I really only care about Webkit, but in general, is Raphael JS expected to perform well when building thousands of rectangles?
Additionally, I would need to be able to handle events on each of these rectangles (yipes).
I've got a C++ solution which works but I'd rather use RaphaelJS.
Thanks :)
I don't know nothing about RaphaelJS but I can give you a performance hint with this code:
<!DOCTYPE html>
<html>
<head>
<meta charset = "utf-8">
<title></title>
<script>
window.onload = function () {
var rectangles = 5000;
for (var i = 0; i < rectangles; i ++) {
var height = 50;
var width = 50;
var canvas = document.createElement ("canvas");
canvas.height = height;
canvas.style.margin = "15px";
canvas.width = width;
canvas.addEventListener ("click", function () {
alert ("You like to MOVE !");
}, false);
var ctx = canvas.getContext ("2d");
ctx.fillStyle = "silver";
ctx.fillRect (0, 0, width, height)
document.body.appendChild (canvas);
}
canvas = document.body.getElementsByTagName ("canvas");
window.setInterval (function () {
for (var i = 0; i < canvas.length; i ++) {
canvas[i].style.margin = (Math.floor (Math.random () * 16)) + "px";
}
}, 100);
}
</script>
</head>
<body></body>
</html>
5000 rectangles moving around with "onclick" event:
If you would like to test out performance of Raphael JS I've posted a quick example of plotting 10,000 points. Tests render and clear times.
http://jsfiddle.net/jaRhY/1049/
Related
Problem:
I am learning p5.js and I am following a tutorial from Coding Train YouTube channel. Everything was fine until I had to call a library function on an Image object. The problem is that I have instantiated the library in an object p and I'm using it's variables through p object. I don't know why it isn't recognizing the loadPixels() function. In the tutorial, the function works fine.
Error Message:
🌸 p5.js says: There's an error as "loadPixels" could not be called as a function
(on line 17 in help.html [file:///G:/Android/help.html:17:11]).
Verify whether "img" has "loadPixels" in it and check the spelling, letter-casing (Javacript is case-sensitive) and its type.
For more: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Errors/Not_a_function#What_went_wrong
Code:
<!DOCTYPE html>
<head>
<script src='p5/p5.js'></script>
</head>
<body>
<div id='container'></div>
<script>
let sketch = function(p) {
p.setup = function(){
p.createCanvas(56, 56);
img = new Image();
img.src = "scott.jpg";
}
p.draw = function() {
// p.drawingContext.drawImage(img, 0, 0);
p.loadPixels();
img.loadPixels();
for (var x=0; x<p.width; x++) {
for (var y=0; y<p.height; y++) {
// var d = p.dist(x, y, p.width/2, p.height/2);
var loc = x+y+p.width;
// p.pixels[loc] = p.color(d);
p.pixels[loc] = img.pixels[loc];
}
}
}
p.updatePixels();
};
new p5(sketch, 'container');
</script>
</body>
</html>
Edit:
As someone pointed out that the problem is that I'm using Image() which is the default Image class for javascript. I did some changes to my code but now it gives me this error.
Error :-
Uncaught DOMException: The operation is insecure. help.html:18
openWindow file:///G:/Android/help.html:18
onclick file:///G:/Android/help.html:1
Code :-
<!DOCTYPE html>
<head>
<script src='p5/p5.js'></script>
</head>
<body>
<button onclick="openWindow()">click me to open a new window.</button>
<div id='container'></div>
<script>
function openWindow() {
var newWindow = window.open("", "Import Image", "height=56,width=56,status=yes,toolbar=no,menubar=no,location=no");
newWindow.document.write("<canvas id='imagePlaceholder'>Canvas not supported!</canvas>");
var canvas = newWindow.document.getElementById("imagePlaceholder");
var ctx = canvas.getContext("2d");
ctx.drawImage(img, 0, 0);
// console.log(ctx.getImageData(0, 0, 56, 56).data);
dest = ctx.getImageData(0, 0, 56, 56).data;
}
let sketch = function(p) {
p.setup = function(){
p.createCanvas(56, 56);
img = new Image();
img.src = "scott.jpg";
let dest = p.createImage(56, 56);
console.log(img);
}
p.draw = function() {
// p.drawingContext.drawImage(img, 0, 0);
// p.loadPixels();
img.loadPixels();
for (var x=0; x<p.width; x++) {
for (var y=0; y<p.height; y++) {
// var d = p.dist(x, y, p.width/2, p.height/2);
var loc = x+y+p.width;
// p.pixels[loc] = p.color(d);
p.pixels[loc] = img.pixels[loc];
}
}
}
p.updatePixels();
};
new p5(sketch, 'container');
</script>
</body>
</html>
Because you are specifically trying to load an image from a local computer as opposed to a publicly accessible URL, a file input with user interaction is going to be the only way to do this. This is a deliberate constraint put in place by web browsers to prevent a malicious webpage from illicitly reading data from your local files. However there is a much simpler way to get the image data from the file input onto your p5js canvas. In fact this exact use case can be seen in the documentation for the createFileInput function.
let input;
let img;
function setup() {
input = createFileInput(handleFile);
input.position(0, 0);
}
function draw() {
background(255);
if (img) {
image(img, 0, 0, width, height);
}
}
function handleFile(file) {
if (file.type === 'image') {
img = createImg(file.data, '');
img.hide();
} else {
img = null;
}
}
<!DOCTYPE html>
<html lang="en">
<head>
<script src="https://cdnjs.cloudflare.com/ajax/libs/p5.js/1.3.1/p5.min.js"></script>
</head>
<body>
</body>
</html>
One obvious problem here is that you are using the builtin Image() constructor, which creates an HTMLImageTag (see the MDN Article) instead of creating a p5js p5.Image object (see the p5js Reference). However there are several other issues. In p5js you need to load images in the preload function to ensure they are available when you start drawing (this is an asynchronous operation). You'd have a much easier time drawing images in p5js using the built in image function. If you are going to use pixel arrays, you need to understand the structure of these arrays. They don't store Color objects, they store 4 separate numbers for each color channel (red, green, blue, and alpha). So the indices in the array are not (x + y * width), but ((x + y * width) * 4 + channel) where channel is a number from 0 to 3. Also you need to account for the fact that the canvas may have a pixel density > 1, whereas the image will have a pixel density of 1. I strongly suggest you read all of the documentation for the Image related p5js functions.
let sketch = function(p) {
let img;
p.preload = function() {
img = p.loadImage("https://s3-ap-southeast-1.amazonaws.com/investingnote-production-webbucket/attachments/41645da792aef1c5054c33de240a52e2c32d205e.png");
};
p.setup = function() {
p.createCanvas(200, 200);
};
p.draw = function() {
// this would be a lot simpler way to draw the image:
// p.image(img, 0, 0);
p.loadPixels();
img.loadPixels();
// Handle high pixel density displays. This code effectively scale the image up so that each 1 pixel in the source image is density * density pixels in the display, thus preserving the size of the image but leading to visible pixelation.
let density = p.pixelDensity();
for (var x = 0; x < p.width && x < img.width; x++) {
for (var y = 0; y < p.height && y < img.height; y++) {
// There are 4 values per pixel in the pixels array:
var srcLoc = (x + y * img.width) * 4;
for (var xd = 0; xd < density; xd++) {
for (var yd = 0; yd < density; yd++) {
var destLoc =
(x * density + xd + (y * density + yd) * p.width * density) * 4;
for (var i = 0; i < 4; i++) {
p.pixels[destLoc + i] = img.pixels[srcLoc + i];
}
}
}
}
}
p.updatePixels();
};
};
new p5(sketch, 'container');
<!DOCTYPE html>
<html lang="en">
<head>
<script src="https://cdnjs.cloudflare.com/ajax/libs/p5.js/1.3.1/p5.min.js"></script>
</head>
<body>
<div id='container'></div>
</body>
</html>
Here is an alternate version of the snippet that handles pixelDensity differently:
let sketch = function(p) {
let img;
p.preload = function() {
img = p.loadImage("https://s3-ap-southeast-1.amazonaws.com/investingnote-production-webbucket/attachments/41645da792aef1c5054c33de240a52e2c32d205e.png");
};
p.setup = function() {
p.createCanvas(200, 200);
};
p.draw = function() {
// this would be a lot simpler way to draw the image:
// p.image(img, 0, 0);
p.loadPixels();
img.loadPixels();
// Handle high pixel density displays. This code shrinks the image down by mapping one pixel in the source image to 1 / (density ^ 2) actual pixels in the canvas.
let density = p.pixelDensity();
for (var x = 0; x < p.width * density && x < img.width; x++) {
for (var y = 0; y < p.height * density && y < img.height; y++) {
// There are 4 values per pixel in the pixels array:
var srcLoc = (x + y * img.width) * 4;
var destLoc = (x + y * p.width * density) * 4;
for (var i = 0; i < 4; i++) {
p.pixels[destLoc + i] = img.pixels[srcLoc + i];
}
}
}
p.updatePixels();
};
};
new p5(sketch, 'container');
<!DOCTYPE html>
<html lang="en">
<head>
<script src="https://cdnjs.cloudflare.com/ajax/libs/p5.js/1.3.1/p5.min.js"></script>
</head>
<body>
<div id='container'></div>
</body>
</html>
I tried a lot of things and almost giveup, but at the end I had to change the code a bit and this worked for me. Although what I got was base64 url as Alice in the comment suggested and I converted it into Uint8ClampedArray. Now if anyone wants a full image or all the pixels of an image then they can follow this link :- https://developer.mozilla.org/en-US/docs/Web/API/Canvas_API/Tutorial/Pixel_manipulation_with_canvas . I hope it will be helpful for anyone who wants to make an offline webcanvas based application and don't want to dabble with CORS.
var fileSelector = document.createElement('input');
fileSelector.setAttribute('type', 'file');
fileSelector.setAttribute('accept', 'image/gif, image/jpeg, image/png');
fileSelector.click();
fileSelector.onchange = function(e) {
img = new Image();
var file = e.target.files[0];
var reader = new FileReader();
reader.onloadend = function() {
img.src = reader.result;
}
reader.readAsDataURL(file);
var newWindow = window.open("", "_blank", "height=56,width=56,status=yes,toolbar=no,menubar=no,location=no");
newWindow.document.write("<canvas id='imagePlaceholder'>Canvas not supported!</canvas>");
var canvas = newWindow.document.getElementById("imagePlaceholder");
var ctx = canvas.getContext("2d");
ctx.drawImage(img, 0, 0);
// console.log(ctx.getImageData(0, 0, 56, 56).data);
var dest = ctx.getImageData(0, 0, img.width, img.height).data;
console.log(dest);
newWindow.close();
}
I attempted to animate a sprite sheet using html and javascript to no avail. Here is my sprite sheet
Below is lines 36-59 of my code. I'm not getting any errors so I don't really know what's wrong. How do I fix/improve my code?
This is for a project I'm doing. I've tried using different methods I've found online but none really worked either. I've tried shifting the image as well.
<html>
<head>
<title>Tree Animation</title>
</head>
<body>
<canvas id='canvas'></canvas>
<script>
var canWidth = 400;
var canHeight = 100;
//position where the frame will be drawn
var x = 0;
var y = 0;
var srcX;
var srcY;
var sheetWidth = 230;
var sheetHeight = 79;
var frameCount = 5;
var width = sheetWidth/frameCount;
var height;
var currentFrame = 0;
var tree = new Image();
tree.src = "tree sprite.jpg"
var canvas = document.getElementById('canvas');
canvas.width = canWidth;
canvas.height = canHeight;
var ctx = canvas.getContext('2d');
function updateFrame(){
currentFrame = ++currentFrame%frameCount
srcX = currentFrame*width;
srcY = 0;
ctx.clearRect(x, y, width, height);
}
function draw(){
updateFrame();
}
setInterval(function(){
draw();
}, 100);
</script>
</body>
</html>
I expect the output to be an animation of a tree growing, but instead I'm getting a blank page.
you should provide more code or a snippet, there are several variables didn't show up in your code
and it's hard to debug your code if u use setInterval, you should make sure your code can work first.
maybe you can try step by step:
draw the whole img on the canvas first. if it works, go next
invoke your draw() function manually, check if the img drawed
invoke more, such assetTimout(draw, 1000), check the result
ok, and i think you can console.log these variables in draw
I want to make a loading bar for my web application and I want to use a html canvas for this. This is the script that I use to fill up the canvas:
<script>
var canvas = document.getElementById("bar");
var c = canvas.getContext("2d");
var xPos = 0;
draw = function() {
if(xPos < 300){
c.rect(0, 0, xPos, 30);
c.fill(255,0,0);
xPos += 0.5;
}
};
</script>
I tested this code on a online code converter (khan academy) and it worked (of course without the first 2 lines and c. in front of most things), and that is also my trouble I don't know where I have to put c. in front of?
I simplified the page a little bit:
<!DOCTYPE html>
<html>
<head>
<link rel="stylesheet" type="text/css" href="test.css">
</head>
<body>
<canvas id="bar"></canvas>
<script>
var canvas = document.getElementById("bar");
var c = canvas.getContext("2d");
c.fillStyle = "#ff0000"
draw = function(){
if(xPos < 300){
c.fillRect(0, 0, xPos, 30);
xPos += 0.5;
}
};
</script>
</body>
</html>
Whatever you are trying to draw... this:
draw = function(){
if(xPos < 300) {
c.fillRect(0, 0, xPos, 30);
xPos += 0.5;
}
};
... it is a definition of variable in global context (context of window object), then assigning a function to it. That's all - it only defines the behavior.
What you need also needs to execute that (a sidenote: to execute it after the canvas is actually created - when you put code in a script tag after canvas tag - it's sufficient and you did it already).
To execute the function use:
draw();
Or don't wrap code in function at all (unless it's to be called multiple times).
Or use a syntax construct to execute the function created in place like this:
(draw = function(){
if(xPos < 300) {
c.fillRect(0, 0, xPos, 30);
xPos += 0.5;
setTimeout(draw,15); // use this to achieve animation effect
}
})();
var xPos = 0;
var canvas = document.getElementById("bar");
var c = canvas.getContext("2d");
c.fillStyle = "#FF0000";
var draw;
(draw = function(){
if(xPos < 300) {
c.fillRect(0, 0, xPos, 30);
xPos += 0.5;
setTimeout(draw,15);
}
})();
#bar {
width: 300px;
height: 50px;
}
<canvas id="bar"></canvas>
Edit: I've been thinking of what you might need, as it's not entirely abvious what you want. I have created this jsfiddle. Maybe it'll be of any help.
Hmmm...
You got some things mixed up. Try this:
<html>
<canvas id = "cvs1" width = "300" height = "30"></canvas>
</html>
And for the script:
var c = document.getElementById("cvs1").getContext("2d");
c.fillStyle = "#ff0000" //Set Fill Color(Set to red)
if(xPos < 300){
c.fillRect(xPos, 0, 30, 30);
xPos += 0.5;
}
If not:
What you did was use fill and rect seperately. You need to set the color, and then use the fillRect() function to draw the rectangle.
EDIT: You got the x,y,width,height as width,height,x,y. Fixed answer.
Good luck!
You need to call draw for every animation step. You could do this using setTimeout, setInterval or requestAnimationFrame :
<!DOCTYPE html>
<html>
<head>
<link rel="stylesheet" type="text/css" href="test.css">
</head>
<body>
<canvas id="bar"></canvas>
<script>
var canvas = document.getElementById("bar");
var c = canvas.getContext("2d");
c.fillStyle = "#ff0000";
xPos=0;
draw = function(){
if(xPos < 300){
c.fillRect(0, 0, xPos, 30);
xPos += 0.5;
requestAnimationFrame(draw);
}
};
requestAnimationFrame(draw);
</script>
</body>
</html>
I am trying to make a HTML5 Canvas/JavaScript game. I watched some tutorials, and I understand what everying is meant for, but I don't get the right controls for touch devices.
I want to get my 'airship', where my finger touches the screen. It is not only working with where my mouse is positioned.
<!DOCTYPE html>
<html>
<head>
<title>Title</title>
<script type="text/javascript">
window.onload = function() {
var canvas = document.getElementById('canvas');
var context = canvas.getContext('2d');
var canvasWidth = canvas.offsetWidth;
var canvasHeight = canvas.offsetHeight;
var bg1 = new Image();
var bg2 = new Image();
bg1.src = "img/spritesheet.png";
bg2.src = "img/spritesheet.png";
var increment = -5;
var sYbg1 = 0;
var sYbg2 = 960;
var ship = new Image();
ship.src = "img/spritesheet.png";
var mouseX;
var mouseY;
canvas.onmousemove = function() {
mouseX = window.event.clientX - canvas.offsetLeft; // mousePositionX
inside the <canvas> element
mouseY = window.event.clientY - canvas.offsetTop; // mousePositionY
inside the <canvas> element
};
var animate = function() {
context.clearRect(0,0,canvasWidth,canvasHeight);
context.drawImage(bg1,0,sYbg1,canvasWidth,canvasHeight,0,0,canvasWidth,canvasHeight);
context.drawImage(bg2,0,sYbg2,canvasWidth,canvasHeight,0,0,canvasWidth,canvasHeight);
sYbg1 += increment;
sYbg2 += increment;
if(sYbg2 <= 0) {
sYbg1 = 0;
sYbg2 = 960;
}
context.drawImage(ship,320,0,65,105,(mouseX-32),(mouseY-52),65,105);
setTimeout(animate,25);
};
animate();
}
</script>
</head>
<body>
<canvas id="canvas" width="320" height="480"></canvas>
</body>
</html>
(!MY CODE IS ONLY WORKING IN CHROME!) --> But thats not important not, I know about the window.event and that it's not working in FF.
I hope someone can explain to me what I need to do. I tried to fix my problem to use onmousemove and onmousedown together, but that wasn't working for me too. Thanks a lot for the help!
I will provide a hint, in case you haven't gotten there yet, and for future researchers. You have a mouse event handler (mousemove). I don't see a touch event handler. There are some options depending on your browser, which is unclear to me which you want to use...
However you can start looking at https://developers.google.com/ or MDN https://developer.mozilla.org/en-US/ as good starting points.
I want to implement dragging of an image within a canvas. I want simplest code for that. So far I have seen a lot of examples but they have used complex ways of implementation. I want an example that is easy to learn and implement.
It's pretty difficult. You'll first need to write a function that can detect when you click a particular element. However, before we can do that, we must define what we mean by "element". Is it the product of a single draw instruction (e.g. a rectangle or arc), or something complex? (Imagine I wanted to draw a cat and make the entire cat draggable as a unit.)
A canvas is nothing but a collection of pixels. If you want your program to have an idea of "shapes" or even "collections of shapes treated as a unit" you'll need to implement them yourself as data structures external to the canvas itself. Once you have that, you can write an onmousedown handler that takes the x/y point clicked and determine what shape (if any) the click falls inside of (and if it falls inside of multiple shapes, check which has the foremost z-index). Then add an onmousemove handler that erases and redraws the shape on the canvas based on the information in the shape data object.
This is a moderately difficult problem with very difficult prerequisite problems (creating data structures that can describe a wide range of shapes as well as collections of shapes). I highly recommend you use a canvas drawing library that has already solved these problems. I use cake.js but there are loads of options available.
If you don't have to use the HTML5 canvas, jQuery UI is a lot simpler:
HTML:
<img class="drag-me" src="http://www.google.com/images/srpr/logo3w.png">​
JavaScript:
$(function() {
$('.drag-me').draggable();
});
​
See it in action:
http://jsfiddle.net/flackend/TQzSe/
The jQuery UI API has a lot of options too to make it act how you want:
http://jqueryui.com/demos/draggable/
Plus, if it doesn't do what you need, it's easy to implement yourself. Post here if you need help with that.
jsfiddle.net/Zevan/QZejF/5 This may help you.
<html>
<head>
<title>Test Page</title>
<script type="text/javascript" src="jquery.js"></script>
</head>
<body>
<canvas id="c" width = "500" height = "500" ></canvas>
<script type="text/javascript">
var canvas = $("#c");
var c = canvas[0].getContext("2d");
//var path = "http://wonderfl.net/images/icon/e/ec/ec3c/ec3c37ba9594a7b47f1126b2561efd35df2251bfm";
var path = "blue.jpg";
var path2 = "purple.jpg";
var image1 = new DragImage(path, 200, 100);
var image2 = new DragImage(path2, 300, 100);
var loop = setInterval(function() {
c.fillStyle = "gray";
c.fillRect(0, 0, 500, 500);
image1.update();
image2.update();
}, 30);
var mouseX = 0,
mouseY = 0;
var mousePressed = false;
var dragging = false;
canvas.mousemove(function(e) {
mouseX = e.offsetX;
mouseY = e.offsetY;
})
$(document).mousedown(function() {
mousePressed = true;
}).mouseup(function() {
mousePressed = false;
dragging = false;
});
function DragImage(src, x, y) {
var that = this;
var startX = 0,
startY = 0;
var drag = false;
this.x = x;
this.y = y;
var img = new Image();
img.src = src;
this.update = function() {
if (mousePressed ) {
var left = that.x;
var right = that.x + img.width;
var top = that.y;
var bottom = that.y + img.height;
if (!drag) {
startX = mouseX - that.x;
startY = mouseY - that.y;
}
if (mouseX < right && mouseX > left && mouseY < bottom && mouseY > top) {
if (!dragging){
dragging = true;
drag = true;
}
}
} else {
drag = false;
}
if (drag) {
that.x = mouseX - startX;
that.y = mouseY - startY;
}
c.drawImage(img, that.x, that.y);
}
}
</script>
</body>
</html>