摘要：這篇文章主要介紹了基于剪輯區(qū)域功能實現(xiàn)橡皮擦效果非常不錯，具有參考借鑒價值，需要的朋友可以參考下這是基礎(chǔ)結(jié)構(gòu)沒什么好說的下面是重點的這里有個坑要十分注意調(diào)用方法的時候，所定義的剪輯區(qū)域總是局限于期初的那個剪輯區(qū)域范圍。

這篇文章主要介紹了基于canvas剪輯區(qū)域功能實現(xiàn)橡皮擦效果,非常不錯，具有參考借鑒價值，需要的朋友可以參考下

這是基礎(chǔ)結(jié)構(gòu) 沒什么好說的

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        Stroke color: 
                 red
                 green
                 blue
                 orange
                 cornflowerblue
                 goldenrod
                 navy
                 purple
                 purple
               
        Fill color: 
                 semi-transparent red
                 green
                 semi-transparent blue
                 orange
                 semi-transparent cornflowerblue
                 goldenrod
                 navy
                 purple
                     582735936
        Draw 
        Erase 
        Eraser: 
                circle
                square
                     582735936
        Eraser width: 
                25
                50
                75
                100
                125
                150
                175
                200
               
       
  

下面是重點的js

這里有個坑要十分注意 調(diào)用clip()方法的時候，所定義的剪輯區(qū)域總是局限于期初的那個剪輯區(qū)域范圍。

簡單來說 clip()方法總是在上一次的剪輯區(qū)域基礎(chǔ)上進行操作，所以說我們要把clip()方法放在save()和restore()方法中

var canvas = document.getElementById("canvas"),
context = canvas.getContext("2d"),
strokeStyleSelect = document.getElementById("strokeStyleSelect"),  //畫圖的描邊顏色
fillStyleSelect = document.getElementById("fillStyleSelect"),    //畫圖填充顏色
drawRadio = document.getElementById("drawRadio"),          //畫圖按鈕
eraserRadio = document.getElementById("eraserRadio"),       //橡皮擦按鈕 
eraserShapeSelect = document.getElementById("eraserShapeSelect"), //橡皮擦形狀
eraserWidthSelect = document.getElementById("eraserWidthSelect"), //橡皮擦寬度
ERASER_LINE_WIDTH = 1,
drawingSurfaceImageData,
lastX,
lastY,
mousedown = {},
rubberbandRect = {},
dragging = false
function windowToCanvas(x,y){ //這個函數(shù)的作用是捕捉鼠標點在canvas上的坐標
  var bbox=canvas.getBoundingClientRect()
  return {
    x:x-bbox.left,
    y:y-bbox.top
  }
}
function saveDrawingSurface(){  //這個函數(shù)的作用是初始化讀取畫布信息并儲存起來
  drawingSurfaceImageData=context.getImageData(0,0,canvas.width,canvas.height)
}
function restoreDrawingSurface(){ //這個函數(shù)的作用是讀取畫布信息
  context.putImageData(drawingSurfaceImageData,0,0)
}
function drawGrid(){ //這個函數(shù)的作用是填充進橡皮擦的剪輯區(qū)域
  context.save()
  context.fillStyle="#fff"
  context.fillRect(0,0,canvas.width,canvas.height)
  context.restore()
}
function drawrubber(x,y){
  context.beginPath()
  context.arc(x,y,eraserWidthSelect.value,0,Math.PI*2,false)
  context.clip()   582735936
}
function drawCri(x,y){
  var x_width=Math.abs(x-mousedown.x)
  var y_width=Math.abs(y-mousedown.y)
  var radius=Math.sqrt(x_width*x_width+y_width*y_width)
 context.save()
  context.beginPath()
  context.fillStyle=fillStyleSelect.value;
  context.arc(mousedown.x,mousedown.y,radius,0,Math.PI*2,false)
  context.fill()
 context.restore()
}
canvas.onmousedown=function(e){
  var loc=windowToCanvas(e.clientX,e.clientY)
  mousedown.x=loc.x
  mousedown.y=loc.y
  lastX=loc.x
  lastY=loc.y
  saveDrawingSurface()
  dragging=true
}
canvas.onmousemove=function(e){
  if(dragging){
    var loc=windowToCanvas(e.clientX,e.clientY)
    if(drawRadio.checked){ //如果是畫圖狀態(tài)
      // 
      restoreDrawingSurface()
      drawCri(loc.x,loc.y)
    }else{ //如果是橡皮擦狀態(tài)
      context.save()
      drawrubber(loc.x,loc.y)
      drawGrid()
      context.restore()
    }
  }
}
canvas.onmouseup=function(e){
  dragging=false;
  var loc=windowToCanvas(e.clientX,e.clientY)
  if(drawRadio.checked){
  lastX=loc.x;
  lastY=loc.y;
  restoreDrawingSurface()
  drawCri(lastX,lastY)
  }else{
  context.save()
  drawrubber(loc.x,loc.y)
  drawGrid()
  context.restore()
  }
}

總結(jié)

以上所述是小編給大家介紹的基于canvas剪輯區(qū)域功能實現(xiàn)橡皮擦效果，希望對大家有所幫助