I've written the code below which works when creating one canvas object dynamically and filling it with pixels, however when I try to create multiples, it clears the first canvas for some reason. Anybody have any ideas as to why and how to fix it?
(JS FIddle doesn't seem to work so somewhat long paste here)
<head>
<script type="text/javascript">
function createnew_canvas()
{
var canvas_number = document.getElementById("hidden_counter").innerHTML.toString();
var new_canvas = parseInt(canvas_number) + 1;
document.getElementById("hidden_counter").innerHTML = new_canvas;
var mydoc = document.getElementById("canvas_area");
var mynewname = "canvas"+ canvas_number.toString();
mydoc.innerHTML = mydoc.innerHTML + '<canvas id="'+ mynewname +'" width="1000" height="600">canvas</canvas><br/>';
draw_canvas(canvas_number);
}
function setPixel(imageData, x, y, r, g, b, a)
{
index = (x + y * imageData.width) * 4;
imageData.data[index+0] = r;
imageData.data[index+1] = g;
imageData.data[index+2] = b;
imageData.data[index+3] = a;
}
function draw_canvas(canvasnum)
{
var myname = "canvas" + canvasnum;
element = document.getElementById(myname);
c = element.getContext("2d");
// read the width and height of the canvas
element.width = document.documentElement.clientWidth ;
element.height = document.documentElement.clientHeight ;
width = element.width;
height = element.height;
// create a new pixel array
imageData = c.createImageData(width, height);
for (i= 0; i < width;i++)
{
for (v =1; v <height - 400; v++)
{
if (i % 12 === 0 )
{
setPixel(imageData, i, 200 + v , 50* canvasnum, 50*canvasnum, 0, 255); // 255 opaque
}
else
{
setPixel(imageData, i, 200 + v, 0, 0, 50*canvasnum, 255); // 255 opaque
}
}
}
c.putImageData(imageData, 0, 0); // at coords 0,0
}
</script>
</head>
<body>
<div class="navbar">
<div class="title">Canvas Maker</div>
<div></div>
<div></div>
<div></div>
<div class="addnewcanvas" onclick="createnew_canvas();"> +</div>
<div id="hidden_counter">1</div>
</div>
<div id="canvas_area"></div>
</body>
It looks like you have:
mydoc.innerHTML = mydoc.innerHTML + '<canvas id="'+ mynewname +'" width="1000" height="600">canvas</canvas><br/>';
that will set the html of the element, but doing so will cause any state of the canvas that was there to be lost.
You might want to just try to append your new elements to the mydoc instead of setting the html.
Append The canvas like this
function createCanvas(id) {
var canvasMade = document.createElement("canvas");
canvasMade.id = id;
document.body.appendChild(canvasMade);
}
Hope this helped...
Related
i am getting frames from gif using Libgif.
and then i am appending those frames in the div with Id = frames.
then i am taking those frames and trying to add each frames one after the other in canvas to make a spritesheet.
in the end i am getting an image in canvas but instead of getting different frames i am getting same image in the spritesheet.
Please help me find the issue.
I had taken canvas width 10000 assuming a gif wont have frames more than 100.
c = document.getElementById("myCanvas");
ctx = c.getContext("2d");
ctx.clearRect(0, 0, ctx.width, ctx.height);
ctx.beginPath();
var imageGiF = "";
var total = 0;
let canvasWidth = 0;
let canvasHeight = 0;
$('div.gifimage img').each(function(idx, img_tag) {
var total = 0;
if (/^.+\.gif$/.test($(img_tag).prop("src"))) {
var rub = new SuperGif({
gif: img_tag,
progressbar_height: 0
});
rub.load(function() {
for (let i = 0; i < rub.get_length(); i++) {
total += 1;
rub.move_to(i);
// var canvas = cloneCanvas(rub.get_canvas());
var canvas = rub.get_canvas().toDataURL("image/png");
img = $('<img id = "gifframe' + i + '"src= "' + canvas + '" class= frameimages>');
$("#frames").append(img);
}
var frameimages = document.getElementById("frames").querySelectorAll(".frameimages");
var totalimages = frameimages.length;
x = 0;
y = 0;
for (let i = 0; i < frameimages.length; i++) {
img = document.getElementById("gifframe" + i + "");
img.onload = function() {
ctx.drawImage(img, i * 100, 0, 100, 100);
total++;
console.log(total);
}
}
totalwidth = (total) * 100;
c.width = totalwidth;
c.height = 100;
setTimeout(() => {
imageGiF = c.toDataURL("image/png");
console.log(imageGiF);
// addBgimg(imageGiF)
}, 10);
});
}
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.6.0/jquery.min.js"></script>
<script src="https://cdn.rawgit.com/buzzfeed/libgif-js/master/libgif.js"></script>
<div class="gifimage" id="placehere">
<img src="https://media1.giphy.com/media/bzUwzbxcvJ3XQlcnoi/giphy.gif" alt="">
</div>
<div id="frames" class="classGIF"></div>
<canvas id='myCanvas' width="10000" height="300"></canvas>
You were looping through the images, using img in your event handler.
However, this variable img in the outer scope was overridden by every loop, until it was finished looping through everything, then img was stuck on the last frame added.
Then when the event handler triggered, it added the last frame in every instance, because that was the value of img at that point. The loop was done before the images could load.
By adding it to it's own scope by wrapping it in a function, the variable is preserved.
I also modified your code to store the DOM img elements in an array, so you don't need expensive DOM lookups which makes your code a tad bit faster.
I added comments in the code to explain my changes.
c = document.getElementById("myCanvas");
ctx = c.getContext("2d");
ctx.clearRect(0, 0, ctx.width, ctx.height);
ctx.beginPath();
var imageGiF = "";
var total = 0;
let canvasWidth = 0;
let canvasHeight = 0;
$('div.gifimage img').each(function(idx, img_tag) {
var total = 0;
if (/^.+\.gif$/.test($(img_tag).prop("src"))) {
var rub = new SuperGif({
gif: img_tag,
progressbar_height: 0
});
rub.load(function() {
// An array for the image references
let images = [];
// Keep the reference to save on expensive DOM lookups every iteration.
let frames = $("#frames");
for (let i = 0; i < rub.get_length(); i++) {
total += 1;
rub.move_to(i);
// var canvas = cloneCanvas(rub.get_canvas());
var canvas = rub.get_canvas().toDataURL("image/png");
img = $('<img id = "gifframe' + i + '"src= "' + canvas + '" class="frameimages">');
// Use the reference to append the image.
frames.append(img);
// Add image to images array with the current index as the array index.
// Use the jQuery get method to get the actual DOM element.
images[i] = img.get(0);
}
var frameimages = document.getElementById("frames").querySelectorAll(".frameimages");
var totalimages = frameimages.length;
x = 0;
y = 0;
// Loop through all the images in the image array
// Using a scope so the reference to img won't be overridden.
images.forEach((img, index) => {
img.onload = () => {
ctx.drawImage(img, index * 100, 0, 100, 100);
total++;
console.log(total);
}
})
totalwidth = (total) * 100;
c.width = totalwidth;
c.height = 100;
setTimeout(() => {
imageGiF = c.toDataURL("image/png");
console.log(imageGiF);
// addBgimg(imageGiF)
}, 10);
});
}
});
#frames { display:none;}
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.6.0/jquery.min.js"></script>
<script src="https://cdn.rawgit.com/buzzfeed/libgif-js/master/libgif.js"></script>
<div class="gifimage" id="placehere">
<img src="https://media1.giphy.com/media/bzUwzbxcvJ3XQlcnoi/giphy.gif" alt="">
</div>
<div id="frames" class="classGIF"></div>
<canvas id='myCanvas' width="10000" height="300"></canvas>
Below is my script which was working fine.
But right now my image url was static at bottom of the script,
But i want to make it dynamic using file upload button.
Means if i select a file from upload button, then it will preview both images.
Below is the line
img.src = "https://image.ibb.co/bGtv0z/Product_Two.jpg";
where my image was fixed. i want to get this URL from file upload button.
Please help me to make it dynamic.
var img = new Image(),
$canvas = $("<canvas>"),
canvas = $canvas[0],
context;
var removeBlanks = function(imgWidth, imgHeight) {
var imageData = context.getImageData(0, 0, imgWidth, imgHeight),
data = imageData.data,
getRBG = function(x, y) {
var offset = imgWidth * y + x;
return {
red: data[offset * 4],
green: data[offset * 4 + 1],
blue: data[offset * 4 + 2],
opacity: data[offset * 4 + 3]
};
},
isWhite = function(rgb) {
// many images contain noise, as the white is not a pure #fff white
return rgb.red > 242 && rgb.green > 240 && rgb.blue > 240;
},
scanY = function(fromTop) {
var offset = fromTop ? 1 : -1;
// loop through each row
for (var y = fromTop ? 0 : imgHeight - 1; fromTop ? (y < imgHeight) : (y > -1); y += offset) {
// loop through each column
for (var x = 0; x < imgWidth; x++) {
var rgb = getRBG(x, y);
if (!isWhite(rgb)) {
return y;
}
}
}
return null; // all image is white
},
scanX = function(fromLeft) {
var offset = fromLeft ? 1 : -1;
// loop through each column
for (var x = fromLeft ? 0 : imgWidth - 1; fromLeft ? (x < imgWidth) : (x > -1); x += offset) {
// loop through each row
for (var y = 0; y < imgHeight; y++) {
var rgb = getRBG(x, y);
if (!isWhite(rgb)) {
return x;
}
}
}
return null; // all image is white
};
var cropTop = scanY(true),
cropBottom = scanY(false),
cropLeft = scanX(true),
cropRight = scanX(false),
cropWidth = cropRight - cropLeft,
cropHeight = cropBottom - cropTop;
var $croppedCanvas = $("<canvas>").attr({
width: cropWidth,
height: cropHeight
});
// finally crop the guy
$croppedCanvas[0].getContext("2d").drawImage(canvas,
cropLeft, cropTop, cropWidth, cropHeight,
0, 0, cropWidth, cropHeight);
$("#oldimg").
append("<p>same image with white spaces cropped:</p>").
append($croppedCanvas);
console.log(cropTop, cropBottom, cropLeft, cropRight);
};
img.crossOrigin = "anonymous";
img.onload = function() {
$canvas.attr({
width: this.width,
height: this.height
});
context = canvas.getContext("2d");
if (context) {
context.drawImage(this, 0, 0);
$("#newimg").append("<p>original image:</p>").append($canvas);
removeBlanks(this.width, this.height);
} else {
alert('Get a real browser!');
}
};
// define here an image from your domain
img.src = "https://image.ibb.co/bGtv0z/Product_Two.jpg";
<script src="https://code.jquery.com/jquery-3.3.1.min.js"></script>
<body style="background-color:#ddd">
<input type="file" src="">
<div id="oldimg"></div>
<div id="newimg"></div>
</body>
When you choose a file in file input it is only in temporary memory and not on a server. Thus you will be unable to display it.
In order to do to what you want, you can either add a form that uploads the file and after file upload you can display it or use a FileReader. But this question was already answered, so please before asking a question try to find the solution by your own first.
Here is an answer with FileReader
I need to find a way to draw a 1000x1000 squares grid, each square is clickable and they must be independently color changeable. Like mines game. I can use HTML (pure or using Canvas or SVG), CSS and JavaScript for this.
I know how to create one grid with these characteristics with JavaScript and CSS, it does well with 10x10 squares, with 100x100 the squares will turn into tall rectangles and 1000x1000 it loads, but the "squares" are soo much compressed that borders meet each other and renders a full gray page.
I tried using HTML and JavaScript to draw SVG squares, the squares' size problem solves, but I don't know how to make they change color when clicked and when I set to load 1000x1000 squares it will freeze the browse and eventually crash the tab.
Is this feasible in any way?
EDIT
Sorry if I wasn't clear, but yes, I need scroll bars in that. They are no problem for me.
You can see the two trials I described here:
JavaScript and CSS
var lastClicked;
var grid = clickableGrid(100,100,function(el,row,col,i){
console.log("You clicked on element:",el);
console.log("You clicked on row:",row);
console.log("You clicked on col:",col);
console.log("You clicked on item #:",i);
el.className='clicked';
if (lastClicked) lastClicked.className='';
lastClicked = el;
});
document.body.appendChild(grid);
function clickableGrid( rows, cols, callback ){
var i=0;
var grid = document.createElement('table');
grid.className = 'grid';
for (var r=0;r<rows;++r){
var tr = grid.appendChild(document.createElement('tr'));
for (var c=0;c<cols;++c){
var cell = tr.appendChild(document.createElement('td'));
++i;
cell.addEventListener('click',(function(el,r,c,i){
return function(){
callback(el,r,c,i);
}
})(cell,r,c,i),false);
}
}
return grid;
}
.grid { margin:1em auto; border-collapse:collapse }
.grid td {
cursor:pointer;
width:30px; height:30px;
border:1px solid #ccc;
}
.grid td.clicked {
background-color:gray;
}
JavaScript and HTML
document.createSvg = function(tagName) {
var svgNS = "http://www.w3.org/2000/svg";
return this.createElementNS(svgNS, tagName);
};
var numberPerSide = 20;
var size = 10;
var pixelsPerSide = 400;
var grid = function(numberPerSide, size, pixelsPerSide, colors) {
var svg = document.createSvg("svg");
svg.setAttribute("width", pixelsPerSide);
svg.setAttribute("height", pixelsPerSide);
svg.setAttribute("viewBox", [0, 0, numberPerSide * size, numberPerSide * size].join(" "));
for(var i = 0; i < numberPerSide; i++) {
for(var j = 0; j < numberPerSide; j++) {
var color1 = colors[(i+j) % colors.length];
var color2 = colors[(i+j+1) % colors.length];
var g = document.createSvg("g");
g.setAttribute("transform", ["translate(", i*size, ",", j*size, ")"].join(""));
var number = numberPerSide * i + j;
var box = document.createSvg("rect");
box.setAttribute("width", size);
box.setAttribute("height", size);
box.setAttribute("fill", color1);
box.setAttribute("id", "b" + number);
g.appendChild(box);
svg.appendChild(g);
}
}
svg.addEventListener(
"click",
function(e){
var id = e.target.id;
if(id)
alert(id.substring(1));
},
false);
return svg;
};
var container = document.getElementById("container");
container.appendChild(grid(100, 10, 2000, ["gray", "white"]));
<div id="container">
</div>
I will be trying implementing the given answers and ASAP I'll accept or update this question. Thanks.
SOLUTION
Just to record, I managed to do it using canvas to draw the grid and the clicked squares and added an event listener to know where the user clicks.
Here is the code in JavaScript and HTML:
function getSquare(canvas, evt) {
var rect = canvas.getBoundingClientRect();
return {
x: 1 + (evt.clientX - rect.left) - (evt.clientX - rect.left)%10,
y: 1 + (evt.clientY - rect.top) - (evt.clientY - rect.top)%10
};
}
function drawGrid(context) {
for (var x = 0.5; x < 10001; x += 10) {
context.moveTo(x, 0);
context.lineTo(x, 10000);
}
for (var y = 0.5; y < 10001; y += 10) {
context.moveTo(0, y);
context.lineTo(10000, y);
}
context.strokeStyle = "#ddd";
context.stroke();
}
function fillSquare(context, x, y){
context.fillStyle = "gray"
context.fillRect(x,y,9,9);
}
var canvas = document.getElementById('myCanvas');
var context = canvas.getContext('2d');
drawGrid(context);
canvas.addEventListener('click', function(evt) {
var mousePos = getSquare(canvas, evt);
fillSquare(context, mousePos.x, mousePos.y)
}, false);
<body>
<canvas id="myCanvas" width="10000" height="10000"></canvas>
</body>
Generating such a large grid with HTML is bound to be problematic.
Drawing the grid on a Canvas and using a mouse-picker technique to determine which cell was clicked would be much more efficient.
This would require 1 onclick and/or hover event instead of 1,000,000.
It also requires much less HTML code.
I wouldn't initialize all the squares right off, but instead as they are clicked -
(function() {
var divMain = document.getElementById('main'),
divMainPosition = divMain.getBoundingClientRect(),
squareSize = 4,
square = function(coord) {
var x = coord.clientX - divMainPosition.x + document.body.scrollLeft +
document.documentElement.scrollLeft,
y = coord.clientY - divMainPosition.y + document.body.scrollTop +
document.documentElement.scrollTop;
return {
x:Math.floor(x / squareSize),
y:Math.floor(y / squareSize)
}
}
divMain.addEventListener('click', function(evt) {
var sqr = document.createElement('div'),
coord = square(evt);
sqr.className = 'clickedSquare';
sqr.style.width = squareSize + 'px';
sqr.style.height = squareSize + 'px';
sqr.style.left = (coord.x * squareSize) + 'px';
sqr.style.top = (coord.y * squareSize) + 'px';
sqr.addEventListener('click', function(evt) {
console.log(this);
this.parentNode.removeChild(this);
evt.stopPropagation();
});
this.appendChild(sqr);
});
}());
#main {
width:4000px;
height:4000px;
background-color:#eeeeee;
position:relative;
}
.clickedSquare {
background-color:#dd8888;
position:absolute;
}
<div id="main">
</div>
Uses CSS positioning to determine which square was clicked on,
doesn't initialize a square until it's needed.
Granted I imagine this would start to have a negative impact to use r experience, but that would ultimately depend on their browser and machine.
Use the same format you noramlly use, but add this:
sqauareElement.height = 10 //height to use
squareElement.width = 10 //width to use
This will add quite a large scroll due to the size, but it's the only logical explanation I can come up with.
The canvas approach is fine, but event delegation makes it possible to do this with a table or <div> elements with a single listener:
const tbodyEl = document.querySelector("table tbody");
tbodyEl.addEventListener("click", event => {
const cell = event.target.closest("td");
if (!cell || !tbodyEl.contains(cell)) {
return;
}
const row = +cell.getAttribute("data-row");
const col = +cell.getAttribute("data-col");
console.log(row, col);
});
const rows = 100;
const cols = 100;
for (let i = 0; i < rows; i++) {
const rowEl = document.createElement("tr");
tbodyEl.appendChild(rowEl);
for (let j = 0; j < cols; j++) {
const cellEl = document.createElement("td");
rowEl.appendChild(cellEl);
cellEl.classList.add("cell");
cellEl.dataset.row = i;
cellEl.dataset.col = j;
}
}
.cell {
height: 4px;
width: 4px;
cursor: pointer;
border: 1px solid black;
}
table {
border-collapse: collapse;
}
<table><tbody></tbody></table>
Currently I'm creating a sheet of graph paper with the canvas object in HTML5. I'm able to create the canvas as well as fill in the selected areas with a color by finding the x/y position. Unfortunately I'm having some troubles using the jQuery mousemove method to display a pop-up of the information selected for the square.
Here's my code:
Canvas Creation/Layout:<br>
<script type="text/javascript">
var canvas;
var context;
var color;
var state;
var formElement;
var number = 0;
function showGrid()
{
canvas = document.getElementById('canvas');
context = canvas.getContext('2d');
context.lineWidth=0.5;
context.strokeStyle='#999999';
lineSpacing=10;
var xPos = 0;
var yPos = 0;
var numHorizontalLines = parseInt(canvas.height/lineSpacing);
var numVerticalLines = parseInt(canvas.width/lineSpacing);
state = new Array(numHorizontalLines);
for (var y = 0; y < numHorizontalLines; ++y)
{
state[y] = new Array(numVerticalLines);
}
for(var i=1; i<=numHorizontalLines;i++)
{
yPos=i*lineSpacing;
context.moveTo(0,yPos);
context.lineTo(canvas.width,yPos);
context.stroke;
}
for(var i=1; i<=numVerticalLines; i++)
{
xPos=i*lineSpacing;
context.moveTo(xPos,0);
context.lineTo(xPos,canvas.height);
context.stroke();
}
}
function fill(s, gx, gy)
{
context.fillStyle = s;
context.fillRect(gx * lineSpacing, gy * lineSpacing, lineSpacing, lineSpacing);
if(s != null)
{
}
}
function getPosition(e)
{
var x = new Number();
var y = new Number();
var canvas = document.getElementById("canvas");
if (e.pageX || e.pageY)
{
x = e.pageX;
y = e.pageY;
}
else
{
x = e.clientX + document.body.scrollLeft +
document.documentElement.scrollLeft;
y = e.clientY + document.body.scrollTop +
document.documentElement.scrollTop;
}
x -= canvas.offsetLeft;
y -= canvas.offsetTop;
var gx = Math.floor((x / lineSpacing));
var gy = Math.floor((y / lineSpacing));
state[gy][gx] = true;
fill(color, gx, gy);
addNumber();
}
HTML:
<div class="graphpaper" id="graphpaper" onclick="getPosition(event)" style="width:956px; height:1186px;">
<img src="images/PosterBorder_Top.png" align="right"/>
<img src="images/posterBorder_left.png" align="left" valign="top"/>
<canvas id ="canvas" width = "920" height = "1160" align="left">
</canvas>
</div>
<!-- HIDDEN / POP-UP DIV -->
<div id="pop-up">
<h3>Pop-up div Successfully Displayed</h3>
<p>
This div only appears when the trigger link is hovered over.
Otherwise it is hidden from view.
</p>
</div>
jQuery for Pop-Up display:
$('#canvas').mousemove(function(event){
console.log("Here I am!");
$('div#pop-up').show().appendTo('body');
});
Any suggestions? I'm obviously missing something but from what I've done this should work I believe.
I'm trying to simulate the Matrix code rain with the canvas element and javascript. I am able to make one element drop at a time but not multiple. How do I drop multiple matrix rain drops. Here is my code:
<html>
<head>
<title>Matrix Code Rain</title>
<style>
*{margin:0; padding:0; }
body{background:black;}
</style>
</head>
<body>
<canvas id="c"></canvas>
<script type="text/javascript">
var canvas = document.getElementById("c");
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
canvas.style.background = "black";
var c = canvas.getContext("2d");
var code = ["<html>","<p>","<b>","<strong>","<head>","<body>","<a>","<i>","<div>","<form>","<ol>","<li>","<ul>","<pre>","<nav>","<footer>","<header>","<article>","<section>","<em>","<style>","<title>","<meta>","<br>","<table>"];
var rain = [ ];
var max = 10;
for(var i = 0; i < max; i++){
var drop = {};
drop.code = Math.round(Math.random() * code.length);
drop.x = Math.random() * canvas.width;
drop.y = 0;
drop.size = Math.random() * 40;
drop.speed = drop.size/4;
rain.push(drop);
}
var y = 0;
c.fillStyle="lime";
setTimeout(function(){
c.clearRect(0,0,canvas.width,canvas.height);
for(var i = 0; i < max; i++){
var drop = rain[i];
c.font = drop.size+"pt arial";
c.fillText(drop.code,drop.x,drop.y);
drop.y += drop.speed;
if(drop.y > canvas.height + drop.size)
drop.y = 0;
}
},1000/60);
</script>
</body>
</html>
Make a bunch of independent objects that all get their own word and position and speed.
Then print them all and advance them by their speed.
Here's a clean example for you:
http://jsfiddle.net/U5eFJ/
The important code:
var code = ["<html>", "<p>", "<b>", "<strong>", "<head>", "<body>", "<a>", "<i>", "<div>", "<form>", "<ol>", "<li>", "<ul>", "<pre>", "<nav>", "<footer>", "<header>", "<article>", "<section>", "<em>", "<style>", "<title>", "<meta>", "<br>", "<table>"];
// make 90 things to fall with a random code element and random starting location
var things = [];
var THINGCOUNT = 90;
for (var i = 0; i < THINGCOUNT; i++) {
var a = {};
//randomly pick one tag
a.code = code[Math.round(Math.random() * code.length)];
a.x = Math.random()*500; //random X
a.y = Math.random()*500 -500; // random Y that is above the screen
a.speed = Math.random()*10;
things.push(a);
}
setInterval(function() {
ctx.clearRect(0,0,500,500);
for (var i = 0; i < THINGCOUNT; i++) {
var a = things[i];
ctx.fillText(a.code, a.x, a.y);
a.y += a.speed; // fall downwards by the speed amount
if (a.y > 600) a.y = -50; // if off the screen at bottom put back to top
}
}, 90);
If you are running a windows computer you can make the java script open a .bat file that just says this.
`#echo off
mode 1000
#color a
:A
echo %random%%random%%random%%random%%random%%random%%random%%random%%random%%random%%random%%random%%random%%random%%random%%random%%random%%random%%random%
goto A'
This may not be what you want but I hope it helps =)
`