微信小程序实现图片多点裁剪_微信小程序 坐标点裁图

话不多说，直接上代码

1、页面布局

<view class="buttons" style="height: 50px;">
  <view 
  class="upload btn" 
  style="background-color: #d18118;"
  bindtap="uploadImage"> 上传图片 
  </view>
  <view
    class="getCropperImage btn"
    style="background-color: #04b00f;"
    bindtap="getCropperImage">
    生成图片
  </view>
</view>
<view class="canvas">
  <canvas 
  style="width: {{canvasWidth}}px;height: {{canvasHeight}}px;"
  type="2d" 
  id="canvas-1" 
  canvas-id="canvas-1"
  disable-scroll="true"
  ></canvas>

  <canvas 
  style="width: {{canvasWidth}}px;height: {{canvasHeight}}px;position: absolute;top: 0;z-index: 999;"
  type="2d" 
  id="canvas-2" 
  disable-scroll="true"
  bindtouchstart="touchStart"
  bindtouchmove="touchMove"
  bindtouchend="touchEnd"
  ></canvas>
</view>

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33

2、页面样式

page{
  padding: 0;
  -webkit-user-select: none;
  user-select: none;
  width: 100%;
  height: 100%;
  background-color: #c0c0c0;
  font-family: Arial, Helvetica, sans-serif;
  overflow-x: hidden;
}
.buttons{
  display: flex;
  flex-direction: row;
  justify-content: space-between;
  align-items: center;
  padding: 0 25rpx;
  border-bottom: 1rpx solid white;
}
.canvas{
  position: relative;
}

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22

3、页面逻辑

let ctx = null;
let canvas = null;
Page({
  data: {
    canvasWidth:300,
    canvasHeight:500,
    pixelRatio:2,

    pointRadius:12,// 裁剪框边角原点半径
    point:[[48,48],[312, 48],[312, 224],[48, 224]],// 裁剪框边角原点位置
    moveIndex:-1//点击的剪切框原点小标
  },

  onLoad (options) {
    const that = this;
    wx.getSystemInfo({
      success (res) {
        that.setData({
          canvasWidth:res.windowWidth,
          canvasHeight:res.windowHeight -50,
          pixelRatio: res.pixelRatio,
        })
      }
    })
  },

  uploadImage(){
    const that = this;
    wx.chooseMedia({
      count: 1,
      mediaType: ['image','video'],
      sourceType: ['album', 'camera'],
      maxDuration: 30,
      camera: 'back',
      success(res) {
        that.drawImage(res.tempFiles[0].tempFilePath);
      }
    })
  },

  drawImage(src){
    const self = this;
    wx.getImageInfo({
      src: src,
      success (res) {
        const width = self.data.canvasWidth;
        const height = self.data.canvasHeight;
        var innerAspectRadio = res.width / res.height;//图片宽高比
        var customAspectRadio = width / height;//画布宽高比
        let x = 0;
        let y = 0;
        let baseWidth = 0;//图片在画布宽度
        let baseHeight = 0;//图片在画布高度
        if (innerAspectRadio > customAspectRadio) {
          baseWidth = width*0.8;
          baseHeight = (width / innerAspectRadio)*0.8;
        } else {
          baseWidth = height * innerAspectRadio;
          baseHeight = height;
        }
        x = (width-baseWidth)/2;
        y = (height-baseHeight)/2;
        // 绘制图片
        wx.createSelectorQuery().select('#canvas-1').fields({ node: true, size: true }).exec((res) => {
          // Canvas 对象
          const canvas = res[0].node
          // 渲染上下文
          const ctx = canvas.getContext('2d');
          // 初始化画布大小
          const dpr = self.data.pixelRatio
          canvas.width = width * dpr
          canvas.height = height * dpr
          ctx.scale(dpr, dpr)
          // 开始绘制
          let image = canvas.createImage();//创建iamge实例
          image.src = src;  //引入图片
          image.onload = function () {
            ctx.drawImage(image, x, y, baseWidth, baseHeight);
            self.setData({
              point:[[x-10,y-10],[x+baseWidth+10,y-10],[x+baseWidth+10,y+baseHeight+10],[x-10,y+baseHeight+10]]
            },()=>{
              self.pointInit()
            })
          }
        })
      }
    })
  },

  pointInit(){
    const that = this;
    const query = wx.createSelectorQuery()
    query.select('#canvas-2').fields({ node: true, size: true }).exec((res) => {
      // Canvas 对象
      const canvas = res[0].node
      that.canvas = canvas;
      // 渲染上下文
      const ctx = canvas.getContext('2d');
      that.ctx = ctx;
      // 初始化画布大小
      const dpr = that.data.pixelRatio
      canvas.width = that.data.canvasWidth * dpr
      canvas.height = that.data.canvasHeight * dpr
      ctx.scale(dpr, dpr)
      // 开始绘制
      that.drawPoint(that.data.point)
    })
  },

  drawPoint(point){
    const ctx = this.ctx;
    const pointRadius = this.data.pointRadius;
    ctx.clearRect(0, 0, this.data.canvasWidth, this.data.canvasHeight)
    ctx.beginPath()
    ctx.fillStyle = 'rgb(0, 0, 200)';
    ctx.arc(point[0][0], point[0][1], pointRadius, 0, 2*Math.PI , true)
    ctx.arc(point[1][0], point[1][1], pointRadius, 0, 2*Math.PI , true)
    ctx.fill()
    ctx.beginPath()
    ctx.arc(point[2][0], point[2][1], pointRadius, 0, 2*Math.PI , true)
    ctx.arc(point[3][0], point[3][1], pointRadius, 0, 2*Math.PI , true)
    ctx.fill()
    ctx.beginPath()
    ctx.lineWidth = 4
    ctx.strokeStyle = 'rgba(255,255,255,0.6)';
    ctx.lineJoin = 'round'
    ctx.lineCap = 'round'
    ctx.lineTo(point[0][0], point[0][1])
    ctx.lineTo(point[1][0], point[1][1])
    ctx.lineTo(point[2][0], point[2][1])
    ctx.lineTo(point[3][0], point[3][1])
    ctx.lineTo(point[0][0], point[0][1])
    ctx.stroke()
    ctx.fillStyle = 'rgb(0, 0, 0, 0.5)';
    ctx.fill()
  },

  //  手势初始监测
  touchStart: function touchStart (e) {
    var that = this;
    var ref = e.touches[0];
    const point = this.data.point;
    const pointRadius = this.data.pointRadius;
    let moveIndex = -1;
    for(var i=0;i<4;i++){
      if(ref.x > (point[i][0]-pointRadius) && ref.x < (point[i][0]+pointRadius)){
        if(ref.y > (point[i][1]-pointRadius) && ref.y < (point[i][1]+pointRadius)){
          moveIndex = i;
          break;
        }
      }
    }
    if(moveIndex!=-1){
      that.setData({
        moveIndex:moveIndex
      })
    }
  },

  //  手势滑动
  touchMove: function touchMove (e) {
    var ref = e.touches[0];
    var x = ref.x;
    var y = ref.y;
    if(this.data.moveIndex!=-1){
      const point = this.data.point;
      const index = this.data.moveIndex;
      point[index][0] = x;
      point[index][1] = y;
      this.setData({
        point:point
      },()=>{
        this.drawPoint(point);
      })
    }
  },

  // 手势滑动结束
  touchEnd: function touchEnd (e) {
    var ref = e.changedTouches[0];
    var x = ref.x;
    var y = ref.y;
    if(this.data.moveIndex!=-1){
      const point = this.data.point;
      const index = this.data.moveIndex;
      point[index][0] = x;
      point[index][1] = y;
      this.setData({
        point:point,
        moveIndex:-1
      })
    }
  },

  getCropperImage(){
    const self = this;
    const point = this.data.point;
    wx.createSelectorQuery().select('#canvas-1').fields({ node: true, size: true }).exec((res) => {
      // Canvas 对象
      const canvas = res[0].node
      // 渲染上下文
      const ctx = canvas.getContext('2d');
      // 初始化画布大小
      // const dpr = self.data.pixelRatio
      // canvas.width = self.data.windowWidth * dpr
      // canvas.height = self.data.windowHeight * dpr
      // ctx.scale(dpr, dpr)
      // // 开始绘制
      // ctx.beginPath()
      // ctx.moveTo(point[0][0], point[0][1]);
      // ctx.lineTo(point[1][0], point[1][1]);
      // ctx.lineTo(point[2][0], point[2][1]);
      // ctx.lineTo(point[3][0], point[3][1]);
      // ctx.lineTo(point[0][0], point[0][1]);
      // //先关闭绘制路径。注意，此时将会使用直线连接当前端点和起始端点。
      // ctx.closePath();
      // ctx.fill()
      // ctx.clip()

      debugger
      wx.canvasToTempFilePath({
        x: 0,
        y: 0,
        width: 200,
        height: 200,
        destWidth: 200,
        destHeight: 200,
        canvasId: 'canvas-1',
        success: function (res) {
          debugger
          console.log(res.tempFilePath)
        },
        fail: function (res) {
          debugger
          console.log(res)
        },
      },this)
    })
    
  }
})

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242