cxt.arc(100,100,30,0,Math.PI*2,true); 括号内第一个和第二个参数,代表圆心坐标.第三个参数是圆的半径.第四个参数代表圆周起始位置.0 PI就是起始位置.沿顺时针路线,分别是0.5 PI（正下方）,1 PI和1.5 PI（正上方）,为画饼图提供了扇形范围的依据.第五个参数是弧长Math.PI*2就是整个圆,Math.PI是半圆.第六个参数是一个布尔值,true是顺时针false是顺时针.
时间： 2024-10-18 00:00:01
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