Unwanted outlines on 300dpi bitmap

[Acorn]

Gary, as if I would ever suggest doing evens.

I have tried a number of approaches and I cannot force a vertical gap in any.

My main suggest would be to work off a page size of 1000x800px and set your dpi to 288.
Work as normal but finally select the resultant image, which will be 800px height and lock-change the height to 768px.
The final image will be at 300dpi.

Technically the width will be 169.8px but make your shape 170x800px for convenience (evens!).
The 300dpi version will be 163.2x768px so you will have a sub-pixel overlap rather than a gap.

The fuller way to achieve fractional pixel widths and positioning is to work with SVG and embedded images.
Create a box, 163x768px.
Placeholder body:
<svg width="100%" height="100%"> <image width="163" height="768" xlink:href="index_html_files/fred.png" />
</svg>
fred is also 163x768px. fred has to be on the page (underneath or some other hiding mechanism).
I get a single artefact in Chrome and none in MS Edge up to 500% scaling.

Are you sure what you are seeing is not just failures in your graphics card and browser to fully render properly?

Acorn