ADVANCED COMPOSITING & RETOUCHING - Chapter 7, Exercise 1
Photoshop's Batch Command vs. GIMP's Command-Line Batch Mode
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QUESTION:
Explain the specific mechanical difference between how Photoshop's Batch
command runs an Action across a folder and how GIMP's command-line batch
mode runs a script across a folder.

SOLUTION / EXPLANATION:

Photoshop's Batch command (File > Automate > Batch) still runs the full,
normal Photoshop application - the same GUI you'd use interactively. What
Batch adds is automation on top of that running application: it takes a
previously recorded Action and, instead of you clicking "play" on one file
at a time, it feeds the application every file in a chosen source folder in
turn, running the Action against each one and handling the recorded
Open/Save steps so they point at the correct file each time. The graphical
application is still fully present and running throughout - Batch is best
understood as "the GUI, automated," not as a separate execution mode.

GIMP's command-line batch mode works on a fundamentally different
mechanism. Launching GIMP with the -i -b flags (as shown in this chapter's
code example) tells GIMP to run WITHOUT its graphical interface at all -
there's no window, no visible canvas, nothing to look at. GIMP runs purely
as a background engine, executing the Script-Fu (or Python-Fu) code passed
to it directly as a command-line argument, then exiting. This is described
in the chapter as GIMP running "headless" - the application's image-
processing capability is being used directly, with the entire graphical
layer skipped entirely, not merely hidden or minimized.

So the core mechanical difference is: Photoshop's Batch automates the GUI
application itself, running it against many files in sequence, while GIMP's
batch mode bypasses the GUI application altogether and runs the underlying
processing engine directly from a script, with no graphical interface ever
launching in the first place.

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WHY THIS WORKS AS AN ANSWER:
It describes precisely what each mechanism actually does at a technical
level (automating a running GUI vs. skipping the GUI entirely and running
headless), rather than treating both as equivalent ways of achieving the
same visible result.