html 2 canvasによるモバイル端末のアップロード画像生成ポスターの実現

原文リンク:リンク記述vue+html 2 canvas+exif-js githubアドレスラインdemoを使用
主な機能

アップロード画像

画像を操作する:

を移動、拡大、縮小する.

合成ポスター

具体的な機能:
画像をアップロード
html:

js

getPhoto () {
    var imageInput = document.querySelector('#image-input')
    var that = this
    imageInput.addEventListener('change', function (e) {
        reads = new FileReader()
        reads.readAsDataURL(this.files[0])
        reads.addEventListener('load', function (e) {
            that.imgUrl = this.result
            that.myImg.position.x = 0
            that.myImg.position.y = 0
            that.myImg.scale = 1
            var orientation
            that.previewImg.addEventListener('load', function () {
                Exif.getData(that.previewImg, function() { //        
                Exif.getAllTags(this); //          ，         
                orientation = Exif.getTag(this, "Orientation"); //          
                var rotateCanvas = document.createElement("canvas"),
                rotateCtx = rotateCanvas.getContext("2d");
                 //           
                switch (orientation) {
                    case 1 :
                        rotateCanvas.width = that.previewImg.width;
                        rotateCanvas.height = that.previewImg.height;
                        rotateCtx.drawImage(that.previewImg, 0, 0, that.previewImg.width, that.previewImg.height);
                        break;
                    case 6 : //     90  
                        rotateCanvas.width = that.previewImg.height;
                        rotateCanvas.height = that.previewImg.width;
                        rotateCtx.translate(0, 0);
                        rotateCtx.rotate(90 * Math.PI / 180);
                        rotateCtx.drawImage(that.previewImg, 0, -that.previewImg.height, that.previewImg.width, that.previewImg.height);
                        break;
                    case 8 :
                        rotateCanvas.width = that.previewImg.height;
                        rotateCanvas.height = that.previewImg.width;
                        rotateCtx.translate(0, 0);
                        rotateCtx.rotate(-90 * Math.PI / 180);
                        rotateCtx.drawImage(that.previewImg, -that.previewImg.width, 0, that.previewImg.width, that.previewImg.height);
                        break;
                    case 3 : // 180  
                        rotateCanvas.width = that.previewImg.width;
                        rotateCanvas.height = that.previewImg.height;
                        rotateCtx.translate(0, 0);
                        rotateCtx.rotate(Math.PI);
                        rotateCtx.drawImage(that.previewImg, -that.previewImg.width, -that.previewImg.height, that.previewImg.width, that.previewImg.height);
                        break;
                    default :
                        rotateCanvas.width = that.previewImg.width;
                        rotateCanvas.height = that.previewImg.height;
                        rotateCtx.drawImage(that.previewImg, 0, 0, that.previewImg.width, that.previewImg.height);
                    }
                    var rotateBase64 = rotateCanvas.toDataURL("image/jpeg", 0.5);
                });
            })
        }) 
    })
}

画像を移動
画像とフォトフレームのバインド@touchstart@touchmove@touchend

getInitPosition (e) {
    event.preventDefault()
    if (this.imgUrl) {
        var length = e.touches.length
         if (length > 1) {
            let pointOne = e.touches[0]
            let pointTwo = e.touches[1]
            this.initTouchX = pointOne.clientX - pointTwo.clientX
            this.initTouchY = pointOne.clientY - pointTwo.clientY
        } else {
            var touches = e.touches[0]
            this.initTouchX = touches.clientX
            this.initTouchY = touches.clientY
        }   
    }
},
 getMovePosition (e) {
    event.preventDefault()
    if (this.imgUrl) {
        var length = e.touches.length
        if (length > 1) {
            let pointOne = e.touches[0]
            let pointTwo = e.touches[1]
            this.changeTouchX = pointOne.clientX - pointTwo.clientX
            this.changeTouchY = pointOne.clientY - pointTwo.clientY
            var scale = (this.changeTouchX - this.initTouchX) > (this.changeTouchY - this.initTouchY) ? (this.changeTouchX / this.initTouchX) : (this.changeTouchY / this.initTouchY) 
            scale *= this.myImg.lastScale
            this.myImg.scale = scale > 3 ? 3 : scale < 0.5 ? 0.5 : scale
        } else {
            var touches = e.touches[0]
            this.changeTouchX = touches.clientX - this.initTouchX
            this.changeTouchY = touches.clientY - this.initTouchY
            this.myImg.position.x = this.lastTouchX + (this.changeTouchX / this.myImg.scale)
            this.myImg.position.y = this.lastTouchY + (this.changeTouchY / this.myImg.scale)
        }   
    }
},
getLeavePosition (e) {
    this.myImg.lastScale = this.myImg.scale
    if (e.touches.length > 0) {
        var touches = e.touches[0]
        this.initTouchX = touches.clientX
        this.initTouchY = touches.clientY
    }
    this.lastTouchX = this.myImg.position.x
    this.lastTouchY = this.myImg.position.y
},

合成画像

createPhoto () {
    if (this.imgUrl) {
        let photoBox = document.querySelector('.photo-box')
        newImgWidth = photoBox.style.offsetWidth
        let newImgHeight = photoBox.style.offsetHeight
        let scale = window.devicePixelRatio
        let that = this
        html2canvas(photoBox, {
            width: newImgWidth,
            height: newImgHeight,
            scale: scale,
            useCORS: true
        }).then(function (canvas) { 
            var dataUrl = canvas.toDataURL('image/jpg')
            localStorage.imgData = dataUrl
            that.$router.push({
                name: 'share',
                params: {
                    storage: 'imgData'
                }
            })
        })
    } else {
        alert('     ')
    }
}

問題
1)ブラウザでズームをブロックする問題

 tounchmove   event.preventDefault()

2)合成画像の鮮明度

 html2canvas    ，scale = window.devicePixelRatio

3)画像を拡大・縮小する際の距離の判断

          ：
-     
-       
                        。   touchend ，e.touches       。            。

4)vueを使用する:style=「インラインスタイル」で発生した書き方の問題

:style="{transform:'scale('+ myImg.scale+ ') translate('+myImg.position.x+'px,'+myImg.position.y+'px)'}"

5)