shot.sh

#!/bin/sh

BGCOLOR='#550000'
TEXTCOLOR='#eeeeee'
TEXTFONT='Ubuntu-Light'
TEXTSIZE=72
TEXT="\nHello this is a very long text\nwrapped in many lines"

# Put screenshot into a frame, change +86+242 if you change a frame PNG
composite -geometry +86+242 $1 frame.png $2

# Scale image down (assuming that the frame and the original screenshots are
# too large)
convert $2 -resize 720x $2 # 720x1280

# Scale image up and align phone frame to the center+bottom
convert $2 -gravity south -background $BGCOLOR -extent 1008x1782 $2

# Add text to the center+top
convert $2 -fill $TEXTCOLOR \
  -font $TEXTFONT -pointsize $TEXTSIZE -gravity north \
  -annotate +0+0 "$TEXT" $2

# Scale up to FullHD adding some padding on the left/right sides
convert $2 -gravity center -background $BGCOLOR -extent 1080x1920 $2