Polygonal lasso tool went mad

Question

When I use the Polygonal lasso tool to select a new layer, the line won't go cross the pixel to another one but go step by step through the pixel's line like the photo below, it turned straight line into strange stair-steps. How can I fix this ?

Answer 1

You are zoomed in to the pixel level of your image.

There's no way to cut a pixel in half, when zoomed out it looks smooth, in reality it's just "a staircase" selection.

What looks like this zoomed out

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...looks like this when zoomed in

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