需要用两个canvas实现类似微信聊天手写文字的功能,屏幕上面两个canvas,在下面的canvas上写文字,写完一个字生成一个图片,放到上面的canvas上,但是每次写完前面的文字都会消失,什么原因呢?
html
<view class="handCenter">
<canvas class="handWriting" canvas-id="handWriting" style="height:300px;width:100%">
</canvas>
</view>
<view style="border:1rpx solid black">
<canvas class="handWritingValue" disable-scroll="true" canvas-id="handWritingValue" bindtouchstart="uploadScaleStart"
bindtouchmove="uploadScaleMove" bindtouchend="uploadScaleEnd" style="height:150px">
</canvas>
<text style="color:blue" catchtap="subCanvas">确定</text>
<!-- <textarea value="{{Instructions}}" bindinput="inputInstructions" maxlength="90"></textarea> -->
</view>
<view class="handBtn">
<!-- <image src='{{img}}' wx:if="{{img}}"></image> -->
<button catchtap="subCanvas1" class="subBtn font-loaded">完成</button>
</view>
<!-- <image src="{{img}}"></image> -->
js
const app = getApp()
Page({
data: {
canvasName: 'handWriting',
ctx: '',
canvasWidth: 0,
canvasHeight: 0,
transparent: 1, // 透明度
selectColor: 'black',
lineColor: '#1A1A1A', // 颜色
lineSize: 1.5, // 笔记倍数
lineMin: 0.5, // 最小笔画半径
lineMax: 4, // 最大笔画半径
pressure: 1, // 默认压力
smoothness: 60, //顺滑度,用60的距离来计算速度
currentPoint: {},
currentLine: [], // 当前线条
firstTouch: true, // 第一次触发
radius: 1, //画圆的半径
cutArea: {
top: 0,
right: 0,
bottom: 0,
left: 0
}, //裁剪区域
bethelPoint: [], //保存所有线条 生成的贝塞尔点;
lastPoint: 0,
chirography: [], //笔迹
currentChirography: {}, //当前笔迹
linePrack: [], //划线轨迹 , 生成线条的实际点
tmpPath: '',
Instructions: '',
fontFamily: '手写字体',
textcount: 0,
canvasName1: 'handWritingValue',
imageList: []
},
// 笔迹开始
uploadScaleStart(e) {
if (e.type != 'touchstart') return false;
let ctx1 = this.data.ctx1;
ctx1.setFillStyle(this.data.lineColor); // 初始线条设置颜色
ctx1.setGlobalAlpha(this.data.transparent); // 设置半透明
let currentPoint = {
x: e.touches[0].x,
y: e.touches[0].y
}
let currentLine = this.data.currentLine;
currentLine.unshift({
time: new Date().getTime(),
dis: 0,
x: currentPoint.x,
y: currentPoint.y
})
this.setData({
currentPoint,
ctx1
// currentLine
})
if (this.data.firstTouch) {
this.setData({
cutArea: {
top: currentPoint.y,
right: currentPoint.x,
bottom: currentPoint.y,
left: currentPoint.x
},
firstTouch: false
})
}
this.pointToLine(currentLine);
},
// 笔迹移动
uploadScaleMove(e) {
if (e.type != 'touchmove') return false;
if (e.cancelable) {
// 判断默认行为是否已经被禁用
if (!e.defaultPrevented) {
e.preventDefault();
}
}
let point = {
x: e.touches[0].x,
y: e.touches[0].y
}
//测试裁剪
if (point.y < this.data.cutArea.top) {
this.data.cutArea.top = point.y;
}
if (point.y < 0) this.data.cutArea.top = 0;
if (point.x > this.data.cutArea.right) {
this.data.cutArea.right = point.x;
}
if (this.data.canvasWidth - point.x <= 0) {
this.data.cutArea.right = this.data.canvasWidth;
}
if (point.y > this.data.cutArea.bottom) {
this.data.cutArea.bottom = point.y;
}
if (this.data.canvasHeight - point.y <= 0) {
this.data.cutArea.bottom = this.data.canvasHeight;
}
if (point.x < this.data.cutArea.left) {
this.data.cutArea.left = point.x;
}
if (point.x < 0) this.data.cutArea.left = 0;
this.setData({
lastPoint: this.data.currentPoint,
currentPoint: point
})
let currentLine = this.data.currentLine
currentLine.unshift({
time: new Date().getTime(),
dis: this.distance(this.data.currentPoint, this.data.lastPoint),
x: point.x,
y: point.y
})
// this.setData({
// currentLine
// })
this.pointToLine(currentLine);
},
// 笔迹结束
uploadScaleEnd(e) {
if (e.type != 'touchend') return 0;
let point = {
x: e.changedTouches[0].x,
y: e.changedTouches[0].y
}
this.setData({
lastPoint: this.data.currentPoint,
currentPoint: point
})
let currentLine = this.data.currentLine
currentLine.unshift({
time: new Date().getTime(),
dis: this.distance(this.data.currentPoint, this.data.lastPoint),
x: point.x,
y: point.y
})
if (currentLine.length > 2) {
var info = (currentLine[0].time - currentLine[currentLine.length - 1].time) / currentLine.length;
//$("#info").text(info.toFixed(2));
}
//一笔结束,保存笔迹的坐标点,清空,当前笔迹
//增加判断是否在手写区域;
this.pointToLine(currentLine);
var currentChirography = {
lineSize: this.data.lineSize,
lineColor: this.data.lineColor
};
var chirography = this.data.chirography
chirography.unshift(currentChirography);
this.setData({
chirography
})
var linePrack = this.data.linePrack
linePrack.unshift(this.data.currentLine);
this.setData({
linePrack,
currentLine: []
})
},
onLoad() {
let that = this
let img = wx.getStorageSync('nameImg')
let canvasName = this.data.canvasName
let canvasName1 = this.data.canvasName1
let ctx = wx.createCanvasContext(canvasName)
let ctx1 = wx.createCanvasContext(canvasName1)
// ctx1.drawImage(img,100, 0, 50, 50) // 宽 高
// ctx1.draw()
this.setData({
ctx: ctx,
img: img,
ctx1: ctx1
})
wx.loadFontFace({
family: this.data.fontFamily,
source: 'url("https://cdn.myxh.kimnxcx.com/public/sxzt.TTF")',
success(res) {
that.setData({
loaded: true
})
}
});
var query = wx.createSelectorQuery();
query.select('.handCenter').boundingClientRect(rect => {
this.setData({
canvasWidth: rect.width,
canvasHeight: rect.height
})
}).exec();
},
inputInstructions: function (e) {
let ctx = this.data.ctx
ctx.setFontSize(1)
ctx.setFillStyle('black')
ctx.lineWidth = 0.5
ctx.font = '30px 手写字体'
let arr = []
arr = this.canvasWorkBreak(e.detail.value)
for (let i in arr) {
let ym = (parseInt(i) + 1) * 30
ctx.fillText(arr[i], 0, ym)
}
let height = (arr.length) * 30
ctx.drawImage(this.data.img, 200, height, 100, 50) // 宽 高
ctx.draw()
this.setData({
ctx: ctx,
Instructions: e.detail.value
})
},
canvasWorkBreak(text) {
const textLength = text.length
let textRowArr = []
let tmp = 0
let leng = Math.ceil(this.data.canvasWidth / 30)
while (1) {
textRowArr.push(text.substr(tmp, leng))
tmp += parseInt(leng)
if (tmp >= textLength) {
return textRowArr
}
}
},
drawText(t, x, y, w) {
var chr = t.split("");
var temp = "";
var row = [];
context.font = "20px Arial";
context.fillStyle = "black";
context.textBaseline = "middle";
for (var a = 0; a < chr.length; a++) {
if (context.measureText(temp).width < w) {
;
} else {
row.push(temp);
temp = "";
}
temp += chr[a];
}
row.push(temp);
for (var b = 0; b < row.length; b++) {
context.fillText(row[b], x, y + (b + 1) * 20);
}
},
subCanvas() {
// 新增我的
let that = this
let canvasDown = this.data.ctx1;
let canvasUp = this.data.ctx
let numx = Math.floor(this.data.canvasWidth / 60)
let numy = Math.floor(this.data.canvasHeight / 60)
let count = this.data.textcount
canvasDown.draw(true, setTimeout(function () { //我的新增定时器及回调
wx.canvasToTempFilePath({
x: 0,
y: 0,
width: that.data.canvasWidth,
height: that.data.canvasHeight,
canvasId: 'handWritingValue',
fileType: 'png',
success: function (res) {
that.setData({
tmpPath: res.tempFilePath
})
that.data.imageList.push(res.tempFilePath)
count += 1
let width = 0
let height = 0
if (count < numx) {
width = 60 * (count - 1)
height = 0
}
let arr = that.split_array(that.data.imageList,numx)
for(let i in arr){
for(let j in arr[i]){
that.data.ctx.drawImage(arr[i][j], 60*j, 60*i, 60, 60) // 宽 高
that.data.ctx.draw()
}
}
// canvasUp.drawImage(res.tempFilePath, width, height, 60, 60) // 宽 高
// canvasUp.draw()
canvasDown.clearRect(0, 0, 700, 730)
canvasDown.draw()
that.setData({
// ctx: canvasUp,
// ctx1: canvasDown,
textcount: count,
imageList:that.data.imageList
})
}
}, canvasDown)
}, 1000))
},
subCanvas1(){
let that = this
let pages = getCurrentPages();
let prevPage = pages[pages.length - 2];
prevPage.setData({
imageList:that.data.imageList
})
// wx.setStorageSync('nameImg', that.data.tmpPath)
wx.navigateBack({
delta: 1,
})
},
split_array(arr, len) {
var a_len = arr.length;
var result = [];
for (var i = 0; i < a_len; i += len) {
result.push(arr.slice(i, i + len));
}
return result;
},
// 新增将保存的图片路径上传到文件服务器
upImgs: function (imgurl, index) {
console.log(imgurl, '看下路径是多少')
var that = this;
wx.uploadFile({
url: apiEev.api + 'xxxx', //后台上传路径
filePath: imgurl,
name: 'file',
header: {
'content-type': 'multipart/form-data'
},
formData: null,
success: function (res) {
console.log(res) //接口返回网络路径
var data = JSON.parse(res.data)
console.log(data, '看下data是个啥')
if (data.code == "success") {
console.log('成功')
}
}
})
},
retDraw() {
this.data.ctx.clearRect(0, 0, 700, 730)
this.data.ctx.draw()
this.setData({
tmpPath: ''
})
},
//画两点之间的线条;参数为:line,会绘制最近的开始的两个点;
pointToLine(line) {
this.calcBethelLine(line);
return;
},
//计算插值的方式;
calcBethelLine(line) {
if (line.length <= 1) {
line[0].r = this.data.radius;
return;
}
let x0, x1, x2, y0, y1, y2, r0, r1, r2, len, lastRadius, dis = 0,
time = 0,
curveValue = 0.5;
if (line.length <= 2) {
x0 = line[1].x
y0 = line[1].y
x2 = line[1].x + (line[0].x - line[1].x) * curveValue;
y2 = line[1].y + (line[0].y - line[1].y) * curveValue;
//x2 = line[1].x;
//y2 = line[1].y;
x1 = x0 + (x2 - x0) * curveValue;
y1 = y0 + (y2 - y0) * curveValue;;
} else {
x0 = line[2].x + (line[1].x - line[2].x) * curveValue;
y0 = line[2].y + (line[1].y - line[2].y) * curveValue;
x1 = line[1].x;
y1 = line[1].y;
x2 = x1 + (line[0].x - x1) * curveValue;
y2 = y1 + (line[0].y - y1) * curveValue;
}
//从计算公式看,三个点分别是(x0,y0),(x1,y1),(x2,y2) ;(x1,y1)这个是控制点,控制点不会落在曲线上;实际上,这个点还会手写获取的实际点,却落在曲线上
len = this.distance({
x: x2,
y: y2
}, {
x: x0,
y: y0
});
lastRadius = this.data.radius;
for (let n = 0; n < line.length - 1; n++) {
dis += line[n].dis;
time += line[n].time - line[n + 1].time;
if (dis > this.data.smoothness) break;
}
this.setData({
radius: Math.min(time / len * this.data.pressure + this.data.lineMin, this.data.lineMax) * this.data.lineSize
});
line[0].r = this.data.radius;
//计算笔迹半径;
if (line.length <= 2) {
r0 = (lastRadius + this.data.radius) / 2;
r1 = r0;
r2 = r1;
//return;
} else {
r0 = (line[2].r + line[1].r) / 2;
r1 = line[1].r;
r2 = (line[1].r + line[0].r) / 2;
}
let n = 5;
let point = [];
for (let i = 0; i < n; i++) {
let t = i / (n - 1);
let x = (1 - t) * (1 - t) * x0 + 2 * t * (1 - t) * x1 + t * t * x2;
let y = (1 - t) * (1 - t) * y0 + 2 * t * (1 - t) * y1 + t * t * y2;
let r = lastRadius + (this.data.radius - lastRadius) / n * i;
point.push({
x: x,
y: y,
r: r
});
if (point.length == 3) {
let a = this.ctaCalc(point[0].x, point[0].y, point[0].r, point[1].x, point[1].y, point[1].r, point[2].x, point[2].y, point[2].r);
a[0].color = this.data.lineColor;
// let bethelPoint = this.data.bethelPoint;
// console.log(a)
// console.log(this.data.bethelPoint)
// bethelPoint = bethelPoint.push(a);
this.bethelDraw(a, 1);
point = [{
x: x,
y: y,
r: r
}];
}
}
this.setData({
currentLine: line
})
},
//求两点之间距离
distance(a, b) {
let x = b.x - a.x;
let y = b.y - a.y;
return Math.sqrt(x * x + y * y);
},
ctaCalc(x0, y0, r0, x1, y1, r1, x2, y2, r2) {
let a = [],
vx01, vy01, norm, n_x0, n_y0, vx21, vy21, n_x2, n_y2;
vx01 = x1 - x0;
vy01 = y1 - y0;
norm = Math.sqrt(vx01 * vx01 + vy01 * vy01 + 0.0001) * 2;
vx01 = vx01 / norm * r0;
vy01 = vy01 / norm * r0;
n_x0 = vy01;
n_y0 = -vx01;
vx21 = x1 - x2;
vy21 = y1 - y2;
norm = Math.sqrt(vx21 * vx21 + vy21 * vy21 + 0.0001) * 2;
vx21 = vx21 / norm * r2;
vy21 = vy21 / norm * r2;
n_x2 = -vy21;
n_y2 = vx21;
a.push({
mx: x0 + n_x0,
my: y0 + n_y0,
color: "#1A1A1A"
});
a.push({
c1x: x1 + n_x0,
c1y: y1 + n_y0,
c2x: x1 + n_x2,
c2y: y1 + n_y2,
ex: x2 + n_x2,
ey: y2 + n_y2
});
a.push({
c1x: x2 + n_x2 - vx21,
c1y: y2 + n_y2 - vy21,
c2x: x2 - n_x2 - vx21,
c2y: y2 - n_y2 - vy21,
ex: x2 - n_x2,
ey: y2 - n_y2
});
a.push({
c1x: x1 - n_x2,
c1y: y1 - n_y2,
c2x: x1 - n_x0,
c2y: y1 - n_y0,
ex: x0 - n_x0,
ey: y0 - n_y0
});
a.push({
c1x: x0 - n_x0 - vx01,
c1y: y0 - n_y0 - vy01,
c2x: x0 + n_x0 - vx01,
c2y: y0 + n_y0 - vy01,
ex: x0 + n_x0,
ey: y0 + n_y0
});
a[0].mx = a[0].mx.toFixed(1);
a[0].mx = parseFloat(a[0].mx);
a[0].my = a[0].my.toFixed(1);
a[0].my = parseFloat(a[0].my);
for (let i = 1; i < a.length; i++) {
a[i].c1x = a[i].c1x.toFixed(1);
a[i].c1x = parseFloat(a[i].c1x);
a[i].c1y = a[i].c1y.toFixed(1);
a[i].c1y = parseFloat(a[i].c1y);
a[i].c2x = a[i].c2x.toFixed(1);
a[i].c2x = parseFloat(a[i].c2x);
a[i].c2y = a[i].c2y.toFixed(1);
a[i].c2y = parseFloat(a[i].c2y);
a[i].ex = a[i].ex.toFixed(1);
a[i].ex = parseFloat(a[i].ex);
a[i].ey = a[i].ey.toFixed(1);
a[i].ey = parseFloat(a[i].ey);
}
return a;
},
bethelDraw(point, is_fill, color) {
// 新增我的
let that = this
let ctx = this.data.ctx1;
ctx.beginPath();
ctx.moveTo(point[0].mx, point[0].my);
if (undefined != color) {
ctx.setFillStyle(color);
ctx.setStrokeStyle(color);
} else {
ctx.setFillStyle(point[0].color);
ctx.setStrokeStyle(point[0].color);
}
for (let i = 1; i < point.length; i++) {
ctx.bezierCurveTo(point[i].c1x, point[i].c1y, point[i].c2x, point[i].c2y, point[i].ex, point[i].ey);
}
ctx.stroke();
if (undefined != is_fill) {
ctx.fill(); //填充图形 ( 后绘制的图形会覆盖前面的图形, 绘制时注意先后顺序 )
}
ctx.draw(true)
},
selectColorEvent(event) {
var color = event.currentTarget.dataset.colorValue;
var colorSelected = event.currentTarget.dataset.color;
this.setData({
selectColor: colorSelected,
lineColor: color
})
}
})
网友回复
想到名字了: