HTTP Content Negotiation/Compression: Use Base64 with Accept-Encoding/Content-Encoding?

I'm wondering if the following idea is working against the spirit and/or letter of HTTP Content Negotiation and HTTP Compression.

The Situation

The HTTP Client requests a resource:

HTTP GET /image.jpeg HTTP/1.1
Accept: image/jpeg

The HTTP Server returns this resource:

HTTP/1.1 200 OK
Content-Type: image/jpeg

The Idea

The Client thinks it's a good idea to request the resource encoded:

HTTP GET /image.jpeg HTTP/1.1
Accept: image/jpeg
Accept-Encoding: base64

The Server honors this request and returns the resource encoded:

HTTP/1.1 200 OK
Content-Type: image/jpeg
Content-Encoding: base64

The Question

I'm not quite happy with this idea. HTTP Compression, for which the Accept-Encoding and Content-Encoding headers are used, is about compressing data, not about increasing its size as Base64 does.

Is the use of base64 as a value for these headers a violation of the spirit and/or letter of HTTP Content Negotiation and HTTP Content Compression?