proposal: image/jpeg: switch on m.ColorModel() instead of type in Encode()

[logica0419]

Proposal Details

The image/jpeg package contains TODO comments in the writer.go file mentioning "Switch on m.ColorModel() instead of type":

• https://cs.opensource.google/go/go/+/refs/tags/go1.23.3:src/image/jpeg/writer.go;l=518
• https://cs.opensource.google/go/go/+/refs/tags/go1.23.3:src/image/jpeg/writer.go;l=611

These TODO comments have been left unresolved for about ten years.

I am considering addressing these comments by implementing a switch statement on m.ColorModel().

Concerns:

• Are there any specific reasons why these comments have not been addressed for a long time?
• Should we account for handling *image.Gray16 images while implementing this change?

[gabyhelp]

Related Issues

• proposal: image/jpeg: support color channels other than 8 bits, eg Gray16 #51904

Related Code Changes

• image/jpeg: switch on m.ColorModel() instead of type assertion

_{(Emoji vote if this was helpful or unhelpful; more detailed feedback welcome in this discussion.)}

[logica0419]

I now fully understand the context.
I'll open another issue if I can find a general solution.