How to automatically update dominant color of an image in Rails 7 using MiniMagick after image upload or change?

Question

I am working on a Rails 7 application and I'm trying to implement a feature where I calculate and update the dominant color of an event image whenever it is uploaded or changed. I'm using MiniMagick to process the image, and I want to store the dominant color in a dominant_color column in the events table.

What I am trying to achieve:

I want to automatically update the dominant color of the image whenever a new image is uploaded or the existing image is changed for an event.
The dominant_color should be stored as a hexadecimal color code (e.g., #ff5733).
I want to ensure this is efficient and only happens when necessary, avoiding unnecessary database updates or callbacks.

What I’ve implemented so far:

I’ve created a dominant_color column in my events table and wrote the following code in my Event model to calculate and store the dominant color when the image is attached or changed:

# app/models/event.rb

require 'mini_magick'

class Event < ApplicationRecord
   # Change to after_commit and use a different detection method
  after_commit :check_and_update_dominant_color, on: [:create, :update]

  private

  def should_update_dominant_color?
    image.attached? && 
    (saved_change_to_attribute?('image_attachment_id') || image.attachment&.saved_change_to_blob_id?)
  end

  def update_dominant_color
    return unless image.attached?

    # Ensure we're working with the actual blob data
    image.open do |tempfile|
      img = MiniMagick::Image.read(tempfile)
      img.resize '1x1'
      pixel = img.get_pixels[0][0]
      hex_color = rgb_to_hex(pixel)
      
      # Use update_column to avoid callbacks
      update_column(:dominant_color, hex_color)
    end
  end

  def rgb_to_hex(rgb_array)
    "#" + rgb_array[0..2].map { |c| c.to_s(16).rjust(2, '0') }.join
  end
end

Problem:

I am using after_commit to ensure that the dominant color is updated after the image is saved. However, it seems like the color isn't updating correctly when I upload or update an image.
The method should_update_dominant_color? is designed to check if the image has changed, but it might not be detecting changes properly, leading to the dominant color not being updated when it should.

What I’ve tried:

I’ve tested using after_save and after_commit, but neither approach seems to properly trigger the update when an image is attached or changed.
I’m using update_column to avoid triggering additional callbacks that might lead to unwanted side effects.

My questions:

Is there a more efficient or reliable way to detect changes to the image attachment that would guarantee the dominant color is updated correctly?
Is using after_commit the best approach for this, or should I consider a different callback?
Any tips on optimizing this process or handling edge cases like image deletion or updates?

I’d really appreciate any feedback, especially from those who’ve worked with MiniMagick or have implemented similar features. Thanks!

Edit: Testing the color extraction manually in the console worked

event = Event.find(3)
event.send(:update_dominant_color)
event.reload.dominant_color