微信小程序怎么实现图片选择区域裁剪功能

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效果图

HTML代码

  开始裁剪 点击上传图片 点击确认      等屏裁剪    区域裁剪           重新裁剪       

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'
　　//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() },

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