leo-mind-map
Version:
一个简单的web在线思维导图
355 lines (341 loc) • 9.59 kB
JavaScript
// 将以空格分隔的字符串值转换成成数字/单位/值数组
const getNumberValueFromStr = value => {
let arr = String(value).split(/\s+/)
return arr.map(item => {
if (/^[\d.]+/.test(item)) {
// 数字+单位
let res = /^([\d.]+)(.*)$/.exec(item)
return [Number(res[1]), res[2]]
} else {
// 单个值
return item
}
})
}
// 缩放宽度
const zoomWidth = (ratio, height) => {
// w / height = ratio
return ratio * height
}
// 缩放高度
const zoomHeight = (ratio, width) => {
// width / h = ratio
return width / ratio
}
// 关键词到百分比值的映射
const keyWordToPercentageMap = {
left: 0,
top: 0,
center: 50,
bottom: 100,
right: 100
}
// 模拟background-size
const handleBackgroundSize = ({
backgroundSize,
drawOpt,
imageRatio,
canvasWidth,
canvasHeight,
canvasRatio
}) => {
if (backgroundSize) {
// 将值转换成数组
let backgroundSizeValueArr = getNumberValueFromStr(backgroundSize)
// 两个值都为auto，那就相当于不设置
if (
backgroundSizeValueArr[0] === 'auto' &&
backgroundSizeValueArr[1] === 'auto'
) {
return
}
// 值为cover
if (backgroundSizeValueArr[0] === 'cover') {
if (imageRatio > canvasRatio) {
// 图片的宽高比大于canvas的宽高比，那么图片高度缩放到和canvas的高度一致，宽度自适应
drawOpt.height = canvasHeight
drawOpt.width = zoomWidth(imageRatio, canvasHeight)
} else {
// 否则图片宽度缩放到和canvas的宽度一致，高度自适应
drawOpt.width = canvasWidth
drawOpt.height = zoomHeight(imageRatio, canvasWidth)
}
return
}
// 值为contain
if (backgroundSizeValueArr[0] === 'contain') {
if (imageRatio > canvasRatio) {
// 图片的宽高比大于canvas的宽高比，那么图片宽度缩放到和canvas的宽度一致，高度自适应
drawOpt.width = canvasWidth
drawOpt.height = zoomHeight(imageRatio, canvasWidth)
} else {
// 否则图片高度缩放到和canvas的高度一致，宽度自适应
drawOpt.height = canvasHeight
drawOpt.width = zoomWidth(imageRatio, canvasHeight)
}
return
}
// 图片宽度
let newNumberWidth = -1
if (backgroundSizeValueArr[0]) {
if (Array.isArray(backgroundSizeValueArr[0])) {
// 数字+单位类型
if (backgroundSizeValueArr[0][1] === '%') {
// %单位
drawOpt.width = (backgroundSizeValueArr[0][0] / 100) * canvasWidth
newNumberWidth = drawOpt.width
} else {
// 其他都认为是px单位
drawOpt.width = backgroundSizeValueArr[0][0]
newNumberWidth = backgroundSizeValueArr[0][0]
}
} else if (backgroundSizeValueArr[0] === 'auto') {
// auto类型，那么根据设置的新高度以图片原宽高比进行自适应
if (backgroundSizeValueArr[1]) {
if (backgroundSizeValueArr[1][1] === '%') {
// 高度为%单位
drawOpt.width = zoomWidth(
imageRatio,
(backgroundSizeValueArr[1][0] / 100) * canvasHeight
)
} else {
// 其他都认为是px单位
drawOpt.width = zoomWidth(imageRatio, backgroundSizeValueArr[1][0])
}
}
}
}
// 设置了图片高度
if (backgroundSizeValueArr[1] && Array.isArray(backgroundSizeValueArr[1])) {
// 数字+单位类型
if (backgroundSizeValueArr[1][1] === '%') {
// 高度为%单位
drawOpt.height = (backgroundSizeValueArr[1][0] / 100) * canvasHeight
} else {
// 其他都认为是px单位
drawOpt.height = backgroundSizeValueArr[1][0]
}
} else if (newNumberWidth !== -1) {
// 没有设置图片高度或者设置为auto，那么根据设置的新宽度以图片原宽高比进行自适应
drawOpt.height = zoomHeight(imageRatio, newNumberWidth)
}
}
}
// 模拟background-position
const handleBackgroundPosition = ({
backgroundPosition,
drawOpt,
imgWidth,
imgHeight,
canvasWidth,
canvasHeight
}) => {
if (backgroundPosition) {
// 将值转换成数组
let backgroundPositionValueArr = getNumberValueFromStr(backgroundPosition)
// 将关键词转为百分比
backgroundPositionValueArr = backgroundPositionValueArr.map(item => {
if (typeof item === 'string') {
return keyWordToPercentageMap[item] !== undefined
? [keyWordToPercentageMap[item], '%']
: item
}
return item
})
if (Array.isArray(backgroundPositionValueArr[0])) {
if (backgroundPositionValueArr.length === 1) {
// 如果只设置了一个值，第二个默认为50%
backgroundPositionValueArr.push([50, '%'])
}
// 水平位置
if (backgroundPositionValueArr[0][1] === '%') {
// 单位为%
let canvasX = (backgroundPositionValueArr[0][0] / 100) * canvasWidth
let imgX = (backgroundPositionValueArr[0][0] / 100) * imgWidth
// 计算差值
drawOpt.x = canvasX - imgX
} else {
// 其他单位默认都为px
drawOpt.x = backgroundPositionValueArr[0][0]
}
// 垂直位置
if (backgroundPositionValueArr[1][1] === '%') {
// 单位为%
let canvasY = (backgroundPositionValueArr[1][0] / 100) * canvasHeight
let imgY = (backgroundPositionValueArr[1][0] / 100) * imgHeight
// 计算差值
drawOpt.y = canvasY - imgY
} else {
// 其他单位默认都为px
drawOpt.y = backgroundPositionValueArr[1][0]
}
}
}
}
// 模拟background-repeat
const handleBackgroundRepeat = ({
ctx,
image,
backgroundRepeat,
drawOpt,
imgWidth,
imgHeight,
canvasWidth,
canvasHeight
}) => {
if (backgroundRepeat) {
// 保存在handleBackgroundPosition中计算出来的x、y
let ox = drawOpt.x
let oy = drawOpt.y
// 计算ox和oy能平铺的图片数量
let oxRepeatNum = Math.ceil(ox / imgWidth)
let oyRepeatNum = Math.ceil(oy / imgHeight)
// 计算ox和oy第一张图片的位置
let oxRepeatX = ox - oxRepeatNum * imgWidth
let oxRepeatY = oy - oyRepeatNum * imgHeight
// 将值转换成数组
let backgroundRepeatValueArr = getNumberValueFromStr(backgroundRepeat)
// 不处理
if (
backgroundRepeatValueArr[0] === 'no-repeat' ||
(imgWidth >= canvasWidth && imgHeight >= canvasHeight)
) {
return
}
// 水平平铺
if (backgroundRepeatValueArr[0] === 'repeat-x') {
if (canvasWidth > imgWidth) {
let x = oxRepeatX
while (x < canvasWidth) {
drawImage(ctx, image, {
...drawOpt,
x
})
x += imgWidth
}
return true
}
}
// 垂直平铺
if (backgroundRepeatValueArr[0] === 'repeat-y') {
if (canvasHeight > imgHeight) {
let y = oxRepeatY
while (y < canvasHeight) {
drawImage(ctx, image, {
...drawOpt,
y
})
y += imgHeight
}
return true
}
}
// 平铺
if (backgroundRepeatValueArr[0] === 'repeat') {
let x = oxRepeatX
while (x < canvasWidth) {
if (canvasHeight > imgHeight) {
let y = oxRepeatY
while (y < canvasHeight) {
drawImage(ctx, image, {
...drawOpt,
x,
y
})
y += imgHeight
}
}
x += imgWidth
}
return true
}
}
}
// 根据参数绘制图片
const drawImage = (ctx, image, drawOpt) => {
ctx.drawImage(
image,
drawOpt.sx,
drawOpt.sy,
drawOpt.swidth,
drawOpt.sheight,
drawOpt.x,
drawOpt.y,
drawOpt.width,
drawOpt.height
)
}
const drawBackgroundImageToCanvas = (
ctx,
width,
height,
img,
{ backgroundSize, backgroundPosition, backgroundRepeat },
callback = () => {}
) => {
// 画布的长宽比
let canvasRatio = width / height
// 加载图片
let image = new Image()
image.src = img
image.onload = () => {
// 图片的宽度及长宽比
let imgWidth = image.width
let imgHeight = image.height
let imageRatio = imgWidth / imgHeight
// 绘制图片
// drawImage方法的参数值
let drawOpt = {
sx: 0,
sy: 0,
swidth: imgWidth,
sheight: imgHeight,
x: 0,
y: 0,
width: imgWidth,
height: imgHeight
}
// 模拟background-size
handleBackgroundSize({
backgroundSize,
drawOpt,
imageRatio,
canvasWidth: width,
canvasHeight: height,
canvasRatio
})
// 模拟background-position
handleBackgroundPosition({
backgroundPosition,
drawOpt,
imgWidth: drawOpt.width,
imgHeight: drawOpt.height,
imageRatio,
canvasWidth: width,
canvasHeight: height,
canvasRatio
})
// 模拟background-repeat
let notNeedDraw = handleBackgroundRepeat({
ctx,
image,
backgroundRepeat,
drawOpt,
imgWidth: drawOpt.width,
imgHeight: drawOpt.height,
imageRatio,
canvasWidth: width,
canvasHeight: height,
canvasRatio
})
// 绘制图片
if (!notNeedDraw) {
drawImage(ctx, image, drawOpt)
}
callback()
}
image.onerror = e => {
callback(e)
}
}
export default drawBackgroundImageToCanvas