Javascript处理旋转图片并得到新的图片base64数据
// 图片旋转处理 -> base64
export const rotateBase64Img = (src, edg, callback) => {
try {
const canvas = document.createElement('canvas')
const ctx = canvas.getContext('2d')
let imgW = 0 // 图片宽度
let imgH = 0 // 图片高度
let size = 0 // canvas初始大小
if (edg % 90 !== 0) {
throw new Error('旋转角度必须是90的倍数!')
}
(edg < 0) && (edg = (edg % 360) + 360)
const quadrant = (edg / 90) % 4 // 旋转象限
const cutCoor = { sx: 0, sy: 0, ex: 0, ey: 0 } // 裁剪坐标
const image = new Image()
image.src = src
image.crossOrigin = 'anonymous'
image.onload = function () {
imgW = image.width
imgH = image.height
size = imgW > imgH ? imgW : imgH
canvas.width = size * 2
canvas.height = size * 2
switch (quadrant) {
case 0:
cutCoor.sx = size
cutCoor.sy = size
cutCoor.ex = size + imgW
cutCoor.ey = size + imgH
break
case 1:
cutCoor.sx = size - imgH
cutCoor.sy = size
cutCoor.ex = size
cutCoor.ey = size + imgW
break
case 2:
cutCoor.sx = size - imgW
cutCoor.sy = size - imgH
cutCoor.ex = size
cutCoor.ey = size
break
case 3:
cutCoor.sx = size
cutCoor.sy = size - imgW
cutCoor.ex = size + imgH
cutCoor.ey = size + imgW
break
}
ctx.translate(size, size)
ctx.rotate(edg * Math.PI / 180)
ctx.drawImage(image, 0, 0)
const imgData = ctx.getImageData(cutCoor.sx, cutCoor.sy, cutCoor.ex, cutCoor.ey)
if (quadrant % 2 === 0) {
canvas.width = imgW
canvas.height = imgH
} else {
canvas.width = imgH
canvas.height = imgW
}
ctx.putImageData(imgData, 0, 0)
if (typeof callback === 'function') {
callback(canvas.toDataURL('image/png', 0.7))
}
}
} catch (e) {
console.log(e)
}
}
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