


html5 Canvas drawing tutorial (5)—arc method of drawing curves in canvas_html5 tutorial skills
In this article Drawing Lines on Canvas, I talked about how to draw straight lines. Logically, this article on drawing curves should have been published long ago, but since drawing curves on canvas is quite special, I haven’t figured it out yet, so Try it step by step.
One of the difficulties in drawing curves in canvas is that there are only 4 functions for curves! They are arc, arcTo, quadraticCurveTo, and bezierCurveTo. Let me start with the simplest arc method.
The function of arc is to draw a regular arc, which can be a complete circle or a certain arc of a circle. The syntax for arc is as follows: 🎜>
context.arc(x, y, radius, startAngle, endAngle, anticlockwise)
I will explain its parameters, that is,
arc(center of circle x, center of circle y, radius, starting angle, ending angle, counterclockwise or not)
The code is as follows:
ctx.arc(400,400,20,0,Math.PI*2); ctx.fill(); ctx.stroke();
Copy code
The code is as follows:
ctx.arc(400,400,20,0 ,Math.PI*2/4);

ctx.arc(400,400,20,0 ,Math.PI*2/4,true);

The code is as follows:
ctx.arc(400,400,20,Math .PI*2/4,Math.PI*2 Math.PI);
If our starting point is 90 degrees and the end point is also 90 degrees, the result is that nothing can be drawn, so I put the end point The angle was changed to 180 degrees, and finally the graph below was obtained.
Copy code
Code As follows:
However, this approach is just looking for trouble, and normal people would not use it.
Summary: The arc method of Canvas is a way to draw a positive arc. It can only draw positive arcs and cannot draw other strange arcs, such as S-shape - although I like it best S-shaped.

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