微信小程序图片选择区域裁剪实现方法

本文介绍了微信小程序图片选择区域屏裁剪实现方法，分享给大家。具体如下：

效果图

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,官方正在修复不知道什么时候好