微信小程序图片选择区域实现裁剪功能方法教程

HTML代码

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

CSS代码

.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;  }

JS代码部分

初始加载带入上一个页面带过来的参数路径

onLoad: function (options) {    var that = this;    const ctx = wx.createCanvasContext('cutImg');    ctx.setGlobalAlpha(0.4)    var aa = 'https://pintuanqu.oss-cn-hangzhou.aliyuncs.com/Uploads/Picture/goodsShow/20171201/5a2125fc86566.png'<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('red')      ctx.fillRect(0, 0, phoneW, cutH)      ctx.draw()      that.setData({       canvasW:w,       canvasH:h,       img:aa,       cutH:cutH      })     }    })   },

确定选择区域开始裁剪

// 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('cutImg');    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: 'cutImg',     success: function(res) {      var aa = res.tempFilePath      that.setData({       cutImgUrl:aa,       prienFlag:false,       alreay:false      })     }     })   },

红框根据手指移动方法

// 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('cutImg');    ctx.setGlobalAlpha(0.4)    ctx.drawImage(that.data.img, 0, 0, canvasW, canvasH)    ctx.setFillStyle('red')    ctx.fillRect(x, y, nowCutW, nowCutH)    ctx.draw()   },

上方两个选择裁剪方式的按钮

等屏裁剪

//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('cutImg');    ctx.setGlobalAlpha(0.4)    ctx.drawImage(that.data.img, 0, 0, canvasW, canvasH)    ctx.setFillStyle('red')    ctx.fillRect(0, 0, nowCutW, nowCutH)    ctx.draw()    that.setData({     nowCutW:nowCutW,     nowCutH:nowCutH,     cutType:true    })   },

局域裁剪

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('cutImg');    ctx.setGlobalAlpha(0.4)    ctx.drawImage(that.data.img, 0, 0, canvasW, canvasH)    ctx.setFillStyle('red')    ctx.fillRect(0,0, nowCutW, nowCutH)    ctx.draw()    that.setData({     nowCutW:nowCutW,     nowCutH:nowCutH,     cutType:false    })   },

局域裁剪上方的滑动选择红框根据宽度等比例缩放

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('cutImg');    ctx.setGlobalAlpha(0.4)    ctx.drawImage(that.data.img, 0, 0, canvasW, canvasH)    ctx.setFillStyle('red')    ctx.fillRect(that.data.cutX||0, that.data.cutY||0,nowCutW, nowCutH)    ctx.draw()    that.setData({     nowCutW:nowCutW,     nowCutH:nowCutH,     propor:propor    })   },

重新裁剪回到初始选择图片的页面

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

现在IOS还有个坑就是裁剪不了,官方正在修复中。

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