`sips` (Scriptable Image Processing System) commandline utility examples and tips in bash syntax (https://ss64.com/osx/sips.html)

bash-sips.sh

# Convert JPEG (filename.jpg) to PNG (filename.png)
sips -s format png filename.jpg --out filename.png

# Convert PNG (filename.png) to JPEG (filename.jpg)
sips -s format jpeg filename.png --out filename.jpeg

# Get PNG Image (filename.png) Size and DPI Info
sips -g dpiHeight -g dpiWidth -g pixelHeight -g pixelWidth -g samplesPerPixel -g bitsPerSample -g typeIdentifier filename.png
# Example Output:
# /path/to/filename-a.png
#   dpiHeight: 72.000
#   dpiWidth: 72.000
#   pixelHeight: 851
#   pixelWidth: 851
#   samplesPerPixel: 3
#   bitsPerSample: 8
#   typeIdentifier: public.png

# SIPS (Scriptable Image Processing System)
#
# References:
# - https://ss64.com/osx/sips.html
#
#
# Note, per Documentation, the `sips -s format {STRING}` command supports the following formats for conversion:
# - jpeg
# - tiff
# - png
# - gif
# - jp2
# - pict
# - bmp
# - qtif
# - psd
# - sgi
# - tga