The circle drawn by canvas is 0 degrees, 90 degrees, 180 degrees and 360 degrees. obviously, there is no circle in other places. what is the reason

  html5, question

The circle drawn by Canvas at 0 degree, 90 degree, 180 degree, 360 degree is obviously flatter than other places ~ is it the canvas’s own problem or is there another solution?
图片描述

It’s not an anti-aliasing problem, I’ve also encountered it.

The reason is that the canvas size is exactly the same as the circle size, and when canvas draws the circle, radius is taken as the center of the lineWidth instead of the periphery, thus leading to the interception of half of the lineWidth.

Just increase the canvas size to four week by half lineWidth.