I have a canvas that I can draw things what I want to do is generate new canvases dynamically when clicking a button.I've defined a generate function but it did not work
here is script
//<![CDATA[
window.addEventListener('load', function () {
// get the canvas element and its context
var canvas = document.getElementById('sketchpad');
var context = canvas.getContext('2d');
// create a drawer which tracks touch movements
var drawer = {
isDrawing: false,
touchstart: function (coors) {
context.beginPath();
context.moveTo(coors.x, coors.y);
this.isDrawing = true;
},
touchmove: function (coors) {
if (this.isDrawing) {
context.lineTo(coors.x, coors.y);
context.stroke();
}
},
touchend: function (coors) {
if (this.isDrawing) {
this.touchmove(coors);
this.isDrawing = false;
}
}
};
// create a function to pass touch events and coordinates to drawer
function draw(event) {
var type = null;
// map mouse events to touch events
switch(event.type){
case "mousedown":
event.touches = [];
event.touches[0] = {
pageX: event.pageX,
pageY: event.pageY
};
type = "touchstart";
break;
case "mousemove":
event.touches = [];
event.touches[0] = {
pageX: event.pageX,
pageY: event.pageY
};
type = "touchmove";
break;
case "mouseup":
event.touches = [];
event.touches[0] = {
pageX: event.pageX,
pageY: event.pageY
};
type = "touchend";
break;
}
// touchend clear the touches[0], so we need to use changedTouches[0]
var coors;
if(event.type === "touchend") {
coors = {
x: event.changedTouches[0].pageX,
y: event.changedTouches[0].pageY
};
}
else {
// get the touch coordinates
coors = {
x: event.touches[0].pageX,
y: event.touches[0].pageY
};
}
type = type || event.type
// pass the coordinates to the appropriate handler
drawer[type](coors);
}
// detect touch capabilities
var touchAvailable = ('createTouch' in document) || ('ontouchstart' in window);
// attach the touchstart, touchmove, touchend event listeners.
if(touchAvailable){
canvas.addEventListener('touchstart', draw, false);
canvas.addEventListener('touchmove', draw, false);
canvas.addEventListener('touchend', draw, false);
}
// attach the mousedown, mousemove, mouseup event listeners.
else {
canvas.addEventListener('mousedown', draw, false);
canvas.addEventListener('mousemove', draw, false);
canvas.addEventListener('mouseup', draw, false);
}
// prevent elastic scrolling
document.body.addEventListener('touchmove', function (event) {
event.preventDefault();
}, false); // end body.onTouchMove
}, false); // end window.onLoad
function generate(){
var newCanvas = document.createElement('canvas');
newCanvas.width = 400;
newCanvas.height = 400;
document.getElementById('container').appendChild(newCanvas);
ctx = newCanvas.getContext('2d');
}
//]]>
here is jsfiddle http://jsfiddle.net/regeme/WVUwn/
ps:drawing not displayed on jsfiddle however it works on my localhost I have totally no idea about it , anyway what I need is generate function , I did but I think I am missing something..
Any ideas? thanks..
Below is a function I wrote to dynamically create canvas.
If the canvas already exists (same ID) then that canvas is returned.
The pixelRatio parameter can be defaulted to 1. It's used for setting the correct size on retina displays (so for iPhone with Retina the value would be 2)
function createLayer(sizeW, sizeH, pixelRatio, id, zIndex) {
// *** An id must be given.
if (typeof id === undefined) {
return false;
}
// *** If z-index is less than zero we'll make it a buffer image.
isBuffer = (zIndex < 0) ? true : false;
// *** If the canvas exist, clean it and just return that.
var element = document.getElementById(id);
if (element !== null) {
return element;
}
// *** If no zIndex is passed in then default to 0.
if (typeof zIndex === undefined || zIndex < 0) {
zIndex = 0;
}
var canvas = document.createElement('canvas');
canvas.width = sizeW;
canvas.height = sizeH;
canvas.id = id;
canvas.style.width = sizeW*pixelRatio + "px";
canvas.style.height = sizeH*pixelRatio + "px";
canvas.style.position = "absolute";
canvas.style.zIndex = zIndex;
if (!isBuffer) {
var body = document.getElementsByTagName("body")[0];
body.appendChild(canvas);
}
return canvas;
}
Change the jsfiddle option
"onLoad"
to
"No Wrap - in <body>"
EDIT: See also similar question over here: Uncaught ReferenceError for a function defined in an onload function
JSFiddle options: http://doc.jsfiddle.net/basic/introduction.html#frameworks-and-extensions
This is the working update of your JSFIDDLE
javascript:
document.getElementById('generate').addEventListener('mousedown', generate, false);
I guess this is what you want.
I've just added an eventListener to your button in javascript code itself.
P.S.: I've also added black background color to canvas to show it on white background.
Related
How can one force a canvas to remain still while you draw on it on android phones?
We have a project in Ionic, where the below code is used to allow the end user to draw on a canvas element, but when he starts drawing, the page scrolls with him.
Strange enough though, the code stops the form from scrolling up and down if the user drags left or right, but if they move their finger up or down before going left or right, the page scrolls with their draw movements, and they end up with basically nothing being drawn...
Does anybody see how I can force the scrolling to hold while the user draw's on the canvas?
//employer_signature_canvas setup
var employer_signature_canvas = document.getElementById("employer_my_canvas");
var ctx = employer_signature_canvas.getContext("2d");
ctx.strokeStyle = "#222222";
ctx.lineWith = 2;
// Set up mouse events for drawing
var drawing = false;
var mousePos = { x:0, y:0 };
var lastPos = mousePos;
employer_signature_canvas.addEventListener("mousedown", function (e) {
drawing = true;
lastPos = getMousePos(employer_signature_canvas, e);
}, false);
employer_signature_canvas.addEventListener("mouseup", function (e) {
drawing = false;
}, false);
employer_signature_canvas.addEventListener("mousemove", function (e) {
mousePos = getMousePos(employer_signature_canvas, e);
}, false);
// Get the position of the mouse relative to the employer_signature_canvas
function getMousePos(employer_signature_canvasDom, mouseEvent) {
var rect = employer_signature_canvasDom.getBoundingClientRect();
return {
x: mouseEvent.clientX - rect.left,
y: mouseEvent.clientY - rect.top
};
}
// Get a regular interval for drawing to the screen
window.requestAnimFrame = (function (callback) {
return window.requestAnimationFrame ||
window.webkitRequestAnimationFrame ||
window.mozRequestAnimationFrame ||
window.oRequestAnimationFrame ||
window.msRequestAnimaitonFrame ||
function (callback) {
window.setTimeout(callback, 1000/60);
};
})();
// Draw to the employer_signature_canvas
function renderemployer_signature_canvas() {
if (drawing) {
ctx.moveTo(lastPos.x, lastPos.y);
ctx.lineTo(mousePos.x, mousePos.y);
ctx.stroke();
lastPos = mousePos;
}
}
// Allow for animation
(function drawLoop () {
requestAnimFrame(drawLoop);
renderemployer_signature_canvas();
})();
// Set up touch events for mobile, etc
employer_signature_canvas.addEventListener("touchstart", function (e) {
mousePos = getTouchPos(employer_signature_canvas, e);
var touch = e.touches[0];
var mouseEvent = new MouseEvent("mousedown", {
clientX: touch.clientX,
clientY: touch.clientY
});
employer_signature_canvas.dispatchEvent(mouseEvent);
}, false);
employer_signature_canvas.addEventListener("touchend", function (e) {
var mouseEvent = new MouseEvent("mouseup", {});
employer_signature_canvas.dispatchEvent(mouseEvent);
}, false);
employer_signature_canvas.addEventListener("touchmove", function (e) {
var touch = e.touches[0];
var mouseEvent = new MouseEvent("mousemove", {
clientX: touch.clientX,
clientY: touch.clientY
});
employer_signature_canvas.dispatchEvent(mouseEvent);
}, false);
// Get the position of a touch relative to the employer_signature_canvas
function getTouchPos(employer_signature_canvasDom, touchEvent) {
var rect = employer_signature_canvasDom.getBoundingClientRect();
return {
x: touchEvent.touches[0].clientX - rect.left,
y: touchEvent.touches[0].clientY - rect.top
};
}
// Prevent scrolling when touching the employer_signature_canvas
document.body.addEventListener("touchstart", function (e) {
if (e.target == employer_signature_canvas) {
e.preventDefault();
}
}, false);
document.body.addEventListener("touchend", function (e) {
if (e.target == employer_signature_canvas) {
e.preventDefault();
}
}, false);
document.body.addEventListener("touchmove", function (e) {
if (e.target == employer_signature_canvas) {
e.preventDefault();
}
}, false);
In your template (ionic page) you can use css to remove bounce and rubberband effects:
<ion-content no-bounce class="no-scroll"><ion-content>
in your scss:
.no-scroll .scroll-content {
overflow: hidden;
float: none;
}
I have a canvas on which I am making a menu screen for my game:
var canvas = document.createElement("canvas");
var ctx = canvas.getContext("2d");
canvas.width = 512;
canvas.height = 480;
document.body.appendChild(canvas);
ctx.font="30px monospace";
ctx.fillStyle = "black";
ctx.strokeText("click to begin",140,260);
When the user clicks "click to begin", I want it to progress to my game, but considering that I can't get the onclick working I just want it to alert that it has worked. So far (based off of tutorials and examples I have found) I have the following code:
mouse = (function (target) {
var isButtonDown = false;
c.addEventListener('mousedown', function () {
isButtonDown = true;
});
return {
isButtonDown: function () {
return isButtonDown;
}
};
}(document));
var isButtonDown = input.isButtonDown();
if (isbuttondown == true) {
alert("Mouse clicked");
}
This code does nothing when I run it. Could someone please explain to me how to get this working, or at least what I need to change?
Thanks in advance,
Riley
Here is a Solution.
Solution
I have removed the alert and instead used console.log. Check the console.
JS
canvas.addEventListener('click', function (evt) {
var mousePos = getMousePos(canvas, evt);
var message = 'Mouse Clicked at ' + mousePos.x + ',' + mousePos.y;
console.log(message);
}, false);
function getMousePos(canvas, evt) {
var rect = canvas.getBoundingClientRect();
return {
x: evt.clientX - rect.left,
y: evt.clientY - rect.top
};
}
EDIT: Here is the same fiddle with Alert option. FIDDLE
I was trying to create a sample paint application using HTML 5 canvas. Then I added a button to redraw what user had drawn earlier. I am not sure what I am doing wrong or may be completely wrong. When I click redraw button multiple times it generates some magical animation by drawing lines all over. Even though if I log the starting point of drawing the image its same every time.
Demo: http://jsfiddle.net/BW57H/6/
Steps to reproduce:
Draw some circle or rectangle or something by clicking the mouse and dragging it on the rectangular box. Then click reset and redraw , click redraw couple of times after that and see the result.
I am not sure what I have done. I have not read a lot about Canvas. But I am curious to know what is going on here. Thanks.
html
<body>
<canvas id="paint" width="600px" height="300px"></canvas>
<div id="controls">
<button name="reset" id="reset">Reset</button>
<button name="redraw" id="redraw">Re-Draw</button>
</div>
</body>
css
#paint{
border: solid;
}
js
$(document).ready(function(){
var x, y, context, painter;
var xCounter = 0 , yCounter = 0;
var xarray = [];
var yarray = [];
function init(){
while(document.getElementById("paint") === undefined){
//do nothing
}
console.log("Loaded document now registering events for canvas");
var canvas = document.getElementById("paint");
context = canvas.getContext('2d');
painter = new Painter();
canvas.addEventListener('mousedown', capture, false);
canvas.addEventListener('mouseup', capture, false);
canvas.addEventListener('mousemove', capture, false);
document.getElementById("reset").addEventListener("click",function(){ clearCanvas(canvas);}, false);
document.getElementById("redraw").addEventListener("click", function(){
autoDraw();
}, false);
}
function clearCanvas(canvas){
context.save();
// Use the identity matrix while clearing the canvas
context.setTransform(1, 0, 0, 1, 0, 0);
context.clearRect(0, 0, canvas.width, canvas.height);
// Restore the transform
context.restore();
};
function capture(event){
if(event.which !== 1){
return;
}
x = event.layerX;
y = event.layerY;
switch(event.type){
case 'mousedown':
painter.startPaint(event);
break;
case 'mouseup':
painter.endPaint(event);
break;
case 'mousemove':
painter.paint(event);
break;
}
};
var Painter = function(){
var self = this;
self.paintStarted = false;
self.startPaint = function(event){
self.resetRecordingParams();
self.paintStarted = true;
context.beginPath();
context.moveTo(x,y);
self.record();
}
self.endPaint = function(event){
self.paintStarted = false;
self.record();
self.paint(event)
}
self.paint = function(event){
if(self.paintStarted){
context.lineTo(x,y);
context.stroke();
self.record();
}
}
self.record = function(){
xarray[xCounter++] = x;
yarray[yCounter++] = y;
}
self.resetRecordingParams = function(){
xarray = [];
yarray = [];
xCounter = 0;
yCounter= 0;
}
return self;
}
function autoDraw(){
context.beginPath();
console.log('starting at: '+xarray[0]+','+yarray[0]);
context.moveTo(xarray[0],yarray[0]);
for (var i = 0; i < xarray.length; i++) {
setTimeout(drawLineSlowly, 1000+(i*20), i);
};
}
function drawLineSlowly(i)
{
context.lineTo(xarray[i],yarray[i]);
context.stroke();
}
init();
});
You don't have any kind of check to see whether or not you are already drawing, so here is your code with those changes commented, as well as the real-pixel-location fixes (http://jsfiddle.net/upgradellc/htJXy/1/):
$(document).ready(function(){
var x, y, context, painter, canvas;
var xCounter = 0 , yCounter = 0;
var xarray = [];
var yarray = [];
function init(){
while(document.getElementById("paint") === undefined){
//do nothing
}
console.log("Loaded document now registering events for canvas");
canvas = document.getElementById("paint");
context = canvas.getContext('2d');
painter = new Painter();
canvas.addEventListener('mousedown', capture, false);
canvas.addEventListener('mouseup', capture, false);
canvas.addEventListener('mousemove', capture, false);
document.getElementById("reset").addEventListener("click",function(){ clearCanvas(canvas);}, false);
document.getElementById("redraw").addEventListener("click", function(){
autoDraw();
}, false);
}
function clearCanvas(canvas){
context.save();
// Use the identity matrix while clearing the canvas
context.setTransform(1, 0, 0, 1, 0, 0);
context.clearRect(0, 0, canvas.width, canvas.height);
// Restore the transform
context.restore();
};
function capture(event){
if(event.which !== 1){
return;
}
tempPos = getMousePos(canvas, event);
x = tempPos.x;
y = tempPos.y;
switch(event.type){
case 'mousedown':
painter.startPaint(event);
break;
case 'mouseup':
painter.endPaint(event);
break;
case 'mousemove':
painter.paint(event);
break;
}
};
var Painter = function(){
var self = this;
self.paintStarted = false;
//this keeps track of whether or not we are currently auto drawing
self.currentlyAutoDrawing = false;
self.startPaint = function(event){
self.resetRecordingParams();
self.paintStarted = true;
context.beginPath();
context.moveTo(x,y);
self.record();
}
self.endPaint = function(event){
self.paintStarted = false;
self.record();
self.paint(event);
}
self.paint = function(event){
if(self.paintStarted){
context.lineTo(x,y);
context.stroke();
self.record();
}
}
self.record = function(){
xarray[xCounter++] = x;
yarray[yCounter++] = y;
}
self.resetRecordingParams = function(){
xarray = [];
yarray = [];
xCounter = 0;
yCounter= 0;
}
return self;
}
function autoDraw(){
context.beginPath();
//If we are already auto-drawing, then we should just return instead of starting another drawing loop cycle
if(painter.currentlyAutoDrawing){
console.log("painter is already auto drawing");
return;
}
painter.currentlyAutoDrawing = true;
console.log('starting at: '+xarray[0]+','+yarray[0]);
context.moveTo(xarray[0],yarray[0]);
for (var i = 0; i < xarray.length; i++) {
setTimeout(drawLineSlowly, 1000+(i*20), i);
};
}
function drawLineSlowly(i)
{
//when we reach the last element in the array, update painter with the fact that autodrawing is now complete
if(xarray.length == i+1){
painter.currentlyAutoDrawing=false;
}
console.log(xarray.length+" "+i);
context.lineTo(xarray[i],yarray[i]);
context.stroke();
}
function getMousePos(canv, evt) {
var rect = canv.getBoundingClientRect();
return {
x: evt.clientX - rect.left,
y: evt.clientY - rect.top
};
}
init();
});
Obviously you don't stop the previous timeout loop before you start a new...
Use setInterval instead of setTimeout, and clearInterval by next push. So I think the problem is not with the canvas, just with your redraw animation. Btw it is strange because there is some difference between the redraw and the original draw...
var drawInterval = null;
function autoDraw(){
if (drawInterval) {
//here your can reset the previous - still running - redraw
clearInterval(drawInterval);
}
context.beginPath();
console.log('starting at: '+xarray[0]+','+yarray[0]);
context.moveTo(xarray[0],yarray[0]);
var i=0;
setInterval(function (){
++i;
if (i<xarray.length)
drawLineSlowly(i);
else
clearInterval(drawInterval);
},20);
}
note:
There is still bug in the redraw, but at least it does not kill the browser...
Btw the strange "animation" is because you does not check by redraw if you are currently drawing or not, so you start draw and redraw together and they interfere... You have to stop redraw when you start drawing.
im learnig javascript and try to develop a page to draw on. Change colors and linewidth are already in place. Now it is drawing, but just when I move the mouse. I'd like to add also on click on just on move. So I'm able to draw also points. I have put the drawCircle function in the function stopDraw, but this is not working as it should. Any ideas?
Second problem is that, I'd like to draw a circle without stroke. But as soon as I change the lineWidth, also my circle gets a stroke around. Please help...
// Setup event handlers
cb_canvas = document.getElementById("cbook");
cb_lastPoints = Array();
if (cb_canvas.getContext) {
cb_ctx = cb_canvas.getContext('2d');
cb_ctx.lineWidth = 14;
cb_ctx.strokeStyle = "#0052f8";
cb_ctx.lineJoin="round";
cb_ctx.lineCap="round"
cb_ctx.beginPath();
cb_canvas.onmousedown = startDraw;
cb_canvas.onmouseup = stopDraw;
cb_canvas.ontouchstart = startDraw;
cb_canvas.ontouchend = stopDraw;
cb_canvas.ontouchmove = drawMouse;
}
function startDraw(e) {
if (e.touches) {
// Touch event
for (var i = 1; i <= e.touches.length; i++) {
cb_lastPoints[i] = getCoords(e.touches[i - 1]); // Get info for finger #1
}
}
else {
// Mouse event
cb_lastPoints[0] = getCoords(e);
cb_canvas.onmousemove = drawMouse;
}
return false;
}
// Called whenever cursor position changes after drawing has started
function stopDraw(e) {
drawCircle(e);
e.preventDefault();
cb_canvas.onmousemove = null;
}
//Draw circle
function drawCircle(e) {
var canvasOffset = canvas.offset();
var canvasX = Math.floor(e.pageX-canvasOffset.left);
var canvasY = Math.floor(e.pageY-canvasOffset.top);
//var canvasPos = getCoords(e);
cb_ctx.beginPath();
cb_ctx.arc(canvasX, canvasY, cb_ctx.lineWidth/2, 0, Math.PI*2, true);
cb_ctx.fillStyle = cb_ctx.strokeStyle;
cb_ctx.fill();
}
function drawMouse(e) {
cb_ctx.beginPath();
if (e.touches) {
// Touch Enabled
for (var i = 1; i <= e.touches.length; i++) {
var p = getCoords(e.touches[i - 1]); // Get info for finger i
cb_lastPoints[i] = drawLine(cb_lastPoints[i].x, cb_lastPoints[i].y, p.x, p.y);
}
}
else {
// Not touch enabled
var p = getCoords(e);
cb_lastPoints[0] = drawLine(cb_lastPoints[0].x, cb_lastPoints[0].y, p.x, p.y);
}
cb_ctx.stroke();
cb_ctx.closePath();
//cb_ctx.beginPath();
return false;
}
// Draw a line on the canvas from (s)tart to (e)nd
function drawLine(sX, sY, eX, eY) {
cb_ctx.moveTo(sX, sY);
cb_ctx.lineTo(eX, eY);
return { x: eX, y: eY };
}
// Get the coordinates for a mouse or touch event
function getCoords(e) {
if (e.offsetX) {
return { x: e.offsetX, y: e.offsetY };
}
else if (e.layerX) {
return { x: e.layerX, y: e.layerY };
}
else {
return { x: e.pageX - cb_canvas.offsetLeft, y: e.pageY - cb_canvas.offsetTop };
}
}
Your drawCircle function is wrapped in the canvas's onclick event. It should be
function drawCircle(e) {
var canvasOffset = canvas.offset();
var canvasX = Math.floor(e.pageX-canvasOffset.left);
var canvasY = Math.floor(e.pageY-canvasOffset.top);
cb_ctx.beginPath();
cb_ctx.lineWidth = 0;
cb_ctx.arc(canvasX,canvasY,cb_ctx.lineWidth/2,0,Math.PI*2,true);
cb_ctx.fillStyle = cb_ctx.strokeStyle;
cb_ctx.fill();
}
So you'll have to pass the event object from stop draw as well
function stopDraw(e) {
drawCircle(e); //notice the change here
e.preventDefault();
cb_canvas.onmousemove = null;
}
Note that you're also setting you circle's radius to 0 which might be another reason why it's not showing up.
cb_ctx.lineWidth = 0;
cb_ctx.arc(canvasX,canvasY,cb_ctx.lineWidth/2,0,Math.PI*2,true);
0 divided by 2 is always zero. If you don't want to stroke around the circle just don't call stroke(). the drawCircle function isn't causing that, since there's a beginPath() call. I suspect it's because you don't beginPath() before calling stroke() in drawMouse.
i am trying to drag and drop an image of a card on the canvas of the javascript but the mouseup event does not seem to be working even though it is inside the main(). Once the card is selected, it follows around the mouse but it does not seem to let go when i let go of the mouse. I also know that the image is repeated from not clearing the screen.
function main(){
var ctx = cvs.getContext("2d");
var img = new Image();
img.src = "allcards.png";
var imgX = 75;
var imgY = 75;
draw();
function draw(){
ctx.drawImage(img,0,0,97,129,imgX,imgY,100,100);
}
cvs.addEventListener("mouseup", function(ev){
greaterX = false;
lessX = false;
greaterY = false;
lessY = false;
}
);
cvs.addEventListener("mousedown", function(ev){
if(ev.clientX <= (imgX + 97)){
var greaterX = true;
}
if(ev.clientY <= (imgY + 129)){
var greaterY = true;
}
if(ev.clientX >= imgX){
var lessX = true;
}
if(ev.clientY >= imgY){
var lessY = true;
}
if(greaterX == true)
if(greaterY == true)
if(lessX == true)
if(lessY == true)
cvs.addEventListener("mousemove", function(ev){
var offsetX = (ev.clientX - imgX);
var offsetY = (ev.clientY - imgY);
imgX = imgX + offsetX;
imgY = imgY + offsetY;
draw();
});
});
};
greaterX, lessX, etc, are all defined with var inside of your mousedown function, meaning their scope is limited to the mousedown function only.
Therefore, it is useless to try and set them back to false inside of your mouseup function. You need to declare your variables in the main part of your function:
function main() {
var greaterX, lessX, greaterY, lessY;
var ctx = cvs.getContext("2D");
//etc...
Now, simply setting greaterX, lessX, etc back to false is not enough, because the mousemove event checker inside of mousedown is still active. When you apply an event listener, it stays there until you remove it.
So, the next step is to separate the mousemove event function into it's own function (I used "mouseMoveHandler" for the name) and remove the event listener using .removeEventListener(type, listener, useCapture) inside of mouseup.
The mousemove function:
function mouseMoveHandler(ev) {
offsetX = (ev.clientX - imgX);
offsetY = (ev.clientY - imgY);
imgX = imgX + offsetX;
imgY = imgY + offsetY;
draw();
}
The mousedown function (important part):
if (greaterX === true) { //you need the brackets for multi-line if statements
if (greaterY === true) {
if (lessX === true) {
if (lessY === true) {
cvs.addEventListener("mousemove",mouseMoveHandler,false);
}
}
}
}
And finally, the mouseup function:
cvs.addEventListener("mouseup", function(ev) {
greaterX = false;
lessX = false;
greaterY = false;
lessY = false;
cvs.removeEventListener('mousemove',mouseMoveHandler,false);
});
Here's a jsFiddle with the solution, but not using your image.