Creating a new object on mouseclick as a way for users to create reference points (which I call 'crumbs') when reading large web documents. I've got this working with a new Image() function, however, that won't let me assign a tabindex to each new image created by mouseclick (posX, posY). 'crumbtoggle' simply acknowledges that the crumb dropping tool has been selected.
working new Image() function:
function draw_crumb()
{
var b_canvas = document.getElementById("b");
var b_context = b_canvas.getContext("2d");
var crumb = new Image();
crumb.src = "crumb.gif";
if(crumbtoggle.className == "on")
{
b_context.drawImage(crumb, posX-20, posY-20, 50, 75);
}
}
non-working new Object () function:
function draw_crumb()
{
var b_canvas = document.getElementById("b");
var b_context = b_canvas.getContext("2d");
var crumb = new Object();
crumb.type = "button";
crumb.src = "crumb.gif";
crumb.tabindex = 1;
if(crumbtoggle.className == "on")
{
b_context.drawObject(crumb, posX-20, posY-20, 50, 75);
}
}
I've looked in to applying focus to the new Image objects, but that doesn't seem to be a good alternative to tabindex attributes. Any ideas would be greatly appreciated.
An HTML5 Canvas is like a real-world canvas with instantly-drying paint. When you paint a rectangle or line or image on the canvas, it becomes part of the canvas. You cannot later re-order the items, or move them relative to each other. It is not a separate entity that can get focus.
Any sort of focus management integrated with the browser's handling of focus will have to be done through form inputs or anchors recognized by the browser.
It's not clear to me why you need a canvas, or if you need one at all.
Related
I'm trying to learn about JavaScript and the html5 canvas, however, it's proving a little confusing and I don't understand why it doesn't seem to work...
I am working on creating a simple map that has some of the capabilities of google maps(drag and drop/zoom in/out/etc). In order to do this, I chose html5 canvas and easeljs for the drag and drop functions.
I have a javascript file (path.js) which contains 2 functions:
pathConstructor() - example function from the easeljs tutorial
drawMap() - copy of the first function slightly modified (and probably wrong right now)
Everything worked fine when I called pathConstructor() from the canvas, however, after I replaced it with drawMap(), everything stopped working. It won't even work if I replace drawMap() with pathContrcutor() right now.
I put some alerts before and after calling the function from the canvas and inside pathConstructor(). The before alert goes off but the others don't so for some reason the function never gets called...
If I use the pathConstructor code as inline code in the canvas then it works just fine, however, I would like to avoid that since I believe it's bad programming. I want it to be neat and each script to have its own file.
Anyone know why this is happening?
HTML
<!Doctype html>
<html>
<head>
<script src="http://code.createjs.com/easeljs-0.7.0.min.js"></script>
<script src="path.js" type="text/javascript"></script>
</head>
<body>
<canvas id="canvas" width="1300px" height="800px"style="border:1px dotted black;">
<script>pathConstructor();</script>
</canvas>
</body>
</html>
Javascript
var stage;
function pathConstructor() {
alert('inside pathConstructor');
stage = new createjs.Stage('canvas');
// this lets our drag continue to track the mouse even when it leaves the canvas:
// play with commenting this out to see the difference.
stage.mouseMoveOutside = true;
var circle = new createjs.Shape();
circle.graphics.beginFill("red").drawCircle(0, 0, 50);
var label = new createjs.Text("drag me", "bold 14px Arial", "#FFFFFF");
label.textAlign = "center";
label.y = -7;
var dragger = new createjs.Container();
dragger.x = dragger.y = 100;
dragger.addChild(circle, label);
stage.addChild(dragger);
dragger.on("pressmove", function(evt) {
// currentTarget will be the container that the event listener was added to:
evt.currentTarget.x = evt.stageX;
evt.currentTarget.y = evt.stageY;
// make sure to redraw the stage to show the change:
stage.update();
});
stage.update();
}
function drawMap() {
stage = new createjs.Stage('canvas');
var bitMap = new createjs.Bitmap('middle-earth-map.jpg');
stage.mouseMoveOutside = true;
var dragger = new createjs.Container();
dragger.x = dragger.y = 0;
dragger.addChild(bitMap);
stage.addChild(dragger);
dragger.on('pressmove', function(evt2)) {
evt2.currentTarget.x = evt2.stageX;
evt2.currentTarget.y = evt2.stageY;
stage.update();
});
stage.update();
}
For me it's working fine, you just have to remove that extra ")" in dragger.on('pressmove', function(evt2)) {;
dragger.on('pressmove', function(evt2)) {
evt2.currentTarget.x = evt2.stageX;
evt2.currentTarget.y = evt2.stageY;
stage.update();
});
I'm having an issue while using canvas in a background page to create data URLs for desktop notifications' images.
I want to use the "image" notifications which require a 3:2 ratio to display properly. The images I want to use (from hulu.com) are a different ratio, so I decided to use the canvas element to create the corresponding data URL off of these images so that the ratio is correct. It kind of works in theory, but…
…I'm having issues if I'm creating more than one canvas/notification in the background page. One image is created properly, but the rest comes out empty.
Confusingly, opening the same background page in a new tab (i.e. exact same code) makes everything works just fine: all the notifications are created with the images loaded from hulu.com. Also, just changing the dimensions from 360x240 to 300x200 makes it work. Finally, though they're similar computers with the same Chrome version (34.0.1847.116), it works without modification at work while it doesn't on my own laptop.
I made a test extension available at the bottom of this post. Basically, it only has a generated background page. The code for that page is this:
var images = ["http://ib2.huluim.com/video/60376901?size=290x160&img=1",
"http://ib2.huluim.com/video/60366793?size=290x160&img=1",
"http://ib4.huluim.com/video/60372951?size=290x160&img=1",
"http://ib1.huluim.com/video/60365336?size=290x160&img=1",
"http://ib3.huluim.com/video/60376290?size=290x160&img=1",
"http://ib4.huluim.com/video/60377231?size=290x160&img=1",
"http://ib4.huluim.com/video/60312203?size=290x160&img=1",
"http://ib1.huluim.com/video/60376972?size=290x160&img=1",
"http://ib4.huluim.com/video/60376971?size=290x160&img=1",
"http://ib1.huluim.com/video/60376616?size=290x160&img=1"];
for (var i = 0; i < 10; i++) {
getDataURL(i);
}
/*
* Gets the data URL for an image URL
*/
function getDataURL(i) {
var img = new Image();
img.onload = function() {
var canvas = document.createElement('canvas');
canvas.width = 360;
canvas.height = 240;
var ctx = canvas.getContext('2d');
ctx.drawImage(this, 0, 0);
ctx.fillStyle = "rgb(200,0,0)";
ctx.fillRect (10, 10, 55, 50);
var dataURL = canvas.toDataURL('image/png');
chrome.notifications.create('', {
type: 'image',
iconUrl: 'logo_128x128.png',
title: String(i),
message: 'message',
imageUrl: dataURL
}, function(id) {});
}
//img.src = chrome.extension.getURL('logo_128x128.png');;
img.src = images[i];
}
The commented out line for img.src = ... is a test where it loads a local file instead of a remote one. In that case, all the images are created.
The red rectangle added to the canvas is to show that it's not just the remote image that is an issue: the whole resulting canvas is empty, without any red rectangle.
If you download and add the test extension below, you should get 10 notifications but only one with an image.
Then, to open the background page in a new tab, you can inspect the background page, type this in the console:
chrome.extension.getURL('_generated_background_page.html')
and right-click the URL, and click "Open in a new Tab" (or window). Once open you should get 10 notifications that look fine.
Any idea of what is going on? I haven't been able to find any kind of limitations for background pages relevant to that. Any help would be appreciated, because this has been driving me crazy!
Files available here: https://www.dropbox.com/s/ejbh6wq0qixb7a8/canvastest.zip
edit: based on #GameAlchemist's comment, I also tried the following: same getDataURL method, but the loop wrapped inside an onload for the logo:
function loop() {
for (var i = 0; i < 10; i++) {
getDataURL(i);
}
}
var logo = new Image();
logo.onload = function () {
loop();
}
logo.src = chrome.extension.getURL('logo_128x128.png');
Remember that the create() method is asynchronous and you should use a callback with. The callback can invoke next image fetching.
I would suggest doing this in two steps:
Load all the images first
Process the image queue
The reason is that you can utilize the asynchronous image loading better this way instead of chaining the callbacks which would force you to load one and one image.
For example:
Image loader
var urls = ["http://ib2.huluim.com/video/60376901?size=290x160&img=1",
"http://ib2.huluim.com/video/60366793?size=290x160&img=1",
"http://ib4.huluim.com/video/60372951?size=290x160&img=1",
"http://ib1.huluim.com/video/60365336?size=290x160&img=1",
"http://ib3.huluim.com/video/60376290?size=290x160&img=1",
"http://ib4.huluim.com/video/60377231?size=290x160&img=1",
"http://ib4.huluim.com/video/60312203?size=290x160&img=1",
"http://ib1.huluim.com/video/60376972?size=290x160&img=1",
"http://ib4.huluim.com/video/60376971?size=290x160&img=1",
"http://ib1.huluim.com/video/60376616?size=290x160&img=1"];
var images = [], // store image objects
count = urls.length; // for loader
for (var i = 0; i < urls.length; i++) {
var img = new Image; // create image
img.onload = loader; // share loader handler
img.src = urls[i]; // start loading
images.push(img); // push image object in array
}
function loader() {
count--;
if (count === 0) process(); // all loaded, start processing
}
//TODO need error handling here as well
Fiddle with concept code for loader
Processing
Now the processing can be isolated from the loading:
function process() {
// share a single canvas (use clearRect() later if needed)
var canvas = document.createElement('canvas'),
ctx = canvas.getContext('2d'),
current = 0;
canvas.width = 360;
canvas.height = 240;
createImage(); // invoke processing for first image
function createImage() {
ctx.drawImage(images[current], 0, 0); // draw current image
ctx.fillStyle = "rgb(200,0,0)";
ctx.fillRect (10, 10, 55, 50);
chrome.notifications.create('', {
type : 'image',
iconUrl : 'logo_128x128.png',
title : String(i),
message : 'message',
imageUrl: canvas.toDataURL() // png is default
},
function(id) { // use callback
current++; // next in queue
if (current < images.length) {
createImage(); // call again if more images
}
else {
done(); // we're done -> continue to done()
}
});
}
}
Disclaimer: I don't have a test environment to test Chrome extensions so typos/errors may be present.
Hope this helps!
I've got multiple images, and I'd like to load them each into a single <canvas> element at different points in time and then manipulate them using CamanJS. I can get the first image to appear like this:
Caman('#canvas-element', '/images/one.jpg');
But then when I subsequently try to update that same element using the following code, it does not work.
Caman('#canvas-element', '/images/two.jpg');
Is there some way to reset/clear/flush the canvas and load new image data into it, or do I really need to create separate <canvas> elements for each image I want to load? I'd prefer a single element because I don't want to eat up all the memory.
Remove the Caman attribute (data-caman-id) from the IMG or CANVAS element, change the image, and then re-render Caman.
document
.querySelector('#view_image')
.removeAttribute('data-caman-id');
const switch_img = '/to/dir/img.png';
Caman("#view_image", switch_img, function() {
this.render();
});
Hope followed code can help others who have same require.
function loadImage(source) {
var canvas = document.getElementById('image_id');
var context = canvas.getContext('2d');
var image = new Image();
image.onload = function() {
context.drawImage(image, 0, 0, 960, 600);
};
image.src = source;
}
function change_image(source) {
loadImage(source);
Caman('#image_id', source, function () {
this.reloadCanvasData();
this.exposure(-10);
this.brightness(5);
this.render();
});
}
Just figured this one out with a lot of trial and error and then a duh moment!
Instead of creating my canvas directly in my html, I created a container and then just did the following:
var retStr = "<canvas id=\"" + myName + "Canvas\"></canvas>";
document.getElementById('photoFilterCanvasContainer').innerHTML = retStr;
Caman("#" + myName + "Canvas", myUrl, function() {
this.render();
});
You want the canvas id to be unique each time you access the Caman function with a new image.
I have the following code in the index.html page of my site, which when the page loads, draws a number of images to the HTML5 canvas:
window.onload = function(){
var sources = {};
sources[0] = document.getElementById("building").src,
sources[1] = document.getElementById("chair").src,
sources[2] = document.getElementById("drink").src,
sources[3] = document.getElementById("food").src,
sources[4] = document.getElementById("fridge").src,
sources[5] = document.getElementById("land").src,
sources[6] = document.getElementById("money").src,
sources[7] = document.getElementById("oven").src,
sources[8] = document.getElementById("table").src,
sources[9] = document.getElementById("van").src,
sources[10] = document.getElementById("burger").src,
sources[11] = document.getElementById("chips").src,
sources[12] = document.getElementById("drink").src,
sources[13] = document.getElementById("franchiseFee").src,
sources[14] = document.getElementById("wages").src,
sources[15] = document.getElementById("admin").src,
sources[16] = document.getElementById("cleaners").src,
sources[17] = document.getElementById("electricity").src,
sources[18] = document.getElementById("insurance").src,
sources[19] = document.getElementById("manager").src,
sources[20] = document.getElementById("rates").src,
sources[21] = document.getElementById("training").src,
sources[22] = document.getElementById("water").src,
sources[23] = document.getElementById("burger").src,
sources[24] = document.getElementById("chips").src,
sources[25] = document.getElementById("drink").src,
sources[26] = document.getElementById("creditors").src,
sources[27] = document.getElementById("electricity").src,
sources[28] = document.getElementById("food").src,
sources[29] = document.getElementById("hirePurchase").src,
sources[30] = document.getElementById("loan").src,
sources[31] = document.getElementById("overdraft").src,
sources[32] = document.getElementById("payeTax").src,
sources[33] = document.getElementById("tax").src
loadImages(sources, drawImage);
};
Sources is the array that I'm using to hold the images in JavaScript so that they can be drawn to the canvas once they've been loaded from a hidden section in my HTML.
This function currently works exactly as it's intended- it has a call to the loadImages function, which loads the images from a hidden section in the HTML into the JavaScript array, and calls the drawImage function on each of the images in the array.
But I also have another function that I want to be called with the window.onload:
The function I want to add to window.onload is this:
function drawGameElements(){
/* Draw a line for the 'score bar'. */
context.moveTo(0, 25);
context.lineTo(1000, 25);
context.stroke();
/* Draw current level/ total levels on the left, and current score on the right. */
context.font = "11pt Calibri"; /* Text font & size */
context.strokeStyle = "black"; /* Font colour */
context.strokeText(currentLevel + "/" + totalLevels, 10, 15);
context.strokeText(currentScore, 950, 15);
}
I tried adding a call to the function just below the loadImages(sources, drawImage); line in window.onload = function(){};
So that I now have:
window.onload = function(){
...
loadImages(sources, drawImage);
drawGameElements();
};
Although this partially works, in that it draws the line across the top of the canvas for the 'score bar' and writes "1/3" for the levels on the left hand side of the canvas just above the line, for some reason it doesn't draw the current score on the right hand side.
Also, as soon as I click on one of the images that's been drawn to the canvas, to drag and drop it around the canvas, the 'score bar' then disappears from the canvas completely.
Does anyone know why this is? How can I get the score bar to remain visible throughout the duration of the game, no matter what else happens on the canvas? Also, how can I get the currentScore variable to be displayed?
I would instead use a callback inside of loadImages to call drawGameElements. That way drawGameElements only runs after loadImages is finished. It sounds like you've created a race condition with your two functions.
If I where you, I would create the score bar outside of the canvas. Set its position to absolute and let it hover above the canvas at the desired location. That way you can just access it as HTML elements and do not need to worry about redrawing.
The major advantage of using HTML elements for these displays is that you don't need to redraw them, for example after moving the images around on the canvas. You also don't have to worry about how to refresh the values (on a canvas, just painting new values over the old ones will not be enough). This way you can just store the values in HTML elements and go wild on the canvas, knowing the score will always stay on top.
I'm trying to build a transform manager for KineticJS that would build a bounding box and allow users to scale, move, and rotate an image on their canvas. I'm getting tripped up with the logic for the anchor points.
http://jsfiddle.net/mharrisn/whK2M/
I just want to allow a user to scale their image proportionally from any corner, and also rotate as the hold-drag an anchor point.
Can anyone help point me in the right direction?
Thank you!
Here is a proof of concept of a rotational control I've made:
http://codepen.io/ArtemGr/pen/ociAD
While the control is dragged around, the dragBoundFunc is used to rotate the content alongside it:
controlGroup.setDragBoundFunc (function (pos) {
var groupPos = group.getPosition()
var rotation = degrees (angle (groupPos.x, groupPos.y, pos.x, pos.y))
status.setText ('x: ' + pos.x + '; y: ' + pos.y + '; rotation: ' + rotation); layer.draw()
group.setRotationDeg (rotation); layer.draw()
return pos
})
I am doing the same thing, and I've posted a question which is allmoast the same, but I found a link where you have the resize and move tool ready developed. So I have used the same. It does not contain the rotate tool however, but this can be a good start for you too, it is very simple and logical. Here is the link: http://www.html5canvastutorials.com/labs/html5-canvas-drag-and-drop-resize-and-invert-images/
I will come back with the rotation tool as well if I manage to get it working perfectly.
I hope I am not late yet for posting this code snippet that I made. I had the same problem with you guys dealing with this kind of task. Its been 3 days since I tried so many workarounds to mimic the fabricjs framework capability when dealing with images and objects. I could use Fabricjs though but it seems that Kineticjs is more faster/consistent to deal with html5.
Luckily, we already have existing plugin/tool that we could easily implement together with kineticjs and this is jQuery Transform tool. SUPER THANKS TO THE AUTHOR OF THIS! Just search this on google and download it.
I hope the code below that I created would help lots of developers out there who is pulling their hair off to solve this kind of assignment.
$(function() {
//Declare components STAGE, LAYER and TEXT
var _stage = null;
var _layer = null;
var simpleText = null;
_stage = new Kinetic.Stage({
container: 'canvas',
width: 640,
height: 480
});
_layer = new Kinetic.Layer();
simpleText = new Kinetic.Text({
x: 60,
y: 55,
text: 'Simple Text',
fontSize: 30,
fontFamily: 'Calbiri',
draggable: false,
name:'objectInCanvas',
id:'objectCanvas',
fill: 'green'
});
//ADD LAYER AND TEXT ON STAGE
_layer.add(simpleText);
_stage.add(_layer);
_stage.draw();
//Add onclick event listener to the Stage to remove and add transform tool to the object
_stage.on('click', function(evt) {
//Remove all objects' transform tool inside the stage
removeTransformToolSelection();
// get the shape that was clicked on
ishape = evt.targetNode;
//Add and show again the transform tool to the selected object and update the stage layer
$(ishape).transformTool('show');
ishape.getParent().moveToTop();
_layer.draw();
});
function removeTransformToolSelection(){
//Search all objects inside the stage or layer who has the name of "objectInCanvas" using jQuery iterator and hide the transform tool.
$.each(_stage.find('.objectInCanvas'), function( i, child ) {
$(child).transformTool('hide');
});
}
//Event listener/Callback when selecting image using file upload element
function handleFileSelect(evt) {
//Remove all objects' transform tool inside the stage
removeTransformToolSelection();
//Create image object for selected file
var imageObj = new Image();
imageObj.onload = function() {
var myImage = new Kinetic.Image({
x: 0,
y: 0,
image: imageObj,
name:'objectInCanvas',
draggable:false,
id:'id_'
});
//Add to layer and add transform tool
_layer.add(myImage);
$(myImage).transformTool();
_layer.draw();
}
//Adding source to Image object.
var f = document.getElementById('files').files[0];
var name = f.name;
var url = window.URL;
var src = url.createObjectURL(f);
imageObj.src = src;
}
//Attach event listener to FILE element
document.getElementById('files').addEventListener('change', handleFileSelect, false);
});