JavaScriptExperiments/Canvas2DGraphics.html at master · DForshner/JavaScriptExperiments · GitHub

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<!DOCTYPE HTML>
<htmllang="en-US">
<head>
<metacharset="UTF-8">
<title>Drawing with the "2D" Canvas</title>
<style>
</style>
</head>
<body>
<div>
<h2>Drawing with the "2D" Canvas</h2>
<canvasid="canvas" width=500height=500></canvas>
</div>
<divid="main-menu">
<ulid="demo-menu">
<li><buttonname="rectangle">Rectangle Demo</button>
<li><buttonname="triangle">Triangle</button>
<li><buttonname="arcs-circles">Arcs & Circles</button>
<li><buttonname="bezier">Bezier curves</button>
<li><buttonname="clipping">Clipping paths</button>
<li><buttonname="line-caps-joints">Line Caps & Joints</button>
<li><buttonname="gradients">Gradients</button>
<li><buttonname="shadow">Shadow Effects</button>
<li><buttonname="state">Canvas State Stack</button>
<li><buttonname="rotate">Rotation</button>
</ul>
</div>

<script>

// Define modules
varapp={
common : {},
demo : {}
};

// Common code
app.common=(function(){

functiongetCanvasContext(){
varcanvas=document.getElementById("canvas");
console.log("Getting ",canvas.width,"X",canvas.height," canvas");
returncanvas.getContext("2d");
}

functiongetCanvas(){
varcanvas=document.getElementById("canvas");
console.log("Getting ",canvas.width,"X",canvas.height," canvas");
returncanvas;

}

// Clears canvas (also clears fill and stroke styles)
functionclearCanvas(){
varcanvas=document.getElementById("canvas");
canvas.width=canvas.width;
}

functionbind(element,event,handler){
if(typeofelement=="string"){
element=document.getElementById(element);
}
console.assert(element!=null);
element.addEventListener(event,handler,false)
}

functionaddCommentLowerRight(ctx,text){
console.assert(ctx!=undefined);
console.assert(typeoftext==="string");

// Save the context state
ctx.save();

ctx.fillStyle="black";
ctx.font="14px Arial, sans-serif";
ctx.fillText(text,400,490,100);// Set max width to 100 so text shrinks to fit.

// Restore the context state to whatever it was before
// this function was called.
ctx.restore();
}

// Public functions
return{
getCanvasContext : getCanvasContext,
getCanvas : getCanvas,
clearCanvas : clearCanvas,
bind : bind,
addCommentLowerRight : addCommentLowerRight
};
})();

app.demo["rectangle"]=(function(ctx){

functionrun(){
console.log("Running rectangle demo");
varctx=app.common.getCanvasContext();

app.common.addCommentLowerRight(ctx,"Rectangle Demo");

// Draw rectangle using lines
ctx.beginPath();
ctx.moveTo(100,100);
ctx.lineTo(100,300);
ctx.lineTo(200,300);
ctx.lineTo(200,100);
ctx.closePath();

ctx.strokeStyle="blue";
ctx.lineWidth=5.0;
ctx.stroke();

// rect - draw single rectangle
ctx.beginPath();
ctx.rect(250,150,200,100);// (x1, y1, width, height)
ctx.fillStyle="red";
ctx.fill();
ctx.strokeStyle="black";
ctx.lineWidth=2.0;
ctx.stroke();

// fillRect - draw single filled rectangle
ctx.fillStyle="pink";
ctx.fillRect(250,250,200,100);// (x1, y1, width, height)

// strokeRect - draw single rectangle
ctx.strokeStyle="orange";
ctx.strokeRect(250,350,200,100);// (x1, y1, width, height)

// clearRect - clears area
ctx.clearRect(150,200,150,200);

}

// Public functions
return{
run : run
};
})();

app.demo["triangle"]=(function(ctx){

functionrun(){
console.log("Running triangle demo");
varctx=app.common.getCanvasContext();

app.common.addCommentLowerRight(ctx,"Triangle Demo");

ctx.beginPath();
ctx.moveTo(250,400);
ctx.lineTo(150,200);
ctx.lineTo(350,200);
ctx.closePath();

ctx.fillStyle="orange";
ctx.fill();

ctx.strokeStyle="red";
ctx.lineWidth=2.0;
ctx.stroke();
}

// Public functions
return{
run : run
};
})();

app.demo["arcs-circles"]=(function(){

functionrun(){
console.log("Running arcs & circles demo");
varctx=app.common.getCanvasContext();

app.common.addCommentLowerRight(ctx,"Arcs & Circles Demo");

// two arcs shifted by 50
ctx.beginPath();
ctx.arc(50,100,50,0,Math.PI,true);// arc(x, y, radius, startAngle, endAngle, ccw)
ctx.arc(100,100,50,0,Math.PI,false);
ctx.closePath();
ctx.fillStyle="red";
ctx.fill();

// 90 deg of arc
ctx.beginPath();
varnintyDeg=90*(180/Math.PI);// Or Math.PI / 2
ctx.arc(50,175,25,0,nintyDeg,true);
ctx.closePath();
ctx.fillStyle="blue";
ctx.fill();

// Pokemon ball?
ctx.beginPath();
ctx.arc(50,300,50,0,Math.PI,true);
ctx.moveTo(100,310);
ctx.arc(50,310,50,0,Math.PI,false);
ctx.closePath;
ctx.fillStyle="red";
ctx.fill();

// Ninja?
ctx.beginPath();
ctx.arc(150,300,50,0,Math.PI,true);
ctx.arc(150,350,50,0,Math.PI,false);
ctx.closePath;
ctx.fillStyle="black";
ctx.fill();

// Full circle
ctx.beginPath();
ctx.arc(300,300,100,0,2*Math.PI,true);
ctx.closePath();
ctx.fillStyle="pink";
ctx.fill();
}

return{
run : run
};
})();

app.demo["bezier"]=(function(){

functionrun(){
console.log("Running bezier curve demo");
varctx=app.common.getCanvasContext();

app.common.addCommentLowerRight(ctx,"Bezier Curve Demo");

// 1 - control point
ctx.beginPath();
ctx.moveTo(50,100);
ctx.lineTo(100,50);
ctx.lineTo(200,100);
ctx.strokeStyle="black";
ctx.stroke();

// 1 - quadratic curve
ctx.beginPath();
ctx.moveTo(50,100);
ctx.quadraticCurveTo(100,50,200,100);// (cx, cy, x, y)
ctx.fillStyle="red";
ctx.fill();

// 2 - control point
ctx.beginPath();
ctx.moveTo(50,300);
ctx.lineTo(175,175);
ctx.lineTo(200,300);
ctx.strokeStyle="black";
ctx.stroke();

// 2 - chaining quadratic curves
ctx.beginPath();
ctx.moveTo(50,300);
ctx.quadraticCurveTo(175,175,200,300);
ctx.moveTo(200,300);
ctx.quadraticCurveTo(250,375,375,300);
ctx.fillStyle="blue";
ctx.fill();

// 3 - control points
ctx.beginPath();
ctx.moveTo(400,50);
ctx.lineTo(350,110);
ctx.lineTo(475,175);
ctx.lineTo(400,300);
ctx.strokeStyle="black";
ctx.stroke();

// 3 - Cubic bezier curve
ctx.beginPath();
ctx.moveTo(400,50);
ctx.bezierCurveTo(350,110,475,175,400,300);
ctx.fillStyle="green";
ctx.fill();
}

// Public functions
return{
run : run
};

})();

app.demo["clipping"]=(function(){

functionrun(){
console.log("Running clipping path demo");
varctx=app.common.getCanvasContext();

app.common.addCommentLowerRight(ctx,"Clipping Path Demo");

// Fill screen
ctx.fillStyle="red";
ctx.fillRect(0,0,500,480);

// Hex clipping path
ctx.beginPath();
ctx.moveTo(100,200);
ctx.lineTo(200,100);
ctx.lineTo(300,100);
ctx.lineTo(400,200);
ctx.lineTo(400,300);
ctx.lineTo(300,400);
ctx.lineTo(200,400);
ctx.lineTo(100,300);
ctx.lineTo(100,200);
ctx.clip();

// Fill screen again
ctx.fillStyle="green";
ctx.fillRect(0,0,500,500);
}

// Public functions
return{
run : run
};
})();


app.demo["line-caps-joints"]=(function(){

ctx={};

functiondrawDot(x,y){
ctx.fillStyle="red";
ctx.beginPath();
ctx.arc(x,y,5,0,2*Math.PI,true);
ctx.closePath();
ctx.fill();
}

functiondrawAngle(x,y,style){
ctx.beginPath();
ctx.moveTo(x,y);
ctx.lineTo(x,y+100);
ctx.lineTo(x+100,y+100);
ctx.strokeStyle="blue";
ctx.lineWidth=25;
ctx.lineCap=style.capStyle||"butt";
ctx.lineJoin=style.jointStyle||"miter";
ctx.stroke();

// Indicate end of line
drawDot(x,y);
drawDot(x,y+100);
drawDot(x+100,y+100);
}

functionrun(){
console.log("Running line caps & joints demo");
ctx=app.common.getCanvasContext();

app.common.addCommentLowerRight(ctx,"Line Caps & Joints Demo");

// line caps
drawAngle(50,100,{capStyle : "butt"});// default
drawAngle(200,100,{capStyle : "round"});
drawAngle(350,100,{capStyle : "square"});

// line joints
drawAngle(50,300,{jointStyle : "bevel"});
drawAngle(200,300,{jointStyle : "round"});
drawAngle(350,300,{jointStyle : "miter"});// default
}

// Public functions
return{
run : run
};

})();

app.demo["gradients"]=(function(){

functionrun(){
console.log("Running gradients demo");
varctx=app.common.getCanvasContext();

app.common.addCommentLowerRight(ctx,"Gradients Demo");

// (x1,y1,x2,y2)
varlineGradient=ctx.createLinearGradient(50,50,200,400);
lineGradient.addColorStop(0,"green");
lineGradient.addColorStop(0.5,"yellow");
lineGradient.addColorStop(1,"red");
ctx.fillStyle=lineGradient;
ctx.fillRect(10,10,240,440);

// (circle1x, circle1y, circle1radius, circle2x, circle2y, circle2radius)
varradialGradient=ctx.createRadialGradient(
400,250,50,
400,250,150
);
radialGradient.addColorStop(0,"red");
radialGradient.addColorStop(0.5,"yellow");
radialGradient.addColorStop(1,"green");
ctx.fillStyle=radialGradient;
ctx.beginPath();
ctx.arc(370,300,120,0,2*Math.PI,true);
ctx.fill();
}

// Public methods
return{
run : run
};
})();

app.demo["shadow"]=(function(){

functionrun(){
console.log("Running shadow effects demo");
varctx=app.common.getCanvasContext();

app.common.addCommentLowerRight(ctx,"Shadow Effects Demo");

ctx.shadowColor="black";
ctx.shadowOffsetX=20;
ctx.shadowOffsetY=20;
ctx.shadowBlur=20;

ctx.lineWidth=15;
ctx.strokeStyle="darkblue";
ctx.fillStyle="blue";

// 1 - Rectangle with only fill
ctx.fillRect(50,50,200,150);

// 2 - Rectangle with only stroke
ctx.strokeRect(150,150,200,150);

// 3 - Rectangle with both fill & stroke
// Prevent shadow from appearing inside rectangle that occurs with fill + stroke
// by setting shadown to transparent while stroking
ctx.fillRect(250,250,200,150);
ctx.shadowColor="transparent";
ctx.strokeRect(250,250,200,150);
ctx.shadowColor="black";

ctx.shadowBlur=5;
ctx.beginPath();
ctx.arc(400,100,50,0,2*Math.PI,true);
ctx.closePath();
ctx.fill();
}

// Public functions
return{
run : run
};

})();

app.demo["state"]=(function(){

varctx={};

functionredRect(x1,y1,x2,y2){
ctx.save();

ctx.lineCap="round";
ctx.lineJoin="round";
ctx.strokeStyle="red";
ctx.lineWidth=20.0;
ctx.strokeRect(x1,y1,(x2-x1),(y2-y1));

ctx.restore();
}

functiongreenRect(x1,y1,x2,y2){
ctx.save();

ctx.lineCap="butt";
ctx.lineJoin="miter";
ctx.strokeStyle="green";
ctx.lineWidth=10.0;
ctx.strokeRect(x1,y1,(x2-x1),(y2-y1));

ctx.restore();
}

functionrun(){
console.log("Running canvas state stack demo");
ctx=app.common.getCanvasContext();

app.common.addCommentLowerRight(ctx,"State Stack Demo");

// Blue
ctx.strokeStyle="blue";
ctx.lineWidth=1;
ctx.strokeRect(50,50,50,50);

redRect(100,100,150,150);

// Blue
ctx.strokeRect(150,150,50,50);

greenRect(200,200,300,300);

// Blue
ctx.strokeRect(300,300,50,50);
}

// Public functions
return{
run : run
}
})();

app.demo["rotate"]=(function(){

functionrun(){
console.log("Running rotation demo");
varcanvas=app.common.getCanvas();
varctx=canvas.getContext("2d");

app.common.addCommentLowerRight(ctx,"Rotation Demo");

// Scale coordinates to be between 0.0 and 1.0
// so we don't need to know actual dimensions
ctx.scale(canvas.width,canvas.height);

// Draw backround
vargradient=ctx.createRadialGradient(
0.5,0.5,0.125,
0.5,0.5,0.75
);
gradient.addColorStop(0.1,"green");
gradient.addColorStop(0.9,"blue");
ctx.fillStyle=gradient;
ctx.fillRect(0,0,1,0.95);

ctx.translate(0.5,0.5);
ctx.lineWidth=0.005;

// Draw rotated inner lines
ctx.beginPath();
for(vari=0;i<51;i++){
ctx.rotate(1/50*Math.PI*2);
ctx.lineTo(0.20,0);
ctx.lineTo(0.30,0.0);
}
ctx.strokeStyle="red";
ctx.stroke();

// Draw counter rotated outer lines
ctx.beginPath();
for(vari=61;i>=0;i--){
ctx.rotate(1/60*Math.PI*2);
ctx.lineTo(0.35,0);
ctx.lineTo(0.40,0.0);
}
ctx.strokeStyle="purple";
ctx.stroke();
}

return{
run : run
}

})();

// main entry point
window.addEventListener("load",function(){

app.common.bind("demo-menu","click",function(e){
if(e.target.nodeName.toLowerCase()==="button"){
varaction=e.target.getAttribute("name");
console.log("button press");

app.common.clearCanvas();
app.demo[action].run();
}
});

},false);

</script>
</body>
</html>