On a button click I call a script to get the canvas Image. I take the location. I need to pass this image source into another jsp file where I need to display this image.
Can you please help me out in this.
<%# page contentType="text/html;charset=UTF-8" %>
<html>
<head>
<script>
function draw() {
var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");
ctx.fillStyle = "black";
ctx.beginPath();
var x;
var y;
canvas.onmousedown = function(e) {
x = e.clientX;
y = e.clientY;
ctx.moveTo(x, y);
}
canvas.onmouseup = function(e) {
x = null;
y = null;
}
canvas.onmousemove = function(e) {
if (x == null || y == null) {
return;
}
x = e.clientX;
y = e.clientY;
x -= canvas.offsetLeft;
y -= canvas.offsetTop;
ctx.lineTo(x, y);
ctx.stroke();
ctx.moveTo(x, y);
}
};
function to_image(){
var canvas = document.getElementById("canvas");
document.getElementById("theimage").src = canvas.toDataURL();
}
function clear_image(){
var canvas = document.getElementById('canvas');
var context = canvas.getContext('2d');
context.fillStyle = '#ffffff';
context.clearRect(0, 0, canvas.width, canvas.height);
canvas.width = canvas.width;
}
</script>
</head>
<body onload="draw();">
<canvas id="canvas" width="300" height="300"
style="border: 1px solid black;"></canvas>
<div><button onclick="to_image()">Draw to Image</button></div>
<div><button onclick="clear_image()">Clear</button></div>
<image id="theimage"></image>
</body>
</html>
I need to pass the value of document.getElementById("theimage").src into another jsp and access that value to dispaly the image.
Can anybody help me out in this.
If you meant you will load that second page with image on a button click from the first page(for which you have pasted code)then just update the code as:
{
var canvas = document.getElementById("canvas");
var dataUrl = canvas.toDataURL();
//-- Following code can be placed wherever you want to call another page.
window.location = "urlToSecondJSPPage.jsp?imgUrl="+dataUrl;
}
And then imgUrl(url parameter) can be accessed from second page.
Related
I have an ASP.NET application that allows users to click or tap on a Canvas to indicate pain locations on a body image. A body image is displayed on the Canvas and is the same size as the Canvas.
function drawBodyMap() {
var c = document.getElementById('myCanvas');
var ctx = c.getContext('2d');
var imageObj = new Image();
imageObj.src = 'https://.../body.jpg';
imageObj.onload = function () {
ctx.drawImage(imageObj, 0, 0, 600, 367);
};
}
<canvas id="myCanvas" width="600" height="367"></canvas>
<script>
function getMousePos(canvas, evt) {
var rect = canvas.getBoundingClientRect();
return {
x: evt.clientX - rect.left,
y: evt.clientY - rect.top
};
}
var canvas = document.getElementById('myCanvas');
var ctx = canvas.getContext('2d');
canvas.addEventListener('mouseup', function (evt) {
if (ixPos > 9)
return;
var mousePos = getMousePos(canvas, evt);
bodyX[ixPos] = mousePos.x;
bodyY[ixPos] = mousePos.y;
painType[ixPos] = pain_type;
ixPos++;
ctx.beginPath();
ctx.arc(mousePos.x, mousePos.y, 8, 0, 2 * Math.PI);
if (pain_type == 1)
ctx.fillStyle = "#DC143C";
else if (pain_type == 2)
ctx.fillStyle = "#EA728A";
else if (pain_type == 3)
ctx.fillStyle = "#DAA520";
else if (pain_type == 4)
ctx.fillStyle = "#008000";
else if (pain_type == 5)
ctx.fillStyle = "#4169E1";
ctx.fill();
}, false);
</script>
The X,Y points added to the Canvas on the body image are saved to a database. These points are then loaded into a WPF application that displays the same body image on an XAML Canvas. C# code then adds the points over the image.
WPF CODE:
private void DisplayBodyPain()
{
List<BodyPain> pain = gFunc.sws.GetBodyPain(MemberID);
foreach (BodyPain bp in pain)
{
Border b = new Border();
b.Tag = bp.PainType.ToString();
b.Cursor = Cursors.Hand;
b.Width = 16;
b.Height = 16;
b.CornerRadius = new CornerRadius(8);
b.Background = GetPainBrush((byte)bp.PainType);
cvsBody.Children.Add(b);
Canvas.SetTop(b, bp.YPos);
Canvas.SetLeft(b, bp.XPos);
}
}
The problem I have is that the points drawn on the XAML Canvas are all slightly different from the points that were drawn on the HTML Canvas. Each point is not in exactly the same location.
Is there a way I can fix this? Should I be doing it differently?
HTML Canvas
WPF Canvas
I think you need to subtract the size of the marker from the coordinate where you want to place it. For the last two lines, try this instead:
Canvas.SetTop(b, bp.YPos - (b.Height / 2));
Canvas.SetLeft(b, bp.XPos - (b.Width / 2));
By subtracting half the marker's height and width, the center of the marker is placed on the desired coordinates.
I want to drag & drop text above image. For that I am using canvas. I am using this code
<img id="scream" src="http://127.0.0.1/demo/images.jpg" alt="The Scream" style="display:none;" width="220" height="277"><p>Canvas:</p>
<canvas id="canvas" width="300" height="300" style="border:1px solid #d3d3d3;">
Your browser does not support the HTML5 canvas tag.</canvas>
var c=document.getElementById("canvas");
var ctx1=c.getContext("2d");
var img=document.getElementById("scream");
ctx1.drawImage(img,10,10);
var canvas;
var ctx;
var x = 75;
var y = 50;
var dx = 5;
var dy = 3;
var WIDTH = 400;
var HEIGHT = 300;
var dragok = false,
text = "Hey there im moving!",
textLength = (text.length * 14)/2;
function rect(x,y,w,h) {
ctx.font = "14px Arial";
ctx.strokeText("Hey there im a moving!!", x, y);
}
function clear() {
ctx.clearRect(0, 0, WIDTH, HEIGHT);
}
function init() {
canvas = document.getElementById("canvas");
ctx = canvas.getContext("2d");
return setInterval(draw, 10);
}
function draw() {
clear();
ctx.fillStyle = "#FAF7F8";
ctx.fillStyle = "#444444";
rect(x - 15, y + 15, textLength, 30);
}
function myMove(e){
if (dragok){
x = e.pageX - canvas.offsetLeft;
y = e.pageY - canvas.offsetTop;
}
}
function myDown(e){
if (e.pageX < x + textLength + canvas.offsetLeft && e.pageX > x - textLength + canvas.offsetLeft && e.pageY < y + 15 + canvas.offsetTop &&
e.pageY > y -15 + 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;
I either able to show image or drag & drop text but I want both, please help me where I am wrong. You can check here:- http://jsfiddle.net/FWdSv/11/
When you're clearing the canvas, you're also clearing your image.
So the easy fix is to redraw the image in your draw function:
function draw() {
clear();
ctx.drawImage(img,0,0);
ctx.fillStyle = "#FAF7F8";
ctx.fillStyle = "#444444";
rect(x - 15, y + 15, textLength, 30);
}
Alternatively:
You could display your image underneath your canvas so it's not affected when you clear the canvas.
actually I'm new in html5 and tring to do something using canvas , the function that i create is drawing a short ray length start from point and end in point , the problem is when I duplicate the function to run twice in the same time it doesn't work correctly , where is the problem in my code ?
first I create the canvas
<canvas id="mycanvas" width="1120" height="700" style="margin:auto;border:1px solid #000000;position:relative;z-index: 10;">
</canvas>
Then i create call a function twice
var path1Number=0;
window.addEventListener('load', function () {
var x = 185, y = 185;
direction1(x,y , path1Number);
direction1(x+91,y+91 , path1Number);
}, false);
then i create a function that draw a path start from point to point
function direction1(x,y , path1Number){
//draw canvas line
var canvas1 = document.getElementById('mycanvas');
var context = canvas1.getContext('2d');
var x2 = x;
var y2 = y;
var ini_x = x;
var ini_y = y;
var done = false;
var interval = setInterval(function() {
context.clearRect(0, 0, canvas1.width, canvas1.height);
context.beginPath();
context.moveTo(x, y);
if(x2<x+20 && !done){
context.lineTo(x2, y2);
context.closePath();
context.strokeStyle = 'red';
context.stroke();
x2+=1;
y2+=1;
}else{
done = true;
x+=1;
y+=1;
if(x2 >= ini_x + 91){
if(x2 == x){
clearInterval(interval);
context.closePath();
context.clearRect(0, 0, canvas1.width, canvas1.height);
path1Number+=1;
path1(x,y,path1Number);
}
}else{
x2+=1;
y2+=1;
}
context.lineTo(x2, y2);
context.closePath();
context.strokeStyle = 'red';
context.stroke();
}
},10);
}
the problem happened when i call this function twice it doesn't work correctly so what is the reason ? Thanks .
Hello all can we place drag and drop functionality inside canvas using html5??
My actual requirement is to drag the image into textbox that should be done inside the canvas...
please share your ideas..The following link i used to learn drag and drop but it should be done inside the canvas..
http://www.w3schools.com/html5/tryit.asp?filename=tryhtml5_draganddrop
You can learn more in this tutorial: http://html5.litten.com/how-to-drag-and-drop-on-an-html5-canvas/
From your limited description in your question, it sounds like you drag items over the canvas and this tutorial is likely the best match.
This is the actual code you can paste into file and open in HTML5 compliant browser and it will work:
<!doctype html>
<html>
<head>
<meta charset="UTF-8" />
<title>Canvas Drag and Drop Test</title>
</head>
<body>
<section>
<div>
<canvas id="canvas" width="400" height="300">
This text is displayed if your browser does not support HTML5 Canvas.
</canvas>
</div>
<script type="text/javascript">
var canvas;
var ctx;
var x = 75;
var y = 50;
var WIDTH = 400;
var HEIGHT = 300;
var dragok = false;
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, 10);
}
function draw() {
clear();
ctx.fillStyle = "#FAF7F8";
rect(0,0,WIDTH,HEIGHT);
ctx.fillStyle = "#444444";
rect(x - 15, y - 15, 30, 30);
}
function myMove(e){
if (dragok){
x = e.pageX - canvas.offsetLeft;
y = e.pageY - canvas.offsetTop;
}
}
function myDown(e){
if (e.pageX < x + 15 + canvas.offsetLeft && e.pageX > x - 15 +
canvas.offsetLeft && e.pageY < y + 15 + canvas.offsetTop &&
e.pageY > y -15 + 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;
</script>
</section>
</body>
</html>
I am trying to move an image from the right to the center and I am not sure if this is the best way.
var imgTag = null;
var x = 0;
var y = 0;
var id;
function doCanvas()
{
var canvas = document.getElementById('icanvas');
var ctx = canvas.getContext("2d");
var imgBkg = document.getElementById('imgBkg');
imgTag = document.getElementById('imgTag');
ctx.drawImage(imgBkg, 0, 0);
x = canvas.width;
y = 40;
id = setInterval(moveImg, 0.25);
}
function moveImg()
{
if(x <= 250)
clearInterval(id);
var canvas = document.getElementById('icanvas');
var ctx = canvas.getContext("2d");
ctx.clearRect(0, 0, canvas.width, canvas.height);
var imgBkg = document.getElementById('imgBkg');
ctx.drawImage(imgBkg, 0, 0);
ctx.drawImage(imgTag, x, y);
x = x - 1;
}
Any advice?
This question is 5 years old, but since we now have requestAnimationFrame() method, here's an approach for that using vanilla JavaScript:
var imgTag = new Image(),
canvas = document.getElementById('icanvas'),
ctx = canvas.getContext("2d"),
x = canvas.width,
y = 0;
imgTag.onload = animate;
imgTag.src = "http://i.stack.imgur.com/Rk0DW.png"; // load image
function animate() {
ctx.clearRect(0, 0, canvas.width, canvas.height); // clear canvas
ctx.drawImage(imgTag, x, y); // draw image at current position
x -= 4;
if (x > 250) requestAnimationFrame(animate) // loop
}
<canvas id="icanvas" width=640 height=180></canvas>
drawImage() enables to define which part of the source image to draw on target canvas. I would suggest for each moveImg() calculate the previous image position, overwrite the previous image with that part of imgBkg, then draw the new image. Supposedly this will save some computing power.
Here's my answer.
var canvas = document.getElementById("canvas");
ctx = canvas.getContext("2d");
var myImg = new Image();
var myImgPos = {
x: 250,
y: 125,
width: 50,
height: 25
}
function draw() {
myImg.onload = function() {
ctx.drawImage(myImg, myImgPos.x, myImgPos.y, myImgPos.width, myImgPos.height);
}
myImg.src = "https://mario.wiki.gallery/images/thumb/c/cc/NSMBUD_Mariojump.png/1200px-NSMBUD_Mariojump.png";
}
function moveMyImg() {
ctx.clearRect(myImgPos.x, myImgPos.y, myImgPos.x + myImgPos.width, myImgPos.y +
myImgPos.height);
myImgPos.x -= 5;
}
setInterval(draw, 50);
setInterval(moveMyImg, 50);
<canvas id="canvas" class="canvas" width="250" height="150"></canvas>
For lag free animations,i generally use kinetic.js.
var stage = new Kinetic.Stage({
container: 'container',
width: 578,
height: 200
});
var layer = new Kinetic.Layer();
var hexagon = new Kinetic.RegularPolygon({
x: stage.width()/2,
y: stage.height()/2,
sides: 6,
radius: 70,
fill: 'red',
stroke: 'black',
strokeWidth: 4
});
layer.add(hexagon);
stage.add(layer);
var amplitude = 150;
var period = 2000;
// in ms
var centerX = stage.width()/2;
var anim = new Kinetic.Animation(function(frame) {
hexagon.setX(amplitude * Math.sin(frame.time * 2 * Math.PI / period) + centerX);
}, layer);
anim.start();
Here's the example,if you wanna take a look.
http://www.html5canvastutorials.com/kineticjs/html5-canvas-kineticjs-animate-position-tutorial/
Why i suggest this is because,setInterval or setTimeout a particular function causes issues when large amount of simultaneous animations take place,but kinetic.Animation deals with framerates more intelligently.
Explaining window.requestAnimationFrame() with an example
In the following snippet I'm using an image for the piece that is going to be animated.
I'll be honest... window.requestAnimationFrame() wasn't easy for me to understand, that is why I coded it as clear and intuitive as possible. So that you may struggle less than I did to get my head around it.
const
canvas = document.getElementById('root'),
btn = document.getElementById('btn'),
ctx = canvas.getContext('2d'),
brickImage = new Image(),
piece = {image: brickImage, x:400, y:70, width:70};
brickImage.src = "https://i.stack.imgur.com/YreH6.png";
// When btn is clicked execute start()
btn.addEventListener('click', start)
function start(){
btn.value = 'animation started'
// Start gameLoop()
brickImage.onload = window.requestAnimationFrame(gameLoop)
}
function gameLoop(){
// Clear canvas
ctx.clearRect(0, 0, canvas.width, canvas.height)
// Draw at coordinates x and y
ctx.drawImage(piece.image, piece.x, piece.y)
let pieceLeftSidePos = piece.x;
let middlePos = canvas.width/2 - piece.width/2;
// Brick stops when it gets to the middle of the canvas
if(pieceLeftSidePos > middlePos) piece.x -= 2;
window.requestAnimationFrame(gameLoop) // Needed to keep looping
}
<input id="btn" type="button" value="start" />
<p>
<canvas id="root" width="400" style="border:1px solid grey">
A key point
Inside the start() function we have:
brickImage.onload = window.requestAnimationFrame(gameLoop);
This could also be written like: window.requestAnimationFrame(gameLoop);
and it would probably work, but I'm adding the brickImage.onload to make sure that the image has loaded first. If not it could cause some issues.
Note: window.requestAnimationFrame() usually loops at 60 times per second.