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Posted July 29, 2016 1:27pm by

How about adding a eraser?

The drawing app is really good. Though, it would be awesome if we can add an eraser. ANy one up for the challenge?

July 29, 2016 3:55pm

That sounds like a good extra-practice project.

You could do it and then show us your revised code.

July 29, 2016 5:52pm

Here it is Steven :)

I used sublime text (created a new project so that I can also review it) that's why it's a single document. Here it is :)

<!DOCTYPE html>
<html>
<title>Drawing board</title>
<meta charset="utf-8">
<style>
* {
box-siing: border-box;
}
body {
text-align:center;
font-family:sans-serif;
}
canvas {
background-color:black;
margin-top:20px;
border-radius:10px;
}

ul {
list-style-type:none;
padding:0;
}
.controls li {
width:50px;
height:50px;
border-radius:100%;
display:inline-block;
margin:0 5px;
cursor:pointer;
}
.red {
background-color:firebrick;
}
.yellow {
background-color:yellow;
}
.blue {
background-color:turquoise;
}
#revealColor {
display:none;
text-align:center;
width:400px;
margin:20px auto;
background:#333;
padding:10px;
position:relative;
}
#newColor {
margin: 40px 20px 20px 10px;
width:80px;
height:80px;
display:inline-block;
border-radius:10px;

border:2px solid white;
}
#colorRange{
display:inline-block;
}
#colorRange p {
vertical-align: middle;
}
.selected {
box-shadow:inset 0 0 0 5px rgba(0,0,0, .5);
}
label {
 vertical-align:super;
 display: inline-block;
 margin: 0 10px 0 0;
 width: 40px;
 font-size: 14px;
 color: white;
}
#addColor {
display:block;
margin:0 auto;
}

button {
 cursor:pointer;
}

.eraser {
 border:2px solid white;
 background:transparent;
 padding:5px;
 border-radius:5px;
 cursor:pointer;
 color:white;
}

</style>

<body>

<canvas width="300" height="175"></canvas>
<div class="controls">
<ul>
<li class="red selected"> </li>
<li class="yellow"> </li>
<li class="blue"> </li>
</ul>
  <button id="showDashboard">Add More Color </button>
  <div id="revealColor">
  <span id="newColor"> </span>
   <div id="colorRange">
    <p>
    <label for="red">RED</label>
    <input id="red" name="red" type="range" min="0" max="255" value="0">
   </p>
   <p>
   <label for="green">GREEN</label>
    <input id="green" name="green" type="range" min="0" max="255" value="0">
    </p>
   <p>
   <label for="blue">BLUE</label>
    <input id="blue" name="blue" type="range" min="0" max="255" value="0">
   </p>
   </div>
  <button id="addColor">add Color</button>
  <button id="eraser">Eraser on </button>
  </div>

</div> 

<script   src="https://code.jquery.com/jquery-3.1.0.min.js"   integrity="sha256-cCueBR6CsyA4/9szpPfrX3s49M9vUU5BgtiJj06wt/s="   crossorigin="anonymous"></script>

<script> 
var color = $(".selected").css("background-color");
var $context = $("canvas")[0].getContext("2d");
var $canvas = $("canvas"); 
var lastPoint;
var mouseDown = false;

$(".controls").on("click", "li", function(){
 $(this).siblings("li").removeClass("selected");
 $(this).addClass("selected");
 color = $(this).css("background-color");
});
$("#showDashboard").click(function(){
$("#revealColor").slideToggle("slow");
$("body").animate({scrollTop: 700}, 1500);
  getColor();
});

function getColor() {
var r = $("#red").val();
var g = $("#green").val();
var b = $("#blue").val();

var rgb = "rgb(" + r + "," + g + "," + b + ")";
 $("#newColor").css("background-color", rgb);
};

$("input[type=range]").on("input", function(){
  getColor();
});

$("#addColor").click(function(){
var newList = $("<li></li>");
var spanColor = $("#newColor").css("background-color");
newList.css("background-color", spanColor);
$(".controls ul").append(newList);
newList.click();
});

$("#eraser").click(function(){
 $(this).toggleClass("eraser");
});

function isEraserOn(){
return $("#eraser").hasClass("eraser");
};

var $canErase = false;

$canvas.mousedown(function(e){
 lastPoint = e;
if (isEraserOn()) {
  $context.clearRect(lastPoint.offsetX, lastPoint.offsetY, 20, 20);
  $canErase = true;
  mouseDown = false;
 } else {
 mouseDown = true;
 $canErase = false; 
 };
}).mousemove(function(e){
  if(mouseDown && !$canErase){
  $context.beginPath();
  $context.moveTo(lastPoint.offsetX, lastPoint.offsetY);
  $context.lineTo(e.offsetX, e.offsetY);
  $context.strokeStyle = color;
  $context.lineWidth = 5;
  $context.stroke();
  lastPoint = e;
} else if (!mouseDown && $canErase){
  $context.moveTo(lastPoint.offsetX, lastPoint.offsetY);
  $context.clearRect(e.offsetX, e.offsetY, 20, 20);
  lastPoint = e;
 }
}).mouseup(function(){
   mouseDown = false;
   $canErase = false;
}).mouseleave(function(){
  $canvas.mouseup();
});

</script>

</body>
</html>

2 Answers

July 29, 2016 4:01pm

This is a quick solution I threw together - with bugs and all - of my take on an eraser.

SnapShot: https://w.trhou.se/x0ejqwt2at

I used a simple solution of setting the eraser to whichever color the canvas' background-color is, a bit of a work around but it can still get the job done :)

Once the eraser is selected a boolean is set to true and the canvas' lineWidth is increased to 10 to make erasing a bit easier.

July 29, 2016 5:51pm

NIce :). I was also able to do it but using a different method. I used sublime text (created a new project so that I can also review it) that's why it's a single document. Here it is :)

<!DOCTYPE html>
<html>
<title>Drawing board</title>
<meta charset="utf-8">
<style>
* {
box-siing: border-box;
}
body {
text-align:center;
font-family:sans-serif;
}
canvas {
background-color:black;
margin-top:20px;
border-radius:10px;
}

ul {
list-style-type:none;
padding:0;
}
.controls li {
width:50px;
height:50px;
border-radius:100%;
display:inline-block;
margin:0 5px;
cursor:pointer;
}
.red {
background-color:firebrick;
}
.yellow {
background-color:yellow;
}
.blue {
background-color:turquoise;
}
#revealColor {
display:none;
text-align:center;
width:400px;
margin:20px auto;
background:#333;
padding:10px;
position:relative;
}
#newColor {
margin: 40px 20px 20px 10px;
width:80px;
height:80px;
display:inline-block;
border-radius:10px;

border:2px solid white;
}
#colorRange{
display:inline-block;
}
#colorRange p {
vertical-align: middle;
}
.selected {
box-shadow:inset 0 0 0 5px rgba(0,0,0, .5);
}
label {
 vertical-align:super;
 display: inline-block;
 margin: 0 10px 0 0;
 width: 40px;
 font-size: 14px;
 color: white;
}
#addColor {
display:block;
margin:0 auto;
}

button {
 cursor:pointer;
}

.eraser {
 border:2px solid white;
 background:transparent;
 padding:5px;
 border-radius:5px;
 cursor:pointer;
 color:white;
}

</style>

<body>

<canvas width="300" height="175"></canvas>
<div class="controls">
<ul>
<li class="red selected"> </li>
<li class="yellow"> </li>
<li class="blue"> </li>
</ul>
  <button id="showDashboard">Add More Color </button>
  <div id="revealColor">
  <span id="newColor"> </span>
   <div id="colorRange">
    <p>
    <label for="red">RED</label>
    <input id="red" name="red" type="range" min="0" max="255" value="0">
   </p>
   <p>
   <label for="green">GREEN</label>
    <input id="green" name="green" type="range" min="0" max="255" value="0">
    </p>
   <p>
   <label for="blue">BLUE</label>
    <input id="blue" name="blue" type="range" min="0" max="255" value="0">
   </p>
   </div>
  <button id="addColor">add Color</button>
  <button id="eraser">Eraser on </button>
  </div>

</div> 

<script   src="https://code.jquery.com/jquery-3.1.0.min.js"   integrity="sha256-cCueBR6CsyA4/9szpPfrX3s49M9vUU5BgtiJj06wt/s="   crossorigin="anonymous"></script>

<script> 
var color = $(".selected").css("background-color");
var $context = $("canvas")[0].getContext("2d");
var $canvas = $("canvas"); 
var lastPoint;
var mouseDown = false;

$(".controls").on("click", "li", function(){
 $(this).siblings("li").removeClass("selected");
 $(this).addClass("selected");
 color = $(this).css("background-color");
});
$("#showDashboard").click(function(){
$("#revealColor").slideToggle("slow");
$("body").animate({scrollTop: 700}, 1500);
  getColor();
});

function getColor() {
var r = $("#red").val();
var g = $("#green").val();
var b = $("#blue").val();

var rgb = "rgb(" + r + "," + g + "," + b + ")";
 $("#newColor").css("background-color", rgb);
};

$("input[type=range]").on("input", function(){
  getColor();
});

$("#addColor").click(function(){
var newList = $("<li></li>");
var spanColor = $("#newColor").css("background-color");
newList.css("background-color", spanColor);
$(".controls ul").append(newList);
newList.click();
});

$("#eraser").click(function(){
 $(this).toggleClass("eraser");
});

function isEraserOn(){
return $("#eraser").hasClass("eraser");
};

var $canErase = false;

$canvas.mousedown(function(e){
 lastPoint = e;
if (isEraserOn()) {
  $context.clearRect(lastPoint.offsetX, lastPoint.offsetY, 20, 20);
  $canErase = true;
  mouseDown = false;
 } else {
 mouseDown = true;
 $canErase = false; 
 };
}).mousemove(function(e){
  if(mouseDown && !$canErase){
  $context.beginPath();
  $context.moveTo(lastPoint.offsetX, lastPoint.offsetY);
  $context.lineTo(e.offsetX, e.offsetY);
  $context.strokeStyle = color;
  $context.lineWidth = 5;
  $context.stroke();
  lastPoint = e;
} else if (!mouseDown && $canErase){
  $context.moveTo(lastPoint.offsetX, lastPoint.offsetY);
  $context.clearRect(e.offsetX, e.offsetY, 20, 20);
  lastPoint = e;
 }
}).mouseup(function(){
   mouseDown = false;
   $canErase = false;
}).mouseleave(function(){
  $canvas.mouseup();
});

</script>

</body>
</html>

October 19, 2016 3:32am

Without adding an element in HTML, you can still set an eraser by just adding a white color with context.linewidth border nearby the color list.

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Welcome to the Treehouse Community

Looking to learn something new?

Ronnelle Torres

Ronnelle Torres

How about adding a eraser?

Steven Parker

Steven Parker

That sounds like a good extra-practice project.

Ronnelle Torres

Ronnelle Torres

2 Answers

Justin Coen

Justin Coen

Ronnelle Torres

Ronnelle Torres

jennyhan

jennyhan