How to fade out an item in canvas - javascript

I have a full screen canvas in my page. There are also some dive elements over this canvas. there is an circle element in the canvas that moves with the cursor everywhere in the page. However when the cursor arrives to the div element over the canvas, the circle shape stays in the last place it was on the canvas before arriving to the div.
DEMO: JSFIDDLE
Is ther any way that I can fade-out the circle shape when the cursor is over the div element and fade it in when it backs to the canvas?
Also is there any other effect rather than fading out? like making it small and then fade-out...
Here is the bit of code related to the circle:
function writeMessage(canvas, message, x, y) {
var context = canvas.getContext('2d');
context.clearRect(0, 0, canvas.width, canvas.height);
var pattern = context.createPattern(imageResized, 'no-repeat');//Use imageResized, not imageObj.
context.fillStyle = pattern;
context.fill();
context.fillStyle = 'black';
context.beginPath();
context.arc(x, y, 60, 0, 2 * Math.PI);
}

Well, you can always create your own fade function that gets called on mouseout (or mouseleave) event. Here's one I quickly built for you:
function fadeOut(canvas, message, x, y, amount) {
var context = canvas.getContext('2d');
context.clearRect(0, 0, canvas.width, canvas.height);
var pattern = context.createPattern(imageResized, 'no-repeat');
context.fillStyle = pattern;
context.fill();
context.font = '28pt Calibri';
context.fillStyle = 'black';
context.beginPath();
context.arc(x, y, amount, 0, 2 * Math.PI);
if (amount > 0) {
setTimeout(function(){
fadeOut(canvas, message, x, y, --amount);
}, 2);
}
else {
context.clearRect(0, 0, canvas.width, canvas.height);
}
}
See it in action here: http://jsfiddle.net/2p9dn8ed/42/
Or in the snippet:
var canvas = document.getElementById('myCanvas');
var context = canvas.getContext('2d');
var x = 0;
var y = 0;
var width = window.innerWidth;
var height = window.innerHeight;
var imageObj = new Image();
console.log(window.innerWidth + "----" + window.innerHeight);
//Create another canvas to darw a resized image to.
var imageResized = document.createElement('canvas');
imageResized.width = width;
imageResized.height = height;
//Wait for the original image to low to draw the resize.
imageObj.onload = function() {
//Find hoe mauch to scale the image up to cover.
var scaleX = width / imageObj.width;
var scaleY = height / imageObj.height;
var scaleMax = Math.max(scaleX, scaleY);
var ctx = imageResized.getContext('2d');
ctx.scale(scaleMax, scaleMax);
ctx.drawImage(imageObj, 0, 0);
};
imageObj.src = 'http://www.html5canvastutorials.com/demos/assets/darth-vader.jpg';
function writeMessage(canvas, message, x, y) {
var context = canvas.getContext('2d');
context.clearRect(0, 0, canvas.width, canvas.height);
var pattern = context.createPattern(imageResized, 'no-repeat');//Use imageResized, not imageObj.
context.fillStyle = pattern;
context.fill();
context.font = '28pt Calibri';
context.fillStyle = 'black';
//context.fillText(message, x, y);
context.beginPath();
context.arc(x, y, 60, 0, 2 * Math.PI);
//context.stroke();
//
}
function fadeOut(canvas, message, x, y, amount) {
var context = canvas.getContext('2d');
context.clearRect(0, 0, canvas.width, canvas.height);
var pattern = context.createPattern(imageResized, 'no-repeat');//Use imageResized, not imageObj.
context.fillStyle = pattern;
context.fill();
context.font = '28pt Calibri';
context.fillStyle = 'black';
//context.fillText(message, x, y);
context.beginPath();
context.arc(x, y, amount, 0, 2 * Math.PI);
//context.stroke();
//
if (amount > 0) {
setTimeout(function(){
fadeOut(canvas, message, x, y, --amount);
}, 2);
}
else {
context.clearRect(0, 0, canvas.width, canvas.height);
}
}
function getMousePos(canvas, evt) {
var rect = canvas.getBoundingClientRect();
return {
x: evt.clientX - rect.left,
y: evt.clientY - rect.top
};
}
canvas.addEventListener('mousemove', function (evt) {
var mousePos = getMousePos(canvas, evt);
var message = 'Mouse position: ' + mousePos.x + ',' + mousePos.y;
writeMessage(canvas, message, mousePos.x, mousePos.y);
}, false);
canvas.addEventListener('mouseout', function(evt){
var mousePos = getMousePos(canvas, evt);
var message = 'Mouse position: ' + mousePos.x + ',' + mousePos.y;
console.log(1);
fadeOut(canvas, message, mousePos.x, mousePos.y, 60);
});
// Get the canvas element form the page
var canvas = document.getElementById("myCanvas");
/* Rresize the canvas to occupy the full page,
by getting the widow width and height and setting it to canvas*/
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
anvas, img {
display:block;
margin:1em auto;
border:1px solid black;
}
canvas {
background:url('../img/spiral_galaxy-1920x1080.jpg');
background-size: cover;
position: absolute;
left: 0; top: 0;
width: 100%; height: 100%;
z-index:-1;
}
div{
width:200px;
height:200px;
background:rgba(0,0,0,0.5);
position: fixed;
top: 20%;
left: 20%;
}
<canvas id="myCanvas" width="578" height="400"></canvas>
<div><h1>TEXT</h1></div>

Related

trying to add a photo instead of color

(function() {
// Creates a new canvas element and appends it as a child
// to the parent element, and returns the reference to
// the newly created canvas element
function createCanvas(parent, width, height) {
var canvas = {};
canvas.node = document.createElement('canvas');
canvas.context = canvas.node.getContext('2d');
canvas.node.width = width || 100;
canvas.node.height = height || 100;
parent.appendChild(canvas.node);
return canvas;
}
function init(container, width, height, fillColor) {
var canvas = createCanvas(container, width, height);
var ctx = canvas.context;
// define a custom fillCircle method
ctx.fillCircle = function(x, y, radius, fillColor) {
this.fillStyle = fillColor;
this.beginPath();
this.moveTo(x, y);
this.arc(x, y, radius, 0, Math.PI * 2, false);
this.fill();
};
ctx.clearTo = function(fillColor) {
ctx.fillStyle = fillColor;
ctx.fillRect(0, 0, width, height);
};
ctx.clearTo(fillColor || "yel");
// bind mouse events
canvas.node.onmousemove = function(e) {
if (!canvas.isDrawing) {
return;
}
var x = e.pageX - this.offsetLeft;
var y = e.pageY - this.offsetTop;
var radius = 40; // or whatever
var fillColor = '#ff0000';
ctx.globalCompositeOperation = 'destination-out';
ctx.fillCircle(x, y, radius, fillColor);
};
canvas.node.onmousedown = function(e) {
canvas.isDrawing = false;
};
canvas.node.onmouseup = function(e) {
canvas.isDrawing = true;
};
}
var img = document.createElement("img");
img.src= "blm.jpg";
var container = document.getElementById('canvas');
init(container, window.innerWidth, window.innerHeight, 'img');
})();
Hi im trying to make a cover for my canvas instead of just a plain black color on my code. instead i would like my image named "blm.jpg" to replace the plain black. Im not sure how to. Im very new to coding and would really appreciate any help that i can get :) I added the var img = document 5 lines from the bottom and the 4th line from the bottom, im not sure if thats meant to be there either.
thank you for any help in advance :)
Here is a simple example on how to do that, I'm just drawing grids over the background image
var canvas = document.querySelector("canvas"),
ctx = canvas.getContext("2d"),
backgroundImage = document.createElement("img");
backgroundImage.src = "https://openclipart.org/image/400px/svg_to_png/260587/Surreal-Fantastic-Nature.png";
function makeLine(start_x, start_y, end_x, end_y) {
ctx.moveTo(start_x, start_y);
ctx.lineTo(end_x, end_y);
}
function drawGrid(val, color) {
ctx.beginPath();
ctx.strokeStyle = color;
for(var i = 0; i <= canvas.height; i += val) {
makeLine(0, i, canvas.width, i);
}
for(var j = 0; j <= canvas.width; j += val) {
makeLine(j, 0, j, canvas.height);
}
ctx.stroke();
}
// draw it first to make it the background and only when it loads
backgroundImage.onload = function() {
ctx.drawImage(this, 0, 0, canvas.width, canvas.height);
drawGrid(10, "blue");
drawGrid(20, "red");
drawGrid(40, "black");
}
canvas {
border-radius: 3px;
box-shadow: 1px 1px 10px blue;
}
<canvas width="320" height="200">
You may noticed that we need to wait for the image to load for drawing it and draw other stuff, but here is another way by wrapping the whole code into the window.onload method and add our image as an HTML element and hide it of course
window.onload = function() {
var canvas = document.querySelector("canvas"),
ctx = canvas.getContext("2d"),
backgroundImage = document.querySelector("#background-img");
function makeLine(start_x, start_y, end_x, end_y) {
ctx.moveTo(start_x, start_y);
ctx.lineTo(end_x, end_y);
}
function drawGrid(val, color) {
ctx.beginPath();
ctx.strokeStyle = color;
for(var i = 0; i <= canvas.height; i += val) {
makeLine(0, i, canvas.width, i);
}
for(var j = 0; j <= canvas.width; j += val) {
makeLine(j, 0, j, canvas.height);
}
ctx.stroke();
}
// no need for the .onload since the code is executing after everything loads
ctx.drawImage(backgroundImage, 0, 0, canvas.width, canvas.height);
drawGrid(10, "blue");
drawGrid(20, "red");
drawGrid(40, "black");
}
canvas {
border-radius: 3px;
box-shadow: 1px 1px 10px blue;
}
.hidden {
display: none;
}
<canvas width="320" height="200"></canvas>
<img id="background-img" class="hidden" src="https://openclipart.org/image/400px/svg_to_png/260587/Surreal-Fantastic-Nature.png" alt="nature painting">

How to rotate an image on HTML5 canvas when the right and left arrow keys are pressed

I need help trying to rotate the rectangle that I have drawn on the canvas. I would like the top of the rectangle to pivot either to the right or left once I press on the arrow keys on my keyboard. This is my code so far:
HTML:
<body >
<div id="canvas-container">
<canvas id="canvas" width="500" height="400"></canvas>
</div>
</body>
CSS:
canvas {
display: inline;
}
Javascript:
document.addEventListener("DOMContentLoaded", function() {
drawBorder();
});
var canvas;
var context;
var size;
drawRectangle();
drawHalfCircle();
function drawBorder() {
canvas = document.getElementById("canvas");
context = canvas.getContext('2d');
size = {
x: canvas.width,
y: canvas.height
};
//have to set colors etc befor it is drawn
context.strokeStyle = 'black';
//takes 4 parameters
context.strokeRect(0, 0, size.x, size.y);
}
function drawRectangle() {
var c = document.getElementById("canvas");
var ctx = c.getContext("2d");
ctx.rect(246, 290, 8, 80);
ctx.stroke();
}
function drawHalfCircle(){
var c= document.getElementById("canvas");
var ctx=c.getContext("2d");
ctx.beginPath();
ctx.arc(250,579,308,1.2*Math.PI, 1.8*Math.PI);
ctx.stroke();
}
I have mocked something up is this along the correct lines of what you are wanting.
document.addEventListener("DOMContentLoaded", function() {
drawBorder();
});
var canvas = document.getElementById("canvas");
var context = canvas.getContext('2d');
var size;
var angle = 0;
setInterval(function () {
context.save();
context.clearRect(0, 0, canvas.width, canvas.height);
drawBorder();
drawHalfCircle();
drawRectangle();
context.restore();
}, 100);
function drawBorder() {
size = {
x: canvas.width,
y: canvas.height
};
//have to set colors etc befor it is drawn
context.strokeStyle = 'black';
//takes 4 parameters
context.strokeRect(0, 0, size.x, size.y);
}
function drawRectangle() {
context.rotate(Math.PI / 180 * (angle));
context.rect(246, 290, 8, 80);
context.stroke();
}
function drawHalfCircle(){
context.beginPath();
context.arc(250,579,308,1.2*Math.PI, 1.8*Math.PI);
context.stroke();
}
document.onkeydown = function(e) {
var event = window.event ? window.event : e;
if (e.keyCode == '37') {
angle += 5;
}
else if (e.keyCode == '39') {
angle -= 5;
}
}
Basically set an interval and redraw (ie frames like in a movie) and rotate via a variable.
See a demo here
https://jsbin.com/qititacazu/edit?js,output
If you want to translate it so it will rotate around a different point do something like this.
context.translate(246, 290);
context.rotate(Math.PI / 180 * (angle));
context.rect(-4, 0, 4, 80);

HTML canvas spotlight effect

Let's say I have the following code.
// Find out window height and width
wwidth = $(window).width();
wheight = $(window).height();
// Place Canvas over current Window
$("body").append($("<canvas id='test' style='position:absolute; top:0; left:0;'></canvas>"));
var context = document.getElementById("test").getContext("2d");
context.canvas.width = wwidth;
context.canvas.height = wheight;
// Paint the canvas black.
context.fillStyle = '#000';
context.clearRect(0, 0, context.canvas.width, context.canvas.height);
context.fillRect(0, 0, context.canvas.width, context.canvas.height);
// On Mousemove, create "Flashlight" around the mouse, to see through the canvas
$(window).mousemove(function(event){
x = event.pageX;
y = event.pageY;
radius = 50;
context = document.getElementById("test").getContext("2d");
// Paint the canvas black. Instead it will draw it white?!
//context.fillStyle = '#000';
//context.clearRect(0, 0, context.canvas.width, context.canvas.height);
//context.fillRect(0, 0, context.canvas.width, context.canvas.height);
context.beginPath();
radialGradient = context.createRadialGradient(x, y, 1, x, y, radius);
radialGradient.addColorStop(0, 'rgba(255,255,255,1)');
radialGradient.addColorStop(1, 'rgba(0,0,0,0)');
context.globalCompositeOperation = "destination-out";
context.fillStyle = radialGradient;
context.arc(x, y, radius, 0, Math.PI*2, false);
context.fill();
context.closePath();
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div>Test</div>
which generates the following effect on mousemove:
How do I refill the canvas with black before the spotlight is drawn? I have already tried with what is in the commented-out code block, but it paints everything white.
EDIT: I dont want this effect over an image. Instead i would like to place the Canvas over the whole Webpage. ALso I want the Canvas to be always black and the mouse generates a Spotlight over its position, to see what is under the Canvas just as u can see in the picture, or in the Snippet where a div was placed in an empty html page with "Test" in it.
You can use compositing to create your flashlight effect:
Clear the canvas
Create a radial gradient to use as a reveal.
Fill the radial gradient.
Use source-atop compositing to draw the background image. The image will display only inside the radial gradient.
Use destination-over compositing to fill the canvas with black. The black will fill "behind" the existing radial-gradient-image.
Here's example code and a Demo:
var canvas=document.getElementById("canvas");
var ctx=canvas.getContext("2d");
var cw=canvas.width;
var ch=canvas.height;
function reOffset(){
var BB=canvas.getBoundingClientRect();
offsetX=BB.left;
offsetY=BB.top;
}
var offsetX,offsetY;
reOffset();
window.onscroll=function(e){ reOffset(); }
window.onresize=function(e){ reOffset(); }
$("#canvas").mousemove(function(e){handleMouseMove(e);});
var radius=30;
var img=new Image();
img.onload=function(){
draw(150,150,30);
}
img.src='https://dl.dropboxusercontent.com/u/139992952/multple/annotateMe.jpg'
function draw(cx,cy,radius){
ctx.save();
ctx.clearRect(0,0,cw,ch);
var radialGradient = ctx.createRadialGradient(cx, cy, 1, cx, cy, radius);
radialGradient.addColorStop(0, 'rgba(0,0,0,1)');
radialGradient.addColorStop(.65, 'rgba(0,0,0,1)');
radialGradient.addColorStop(1, 'rgba(0,0,0,0)');
ctx.beginPath();
ctx.arc(cx,cy,radius,0,Math.PI*2);
ctx.fillStyle=radialGradient;
ctx.fill();
ctx.globalCompositeOperation='source-atop';
ctx.drawImage(img,0,0);
ctx.globalCompositeOperation='destination-over';
ctx.fillStyle='black';
ctx.fillRect(0,0,cw,ch);
ctx.restore();
}
function handleMouseMove(e){
// tell the browser we're handling this event
e.preventDefault();
e.stopPropagation();
mouseX=parseInt(e.clientX-offsetX);
mouseY=parseInt(e.clientY-offsetY);
draw(mouseX,mouseY,30);
}
body{ background-color: ivory; }
#canvas{border:1px solid red; }
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>
<h4>Move mouse to reveal image with "flashlight"</h4>
<canvas id="canvas" width=300 height=300></canvas>
If your spotlight radius will never change, here's a much faster method:
The speed is gained by caching the spotlight to a second canvas and then...
Draw the image on the canvas.
Draw the spotlight on the canvas.
Use fillRect to black out the 4 rectangles outside the spotlight.
Example code and a Demo:
var canvas=document.getElementById("canvas");
var ctx=canvas.getContext("2d");
var cw=canvas.width;
var ch=canvas.height;
function reOffset(){
var BB=canvas.getBoundingClientRect();
offsetX=BB.left;
offsetY=BB.top;
}
var offsetX,offsetY;
reOffset();
window.onscroll=function(e){ reOffset(); }
window.onresize=function(e){ reOffset(); }
var radius=50;
var cover=document.createElement('canvas');
var cctx=cover.getContext('2d');
var size=radius*2+10;
cover.width=size;
cover.height=size;
cctx.fillRect(0,0,size,size);
var radialGradient = cctx.createRadialGradient(size/2, size/2, 1, size/2, size/2, radius);
radialGradient.addColorStop(0, 'rgba(0,0,0,1)');
radialGradient.addColorStop(.65, 'rgba(0,0,0,1)');
radialGradient.addColorStop(1, 'rgba(0,0,0,0)');
cctx.beginPath();
cctx.arc(size/2,size/2,size/2,0,Math.PI*2);
cctx.fillStyle=radialGradient;
cctx.globalCompositeOperation='destination-out';
cctx.fill();
var img=new Image();
img.onload=function(){
$("#canvas").mousemove(function(e){handleMouseMove(e);});
ctx.fillRect(0,0,cw,ch);
}
img.src='https://dl.dropboxusercontent.com/u/139992952/multple/annotateMe.jpg'
function drawCover(cx,cy){
var s=size/2;
ctx.clearRect(0,0,cw,ch);
ctx.drawImage(img,0,0);
ctx.drawImage(cover,cx-size/2,cy-size/2);
ctx.fillStyle='black';
ctx.fillRect(0,0,cx-s,ch);
ctx.fillRect(0,0,cw,cy-s);
ctx.fillRect(cx+s,0,cw-cx,ch);
ctx.fillRect(0,cy+s,cw,ch-cy);
}
function handleMouseMove(e){
// tell the browser we're handling this event
e.preventDefault();
e.stopPropagation();
mouseX=parseInt(e.clientX-offsetX);
mouseY=parseInt(e.clientY-offsetY);
drawCover(mouseX,mouseY);
}
body{ background-color: ivory; }
#canvas{border:1px solid red; }
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>
<h4>Move mouse to reveal image with "flashlight"</h4>
<canvas id="canvas" width=300 height=300></canvas>
You can achieve the spotlight effect by positioning a canvas directly over the image. Make the canvas the same size as the image and set the compositing operation to xor so that two black pixels drawn in the same place cancel each other out.
context.globalCompositeOperation = 'xor';
Now you can paint the canvas black and fill a black circle around the mouse cursor. The result is a hole in the black surface, showing the image underneath.
// Paint the canvas black.
context.fillStyle = '#000';
context.clearRect(0, 0, width, height);
context.fillRect(0, 0, width, height);
// Paint a black circle around x, y.
context.beginPath();
context.arc(x, y, spotlightRadius, 0, 2 * Math.PI);
context.fillStyle = '#000';
context.fill();
// With xor compositing, the result is a circular hole.
To make a spotlight with blurry edges, define a radial gradient centered on the mouse position and fill a square around it.
var gradient = context.createRadialGradient(x, y, 0, x, y, spotlightRadius);
gradient.addColorStop(0, 'rgba(0, 0, 0, 1)');
gradient.addColorStop(0.9, 'rgba(0, 0, 0, 1)');
gradient.addColorStop(1, 'rgba(0, 0, 0, 0)');
context.fillStyle = gradient;
context.fillRect(x - spotlightRadius, y - spotlightRadius,
2 * spotlightRadius, 2 * spotlightRadius);
The following snippet demonstrates both approaches using pure JavaScript. To change from a crisp-edged spotlight to a blurry-edged spotlight, click on the checkbox above the image.
function getOffset(element, ancestor) {
var left = 0,
top = 0;
while (element != ancestor) {
left += element.offsetLeft;
top += element.offsetTop;
element = element.parentNode;
}
return { left: left, top: top };
}
function getMousePosition(event) {
event = event || window.event;
if (event.pageX !== undefined) {
return { x: event.pageX, y: event.pageY };
}
return {
x: event.clientX + document.body.scrollLeft +
document.documentElement.scrollLeft,
y: event.clientY + document.body.scrollTop +
document.documentElement.scrollTop
};
}
window.onload = function () {
var spotlightRadius = 60,
container = document.getElementById('container'),
canvas = document.createElement('canvas'),
image = container.getElementsByTagName('img')[0],
width = canvas.width = image.width,
height = canvas.height = image.height,
context = canvas.getContext('2d');
context.globalCompositeOperation = 'xor';
container.insertBefore(canvas, image.nextSibling);
container.style.width = width + 'px';
container.style.height = height + 'px';
var offset = getOffset(canvas, document.body);
clear = function () {
context.fillStyle = '#000';
context.clearRect(0, 0, width, height);
context.fillRect(0, 0, width, height);
};
clear();
image.style.visibility = 'visible';
canvas.onmouseout = clear;
canvas.onmouseover = canvas.onmousemove = function (event) {
var mouse = getMousePosition(event),
x = mouse.x - offset.left,
y = mouse.y - offset.top;
clear();
if (document.getElementById('blurry').checked) {
var gradient = context.createRadialGradient(x, y, 0, x, y, spotlightRadius);
gradient.addColorStop(0, 'rgba(0, 0, 0, 1)');
gradient.addColorStop(0.875, 'rgba(0, 0, 0, 1)');
gradient.addColorStop(1, 'rgba(0, 0, 0, 0)');
context.fillStyle = gradient;
context.fillRect(x - spotlightRadius, y - spotlightRadius,
2 * spotlightRadius, 2 * spotlightRadius);
} else {
context.beginPath();
context.arc(x, y, spotlightRadius, 0, 2 * Math.PI);
context.fillStyle = '#000';
context.fill();
}
};
};
* {
margin: 0;
padding: 0;
}
.control {
font-family: sans-serif;
font-size: 15px;
padding: 10px;
}
#container {
position: relative;
}
#container img, #container canvas {
position: absolute;
left: 0;
top: 0;
}
#container img {
visibility: hidden;
}
#container canvas {
cursor: none;
}
<p class="control">
<input type="checkbox" id="blurry" /> blurry edges
</p>
<div id="container">
<img src="https://dl.dropboxusercontent.com/u/139992952/multple/annotateMe.jpg" />
</div>
this code works for me:
x = event.pageX;
y = event.pageY;
radius = 10;
context = canvas.getContext("2d");
context.fillStyle = "black";
context.fillRect(0, 0, context.canvas.width, context.canvas.height);
context.beginPath();
var radialGradient= context.createRadialGradient(x,y,1,x,y,radius);
radialGradient.addColorStop(0,"rgba(255,255,255,1");
radialGradient.addColorStop(1,"rgba(0,0,0,1)");
//context.globalCompositeOperation = "destination-out";
context.fillStyle = radialGradient;
context.arc(x, y, radius, 0, Math.PI*2, false);
context.fill();
context.closePath();
it seems that this line was messing it context.globalCompositeOperation = "destination-out";
there were also pointless lines in your code like beginnig path before filling rect and fill() function after filling path

How would I fillRect with an image?

Normally you can fill a rectangle in a canvas withctx.fillStyle = "whatever color here" and then ctx.fillRect(cords and length and width here). Is there a syntax where I can say ctx.fillRect(someImagePathHere, xOfTopLeft, yofTopLeft)
If not, how else can I achieve this?
The question is ambiguous as there are many ways to "fillRect with an image".
First off images in the browser are downloaded asynchronously so you need to wait for an image to load before you can use it. For canvas situations the most common way to get an image is to create a new Image and set an onload listener
const img = new Image();
img.onload = someFunctionToCallWhenTheImageHasLoaded
img.src = 'http://url/to/image';
Then the question is what do mean by "fillRect"
Using this 256x256 image
For example to draw the image at the size it was downloaded you can use drawImage with 3 arguments
ctx.drawImage(img, x, y);
const img = new Image();
img.onload = draw;
img.src = 'https://i.imgur.com/ZKMnXce.png';
function draw() {
const ctx = document.querySelector('canvas').getContext('2d');
ctx.drawImage(img, 0, 0);
}
canvas { border: 1px solid black; }
<canvas></canvas>
To draw the image at a different size you can use
ctx.drawImage(img, x, y, width, height);
const img = new Image();
img.onload = draw;
img.src = 'https://i.imgur.com/ZKMnXce.png';
function draw() {
const ctx = document.querySelector('canvas').getContext('2d');
const destX = 10;
const destY = 20;
const destWidth = 30;
const destHeight = 40;
ctx.drawImage(img, destX, destY, destWidth, destHeight);
}
canvas { border: 1px solid black; }
<canvas></canvas>
To draw part of the image you can use
// part of image to draw
const srcX = 10;
const srcY = 20;
const srcWidth = 130;
const srcHeight = 140;
// where to draw it
const dstX = 60;
const dstY = 70;
const dstWidth = 160;
const dstHeight = 40;
ctx.drawImage(img, srcX, srcY, srcWidth, srcHeight,
dstX, dstY, dstWidth, dstHeight);
const img = new Image();
img.onload = draw;
img.src = 'https://i.imgur.com/ZKMnXce.png';
function draw() {
const ctx = document.querySelector('canvas').getContext('2d');
// part of image to draw
const srcX = 10;
const srcY = 20;
const srcWidth = 130;
const srcHeight = 140;
// where to draw it
const dstX = 60;
const dstY = 70;
const dstWidth = 160;
const dstHeight = 40;
ctx.drawImage(img, srcX, srcY, srcWidth, srcHeight,
dstX, dstY, dstWidth, dstHeight);
}
canvas { border: 1px solid black; }
<canvas></canvas>
That said, "fillRect" being ambiguous maybe you wanted to use the image as a pattern in which case you need to make a pattern out of it using createPattern
const pattern = ctx.createPatttern(img, 'repeat');
For these let's use this 16x16 pixel image
You can then use the pattern as your fillStyle as in
ctx.fillStyle = pattern;
ctx.fillRect(10, 20, 30, 40);
const img = new Image();
img.onload = draw;
img.src = 'https://i.imgur.com/fqgm8uh.png';
function draw() {
const ctx = document.querySelector('canvas').getContext('2d');
const pattern = ctx.createPattern(img, 'repeat');
ctx.fillStyle = pattern;
ctx.fillRect(10, 20, 30, 40);
}
canvas { border: 1px solid black; }
<canvas></canvas>
Patterns are relative to the origin of the canvas which means if you just use ctx.fillRect (or any other fill) the pattern will match across fills.
ctx.fillRect(10, 20, 30, 40);
ctx.beginPath();
ctx.arc(50, 60, 25, 0, Math.PI * 2);
ctx.fill();
const img = new Image();
img.onload = draw;
img.src = 'https://i.imgur.com/fqgm8uh.png';
function draw() {
const ctx = document.querySelector('canvas').getContext('2d');
const pattern = ctx.createPattern(img, 'repeat');
ctx.fillStyle = pattern;
ctx.fillRect(10, 20, 30, 40);
ctx.beginPath();
ctx.arc(50, 60, 25, 0, Math.PI * 2);
ctx.fill();
}
canvas { border: 1px solid black; }
<canvas></canvas>
Because patterns are anchored at the origin if you are animating without changing the origin you'll notice the pattern doesn't move
const img = new Image();
img.onload = start;
img.src = 'https://i.imgur.com/fqgm8uh.png';
function start() {
const ctx = document.querySelector('canvas').getContext('2d');
const pattern = ctx.createPattern(img, 'repeat');
function render(time) {
time *= 0.001; // seconds;
ctx.clearRect(0, 0, ctx.canvas.width, ctx.canvas.height);
const x = Math.sin(time * 1.1) * 150 + 150;
const y = Math.sin(time * 1.2) * 50 + 50;
ctx.fillStyle = pattern;
ctx.fillRect(x, y, 30, 40);
ctx.beginPath();
ctx.arc(x, y, 25, 0, Math.PI * 2);
ctx.fill();
requestAnimationFrame(render);
}
requestAnimationFrame(render);
}
canvas { border: 1px solid black; }
<canvas></canvas>
In order to move the pattern you need to move the origin of the canvas using ctx.translate (as well as ctx.rotate, ctx.scale, ctx.setTransform)
const img = new Image();
img.onload = start;
img.src = 'https://i.imgur.com/fqgm8uh.png';
function start() {
const ctx = document.querySelector('canvas').getContext('2d');
const pattern = ctx.createPattern(img, 'repeat');
function render(time) {
time *= 0.001; // seconds;
ctx.clearRect(0, 0, ctx.canvas.width, ctx.canvas.height);
const x = Math.sin(time * 1.1) * 150 + 150;
const y = Math.sin(time * 1.2) * 50 + 50;
ctx.translate(x, y);
ctx.fillStyle = pattern;
ctx.fillRect(0, 0, 30, 40);
ctx.beginPath();
ctx.arc(0, 0, 25, 0, Math.PI * 2);
ctx.fill();
ctx.setTransform(1, 0, 0, 1, 0, 0); // set it back to the default
requestAnimationFrame(render);
}
requestAnimationFrame(render);
}
canvas { border: 1px solid black; }
<canvas></canvas>
Here's an illustration of some of the possibilities:
var im = new Image();
im.src = "https://upload.wikimedia.org/wikipedia/commons/7/79/Face-smile.svg";
im.onload = function () { /* first, wait until the image is loaded */
/* create five canvases, and draw something in each */
for (var i=1; i<=5; i++) {
var canvas = document.createElement("canvas");
document.body.appendChild(canvas);
canvas.width = canvas.height = 200;
var ctx=canvas.getContext("2d");
var x=50, y=50; /* where to plot */
var w=20, h=60; /* width and height of rectangle, if applicable */
switch (i) {
case 1:
/* first canvas: draw a rectangle */
ctx.fillRect(x, y, w, h);
break;
case 2:
/* second canvas: draw an image, actual size, no clipping */
/* coordinates are where the top left of the image is plotted */
ctx.drawImage(im, x, y);
break;
case 3:
/* third canvas: draw an image, scaled to rectangle */
ctx.drawImage(im, x, y, w, h);
break;
case 4:
/* fourth canvas: draw an image, actual size, clipped to rectangle */
ctx.save();
ctx.rect(x, y, w, h);
ctx.clip();
ctx.drawImage(im, x, y);
ctx.restore();
break;
case 5:
/* fifth canvas: draw shapes filled with a background image */
ctx.fillStyle = ctx.createPattern(im, 'repeat'); /* or 'no-repeat', or 'repeat-x', or 'repeat-y' */
/* note that the image is tiled from the top left of the canvas */
ctx.fillRect(x, y, w, h);
/* also draw a circle, why not */
ctx.beginPath();
ctx.arc(150, 150, 40, 0, Math.PI*2);
ctx.fill();
break;
}
}
}
im.onerror = function() { alert("failed to load image"); };
Jsfiddle: http://jsfiddle.net/efeqjjno/
Here is a quick example of how you can use drawImage to draw an image to a canvas. The element on the left is the image, the element on the right is the canvas with the image drawn on it.
JSFiddle: https://jsfiddle.net/gw8ncg7g/
window.onload = function() {
var c = document.getElementById("myCanvas");
var ctx = c.getContext("2d");
var img = document.getElementById("image");
ctx.drawImage(img, 0, 0);
}
canvas {
border:1px solid #d3d3d3;
}
<img id="image" width="300" height="300" src="http://i.imgur.com/LDR6AWn.png?1">
<canvas id="myCanvas" width="300" height="300" >

Mask image in html canvas

Im trying to change a mask to an image in a html5 canvas when the mouse enters the canvas.
When the mouse enters the canvas i draw a shape thats gonna act as a mask. It draws as i want but it wont mask the image.
The function that draws the mask is drawLine();
What is wrong here?
var canvas = document.getElementById('canvas');
var context = canvas.getContext('2d');
var img = document.createElement('IMG');
var mY;
var mX;
img.onload = function () {
context.save();
context.beginPath();
context.moveTo(0, 0);
context.lineTo(160, 600);
context.rect(0, 0, 160, 600);
context.closePath();
context.clip();
context.drawImage(img, 0, 0);
context.restore();
};
img.src = "http://placekitten.com/160/600";
canvas.addEventListener('mouseenter', function(evt) {
var mousePos = getMousePos(canvas, evt);
var message = mousePos.y + ', ' + mousePos.x;
mY = mousePos.y;
mX = mousePos.x;
drawLine();
}, false);
function getMousePos(canvas, evt) {
var rect = canvas.getBoundingClientRect();
return {
x: evt.clientX - rect.left,
y: evt.clientY - rect.top
};
}
function drawLine() {
if(mX > 80) {
context.restore();
context.fillStyle = "rgb(000,000,000)";
context.beginPath();
context.moveTo(160, mY);
context.lineTo(0,mY+setCutAngle());
context.lineTo(0,600);
context.lineTo(160,600);
context.fill();
context.closePath();
} else {
}
context.stroke();
}
function setCutAngle() {
return Math.floor(Math.random() * 45) + 10;
}
Is this what you are looking for? JSFIDDLE Updated so image loads at the start.
I believe your main problem was caused by not clearing the canvas. Thus your clip would not show
Updated JSFIDDLE to match your code. Remove that logic from your load event. It should only happen on your drawevent. You are also not clearling or clipping your image in the draw event.
var canvas = document.getElementById('canvas');
var context = canvas.getContext('2d');
var img = document.createElement('IMG');
var mY;
var mX;
img.onload = function () {
context.drawImage(img, 0, 0);
};
img.src = "http://placekitten.com/160/600";
canvas.addEventListener('mouseenter', function(evt) {
var mousePos = getMousePos(canvas, evt);
var message = mousePos.y + ', ' + mousePos.x;
mY = mousePos.y;
mX = mousePos.x;
drawLine();
}, false);
function getMousePos(canvas, evt) {
var rect = canvas.getBoundingClientRect();
return {
x: evt.clientX - rect.left,
y: evt.clientY - rect.top
};
}
function drawLine() {
context.save();
context.clearRect(0, 0, canvas.width, canvas.height);
if(mX > 80) {
context.restore();
context.fillStyle = "rgb(000,000,000)";
context.beginPath();
context.moveTo(160, mY);
context.lineTo(0,mY+setCutAngle());
context.lineTo(0,600);
context.lineTo(160,600);
context.clip();
context.drawImage(img, 0, 0);
context.closePath();
} else {
}
context.stroke()
}
function setCutAngle() {
return Math.floor(Math.random() * 45) + 10;
}

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