Replicating Photoshop's auto white-balance feature

[dmitrizzle]

What are you trying to achieve?

I'd like to set a white balance based on either a custom colour or the brightest pixel in the image:

Have you searched for similar questions?

Yes. Any help is appreciated, even a starting point of some sort — I am clueless.

Are you able to provide a minimal, standalone code sample that demonstrates this question?

Any image will do sharp("image.jpg")

Are you able to provide a sample image that helps explain the question?

[lovell]

I'm unsure if it's exactly what you're looking for, but the white point of an image can be altered by compositing solid grey over it using the colour-dodge blend mode.

https://sharp.pixelplumbing.com/api-composite

The following example uses middle grey:

sharp(input)
  .composite([
    {
      input: {
        create: {
          width: 3406,
          height: 2256,
          channels: 3,
          background: "#777",
        },
      },
      blend: "colour-dodge",
    },
  ])
  ...

[dmitrizzle]

Thank you, that answers my question.