Why not just take a screenshot
A screenshot captures what fits on the screen. A table with two hundred rows becomes a picture of the first thirty, and there is no way to get the rest into one image without stitching several together by hand.
A screenshot is also whatever resolution your display happens to be. Here the scale is a control, so a table meant for a slide or a print layout can be drawn at two or three times the size and stay sharp.
PNG or JPEG
PNG for anything with text in it. It compresses without loss, so the letters stay crisp and the table rules stay one pixel wide.
JPEG compresses by throwing away detail around sharp edges, which is exactly what text and table rules are made of. The result has visible fuzz around every character. Use it only when something you are uploading to refuses PNG.
JPEG also has no transparency, so a background colour is always painted. That is why the background control exists rather than defaulting to none.
What you lose
Everything that made it data. An image cannot be sorted, searched, summed or pasted into a spreadsheet. If the recipient might want to work with the numbers, send them the table and the image, or just the table.