Develop Reference

How to drag points with it's connecting line in html5 canvas?

Following is my code. I have face issue when I drag a point. The problem is that whenever I drag point all the line connect to one point. I need to have draggable points in a html5 Canvas. But I have a supplementary constraint: the 2 points must be linked by a line. When I drag a point, the line must be dynamically drawn, and still linked to the 2 points.
let points= [];
let drag_point= -1;
let pointSize= 6;
let canvas = document.querySelector("#myCanvas");
let w = canvas.width;
let h = canvas.height;
var ctx = canvas.getContext("2d");
$("#myCanvas").mousedown(function (e) {
var pos = getPosition(e);
drag_point = getPointAt(pos.x, pos.y);
console.log("pos", drag_point);
if (drag_point == -1) {
// no point at that position, add new point
drawlines(pos.x, pos.y);
points.push(pos);
}
});
$("#myCanvas").mousemove(function (e) {
if (drag_point != -1) {
// if currently dragging a point...
var pos = getPosition(e);
//...update that.points position...
points[drag_point].x = pos.x;
points[drag_point].y = pos.y;
redraw(); // ... and redraw myCanvas
}
});
$("#myCanvas").mouseup(function (e) {
drag_point = -1;
});
function getPosition(event) {
var rect = canvas.getBoundingClientRect();
var x = event.clientX - rect.left;
var y = event.clientY - rect.top;
console.log(x, y);
return { x: x, y: y };
}
function getPointAt(x, y) {
for (var i = 0; i < points.length; i++) {
if (
Math.abs(points[i].x - x) < pointSize &&
Math.abs(points[i].y - y) < pointSize
)
// check if x,y is inside points bounding box. replace with pythagoras theorem if you like.
return i;
}
return -1; // no point at x,y
}
function redraw() {
ctx.clearRect(0, 0, canvas.width, canvas.height); // clear canvas
for (var i = 0; i < points.length; i++) {
// draw all points again
drawlines(points[i].x, points[i].y);
}
}
function drawlines(x, y) {
drawImages(x, y);
if (points.length > 0) {
var last = points[points.length - 1];
ctx.beginPath();
ctx.moveTo(last.x, last.y);
ctx.lineTo(x, y);
ctx.strokeStyle = "blue";
ctx.stroke();
}
}
function drawImages(x, y) {
var ctx = document.getElementById("myCanvas").getContext("2d");
ctx.beginPath();
ctx.arc(x, y, pointSize, 0, Math.PI * 2, true);
ctx.strokeStyle = "red";
ctx.stroke();
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<canvas
id="myCanvas"
width="1000"
height="1000"
style="border: 1px solid #d3d3d3"
></canvas>
.

See code below...
I refactored your drawlines and drawImages to be called independently not inside a common loop, in my code we draw all lines, then we draw all circles, that way we don't have to change colors back and forth all the time and prevents any overlaps of the lines over the circles, also another change is in the mousedown I call the redraw instead of drawlines.
Looking at your code educated guess the problem is in your:
var last = points[points.length - 1];
that seems very off, technically that is making the last always be the same
let points = [{x:10,y:10},{x:55,y:50},{x:100,y:10}];
let drag_point = -1;
let pointSize = 6;
let canvas = document.getElementById("myCanvas");
var ctx = canvas.getContext("2d");
canvas.onmousedown = function(e) {
var pos = getPosition(e);
drag_point = getPointAt(pos.x, pos.y);
if (drag_point == -1) {
points.push(pos);
redraw();
}
};
canvas.onmousemove = function(e) {
if (drag_point != -1) {
var pos = getPosition(e);
points[drag_point].x = pos.x;
points[drag_point].y = pos.y;
redraw();
}
};
canvas.onmouseup = function(e) {
drag_point = -1;
};
function getPosition(event) {
var rect = canvas.getBoundingClientRect();
var x = event.clientX - rect.left;
var y = event.clientY - rect.top;
return {x, y};
}
function getPointAt(x, y) {
for (var i = 0; i < points.length; i++) {
if (
Math.abs(points[i].x - x) < pointSize &&
Math.abs(points[i].y - y) < pointSize
)
return i;
}
return -1;
}
function redraw() {
if (points.length > 0) {
ctx.clearRect(0, 0, canvas.width, canvas.height);
drawLines()
drawCircles()
}
}
function drawLines() {
ctx.beginPath();
ctx.moveTo(points[0].x, points[0].y);
ctx.strokeStyle = "blue";
ctx.lineWidth = 2;
points.forEach((p) => {
ctx.lineTo(p.x, p.y);
})
ctx.stroke();
}
function drawCircles() {
ctx.strokeStyle = "red";
ctx.lineWidth = 4;
points.forEach((p) => {
ctx.beginPath();
ctx.arc(p.x, p.y, pointSize, 0, Math.PI * 2, true);
ctx.stroke();
})
}
redraw()
<canvas id="myCanvas" width=160 height=160 style="border: 1px solid"></canvas>

Issue when dragging text on canvas if slightly scrolled down

When I scroll slightly down on my canvas, it does not allow me to drag my text at all. Examples (These are GIFs) -
https://gyazo.com/e60d2efd924ced758c2c6441391804db
GIF explained: So you saw the drag was working when I was on top of the page but when I scrolled slightly down. It completely stopped working. I added a few console.logs around, and what I know is the click event listener for the canvas is working but it isn't detected the text when I slightly scroll down on the page.
I based my drag code from: http://jsfiddle.net/m1erickson/9xAGa/ | What you can see is if you change the canvas size width: 667 and height: 800, and when you scroll slightly down, you will have the same issue I am having.
HTML Code:
<div id="middle_container">
<div class="center_container">
<canvas id="canvas" width="667px" height="800px"></canvas>
</div>
</div>
JavaScript Code:
var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");
var $canvas = $("#canvas");
var BB=canvas.getBoundingClientRect();
var offsetX = BB.left;
var offsetY = BB.top;
var mx;
var my;
var texts = [];
var images = [];
var dragF = -1;
var mode = "none";
function draw() {
ctx.clearRect(0, 0, canvas.width, canvas.height);
for(const { text, x, y, width, height } of texts) {
ctx.fillText(text, x, y);
}
}
function addNewText(string_text) {
var y = texts.length * 20 + 20;
var text = {
text: string_text,
x: 20,
y: y
};
ctx.font = "32px verdana";
ctx.textBaseline = "top";
text.width = ctx.measureText(text.text).width;
text.height = 32;
texts.push(text);
draw();
}
function hitDrag(x,y,textIndex) {
var r=texts[textIndex];
return (x>r.x && x<r.x+r.width && y>r.y && y<r.y+r.height);
}
function myDrag(a,e) {
if (a == "down") {
e.preventDefault();
e.stopPropagation();
mx=parseInt(e.clientX-offsetX);
my=parseInt(e.clientY-offsetY);
for(var i=0;i<texts.length;i++){
if(hitDrag(mx,my,i)){
console.log("found");
dragF = i;
}
}
}
}
addNewText("Hello World")
$("#canvas").mousedown(function(e) {
myDrag("down", e);
});

The problem is this line of code:
var BB=canvas.getBoundingClientRect();
which is only populated once at the start of your script. The .getBoundingClientRect() method returns the position of a HTML element relative to the viewport.
Well if you scroll the window, the viewport moves - as the canvas element - but the BB object still holds the position of your canvas at startup.
The fix is rather simple - you need to use the actual position of the canvas element by calling .getBoundingClientRect() again on mouse down and on mouse move.
I've prepared a little sample based on your code and the fiddle you've linked:
var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");
var $canvas = $("#canvas");
var BB = canvas.getBoundingClientRect();
var offsetX = BB.left;
var offsetY = BB.top;
var mx;
var my;
var texts = [];
var images = [];
var dragF = -1;
var mode = "none";
function draw() {
ctx.clearRect(0, 0, canvas.width, canvas.height);
for (const {
text,
x,
y,
width,
height
} of texts) {
ctx.fillText(text, x, y);
}
}
function addNewText(string_text) {
var y = texts.length * 20 + 20;
var text = {
text: string_text,
x: 20,
y: y
};
ctx.font = "32px verdana";
ctx.textBaseline = "top";
text.width = ctx.measureText(text.text).width;
text.height = 32;
texts.push(text);
draw();
}
function myDrag(a, e) {
if (a == "down") {
e.preventDefault();
e.stopPropagation();
let rect = canvas.getBoundingClientRect();
mx = parseInt(e.clientX - rect.left);
my = parseInt(e.clientY - rect.top);
for (var i = 0; i < texts.length; i++) {
if (hitDrag(mx, my, i)) {
// console.log("found");
dragF = i;
}
}
}
}
function hitDrag(x, y, textIndex) {
var r = texts[textIndex];
return (x > r.x && x < r.x + r.width && y > r.y && y < r.y + r.height);
}
function handleMouseMove(e) {
if (dragF < 0) {
return;
}
e.preventDefault();
let rect = canvas.getBoundingClientRect();
mouseX = parseInt(e.clientX - rect.left);
mouseY = parseInt(e.clientY - rect.top);
var dx = mouseX - mx;
var dy = mouseY - my;
mx = mouseX;
my = mouseY;
var text = texts[dragF];
text.x += dx;
text.y += dy;
draw();
}
function handleMouseUp(e) {
e.preventDefault();
dragF = -1;
}
addNewText("Hello World")
$("#canvas").mousedown(function(e) {
myDrag("down", e);
});
$("#canvas").mousemove(function(e) {
handleMouseMove(e);
});
$("#canvas").mouseup(function(e) {
handleMouseUp(e);
});
body {
background-color: ivory;
}
#canvas {
border: 1px solid red;
}
#theText {
width: 10em;
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<div id="middle_container">
<div class="center_container">
<canvas id="canvas" width="667px" height="800px"></canvas>
</div>
</div>
<br><br><br><br><br><br><br><br><br><br>
<br><br><br><br><br><br><br><br><br><br>

Is it possible to drag an image within canvas as well as draw on the same canvas?

Here I'm trying to draw on a html5 canvas as well as upload some images and drag them within the canvas. The problem is I can do one or the other but not both.
What I've realised is that the canvas must be Cleared before dragging takes place but by doing that I'm clearing the drawing and if I don't clear the canvas it draws but dragging an image leaves trail behind. Can anyone point me to right direction please.
function init() {
canvas = document.getElementById('can');
ctx = canvas.getContext("2d");
w = canvas.width;
h = canvas.height;
img = document.getElementById("drag");
canvas.addEventListener("mousemove", function (e) { findxy('move', e) }, false);
canvas.addEventListener("mousedown", function (e) { findxy('down', e) }, false);
canvas.addEventListener("mouseup", function (e) { findxy('up', e) }, false);
canvas.addEventListener("mouseout", function (e) { findxy('out', e) }, false);
imageLoader = document.getElementById('imageLoader');
imageLoader.addEventListener('change', handleImage, false);
var contexts = [];
contexts.push(canvas.getContext('2d'));
function clearAll() {
ctx.clearRect(0, 0, canvas.width, canvas.height);
}
canvas.onclick = function (e) { handleClick(e, 1); };
function handleClick(e, contextIndex) {
e.stopPropagation();
var mouseX = parseInt(e.clientX - e.target.offsetLeft);
var mouseY = parseInt(e.clientY - e.target.offsetTop);
// clearAll();
for (var i = 0; i < states.length; i++) {
var state = states[i];
if (state.dragging) {
state.dragging = false;
state.draw();
continue;
}
if (state.contextIndex === contextIndex
&& mouseX > state.x && mouseX < state.x + state.width
&& mouseY > state.y && mouseY < state.y + state.height)
{
state.dragging = true;
state.offsetX = mouseX - state.x;
state.offsetY = mouseY - state.y;
state.contextIndex = contextIndex;
}
state.draw();
}
}
canvas.onmousemove = function (e) { handleMousemove(e, 1); }
function handleMousemove(e, contextIndex) {
e.stopPropagation();
var mouseX = parseInt(e.clientX - e.target.offsetLeft);
var mouseY = parseInt(e.clientY - e.target.offsetTop);
// clearAll();
for (var i = 0; i < states.length; i++) {
var state = states[i];
if (state.dragging) {
state.x = mouseX - state.offsetX;
state.y = mouseY - state.offsetY;
state.contextIndex = contextIndex;
}
state.draw();
}
}
var states = [];
states.push(addState(0, 0, img));
function addState(x, y, image) {
state = {}
state.dragging = false;
state.contextIndex = 1;
state.image = image;
state.x = x;
state.y = y;
state.width = image.width;
state.height = image.height;
state.offsetX = 0;
state.offsetY = 0;
state.draw = function () {
var context = contexts[this.contextIndex - 1];
if (this.dragging) {
context.strokeStyle = 'red';
context.strokeRect(this.x, this.y, this.width + 5, this.height + 5);
}
context.drawImage(this.image, this.x, this.y);
};
state.draw();
return(state);
}
}//end of init()
var imgArray = [];
function handleImage(e) {
var reader = new FileReader();
reader.onload = function (event) {
imgArray.push(img);
for(i = 0; i < imgArray.length; i++){
img.src = imgArray[i];
img.setAtX = i * 50;
img.setAtY = i * 0;
img.onload = function() {
ctx.drawImage(this, this.setAtX, this.setAtY);
};
img.src = event.target.result;
}
};
reader.readAsDataURL(e.target.files[0]);
}
function findxy(res, e) {
if (res === 'down') {
prevX = currX;
prevY = currY;
currX = e.clientX - canvas.offsetLeft;
currY = e.clientY - canvas.offsetTop;
flag = true;
dot_flag = true;
if (dot_flag) {
ctx.beginPath();
ctx.fillStyle = x;
ctx.fillRect(currX, currY, 2, 2);
ctx.closePath();
dot_flag = false;
}
}
if (res === 'up' || res === "out") {
flag = false;
}
if (res === 'move') {
if (flag) {
prevX = currX;
prevY = currY;
currX = e.clientX - canvas.offsetLeft;
currY = e.clientY - canvas.offsetTop;
draw();
}
}
}
//Draw lines or text
function draw() {
ctx.beginPath();
ctx.moveTo(prevX, prevY);
ctx.lineTo(currX, currY);
ctx.strokeStyle = x;
ctx.lineWidth = y;
ctx.stroke();
ctx.closePath();
ctx.fillStyle = x;
ctx.font = "Italic Bold 14pt Times, serif";
ctx.fillText(message, prevX, prevY);
}

Here is a mashup of the code i linked to and your own.
All parameters related to drawing the image and translating it around the canvas is covered.
var canvas = document.getElementById("canvas");
var ctx;
var x = 75;
var y = 50;
var WIDTH = 400;
var HEIGHT = 300;
var dragok = false;
var img = document.getElementById("img");
var lines = [{
x: x,
y: y
}];
function rect(x, y, w, h) {
ctx.beginPath();
ctx.rect(x, y, w, h);
ctx.closePath();
ctx.fill();
}
function clear() {
ctx.clearRect(0, 0, WIDTH, HEIGHT);
}
function init() {
canvas = document.getElementById("canvas");
ctx = canvas.getContext("2d");
return setInterval(draw, 1000/24);
}
function draw() {
clear();
ctx.drawImage(img, x - img.width / 2, y - img.height / 2);
ctx.beginPath();
ctx.moveTo(lines[0].x,lines[0].y);
for(var i = 1; i < lines.length; i++) {
var line = lines[i];
ctx.lineTo(lines[i].x,lines[i].y);
}
ctx.stroke();
ctx.closePath();
//rect(x - 15, y - 15, 30, 30);
}
function myMove(e) {
if (dragok) {
x = e.pageX - canvas.offsetLeft;
y = e.pageY - canvas.offsetTop;
lines = lines.slice(lines.length - 100)
lines.push({
x: x,
y: y
});
}
}
function myDown(e) {
if (e.pageX < x + img.width / 2 + canvas.offsetLeft && e.pageX > x - img.width / 2 +
canvas.offsetLeft && e.pageY < y + img.height / 2 + canvas.offsetTop &&
e.pageY > y - img.height / 2 + canvas.offsetTop) {
x = e.pageX - canvas.offsetLeft;
y = e.pageY - canvas.offsetTop;
dragok = true;
canvas.onmousemove = myMove;
}
}
function myUp() {
dragok = false;
canvas.onmousemove = null;
}
init();
canvas.onmousedown = myDown;
canvas.onmouseup = myUp;
//Change image for the heck of it ^^
setInterval(function() {
img.src = 'https://placeholdit.imgix.net/~text?txtsize=60&txt=' +
Math.floor(Math.random() * 10) +
'&w=100&h=100';
}, 3000)
<canvas id="canvas" width="400" height="300">
This text is displayed if your browser does not support HTML5 Canvas.
</canvas>
<img id="img" src="https://placeholdit.imgix.net/~text?txtsize=60&txt=1&w=100&h=100">
Updated my answer to draw lines

My final code that's working , I had to add two canvases one for the drawing and one for the dragging images. Fabric frame work helped a lot. https://jsfiddle.net/tn07Bond/982s4bgv/2/
<div id="canvasesdiv">
<canvas id="images" width=600 height=400 style="position: absolute;
left: 0;
top: 0;
border: 1px solid blue;
z-index: 1;">
This text is displayed if your browser does not support HTML5 Canvas</canvas>
<canvas id="drawing" width=600 height=400 style="position: absolute;
left: 0;
top: 0;
border: 1px solid red;
z-index: 2;">
This text is displayed if your browser does not support HTML5 Canvas</canvas>
<input type="file" id="imageLoader" class="imageLoader" name="imageLoader"/>
<input type="image" src="images/PenForCanvas.png" alt="pen" title="Draw on canvas"
id="Drawing" style="cursor: pointer; margin: 5px 0 0 200px;">
<input type="image" src="images/drag.png" alt="drag" title="Drag this image" id="Images" style="cursor: pointer;">
</div>
<script>
var drawing, drawingCtx,images,imagesCtx, message = "", img, imageLoader, prevX = 10, currX = 10, prevY = 10, currY = 10,
dot_flag = false, flag = false, x = "black", y = 2, formElement, canvasLeft, canvasTop, imgData, data,
startOffsetX = 0, startOffsetY = 0;
(function () {
// Drawing canvas
drawing = document.getElementById("drawing");
drawingCtx = drawing.getContext("2d");
//Uploading and dragging images
images = new fabric.Canvas('images');
document.getElementById('imageLoader').addEventListener("change", function (e) {
var file = e.target.files[0];
var reader = new FileReader();
reader.onload = function (f) {
var data = f.target.result;
fabric.Image.fromURL(data, function (img) {
var oImg = img.set({left: 0, top: 0, angle: 00,width:40, height:40}).scale(0.9);
images.add(oImg).renderAll();
var a = images.setActiveObject(oImg);
var dataURL = images.toDataURL({format: 'png', quality: 0.8});
});
};
reader.readAsDataURL(file);
});
w = drawing.width;
h = drawing.height;
//Mouse events
drawing.addEventListener("mousemove", function (e) { findxy('move', e) }, false);
drawing.addEventListener("mousedown", function (e) { findxy('down', e) }, false);
drawing.addEventListener("mouseup", function (e) { findxy('up', e) }, false);
drawing.addEventListener("mouseout", function (e) { findxy('out', e) }, false);
Drawing = document.getElementById("Drawing");
Drawing.addEventListener("click", bringDrawingToFront);
Images = document.getElementById("Images");
Images.addEventListener("click", bringImagesToFront);
imageLoader = document.getElementById('imageLoader');
imageLoader.addEventListener('change', bringImagesToFront);
//Drawing
function findxy(res, e) {
if (res === 'down') {
prevX = currX;
prevY = currY;
currX = e.clientX - drawing.offsetLeft;
currY = e.clientY - drawing.offsetTop;
flag = true;
dot_flag = true;
if (dot_flag) {
drawingCtx.beginPath();
drawingCtx.fillStyle = x;
drawingCtx.fillRect(currX, currY, 2, 2);
drawingCtx.closePath();
dot_flag = false;
}
}
if (res === 'up' || res === "out") {
flag = false;
}
if (res === 'move') {
if (flag) {
prevX = currX;
prevY = currY;
currX = e.clientX - drawing.offsetLeft;
currY = e.clientY - drawing.offsetTop;
draw();
}
}
}
function save() {
imgData = drawingCtx.getImageData(0, 0, drawing.width, drawing.height);
}
function restore() {
drawingCtx.putImageData(imgData, 0, 0);
}
function bringDrawingToFront() {
drawing.style.zIndex = 1;
document.getElementById("images").style.zIndex = 0;
}
function bringImagesToFront() {
drawing.style.zIndex = 0;
document.getElementById("images").style.zIndex = 1;
}
//Draw lines or text
function draw() {
drawingCtx.beginPath();
drawingCtx.moveTo(prevX, prevY);
drawingCtx.lineTo(currX, currY);
drawingCtx.strokeStyle = x;
drawingCtx.lineWidth = y;
drawingCtx.stroke();
drawingCtx.closePath();
drawingCtx.fillStyle = x;
drawingCtx.font = "Italic Bold 14pt Times, serif";
drawingCtx.fillText(message, prevX, prevY);
save();
}
})();
</script>

How to create Blur Eraser and Blur Drawing effect in JQuery or Javascript?

I want to make blur erasing and blur drawing effect in JQuery or Javascript. I have written the code for erasing the blurred image when I hover it and to reveal the unblurred image. Here's the screenshot.
I am able to erase the blur image when I hover over the image, but I couldn't redraw the blurred image at the same position, may be like after 500ms. How do I redraw the blur again over where I hovered with my mouse?
Here's the code for reference:
<!DOCTYPE html>
<html>
<head>
<title>Blur Testing</title>
<meta name="content-type" content="text/html; charset=UTF-8">
<style>
body {
margin: 0;
}
#item {
background: url("http://i66.tinypic.com/2z6uq9f.jpg");
background-size: cover;
background-position: center;
}
</style>
<script src="https://code.jquery.com/jquery-1.12.4.min.js" type="text/javascript"></script>
</head>
<body>
<canvas id="item"></canvas>
<script>
var canvas = document.getElementById('item');
var ctx = canvas.getContext('2d'),
img = new Image,
radius = 30;
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
$('#item').css({
"-webkit-filter": "blur(0px)",
"filter": "blur(0px)"
});
$(img).on('load', function () {
$('#item').mouseover(function (e) {
erase(getXY(e));
}).mousemove(function (e) {
erase(getXY(e));
//setTimeout(redraw(getXY(e)), 400);
});
ctx.drawImage(img, 0, 0);
ctx.globalCompositeOperation = 'destination-out';
});
img.src = 'http://i64.tinypic.com/14mt7yx.jpg';
img.width = window.width;
img.height = window.height;
function getXY(e) {
var r = $('#item')[0].getBoundingClientRect();
return {x: e.clientX - r.left, y: e.clientY - r.top};
}
// function redraw(pos) {
// ctx.globalCompositeOperation = 'source-in';
// ctx.beginPath();
// ctx.arc(pos.x, pos.y, radius, 0, 2 * Math.PI);
// ctx.closePath();
// ctx.fill();
// };
function erase(pos) {
ctx.globalCompositeOperation = 'destination-out';
ctx.beginPath();
ctx.arc(pos.x, pos.y, radius, 0, 2 * Math.PI);
ctx.closePath();
ctx.fill();
}
</script>
</body>
</html>

The following is a quick modification on Alpha Mask Filter question. I have simply reversed the blur and sharp images. See the linked question for details.
The extra bit to fade out the blur mask
blurMaskFadeCounter += 1;
if((blurMaskFadeCounter % blurMaskFadeRate) === 0){
maskImage.ctx.globalCompositeOperation = "destination-out";
maskImage.ctx.fillStyle = "#000";
maskImage.ctx.globalAlpha = 0.1;
maskImage.ctx.fillRect(0,0,maskImage.width,maskImage.height);
maskImage.ctx.globalAlpha = 1;
maskImage.ctx.globalCompositeOperation = "source-over";
}
Simply draws over the mask with destination-out composition and alpha set low. It is timed to every so many frames to slow it down. If you set alpha below 0.1 you get some pixels that wont completely clear so the frame skipping give a slower response
var imageLoadedCount = 0;
var error = false;
var maskImage;
var flowerImage;
var flowerImageBlur;
/** ImageTools.js begin **/
var imageTools = (function () {
var tools = {
canvas : function (width, height) { // create a blank image (canvas)
var c = document.createElement("canvas");
c.width = width;
c.height = height;
return c;
},
createImage : function (width, height) {
var image = this.canvas(width, height);
image.ctx = image.getContext("2d");
return image;
},
loadImage : function (url, callback) {
var image = new Image();
image.src = url;
image.addEventListener('load', callback);
image.addEventListener('error', callback);
return image;
}
};
return tools;
})();
var mouse;
var demo = function(){
/** fullScreenCanvas.js begin **/
var canvas = (function(){
var canvas = document.getElementById("canv");
if(canvas !== null){
document.body.removeChild(canvas);
}
// creates a blank image with 2d context
canvas = document.createElement("canvas");
canvas.id = "canv";
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
canvas.style.position = "absolute";
canvas.style.top = "0px";
canvas.style.left = "0px";
canvas.style.zIndex = 1000;
canvas.ctx = canvas.getContext("2d");
document.body.appendChild(canvas);
return canvas;
})();
var ctx = canvas.ctx;
/** fullScreenCanvas.js end **/
/** MouseFull.js begin **/
if(typeof mouse !== "undefined"){ // if the mouse exists
if( mouse.removeMouse !== undefined){
mouse.removeMouse(); // remove previouse events
}
}else{
var mouse;
}
var canvasMouseCallBack = undefined; // if needed
mouse = (function(){
var mouse = {
x : 0, y : 0, w : 0, alt : false, shift : false, ctrl : false,
interfaceId : 0, buttonLastRaw : 0, buttonRaw : 0,
over : false, // mouse is over the element
bm : [1, 2, 4, 6, 5, 3], // masks for setting and clearing button raw bits;
getInterfaceId : function () { return this.interfaceId++; }, // For UI functions
startMouse:undefined,
mouseEvents : "mousemove,mousedown,mouseup,mouseout,mouseover,mousewheel,DOMMouseScroll".split(",")
};
function mouseMove(e) {
var t = e.type, m = mouse;
m.x = e.offsetX; m.y = e.offsetY;
if (m.x === undefined) { m.x = e.clientX; m.y = e.clientY; }
m.alt = e.altKey;m.shift = e.shiftKey;m.ctrl = e.ctrlKey;
if (t === "mousedown") { m.buttonRaw |= m.bm[e.which-1];
} else if (t === "mouseup") { m.buttonRaw &= m.bm[e.which + 2];
} else if (t === "mouseout") { m.buttonRaw = 0; m.over = false;
} else if (t === "mouseover") { m.over = true;
} else if (t === "mousewheel") { m.w = e.wheelDelta;
} else if (t === "DOMMouseScroll") { m.w = -e.detail;}
if (canvasMouseCallBack) { canvasMouseCallBack(mouse); }
e.preventDefault();
}
function startMouse(element){
if(element === undefined){
element = document;
}
mouse.element = element;
mouse.mouseEvents.forEach(
function(n){
element.addEventListener(n, mouseMove);
}
);
element.addEventListener("contextmenu", function (e) {e.preventDefault();}, false);
}
mouse.removeMouse = function(){
if(mouse.element !== undefined){
mouse.mouseEvents.forEach(
function(n){
mouse.element.removeEventListener(n, mouseMove);
}
);
canvasMouseCallBack = undefined;
}
}
mouse.mouseStart = startMouse;
return mouse;
})();
if(typeof canvas !== "undefined"){
mouse.mouseStart(canvas);
}else{
mouse.mouseStart();
}
/** MouseFull.js end **/
// load the images and create the mask
if(imageLoadedCount === 0){
imageLoadedCount = 0;
error = false;
maskImage;
flowerImage = imageTools.loadImage("http://www.createjs.com/demos/_assets/art/flowers.jpg", function (event) {
if (event.type === "load") {
imageLoadedCount += 1;
} else {
error = true;
}
})
flowerImageBlur = imageTools.loadImage("http://i.stack.imgur.com/3S5m8.jpg", function () {
if (event.type === "load") {
maskImage = imageTools.createImage(this.width, this.height);
imageLoadedCount += 1;
} else {
error = true;
}
})
}
// set up the canvas
var w = canvas.width;
var h = canvas.height;
var cw = w / 2;
var ch = h / 2;
// calculate time to download image using the MS algorithum. As this code is a highly gaurded secret I have obsficated it for your personal safty.
var calculateTimeToGo= (function(){var b="# SecondQMinuteQHourQDayQWeekQMonthQMomentQTick#.,Some time soon,Maybe Tomorrow.".replace(/Q/g,"#.,# ").split(","),r=Math.random,f=Math.floor,lc=0,pc=0,lt=0,lp=0;var cttg=function(a){if(lc===0){lc=100+r(r()*60);lt=f(r()*40);if(pc===0||r()<(lp/b.length)-0.2){lp=f(r()*b.length);pc=1+f(r()*10)}else{pc-=1}}else{lc-=1}a=lt;if(lp===0){a=lt;if(r()<0.01){lt-=1}}var s=b[lp].replace("#",a);if(a===1){s=s.replace("#","")}else{s=s.replace("#","s")}return s};return cttg})();
// draws circle with gradient
function drawCircle(ctx, x, y, r) {
var gr = ctx.createRadialGradient(x, y, 0, x, y, r)
gr.addColorStop(1, "rgba(0,0,0,0)")
gr.addColorStop(0.5, "rgba(0,0,0,0.08)")
gr.addColorStop(0, "rgba(0,0,0,0.1)")
ctx.fillStyle = gr;
ctx.beginPath();
ctx.arc(x, y, r, 0, Math.PI * 2);
ctx.fill();
}
// draw text
function drawText(ctx, text, size, x, y, c) {
ctx.fillStyle = c;
ctx.strokeStyle = "black";
ctx.lineWidth = 5;
ctx.lineJoin = "round";
ctx.font = size + "px Arial Black";
ctx.textAlign = "center";
ctx.textBaseline = "middle";
if (c !== "black") {
ctx.strokeText(text, x, y + 1);
}
ctx.fillText(text, x, y);
}
// draw the image to fit the current canvas size
function drawImageCentered(ctx, image, x, y) {
var scale = Math.min(w / image.width, h / image.height);
ctx.setTransform(scale, 0, 0, scale, cw, ch);
ctx.drawImage(image, -image.width / 2, -image.height / 2);
ctx.setTransform(1, 0, 0, 1, 0, 0);
}
// how often to fade blur mask
var blurMaskFadeRate =8; // number of frames between fading mask out
var blurMaskFadeCounter = 0;
// points for filling gaps between mouse moves.
var lastMX,lastMY;
// update function will try 60fps but setting will slow this down.
function update(time){
ctx.setTransform(1, 0, 0, 1, 0, 0); // restore transform
ctx.clearRect(0, 0, w, h); // clear rhe canvas
// have the images loaded???
if (imageLoadedCount === 2) {
// draw the unblured image that will appear at the top
ctx.globalCompositeOperation = "source-over";
drawImageCentered(ctx, flowerImageBlur, cw, ch);
drawText(ctx, "Move mouse over image to unblur.", 20 + Math.sin(time / 100), cw, ch - 30, "White");
// Mask out the parts when the mask image has pixels
ctx.globalCompositeOperation = "destination-out";
drawImageCentered(ctx, maskImage, cw, ch);
// draw the blured image only where the destination has been masked
ctx.globalCompositeOperation = "destination-atop";
drawImageCentered(ctx, flowerImage, cw, ch);
blurMaskFadeCounter += 1;
if((blurMaskFadeCounter % blurMaskFadeRate) === 0){
maskImage.ctx.globalCompositeOperation = "destination-out";
maskImage.ctx.fillStyle = "#000";
maskImage.ctx.globalAlpha = 0.1;
maskImage.ctx.fillRect(0,0,maskImage.width,maskImage.height);
maskImage.ctx.globalAlpha = 1;
maskImage.ctx.globalCompositeOperation = "source-over";
}
// because image has been scaled need to get mouse coords on image
var scale = Math.min(w / flowerImage.width, h / flowerImage.height);
var x = (mouse.x - (cw - (maskImage.width / 2) * scale)) / scale;
var y = (mouse.y - (ch - (maskImage.height / 2) * scale)) / scale;
// draw circle on mask
drawCircle(maskImage.ctx, x, y, 60);
// if mouse is draging then draw some points between to fill the gaps
if (lastMX !== undefined) {
drawCircle(maskImage.ctx, ((x + lastMX) / 2 + x) / 2, ((y + lastMY) / 2 + y) / 2, 60);
drawCircle(maskImage.ctx, (x + lastMX) / 2, (y + lastMY) / 2, 60);
drawCircle(maskImage.ctx, ((x + lastMX) / 2 + lastMX) / 2, ((y + lastMY) / 2 + lastMY) / 2, 60);
}
// save las mouse pos on image
lastMX = x;
lastMY = y;
} else {
// Laoding images so please wait.
drawText(ctx, "Please wait.", 40 + Math.sin(time / 100), cw, ch - 30, "White");
drawText(ctx, "loading images... ", 12, cw, ch, "black")
drawText(ctx, "ETA " + calculateTimeToGo(time), 14, cw, ch + 20, "black")
}
// if not restart the request animation frame
if(!STOP){
requestAnimationFrame(update);
}else{
var can = document.getElementById("canv");
if(can !== null){
document.body.removeChild(can);
}
STOP = false;
}
}
update();
}
var STOP = false; // flag to tell demo app to stop
function resizeEvent() {
var waitForStopped = function () {
if (!STOP) { // wait for stop to return to false
demo();
return;
}
setTimeout(waitForStopped, 200);
}
STOP = true;
setTimeout(waitForStopped, 100);
}
window.addEventListener("resize", resizeEvent);
demo();

Html5 canvas image on click

I'm having a problem whit my code.
I draw some circles in a circular path and I expect when to click on them to return something other than 0 in firebug console but that's not happening;
I don't know what is wrong with my code and i hope someone will tell me.
Here's my code:
var canvas, ctx;
var circle_data = [];
function circles(x, y, radius) {
this.x = x;
this.y = y;
this.radius = radius;
circle_data.push(this);
}
circles.prototype = {
draw: function (context) {
context.beginPath();
context.arc(this.x, this.y, this.radius / 5, 0, 2 * Math.PI, false);
context.fillStyle = "red";
context.fill();
}
}
function draw() {
ctx.translate(250, 250);
for (var n = 0; n < 10; n++) {
var radi = (Math.PI / 180);
var x = Math.sin(radi * n * 36) * 70;
var y = Math.cos(radi * n * 36) * 70;
var radius = 50;
var thiscircle = new circles(x, y, radius);
thiscircle.draw(ctx);
}
}
function mouseDown(e) {
var img_data = ctx.getImageData(e.pageX, e.pageY, 1, 1);
console.log(img_data.data[3]);
}
function init() {
canvas = document.getElementById('canvas'),
ctx = canvas.getContext('2d');
canvas.addEventListener('mousedown', mouseDown, false);
}
init();
It dosen't matter is i use data[3];
I tried whit console.log(img_data.data[0]+" "+img_data.data[1]+" "+img_data.data[2]);
Still getting 0 0 0

Your detecting the mouse position relative to the page and not the canvas, you need to get the position of the canvas on the page and subtract that from the X and Y of the mouse to find you position relative to the canvas. I use functions similar to the ones below when working with canvas.
getOffsetPosition = function(obj){
/*obj is the Canvas element*/
var offsetX = offsetY = 0;
if (obj.offsetParent) {
do {
offsetX += obj.offsetLeft;
offsetY += obj.offsetTop;
}while(obj = obj.offsetParent);
}
return [offsetX,offsetY];
}
getMouse = function(e,canvasElement){
OFFSET = getOffsetPosition(canvasElement);
mouse_x = (e.pageX || (e.clientX + document.body.scrollLeft + document.documentElement.scrollLeft)) - OFFSET[0];
mouse_y = (e.pageY || (e.clientY + document.body.scrollTop + document.documentElement.scrollTop)) - OFFSET[1];
return [mouse_x,mouse_y];
}
The following code works.
<!DOCTYPE HTML>
<html>
<head>
<meta charset="utf-8">
<title>Untitled Document</title>
</head>
<body>
<canvas id="canvas" width="500" height="500" style="background-color:#999999;"></canvas>
</body>
<script>
var canvas,ctx;
var circle_data = [];
function circles(x,y,radius)
{
this.x = x;
this.y = y;
this.radius = radius;
circle_data.push(this);
}
circles.prototype = {
draw: function(context){
context.beginPath();
context.arc(this.x, this.y, this.radius / 5, 0, 2* Math.PI, false);
context.fillStyle = "red";
context.fill();
}
}
getOffsetPosition = function(obj){
/*obj is the Canvas element*/
var offsetX = offsetY = 0;
if (obj.offsetParent) {
do {
offsetX += obj.offsetLeft;
offsetY += obj.offsetTop;
}while(obj = obj.offsetParent);
}
return [offsetX,offsetY];
}
getMouse = function(e,canvasElement){
OFFSET = getOffsetPosition(canvasElement);
mouse_x = (e.pageX || (e.clientX + document.body.scrollLeft + document.documentElement.scrollLeft)) - OFFSET[0];
mouse_y = (e.pageY || (e.clientY + document.body.scrollTop + document.documentElement.scrollTop)) - OFFSET[1];
return [mouse_x,mouse_y];
}
function draw(){
ctx.translate(250, 250);
for (var n = 0; n < 10; n++) {
var radi = (Math.PI/180);
var x = Math.sin(radi*n*36)*70;
var y = Math.cos(radi*n*36)*70;
var radius = 50;
var thiscircle = new circles(x,y,radius);
thiscircle.draw(ctx);
}
}
function mouseDown(e)
{
var pos = getMouse(e,ctx.canvas);
var img_data = ctx.getImageData(pos[0],pos[1],1,1);
console.log(img_data.data[3]);
}
function init() {
canvas = document.getElementById('canvas'),
ctx = canvas.getContext('2d');
draw();
canvas.addEventListener('mousedown', mouseDown, false);
}
init();
</script>
</html>