Subtlemark: Tool for adding subtle watermarks to images. Parameter customization: position (TL,TC,TR,BL,BC,BR), font, font-size, caption, textcolor, bgcolor. Also supports predefined styles.

subtlemark.sh

#!/bin/bash

version=0.1.4
versionDate="2014-09-02"

function showHelp() {
echo "subtlemark - add subtle watermarks to images

Usage:
----------------------------------------
\$ subtlemark [options] FILE OUTPUT

Options:
-e, --extend                If set, image is extended by label.
-s STYLE, --style STYLE     Select a user defined style
-c COLOR, --color COLOR     Override text color
-b COLOR, --bgcolor COLOR   Override background color
-f FONT,  --font FONT       Override font name
-F SIZE,  --font-size SIZE  Override font point size
-t TEXT,  --text TEXT       Override image caption
-p PLACE, --place PLACE     Override caption location
                            Where PLACE is any of:
                              NorthWest, North, NorthEast,
                              SouthWest, South, SouthEast

Other:
-h, --help                  Show help
-V, --version               Outputs version information
-v, --verbose               Enables verbose mode

Examples
----------------------------------------
Add watermark w/default settings
\$ subtlemark image.png out.png

Extend image to add watermark w/default settings
\$ subtlemark -e image.png out.png

Add watermark using style \"A\"
\$ subtlemark -s A image.png out.png

Add watermark with solid white bakground and red text
\$ subtlemark -c red -b white image.png out.png

Same as above, with RGB color code
\$ subtlemark -c '#F00' -b '#FFF' image.png out.png

Transparent background
\$ subtlemark -b none image.png out.png

Semi-Transparent text and background color (#RGBA)
\$ subtlemark -c '#FF05BB77' -b '#7775' image.png out.png

Custom caption
\$ subtlemark -t \"This is my caption\" image.png out.png

Specify font and font size to use
\$ subtlemark -f 'Verdana-Regular' image.png out.png

Place the watermark on top left corner
\$ subtlemark -p NorthWest image.png out.png

Mainted at: https://gist.github.com/swarminglogic/e563571ec4d11ec0901b
Author:     Roald Fernandez (github@swarminglogic.com)
Version:    $version ($versionDate)
License:    CC-zero (public domain)
"
    exit $1
}

leftovers=""
function parseParameters() {
    while test $# -gt 0; do
        case "$1" in
            -h|--help)
                showHelp 0 ;;
            -V|--version)
                shift ; echo "subtlemark $version" ; exit 1 ;;
            -e|--extend)
                shift ; param_is_extended=true ;;
            -s|--style)
                shift ; param_style=$1 ;     shift ;;
            -c|--color)
                shift ; param_color=$1 ;     shift ;;
            -b|--bgcolor)
                shift ; param_bgcolor=$1 ;   shift ;;
            -f|--font)
                shift ; param_font=$1 ;      shift ;;
            -F|--font-size)
                shift ; param_fontsize=$1 ;  shift ;;
            -t|--text)
                shift ; param_caption=$1 ;   shift ;;
            -p|--place)
                shift ; param_placement=$1 ; shift ;;
            -v|--verbose)
                shift ; is_verbose=true ;;
            *)
                leftovers="$leftovers "$1 ;  shift ;;
        esac
    done
}

# Creates a dummy text image to determine line height of font/fontsize combo
# $1 fontname $2 pointsize
function computeFontLineHeight() {
    if ! identify -list font | grep -q "Font: $1\$" ; then
        echo "Error: Could not locate font: $1" >&2
        if identify -list font | grep -qi "Font: .*$1" ; then
            echo "Try one of these:" >&2
            identify -list font | grep -i "Font: .*$1" >&2
        fi
        return 1;
    fi
    tmpfile=$(tempfile --suffix ".png")
    convert -background none -fill black \
        -font "$1" -pointsize $2 label:'abcXYZ' $tmpfile
    echo $(identify -format %h $tmpfile)
    rm $tmpfile
    return 0;
}

# Parse parameters, or exit with help if none
if [ $# -gt 0 ] ; then parseParameters "$@" ; else
    echo "Error: Missing parameters. See: $0 --help" >&2
    exit 1
fi

# Set $leftovers as script parameters
# Check if either or both FILE OUTPUT is missing:
set -- $leftovers
if [ ! $# -eq 2 ] ; then
    echo "Error: Missing input/output parameters" >&2
    exit 1
fi

# Validate input file
file=$1
ofile=$2

# Configure based on specified styles:
if [ -n "$param_style" ] ; then
    # Dummy style "A". Only include desired fields
    if [ "$param_style" == "A" ] ; then
        color="#AAA"
        bgcolor="#F00"
        font="Arial-Regular"
        fontsize=10
        is_extended=false
        placement=SouthEast
        caption="Roald Fernandez  swarminglogic.com CC-BY"
    else
        echo "Error: Unknown style: $param_style" >&2
        exit 1
    fi
fi

# Priority of paramter configurations:
# [User override] >> [Style Override] >> [Defaults]
is_extended=${param_is_extended:-${is_extended:-false}}

color=${param_color:-${color:-"#8888"}}
bgcolor=${param_bgcolor:-${bgcolor:-"#3339"}}

font=${param_font:-${font:-"Silkscreen"}}
fontsize=${param_fontsize:-${fontsize:-8}}
font_line_height=$(computeFontLineHeight "$font" "$fontsize")
[ $? -eq 1 ] && exit 1;

if [ -n "$param_placement" ] ; then
    if [ "$param_placement" != NorthWest ] && \
        [ "$param_placement" != North     ] && \
        [ "$param_placement" != NorthEast ] && \
        [ "$param_placement" != SouthWest ] && \
        [ "$param_placement" != South     ] && \
        [ "$param_placement" != SouthEast ] ; then
        echo "Error: Bad placement parameter: $param_placement" >&2
        exit 1
    fi
fi
placement=${param_placement:-${placement:-SouthEast}}

default_caption="Roald Fernandez  swarminglogic.com  $(date +'%Y-%m-%d')  CC-BY"
caption=${param_caption:-${caption:-$default_caption}}


if [ "$is_verbose" == "true" ] ; then
    echo "------------ VERBOSE ------------"
    echo "Input file:   ${file}"
    echo "Output file:  ${ofile}"
    echo "Is Extended:  ${is_extended}"
    echo "Style:        ${param_style:-N/A}"
    echo "Text color:   ${color}"
    echo "BG color:     ${bgcolor}"
    echo "Text:         ${caption}"
    echo "Placement:    ${placement}"
    echo "Font:         ${font}"
    echo "Font size:    ${fontsize} "
    echo "Font line height (calculated): ${font_line_height:-N/A}"
    echo "---------------------------------"
fi

# Check of input file exists.
if [ ! -e "$file" ] ; then
    echo "Error: Cannot access input file: $file" >&2
    exit 1
fi

if [ "$placement" == NorthWest ] || \
    [ "$placement" == North ] || \
    [ "$placement" == NorthEast ] ; then
    is_top=true
fi

if [ "$is_extended" == "true" ] ; then
    [  "$is_top" == true ] && swap="+swap"
    convert $file  -background "$bgcolor" \
        -font "$font" \
        -pointsize $fontsize \
        -fill "$color" \
        label:"  $caption  " \
        $swap -gravity $placement -append $ofile
else
    width=$(identify -format %w $file)
    height=$(identify -format %h $file)
    if [ "$is_top" == true ] ; then
        rect="0,0,${width},${font_line_height}"
    else
        rect="0,$((height-$font_line_height)),${width},${height}"
    fi
    convert $file \
        -fill "$bgcolor" -draw "rectangle ${rect}" \
        -font "$font" \
        -pointsize $fontsize \
        -fill "$color" \
        -gravity $placement \
        -draw "text 0,1 '  $caption  '" \
        $ofile
fi