I have a problem with the click function in javascript. This is my code:
var canvas = document.getElementsByTagName("canvas")[0];
var ctx = canvas.getContext('2d');
BigCircle = function(x, y, color, circleSize) {
ctx.shadowBlur = 10;
ctx.shadowColor = color;
ctx.beginPath();
ctx.arc(x, y, circleSize, 0, Math.PI * 2, true);
ctx.fill();
ctx.closePath();
};
var bigGreen = new BigCircle(1580, 800, '#5eb62b', 180);
function init() {
$("#bigGreen").click(function(e){
alert("test");
});
}
$(document).ready(function() {
init();
});
But the click event is not working! Does anybody know why? Thank you so much in advance!
You can now use hit regions in Chrome and Firefox:
https://developer.mozilla.org/en-US/docs/Web/API/Canvas_API/Tutorial/Hit_regions_and_accessibility#Hit_regions
(Edit: Hit regions are now obsolete)
or just use one of the many canvas APIs:
http://www.fabricjs.com/
http://www.createjs.com/easeljs
http://www.paperjs.org
etc...
without seeing your html this question is a little bit unclear, it seems you would like to draw something on a canvas and use jquery to add click events for the circle, this isn't possible.
you can use jquery to get the click event ON the canvas and from the cursor position you can calculate if the user clicked the circle or not, but jquery won't help you here you have to do the math yourself.
jquery does only work for dom elements.
BigCircle = function(ctx,x, y, color, circleSize) {
ctx.beginPath();
ctx.arc(x, y, circleSize, 0, Math.PI * 2, true);
ctx.fillStyle=color
ctx.fill();
ctx.closePath();
this.clicked=function(){
ctx.fillStyle='#ff0000'
ctx.fill();
}
};
function init() {
var canvas = document.getElementsByTagName("canvas")[0];
var ctx = canvas.getContext('2d');
var bigGreen = new BigCircle(ctx,50, 50, '#5eb62b', 50);
$('#canvas').click(function(e){
var x = e.clientX
, y = e.clientY
if(Math.pow(x-50,2)+Math.pow(y-50,2) < Math.pow(50,2))
bigGreen.clicked()
})
}
$(document).ready(function() {
init();
});
jsfiddle is here
http://jsfiddle.net/yXVrk/1/
Canvas API function isPointInPath() can be used to assist with hit detection. This function can at least tell if mouse coordinates are within a complex shape without doing sophisticated math yourself. May work for simple shapes as well but my use case was for on a bezier curve path. However, you need to either incorporate this function in your drawing logic to test while paths are open or keep an array of Path2d objects to test against. I redraw on onClick handler and pass in mouse coords from event args, but I think I could have kept an array of Path2d objects instead.
https://developer.mozilla.org/en-US/docs/Web/API/CanvasRenderingContext2D/isPointInPath
bigGreen is not in the HTML, so $("#bigGreen") selects nothing. You can't put a click function on things like JavaScript functions; since they don't exist in the DOM, how could you click one? You should replace #bigGreen with #canvas, since "canvas" is your HTML element.
I forked your fiddle to show this here.
Edit: If you want to see that the user clicked on a particular circle, you use the canvas click event, and then, you determine which circle was clicked by the coordinates passed into the click event.
Related
I'm creating a UI for myself in which I define boxes on which to perform OCR. That's not the important part. We are considering the frontend. For the UI, the idea is to draw a rectangle using the mouse (mousedown, mousemove, mouseup). But my script draws multiple rectangles instead of just one. Here is an image of the problem.
I want to draw only one rectangle for each selection rectangle. How can I do this? Here is my selection code.
var ctx = Data.ctx_items[index];
//get box
Data.canvas_items[index].addEventListener('mousedown', function(e){
Data.x1 = e.offsetX;
Data.y1 = e.offsetY;
Data.is_drawing = true;
})
Data.canvas_items[index].addEventListener('mousemove', function(e){
if(Data.is_drawing){
Data.x2 = e.offsetX - Data.x1;
Data.y2 = e.offsetY - Data.y1;
ctx.beginPath();
ctx.rect(Data.x1, Data.y1, Data.x2, Data.y2);
ctx.stroke();
}
})
Data.canvas_items[index].addEventListener('mouseup', function(e){
Data.is_drawing = false;
})
Any help is appreciated. Thanks
I am seeking for a way that allows players to draw their own characters and later to be able to play with them in-game. To make the concept very simple lets make the drawn player just a 2d shape or a group of lines and circles or even a mix of both. I think this can be decomposed in these steps:
An empty canvas is made for the user to create what he wants:
By painting or something of that genre
By using a specific polygon creation interface that allows dragging and molding shapes;
Note: I was able to create a way to paint on canvas *** but I didn't find a way to let user drag and create shapes or something of that kind. I would more likely opt for the second option so some suggestions on how do this would be really appreciated.
window.onload = init;
function init() {
var canvas = document.getElementById('myCanvas');
var ctx = canvas.getContext('2d');
var painting = document.getElementById('paint');
var paint_style = getComputedStyle(painting);
canvas.width = "1024"
canvas.height = "1024";
var mouse = {
x: 0,
y: 0
};
canvas.addEventListener('mousemove', function(e) {
mouse.x = e.pageX - this.offsetLeft;
mouse.y = e.pageY - this.offsetTop;
}, false);
ctx.lineWidth = 3;
ctx.lineJoin = 'round';
ctx.lineCap = 'round';
ctx.strokeStyle = '#00CC99';
canvas.addEventListener('mousedown', function(e) {
ctx.beginPath();
ctx.moveTo(mouse.x, mouse.y);
canvas.addEventListener('mousemove', onPaint, false);
}, false);
canvas.addEventListener('mouseup', function() {
canvas.removeEventListener('mousemove', onPaint, false);
}, false);
var onPaint = function() {
ctx.lineTo(mouse.x, mouse.y);
ctx.stroke();
};
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<html lang="en">
<head>
<meta charset="utf-8">
<title>Tojo - canvas draw</title>
<link rel="stylesheet" href="index.css">
</head>
<body>
<script src="app.js"></script>
<div id="paint"></div>
<canvas id="myCanvas" style="border: 3px solid black;"></canvas>
</body>
</html>
(paint on canvas snippet) ***
Somehow, I need to only get the user drawn / shaped creation from all the canvas. There should be a way to "surround" what the user has created and then save it:
By (in the drawing case probably) checking only for the color comparison between the white and the player color;
By, somehow, defining different points that all together would countain the user creation (either drawn or shaped);
Note: In this case I am kind of lost. I have almost no clue of how this could be made. However, I have heard of box2d but I think it was more focused in C or something of that kind? Would it work and how could I do it?
I would finally have the user creation stored and ready to load it in game as an image of a sprite.
I hope I could explain it all correctly. Can someone give me some orientation on this? FYI I am using Phaser.js as js game engine. (sorry for any mistakes, I am not very experienced with this matters).
Hopefully this will get you headed in the right direction:
Instead of drawing to the canvas, create a Phaser bitmapData object and have the user draw to that object. See this example that shows how to draw to a bitmapData object.
If you follow #1, then all of the data that you want will be stored in the bitmapData object, and you can create a Sprite directly from your bitmapData object, e.g.:
// Create a bitmapData object for the user to draw on
var bmd = this.game.make.bitmapData(64, 64);
// code to draw on `bmd` goes here
// Create a Sprite based on the bitmapData from above
var userSprite = this.game.add.sprite(0, 0, bmd);
I am using html5 and javascript for rendering a text. I want to update content of text drawn in canvas. I use the following code
var drawArea = document.getElementById('drawingPlane');
var ctx = drawArea.getContext("2d");
ctx.font = "60px Arial";
var counter = 0;
function update() {
counter++;
ctx.strokeText(counter , 50 , 30);
}
setInterval(update , 1000);
The problem is text is not cleared before writing the next value of counter. It is rendering above the previous value of counter. How can I solve this??
Thanks in advance.
You can use the clearRect method to clear the canvas like this:
<script>
var drawArea = document.getElementById('drawingPlane');
var ctx = drawArea.getContext("2d");
ctx.font = "60px Arial";
var counter = 0;
function update() {
ctx.clearRect ( 0 , 0 , drawArea.width, drawArea.height ); // clear canvas
counter++;
ctx.strokeText(counter , 50 , 30);
}
setInterval(update , 1000);
</script>
In HTML5 Canvas shapes (including text) are immediately pixelated (rasterized) and cannot be edited once drawn. The only way to get rid of something you've drawn is clearing the area where it was drawn as suggested by MUG4N. If you want to edit shaped later you need to either use a HTML5 library such as KineticJS which has built a workaround for retaining shapes, or use SVG.
I'm trying to change the color of the contents of the canvas after it is drawn. So if you start drawing a green circle, you could then decide later to make your previously drawn circle into a red a circle.
I'm using the signaturePad plugin here:
https://github.com/szimek/signature_pad
I have some of the functionality built, but the pen color change doesn't change previously drawn elements. Here's a fiddle:
http://jsfiddle.net/Z6g5Z/
Thanks for your help! The fiddle is prob. the best way to see the issue, but the JS and markup are below.
var canvas = $("#can")[0];
var signaturePad = new SignaturePad(canvas, {
minWidth: 2,
maxWidth: 5,
penColor: "rgb(66, 133, 244)"
});
$('#clear').click(function(){
signaturePad.clear();
});
$('.global-color li').click(function(){
$('.on').removeClass('on');
var $t = $(this);
$t.addClass('on');
var selectedColor = $t.data('color');
signaturePad.penColor = hexToRgb(selectedColor);
});
<ul class="global-color">
<li class="yellow-pick" data-color="#f8c90d">yellow</li>
<li class="green-pick" data-color="#3dae49">green</li>
<li class="orange-pick" data-color="#e87425">orange</li>
<li class="blue-pick on" data-color="#009cc5">blue</li>
</ul>
<div>
<input id="clear" type="button" value="clear" />
</div>
<canvas id="can" width="200px" height="200px"></canvas>
In your color change handler, have all canvas change its (non-transparent) pixels to the new color.
For this, most simple is to use globalComposite operation mode 'source-in', and fill over the canvas with the new color :
// set all pixels of the image to this color
function setCurrentColor(canvas, color) {
var context = canvas.getContext('2d');
context.save();
context.fillStyle = color;
context.globalCompositeOperation = 'source-in';
context.fillRect(0,0,canvas.width, canvas.height);
context.restore();
}
i updated your demo :
http://jsfiddle.net/gamealchemist/Z6g5Z/3/
You can by changing composite mode and fill in the color you want on the existing content.
With a library like this you have no guarantee of the inner workings of it so it may work today and may not work tomorrow - if the author decides to change the way it behaves internally.
So with that disclaimer you can use the following code to change the color of the existing drawing - this works in general with all canvas drawings and changes non-transparent pixels to what you draw on top:
function changeColor() {
ctx.save();
ctx.globalCompositeOperation = 'source-atop';
ctx.fillStyle = selectedColor;
ctx.fillRect(0, 0, ctx.canvas.width, ctx.canvas.height);
ctx.restore();
}
However, since we are going to tap into the library there are at least one other limitation here. The library seem to use a second canvas on top where it registers the mouse. When pen is up it transfer that drawing to the main canvas. The drawback with this, for us, is that the pen change won't happen until we draw something new; we can't change the pen color visually just by using the above function - for that you would have to patch the library to add for example a method which did all the steps needed internally.
But we do get close by adding the following setting:
var signaturePad = new SignaturePad(canvas, {
minWidth: 2,
maxWidth: 5,
penColor: "rgb(66, 133, 244)",
onBegin: changeColor /// add callback here
});
Live demo here
Hope this helps!
Based on Creating an HTML 5 canvas painting application I created a HTML5 canvas painting application. It works fine, but after creating each object I just need to drag the objects.
Working demo
How to implement drag and drop of the figures?
When the user clicks on the canvas, you have to check the coordinates (compare it to the coordinates for the objects), and see if it's on an object. E.g. You can test if a point (e.g. the coordinates for the mousedown even) is within a circle with this method:
function (pt) {
return Math.pow(pt.x - point.x,2) + Math.pow(pt.y - point.y,2) <
Math.pow(radius,2);
};
If the mousedown is on the object, you have to change the objects coordinates according to how the mouse is moved.
Here is an example, where you can drag a circle:
<!DOCTYPE html>
<html>
<head>
<script>
window.onload = function() {
drawCircle(circle);
element = document.getElementById('canvas');
element.addEventListener('mousedown', startDragging, false);
element.addEventListener('mousemove', drag, false);
element.addEventListener('mouseup', stopDragging, false);
element.addEventListener('mouseout', stopDragging, false);
}
function mouseX(e) {
return e.clientX - element.offsetLeft;
}
function mouseY(e) {
return e.clientY - element.offsetTop;
}
var Point = function (x, y) {
this.x = x;
this.y = y;
return this;
}
var Circle = function (point, radius) {
this.point = point;
this.radius = radius;
this.isInside = function (pt) {
return Math.pow(pt.x - point.x, 2) + Math.pow(pt.y - point.y, 2) <
Math.pow(radius, 2);
};
return this;
}
function startDragging(e) {
var p = new Point(e.offsetX, e.offsetY);
if(circle.isInside(p)) {
deltaCenter = new Point(p.x - circle.point.x, p.y - circle.point.y);
}
}
function drag(e) {
if(deltaCenter != null) {
circle.point.x = (mouseX(e) - deltaCenter.x);
circle.point.y = (mouseY(e) - deltaCenter.y);
drawCircle(circle);
}
}
function stopDragging(e) {
deltaCenter = null;
}
function drawCircle(circle) {
var canvas = document.getElementById('canvas');
var ctx = canvas.getContext('2d');
ctx.clearRect(0, 0, canvas.width, canvas.height);
ctx.beginPath();
ctx.arc(circle.point.x, circle.point.y, circle.radius, 0, Math.PI*2, true);
ctx.fill();
}
var circle = new Circle(new Point(30, 40), 25);
var deltaCenter = null;
var element;
</script>
</head>
<body>
<canvas id="canvas" width="400" height="300"></canvas>
</body>
</html>
Try it on jsFiddle
The same effect can be accomplished using Raphael.js (http://raphaeljs.com/) with Joint.jS (http://www.jointjs.com/).
Shapes created with Raphael can be accessed like any DOM element and can be manipulated via attributes. It is an awesome framework.
Joint.js helps in connecting the shapes. They also have a diagramming library and can help create ERD, Statemachine and several common diagrams. The best part is that you can extend their diagram element and create your own custom elements. Its jaw-dropingly cool.
Checkout their demos with source code at http://www.jointjs.com/demos
If you are using the raphael as "raw" lib you must handle the undo/redo by yourself.
The graphiti lib did have Undo/Redo Stack inside and supports the export for SVG, PNG, JSON,...
Additional you have some kind of Viso like connectors and ports.
http://www.draw2d.org/graphiti/jsdoc/#!/example
Greetings
I don't think there's an easy way to do this.
If you're just dealing with lines, my approach would be to keep track of all lines created, with starting coordinates, ending coordinates and some kind of z-index. When the user starts a dragging action (onmousedown), you have to check if the point is near the line, and then update the object and redraw the canvas when the mouse is moved.
How can I tell if a point belongs to a certain line?
This gets a lot more complicated if you're dealing with complex objects though. You'll probably have to find a solution to check if a point is inside a path.
Objects drawn into HTML5 Canvas are turned into pixels and then forgotten. You can't adjust properties on them and have the canvas update to see the effects. You can remember them yourself, but the canvas will still have those pixels set, so you'd have to basically redraw the whole canvas (or at least some of it) when you adjust a property.
You might want to consider SVG for this application instead, SVG elements are remembered in the DOM and when their properties are updated the browser will update the graphic to reflect the changes.
If you must use canvas, then you're going to need to write quite a bit of code to handle mouse-hits, object properties, and repaints.