What is the issue with the HTML Standard?

The HTML specification currently specifies the ImageData interface as a sort of "afterthought" inside the CanvasImageData interface specification.

E.g, here, at the very beginning of the normative text for the Pixel Manipulation section, we read

Objects that implement the CanvasImageData interface provide the following methods for reading and writing pixel data to the bitmap.

The new ImageData(sw, sh, settings) constructor steps are: [...]

This doesn't make much sense. The ImageData constructor isn't a method on CanvasImageData, or related to it at all.

What's missing is a separate "ImageData objects" section. The lowest-friction change here would be to add this section just before the "Pixel manipulation" subsection of the "The 2D rendering context" section. That said, because ImageData is quite is own independent thing (it's used by WebGL and WebGPU), it may be that it should be pulled out of the canvas section entirely.

In addition to the "the reorganized thing would make more sense" benefit, this would allow us to clean up the way that ImageData is written. In particular, this review comment observed that ImageData is initializing attributes (for all attributes), rather than defining internal fields and getters.