canvas基础2 -- 形状

 七巧板

七巧板本质上就是 分别由几个直线 拼成一个个图形，再将这些图形结合起来

var tangram = [
      { p: [{ x: 0, y: 0 }, { x: 800, y: 0 }, { x: 400, y: 400 }], color: "#caff67" },
      { p: [{ x: 0, y: 0 }, { x: 400, y: 400 }, { x: 0, y: 800 }], color: "#67beef" },
      { p: [{ x: 800, y: 0 }, { x: 800, y: 400 }, { x: 600, y: 600 }, { x: 600, y: 200 }], color: "#ef3d61" },
      { p: [{ x: 600, y: 200 }, { x: 600, y: 600 }, { x: 400, y: 400 }], color: "#f9f5la" },
      { p: [{ x: 400, y: 400 }, { x: 600, y: 600 }, { x: 400, y: 800 }, { x: 200, y: 600 }], color: "#a594c0" },
      { p: [{ x: 200, y: 600 }, { x: 400, y: 800 }, { x: 0, y: 800 }], color: "#fa8ecc" },
      { p: [{ x: 800, y: 400 }, { x: 800, y: 800 }, { x: 400, y: 800 }], color: "#f6ca29" }
    ]
    const canvas = document.getElementById('canvas')
    canvas.width = 800
    canvas.height = 800
    const context = canvas.getContext('2d')

    for (let i = 0; i < tangram.length; i++) {
      draw(tangram[i], context)
    }

    function draw(piece, cxt) {
      cxt.beginPath()
      cxt.moveTo(piece.p[0].x, piece.p[0].y)
      for (var i = 1; i < piece.p.length; i++) {
        cxt.lineTo(piece.p[i].x, piece.p[i].y)
      }
      cxt.closePath()

      cxt.fillStyle = piece.color
      cxt.fill()

      cxt.strokeStyle = "black"
      cxt.lineWidth = 3
      cxt.stroke()
    }

图示：

箭头

    context.beginPath()
    context.moveTo(100, 350) 
    context.lineTo(500, 350) 
    context.lineTo(500, 200) 
    context.lineTo(700, 400)
    context.lineTo(500, 600)
    context.lineTo(500, 450)
    context.lineTo(100, 450)
    context.closePath()
    
    context.lineWidth = 5  
    context.strokeStyle = '#058'

    context.stroke() 

图示：

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