How to use WeChat applet to crop image selection area-JS Tutorial-php.cn

How to use WeChat applet to crop image selection area

亚连

Release： 2018-06-22 18:02:34

Original

2102 people have browsed it

This article mainly introduces the method of screen cropping in the selected area of the WeChat applet image. The editor thinks it is quite good, so I will share it with you now and give it as a reference. Let’s follow the editor and take a look.

This article introduces the method of screen cropping in the selected area of WeChat applet pictures, and shares it with everyone. The details are as follows:

Rendering

##HTML code

<view class="index_all_box">
 <view class="imgCut_header">
 <view class="imgCut_header_l" bindtap=&#39;okCutImg&#39;>开始裁剪</view>
 <view class="imgCut_header_m" bindtap=&#39;clickUpImg&#39;>点击上传图片</view>
 <view class="imgCut_header_r" bindtap=&#39;okBtn&#39;>点击确认</view>
 </view>
 <!-- 选择裁剪模式 -->
 <view class="selectCutMode" wx:if=&#39;{{alreay}}&#39;>
 <view class="selectCutMode_in {{cutType?&#39;selectCutMode_in_act&#39;:&#39;&#39;}}" bindtap=&#39;etcType&#39;>
  等屏裁剪
 </view>
 <view class="selectCutMode_in {{!cutType?&#39;selectCutMode_in_act&#39;:&#39;&#39;}}" bindtap=&#39;areaType&#39;>
  区域裁剪
 </view>
 </view>
 <view class="areaSelct_box" wx:if=&#39;{{!cutType && alreay}}&#39;>
 <slider bindchange="areaChange" min="50" max="100" show-value value=&#39;{{propor}}&#39;/>
 </view>
 <view class="cutImg_box" wx:if=&#39;{{!prienFlag}}&#39;>
 <view class="cutImg_box_t">
  <image src="{{cutImgUrl}}" mode=&#39;widthFix&#39;></image>
 </view>
 <view class="clickCutImg_txt" bindtap=&#39;againBtn&#39;>重新裁剪</view>
 </view>
 <view class="allCavans" wx:if=&#39;{{prienFlag}}&#39; style=&#39;width: {{canvasW}}px;height: {{canvasH}}px&#39; >
 <canvas class=&#39;canvasSty&#39; style=&#39;width: {{canvasW}}px;height: {{canvasH}}px&#39; canvas-id=&#39;cutImg&#39; disable-scroll=&#39;true&#39; bindtouchmove=&#39;canvasMove&#39;></canvas>
 <view class="allCavans_inbg" style=&#39;width: {{canvasW}}px;height:{{canvasH}}px; background: url({{img}});background-size: 100% 100%&#39;></view>
 </view>
 
 
</view>

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CSS code

.imgCut_header{
 padding: 30rpx;
 display: flex;
 justify-content: space-between;
 align-items: center;
 background: #000;
 color: #fff;
 font-size: 24rpx;
}
.allCavans{
 margin: 20rpx auto;
 position: relative;
}
.canvasSty{
 position: absolute;
}
.cutImg_box{
 width: 100%;
 
 border-bottom: 2rpx #f98700 solid;
 padding-bottom: 20rpx;
}
.cutImg_box .cutImg_box_t{
 width: 90%;
 margin: 20rpx auto;
}
.cutImg_box image{
 width: 100%;
}
.cutImg_box .cutImg_box_b{
 margin-top: 20rpx;
 width: 80%;
 height: 80rpx;
 line-height: 80rpx;
 background: #f98700;
 color: #fff;
 border-radius: 10rpx;
 text-align: center;
 margin:0rpx auto;
}
.selectCutMode{
 background: #fff;
 display: flex;
 justify-content: space-between;
 align-items: center;
}
.selectCutMode .selectCutMode_in{
 width: 100%;
 text-align: center;
 background: #fff;
 color: #f98700;
 font-size: 24rpx;
 padding: 20rpx;
}
.selectCutMode .selectCutMode_in_act{
 background: #f98700;
 color: #fff;
 padding: 20rpx;
}
.areaSelct_box{
 width: 100%;
 display: flex;
 align-items: center;
 height: 50rpx;
 justify-content: center;
 margin-top: 20rpx;
}
.areaSelct_box slider{
 width: 80%;
}
.cutImg_box .clickCutImg_txt{
 width: 100%;
 text-align: center;
 height: 50rpx;
 font-size: 24rpx;
 line-height: 50rpx;
 color: #999;
}

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JS code part

Initial loading brings in the parameter path brought from the previous page

onLoad: function (options) {
  var that = this;
  const ctx = wx.createCanvasContext(&#39;cutImg&#39;);
  ctx.setGlobalAlpha(0.4)
  var aa = &#39;https://pintuanqu.oss-cn-hangzhou.aliyuncs.com/Uploads/Picture/goodsShow/20171201/5a2125fc86566.png&#39;<br />　　//获取当前屏幕宽度
  var phoneW = Number(util.nowPhoneWH()[0]*90)/100;
  var cutH = 150;
  wx.getImageInfo({
   src: aa,
   success: function (res) {
    var w = phoneW;
    var h = (phoneW/Number(res.width))*Number(res.height)
    ctx.save() 
    ctx.drawImage(aa, 0, 0, w, h)
    ctx.restore()
    ctx.setFillStyle(&#39;red&#39;)
    ctx.fillRect(0, 0, phoneW, cutH)
    ctx.draw()
    that.setData({
     canvasW:w,
     canvasH:h,
     img:aa,
     cutH:cutH
    })
   }
  })
 },

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Confirm the selected area and start cropping

// 点击确认裁剪图片
 okCutImg:function(){
  var that = this;
  var canvasW = that.data.canvasW;
  var canvasH = that.data.canvasH;
  var nowCutW = that.data.cutType?canvasW:that.data.nowCutW;
  var nowCutH = that.data.cutType?that.data.cutH:that.data.nowCutH;
  var cutX = that.data.cutX;
  var cutY = that.data.cutY;
  const ctx = wx.createCanvasContext(&#39;cutImg&#39;);
  ctx.setGlobalAlpha(1)
  ctx.drawImage(that.data.img, 0, 0, canvasW, canvasH)
  ctx.draw()
  wx.canvasToTempFilePath({
   x: cutX,
   y: cutY,
   width: nowCutW,
   height: nowCutH,
   destWidth: nowCutW,
   destHeight: nowCutH,
   canvasId: &#39;cutImg&#39;,
   success: function(res) {
    var aa = res.tempFilePath
    that.setData({
     cutImgUrl:aa,
     prienFlag:false,
     alreay:false
    })
   } 
  })
 },

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How to move the red frame according to your fingers

// 点击红框开始移动
 canvasMove:function(e){
  var that = this;
  var canvasW = that.data.canvasW;
  var canvasH = that.data.canvasH;
  var nowCutW = that.data.cutType?canvasW:that.data.nowCutW;
  var nowCutH = that.data.cutType?that.data.cutH:that.data.nowCutH
  var touches = e.touches[0];  
  var x = touches.x;
  var y = touches.y-(Number(nowCutH)/2);
  that.data.cutType?x=0:x=x-(Number(nowCutW)/2);
  that.setData({
   cutX:x,
   cutY:y
  })
  const ctx = wx.createCanvasContext(&#39;cutImg&#39;);
  ctx.setGlobalAlpha(0.4)
  ctx.drawImage(that.data.img, 0, 0, canvasW, canvasH)
  ctx.setFillStyle(&#39;red&#39;)
  ctx.fillRect(x, y, nowCutW, nowCutH)
  ctx.draw()
 },

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The two buttons above to select the cropping method

Equal screen cropping

//等屏裁剪
 etcType:function(){
  var that = this;
  var propor = 100;
  var canvasW = that.data.canvasW;
  var canvasH = that.data.canvasH;
  var cutH = that.data.cutH;
  var nowCutW = (Number(canvasW)*propor)/100
  var nowCutH = (Number(cutH)*propor)/100
  const ctx = wx.createCanvasContext(&#39;cutImg&#39;);
  ctx.setGlobalAlpha(0.4)
  ctx.drawImage(that.data.img, 0, 0, canvasW, canvasH)
  ctx.setFillStyle(&#39;red&#39;)
  ctx.fillRect(0, 0, nowCutW, nowCutH)
  ctx.draw()
  that.setData({
   nowCutW:nowCutW,
   nowCutH:nowCutH,
   cutType:true
  })
 },

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Local cropping

areaType:function(){
  var that = this;
  var propor = that.data.propor;
  var canvasW = that.data.canvasW;
  var canvasH = that.data.canvasH;
  var cutH = that.data.cutH;
  var nowCutW = (Number(canvasW)*propor)/100
  var nowCutH = (Number(cutH)*propor)/100
  const ctx = wx.createCanvasContext(&#39;cutImg&#39;);
  ctx.setGlobalAlpha(0.4)
  ctx.drawImage(that.data.img, 0, 0, canvasW, canvasH)
  ctx.setFillStyle(&#39;red&#39;)
  ctx.fillRect(0,0, nowCutW, nowCutH)
  ctx.draw()
  that.setData({
   nowCutW:nowCutW,
   nowCutH:nowCutH,
   cutType:false
  })
 },

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Bureau The sliding selection red box above the domain crop is scaled proportionally to the width

areaChange:function(e){
  var that = this;
  var propor = e.detail.value;
  var canvasW = that.data.canvasW;
  var canvasH = that.data.canvasH;
  var cutH = that.data.cutH;
  var nowCutW = (Number(canvasW)*propor)/100
  var nowCutH = (Number(cutH)*propor)/100
  const ctx = wx.createCanvasContext(&#39;cutImg&#39;);
  ctx.setGlobalAlpha(0.4)
  ctx.drawImage(that.data.img, 0, 0, canvasW, canvasH)
  ctx.setFillStyle(&#39;red&#39;)
  ctx.fillRect(that.data.cutX||0, that.data.cutY||0,nowCutW, nowCutH)
  ctx.draw()
  that.setData({
   nowCutW:nowCutW,
   nowCutH:nowCutH,
   propor:propor
  })
 },

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Re-crop and return to the page where the initial picture was selected

// 重新裁剪
 againBtn:function(){
  var that = this;
  var data = that.data
  this.setData({
   prienFlag:true,
   alreay:true
  })
  const ctx = wx.createCanvasContext(&#39;cutImg&#39;);
  ctx.setGlobalAlpha(0.4)
  ctx.drawImage(data.img, 0, 0, data.canvasW, data.canvasH)
  ctx.setFillStyle(&#39;red&#39;)
  ctx.fillRect(that.data.cutX||0, that.data.cutY||0, data.nowCutW||data.canvasW, data.nowCutH||data.cutH)
  ctx.draw()
 },

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There is still a bug in IOS that cannot be cropped, and the official is fixing it Know when it’s good

The above is what I compiled for everyone. I hope it will be helpful to everyone in the future.

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