watermark png image with its created date-CodePudding

I need to watermark my png images with its created date.

I am trying to read png files exif data. But Captured png file with screenshot tool on linux doesn't have exif data.

I am using below script to watermark my png images with its created date :

#!/bin/bash

echo "Script for addding time stamp"
date --iso-8601=seconds  
shopt -s extglob

find . -iname "*.jpg" -o -iname "*.jpeg" -o -iname "*.tif" -o \
 -iname "*.tiff" -o -iname "*.png" | 

## Go through the results, saving each as $img
while IFS= read -r img; do
    ## Find will return full paths, so an image in the current
    ## directory will be ./foo.jpg and the first dot screws up 
    ## bash's pattern matching. Use basename and dirname to extract
    ## the needed information.
    name=$(basename "$img")
    path=$(dirname "$img")
    ext="${name/#*./}";
    
    ## Check whether this file has exif data
    if exiv2 "$img" 2>&1 | grep timestamp >/dev/null 
    ## If it does, read it and add the water mark   
    then
    echo "Processing $img...";
    convert "$img" -gravity SouthEast  -pointsize 22 -fill black \
             -annotate  30 30  %[exif:DateTimeOriginal] \
             "$path"/"${name/%.*/.time.$ext}";
    ## If the image has no exif data, use the creation date of the file.
    else
    echo "No Exif data in $img...";
      date=$(stat "$img" | grep Modify | cut -d ' ' -f 2,3 | cut -d ':' -f1,2)
      convert "$img" -gravity SouthEast  -pointsize 22 -fill black \
             -annotate  30 30  "$date" \
             "$path"/"${name/%.*/.time.$ext}";
    fi 
done

Expected Watermark format output:

But I need watermark with below date format (like its output $ date --iso-8601=seconds) -

2021-11-29T07:46:15 01:00

Actual WaterMark format output: But png image stat doesn't have this format so my watermark comes as -

2021-11-29 07:27

Can any one suggest me how can I modify my script to get the expected watermark on my png image.

Is there any another best way to watermark png images with its date created.

CodePudding user response：

On Linux, you can get the date format you want like this:

date=$(date -d "@$(stat -c %Y "$img")" --iso-8601=seconds)

stat -c %Y to use format specifiers for stat output
%Y is the date of last modification, in epoch seconds
GNU date -d @<epoch-seconds> to specify an input date, @ specifies epoch seconds format
Then specify the output format (--iso-8601=seconds)
BSD/Mac has slightly different syntax for stat

CodePudding user response：

Please try this on a COPY of a few images in a spare directory as I have not tested it. I think exiftool will add file modification date to your images in place of EXIF DateTimeOriginal:

exiftool -v "-FileModifyDate>DateTimeOriginal" *.png

You can see a summary of all time-related data about an image like this:

exiftool -time:all -G1 -a -s SOMEIMAGE.PNG
[System]        FileModifyDate                  : 2021:11:23 09:48:30 00:00
[System]        FileAccessDate                  : 2021:11:27 13:38:21 00:00
[System]        FileInodeChangeDate             : 2021:11:26 23:41:21 00:00

If you add the exiftool tag to your question, one of the specialists will probably suggest how you can change it to only add the data if not already present.

Also, consider using GNU Parallel if you have lots of images. Just put [gnu-parallel] in the Search box, along with image.

CodePudding user response：

If you want to tweak the output of the stat command on the image file, would you please try:

datestr=$(date --iso-8601=seconds -d @$(stat --printf='%Z\n' "$img"))

It assumes your date command supports -d option.
BTW I've changed the variable name to datestr to avoid the namespace conflict although it is harmless and just confusing.