java - 椭圆与圆

Question

        Canvas canvas = Canvas.createIfSupported();

        canvas.setWidth("200px");
        canvas.setHeight("200px");

        RootPanel.get().add(canvas);

        Context2d context = canvas.getContext2d();
        context.setStrokeStyle("black");

        context.arc(50, 50, 20, 0, Math.PI*2);

        context.stroke();

为什么我这里用的是椭圆而不是圆？

Answer 1

您还必须设置坐标空间，使其与 Canvas 的宽高比 匹配。所以你可以添加以下行:

canvas.setCoordinateSpaceWidth(200);
canvas.setCoordinateSpaceHeight(200);