Possible optimization

From: Clement Breaker

> Am just wondering if this could be made more efficient by using `javafx.scene.image.PixelBuffer` - would it allow you to arrange for `ReadPixels` to put the OpenGL image directly into a `PixelBuffer` that is used by a `WritableImage`? Then this means you could avoid the overhead of using an intermediate buffer that you have to first write into using `glReadPixels` and then read from using `setPixels`?

Patch: https://gist.github.com/Col-E/b6427eade7410663c97ec0b5a5f7fc02

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I have not yet done digging into whether or not this has measurable gains. Opening this so I don't forget about this.

Start with the linked patch and inspect the existing ReadPixels path, especially the use of glReadPixels and setPixels. Review JavaFX PixelBuffer and WritableImage integration, then measure whether avoiding the intermediate buffer provides a measurable gain. Done means documenting the benchmark result and, if beneficial, implementing the verified approach.

Written by the indexing model from the issue text.