMagick to adjust the page size
pdfjam --paper a4paper --outfile myoutA4.pdf myout.pdf
pdfjam offers other options, which may fit your needs.
Solution 3:
Found this somewhere on stackoverflow:
convert *.jpg -resize 1240x1753 \
-extent 1240x1753 -gravity center \
-units PixelsPerInch -density 150x150 multipage.pdf