嫌麻烦的可以直接点击小程序代码片段体验,下面是代码:
<image
src="https://qcloudimg.tencent-cloud.cn/raw/7ff4215737d7877346c0ec6ea1514d94.jpg"
mode="widthFix"
style="width: 100vw;"
/>
<picker mode="selector"
range="{{options}}"
value="{{degree}}"
range-key="text"
bindchange="handleChange"
>
<View>当前旋转: {{degree * 90}}° ></View>
</picker>
<canvas id="myCanvas" type="2d" style="width:{{canvasStyle.width}};height:{{canvasStyle.height}}" />
<button bindtap="saveImg" type="primary">保存</button>
const app = getApp()
Page({
data: {
tempFilePath: '',
canvasStyle: {width: '100vw', height: '300px'},
options: [
{
text: '0°',
},
{
text: '90°',
},
{
text: '180°',
}, {
text: '270°',
},
],
degree: 0
},
handleChange(e) {
this.setData({
degree: Number(e.detail.value)
});
this.rotate(Number(e.detail.value * 90))
},
onl oad() {
this.rotate(this.data.degree * 90);
},
rotate(degree) {
console.log(degree)
wx.createSelectorQuery()
.select('#myCanvas') // 在 WXML 中填入的 id
.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')
// 图片对象
const image = canvas.createImage()
const transformCtx = (degree, width, height) => {
switch(degree) {
case Math.PI/2: {
ctx.translate(height, 0);
ctx.rotate(degree);
return {width:height, height:width};
}
case Math.PI: {
ctx.translate(width, height);
ctx.rotate(degree);
return {width, height};
}
case 3 * Math.PI/2: {
ctx.translate(0, width);
ctx.rotate(degree);
return {width:height, height:width};
}
default: {
return {width: height}
}
}
}
// 图片加载完成回调
image.onload = () => {
// 将图片绘制到 canvas 上
console.log(image.width, image.height);
// 初始化画布大小
const dpr = wx.getWindowInfo().pixelRatio
if (degree === 90 || degree === 270) {
canvas.width = image.height
canvas.height = image.width
} else {
canvas.width = image.width
canvas.height = image.height
}
// canvas css 的长宽比和 canvas 的长宽比保持一致,防止图片被拉伸
this.setData({
canvasStyle: {
width: `${canvas.width/dpr}px`,
height: `${canvas.height/dpr}px`,
}
})
ctx.clearRect(0,0,canvas.width,canvas.height)
ctx.scale(dpr, dpr)
const {imgWidth, imgHeight } = transformCtx(degree * Math.PI / 180, image.width/dpr, image.height/dpr)
ctx.drawImage(image, 0, 0, image.width/dpr, image.height/dpr);
wx.canvasToTempFilePath({
x: 0,
y:0,
width: imgWidth,
height: imgHeight,
canvas,
fileType: 'jpg',
success: ({tempFilePath}) =>{
this.setData({tempFilePath});
console.log(tempFilePath);
}
})
}
// 设置图片src
image.src = 'https://qcloudimg.tencent-cloud.cn/raw/7ff4215737d7877346c0ec6ea1514d94.jpg'
})
},
saveImg() {
wx.saveImageToPhotosAlbum({
filePath: this.data.tempFilePath,
success(res) {
wx.showToast({
title: '保存成功',
icon: 'success',
duration: 1000,
})
},
});
}
})
标签:canvas,degree,image,ctx,保存,height,width,旋转,图片
From: https://www.cnblogs.com/imgss/p/17639930.html