108 lines
2.2 KiB
JavaScript
108 lines
2.2 KiB
JavaScript
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class Scratch {
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constructor(page, opts) {
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opts = opts || {}
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this.page = page
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this.canvasId = opts.canvasId || 'canvas'
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this.width = opts.width || 340
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this.height = opts.height + 20 || 150
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this.maskColor = opts.maskColor || '#D2D2D2'
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this.size = opts.size || 10
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this.r = this.size * 2
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this.area = this.r * this.r
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this.scale = opts.scale || 0.3
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this.totalArea = this.width * this.height
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this.init()
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}
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init() {
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this.show = false
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this.clearPoints = []
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this.ctx = uni.createCanvasContext(this.canvasId)
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this.drawMask()
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this.bindTouch()
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}
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drawMask() {
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this.ctx.setFillStyle(this.maskColor)
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this.ctx.fillRect(0, 0, this.width, this.height)
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this.ctx.draw()
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}
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bindTouch() {
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this.page.touchStart = (e) => {
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this.eraser(e, true)
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}
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this.page.touchMove = (e) => {
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this.eraser(e, false)
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}
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this.page.touchEnd = (e) => {
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if (this.show) {
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this.ctx.clearRect(0, 0, this.width, this.height)
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this.ctx.draw()
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}
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}
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}
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eraser(e, bool) {
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const len = this.clearPoints.length
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let count = 0
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const x = e.touches[0].x;
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const y = e.touches[0].y
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const x1 = x - this.size
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const y1 = y - this.size
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if (bool) {
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this.clearPoints.push({
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x1: x1,
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y1: y1,
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x2: x1 + this.r,
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y2: y1 + this.r
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})
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}
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for (const item of this.clearPoints) {
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if (item.x1 > x || item.y1 > y || item.x2 < x || item.y2 < y) {
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count++
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} else {
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break
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}
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}
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if (len === count) {
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this.clearPoints.push({
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x1: x1,
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y1: y1,
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x2: x1 + this.r,
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y2: y1 + this.r
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})
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}
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if (len && this.r * this.r * len > this.scale * this.totalArea) {
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this.show = true
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}
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this.clearArcFun(x, y, this.r, this.ctx)
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this.ctx.draw(true)
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}
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clearArcFun(x, y, r, ctx) {
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let stepClear = 1
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clearArc(x, y, r)
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function clearArc(x, y, radius) {
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const calcWidth = radius - stepClear
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const calcHeight = Math.sqrt(radius * radius - calcWidth * calcWidth)
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const posX = x - calcWidth
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const posY = y - calcHeight
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const widthX = 2 * calcWidth
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const heightY = 2 * calcHeight
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if (stepClear <= radius) {
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ctx.clearRect(posX, posY, widthX, heightY)
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stepClear += 1
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clearArc(x, y, radius)
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}
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}
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}
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}
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export default Scratch
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