Develop Reference

Fabricjs canvas reset after zooming

I have a fabricjs canvas that I need to be able to zoom in and out and also change the image/object inside several times.
For this I setup the canvas in the first time the page loads like this:
fabric.Object.prototype.hasBorders = false;
fabric.Object.prototype.hasControls = false;
canvas = new fabric.Canvas('my_canvas', {renderOnAddRemove: false, stateful: false});
canvas.defaultCursor = "pointer";
canvas.backgroundImageStretch = false;
canvas.selection = false;
canvas.clear();
var image = document.getElementById('my_image');
if (image != null) {
imageSrc = image.src;
if(imageSrc.length > 0){
fabric.Image.fromURL(imageSrc, function(img) {
img = scaleImage(canvas, img); //shrinks the image to fit the canvas
img.selectable = false;
canvas.centerObject(img);
canvas.setActiveObject(img);
canvas.add(img);
});
}
}
canvas.deactivateAll().renderAll();
Then when I need to change the image/object in the canvas or when the page reloads, I try to reset the canvas like this:
canvas.clear();
canvas.remove(canvas.getActiveObject());
var image = document.getElementById('my_image');
if (image != null) {
imageSrc = image.src;
if(imageSrc.length > 0){
fabric.Image.fromURL(imageSrc, function(img) {
img = scaleImage(canvas, img); //shrinks the image to fit the canvas
img.selectable = false;
canvas.centerObject(img);
canvas.setActiveObject(img);
canvas.add(img);
});
}
}
Not sure if it matters but the way I change the image is by changing the source in 'my_image' and reseting the canvas with the above method.
This works well until I use canvas.zoomToPoint, as per this thread, after this, the image/object starts changing position when I reset the zoom or click the canvas with the mouse while it is zoomed, seeming to jump at each change in the top left corner direction, eventually disappearing from view.
Reset Zoom:
canvas.setZoom(1);
resetCanvas(); //(above method)
How can I restore the image/object position?
I tried doing the initial setup instead of the reset and seamed to work visually but was in fact adding a new layer of upper canvas at each new setup so it is no good.
Is there a way to reset the canvas to original state without causing this behavior and still be able to zoom in/out correctly?

Although this question is very old, here is what I did using the current version of fabric.js 2.2.4:
canvas.setViewportTransform([1,0,0,1,0,0]);
For your information: zooming to a point is a recalculation of the viewport transformation. The upper matrix is this is the initial viewport transform matrix.

I eventually fixed the problems I was having.
To reset the zoom, instead of just setting the zoom to 1 with canvas.setZoom(1), I reapplied the canvas.zoomToPoint method to the same point but with zoom 1, to force the initial zoom but regarding the same point that was used to zoom in.
As for the problem of restoring the image position in canvas (after panning for instance) it is as simple as removing the image, centering it in the canvas and re-adding it to the canvas as was done when adding first time:
var img = canvas.getActiveObject();
canvas.remove(img);
canvas.centerObject(img);
canvas.setActiveObject(img);
canvas.add(img);
canvas.renderAll();

See below snippet - here I do the same - zooming together, but degrouping the objects in case somebody clicks on it.
The problem to get to original object properties can be solved, ungrouping the group and creating copies of them and reattaching - a bit annoying, but the only solution I found.
<script id="main">
// canvas and office background
var mainGroup;
var canvas = this.__canvas = new fabric.Canvas('c');
fabric.Object.prototype.transparentCorners = false;
fabric.Object.prototype.originX = fabric.Object.prototype.originY = 'center';
createOnjects(canvas);
// events - zoom
$(canvas.wrapperEl).on('mousewheel', function(e) {
var target = canvas.findTarget(e);
var delta = e.originalEvent.wheelDelta / 5000;
if (target) {
target.scaleX += delta;
target.scaleY += delta;
// constrain
if (target.scaleX < 0.1) {
target.scaleX = 0.1;
target.scaleY = 0.1;
}
// constrain
if (target.scaleX > 10) {
target.scaleX = 10;
target.scaleY = 10;
}
target.setCoords();
canvas.renderAll();
return false;
}
});
// mouse down
canvas.on('mouse:up', function(options) {
if (options.target) {
var thisTarget = options.target;
var mousePos = canvas.getPointer(options.e);
if (thisTarget.isType('group')) {
// unGroup
console.log(mousePos);
var clone = thisTarget._objects.slice(0);
thisTarget._restoreObjectsState();
for (var i = 0; i < thisTarget._objects.length; i++) {
var o = thisTarget._objects[i];
if (o._element.alt == "officeFloor")
continue;
else {
if (mousePos.x >= o.originalLeft - o.currentWidth / 2 && mousePos.x <= o.originalLeft + o.currentWidth / 2
&& mousePos.y >= o.originalTop - o.currentHeight / 2 && mousePos.y <= o.originalTop + o.currentHeight / 2)
console.log(o._element.alt);
}
}
// remove all objects and re-render
canvas.remove(thisTarget);
canvas.clear().renderAll();
var group = new fabric.Group();
for (var i = 0; i < clone.length; i++) {
group.addWithUpdate(clone[i]);
}
canvas.add(group);
canvas.renderAll();
}
}
});
// functions
function createOnjects(canvas) {
// ToDo: jQuery.parseJSON() for config file (or web service)
fabric.Image.fromURL('pics/OfficeFloor.jpg', function(img) {
var back = img.set({ left: 100, top: 100 });
back._element.alt = "officeFloor";
back.hasControls = false;
fabric.Image.fromURL('pics/me.png', function(img) {
var me = img.set({ left: -420, top: 275 });
me._element.alt = "me";
console.log(me);
var group = new fabric.Group([ back, me], { left: 700, top: 400, hasControls: false });
canvas.clear().renderAll();
canvas.add(group);
// remove all objects and re-render
});
});
}
</script>

How to create an eraser in EaselJS?

I am developing a canvas paint but I want to have an eraser there. So I use this lines to erase de content but when I click is clear the whole canvas.
//undo tool
var undo = new createjs.Bitmap(app.loader.getResult('undo'));
undo.name = 'undo';
undo.x = brush.x + 90;
undo.y = brush.y;
undo.addEventListener('click', this.undoHandler);
this.toolsContainer.addChild(undo);
//trash tool
var clear = new createjs.Bitmap(app.loader.getResult('clear'));
clear.name = 'clear';
clear.x = undo.x + 90;
clear.y = undo.y;
clear.addEventListener('click', this.clearHandler);
this.toolsContainer.addChild(clear);
undoHandler:function(){
if(tools.undoArray.length){
var lastItem = tools.undoArray.pop();
app.container.removeChild(lastItem);
var lastItem2 = tools.undoArray2.pop();
app.container.removeChild(lastItem2);
var lastItem3 = tools.undoArray3.pop();
app.container.removeChild(lastItem3);
app.stage.update();
}
},
clearHandler:function(){
app.container.removeAllChildren();
app.container.updateCache(clearhandler?"destination-out":"source-over");;
app.stage.update();
},
I trying to develop something like this erase
http://jsfiddle.net/lannymcnie/ZNYPD/
any idea?

well here http://jsfiddle.net/lannymcnie/ZNYPD/, the key is this:
wrapper.updateCache(erase?"destination-out":"source-over");
so...
var stage, wrapper,erase;
function init() {
var stage = new createjs.Stage("canvas");
createjs.Ticker.addEventListener("tick", stage);
// Add some text to draw on top of (also instructions)
stage.addChild(new createjs.Text("Click and Drag to Draw", "40px Arial", "#000000").set({x:200,y:200}));
// Set up the container. We use it to draw in, and also to get mouse events.
var wrapper = new createjs.Container();
wrapper.hitArea = new createjs.Shape(new createjs.Graphics().f("#000").dr(0,0,800,600));
wrapper.cache(0,0,800,600); // Cache it.
stage.addChild(wrapper);
// Create the shape to draw into
var drawing = new createjs.Shape();
wrapper.addChild(drawing);
var lastPoint = new createjs.Point();
wrapper.addEventListener("mousedown", function(event) {
// Store the position. We have to do this because we clear the graphics later.
lastPoint.x = event.stageX;
lastPoint.y = event.stageY;
erase = Math.floor(Math.random()*2);
wrapper.addEventListener("pressmove", function(event){
// Draw a round line from the last position to the current one.
drawing.graphics.ss(20, "round").s("#ff0000");
drawing.graphics.mt(lastPoint.x, lastPoint.y);
drawing.graphics.lt(event.stageX, event.stageY);
// Update the last position for next move.
lastPoint.x = event.stageX;
lastPoint.y = event.stageY;
// Draw onto the canvas, and then update the container cache.
wrapper.updateCache(erase==1?"destination-out":"source-over");
drawing.graphics.clear();
});
// Listen for mousemove
});
}
$(function(){
init();
})
the only difference is that the drawing is based on a random from 0 to 1 because in my example the erase gets these values from here erase = Math.floor(Math.random()*2);

I have achieved this by maintaining a array of mid points and using the globalCompositeOperation as destination-out and source-over to make a transparent eraser trail .
Following is the code that you need to use with a mouse move function
`var handleMouseMove = function (event) {
midPt = new createjs.Point(oldPt.x + stage.mouseX>>1, oldPt.y+stage.mouseY>>1);
if(curTool.type=="eraser"){
var tempcanvas = document.getElementById('drawcanvas');
var tempctx=tempcanvas.getContext("2d");
tempctx.beginPath();
tempctx.globalCompositeOperation = "destination-out";
tempctx.arc(midPt.x, midPt.y, 20, 0, Math.PI * 2, false);
tempctx.fill();
tempctx.closePath();
tempctx.globalCompositeOperation = "source-over";
drawingCanvas.graphics.clear();
// keep updating the array for points
arrMidPtx.push(midPt.x);
arrMidPty.push(midPt.y);
stage.addChild(drawingCanvas);
stage.update();
}
else if ( curTool.type=="pen"){
drawingCanvas.graphics.clear().setStrokeStyle(stroke, 'round', 'round').beginStroke(color).moveTo(midPt.x, midPt.y).curveTo(oldPt.x, oldPt.y, oldMidPt.x, oldMidPt.y);
arrMidPtx.push(midPt.x);
arrMidPty.push(midPt.y);
arrOldPtx.push(oldPt.x);
arrOldPty.push(oldPt.y);
arrOldMidPtx.push(oldMidPt.x);
arrOldMidPty.push(oldMidPt.y);
oldPt.x = stage.mouseX;
oldPt.y = stage.mouseY;
oldMidPt.x = midPt.x;
oldMidPt.y = midPt.y;
stage.addChild(drawingCanvas);
stage.update();
}
};`

Resize a draggable fill with EaselJS

I've got a project where I'm using EaselJS to create a fill (rectangle) and text over it inside a container. My objective is to make this rectangle and text draggable to move it over the canvas. This is already done and working well.
My problem is when I try to resize the rectangle using scaleX and scaleY using a onMouseOver handler. This is indeed done, BUT the rectangle just moves away from it's initial point to some other location.
I've read I need to use the regX and regY properties to override this, but in the context of my code I just can't. What am I doing wrong?
Here's my Javascript code:
(function(){
var stage, myCanvas;
var update = true;
this.init = function() {
myCanvas = document.getElementById("stageCanvas");
stage = new createjs.Stage(myCanvas);
stage.enableMouseOver();
stage.mouseEnabled = true;
stage.mouseMoveOutside = true;
// Reference Shape
var rectFijo0 = new createjs.Shape();
rectFijo0.graphics.beginFill("#DCD8D4").rect(140,160,78,35);
stage.addChild(rectFijo0);
// Shape
var rectOpt0 = new createjs.Shape();
rectOpt0.graphics.beginFill("#C51A76").rect(140,160,78,35);
txtOpt0 = new createjs.Text("TEST","bold 20px","#FFF");
txtOpt0.textAlign ="center";
txtOpt0.x = 50;
txtOpt0.y = 50;
// Container
var containerOpt0= new createjs.Container();
containerOpt0.mouseEnabled = true;
//#######
// Probably here is my problem. I don't understand why if I use regX and regY the rectangle moves the lower right corner to the center, instead of just using this point as a registration point. Why? What I am not understanding?
//containerOpt0.regX = 78/2;
//containerOpt0.regY = 35/2;
//#######
containerOpt0.onPress = pressHandler;
containerOpt0.onMouseOver = mouseOverHandler;
containerOpt0.addChild(rectOpt0, txtOpt0);
stage.addChild(containerOpt0);
stage.update();
createjs.Ticker.setFPS(60);
createjs.Ticker.addEventListener("tick", tick);
}
function pressHandler(e){
// onPress Handler to drag
var offset = {x:e.target.x-e.stageX, y:e.target.y-e.stageY};
e.onMouseMove = function(ev) {
e.target.x = ev.stageX+offset.x;
e.target.y = ev.stageY+offset.y;
update = true;
}
}
function mouseOverHandler(e){
e.target.scaleX = .5;
e.target.scaleY = .5;
update = true;
}
function tick() {
if (update) {
update = false;
stage.update();
}
}
window.onload = init();
}());
Here's my JS Fiddle example so you can see exactly what's going on. Just drag the mouse over the rectangle to see what I mean. It must be something easy to achieve but I'm not certain how.

You issue is, that you are drawing your rects not at 0|0, the "standard" way is to draw your shape starting at 0|0 and then position the shape itself somewhere through .x and .y
rectOpt0.graphics.beginFill("#C51A76").rect(140,160,78,35);
=> changed to
rectOpt0.graphics.beginFill("#C51A76").rect(0,0,78,35);
and additionally I then placed the container at 140|160 + the regX/Y offset:
containerOpt0.regX = 78/2; //regX/Y to have is scale to the center point
containerOpt0.regY = 35/2;
containerOpt0.x = 140 + 78/2; //placement + regX offset/correction
containerOpt0.y = 160 + 35/2;
here's the updated fiddle: http://jsfiddle.net/WfMGr/2/

Redraw images on canvas

I need to have a couple of images on one canvas.
I have a trouble with a function clear(); which is used when I need to drag images on canvas.
The problem is that we are Canvas appears only on the last image.
I try to use context.save() and context.restore() but it was not usefull in my case.
switch(i)
{
case 0:
challengerImg = new Image();
challengerImg.onload = function(){
drawImage(this,x,y,i);
};
challengerImg.src = "<?php echo $base_url; ?>/themes/bartik/images/sheep.png";
break;
case 1:
tshirt = new Image();
tshirt.onload = function(){
drawImage(this,x,y,i);
};
tshirt.src = "<?php echo $base_url; ?>/themes/bartik/images/tshirt.png";
break;
}
And function which draw on canvas:
function drawImage(challengerImg,x,y,i){
console.log("Function drawImage start");
var events = new Events("layer0");
var canvas = events.getCanvas();
var context = events.getContext();
var rectX = x;
var rectY = y;
var draggingRect = false;
var draggingRectOffsetX = 0;
var draggingRectOffsetY = 0;
events.setStage(function(){
var mousePos = this.getMousePos();
if (draggingRect) {
rectX = mousePos.x - draggingRectOffsetX;
rectY = mousePos.y - draggingRectOffsetY;
}
this.clear(); //Here is trouble
this.beginRegion();
context.drawImage(challengerImg, rectX, rectY, challengerImg.width, challengerImg.height);
// draw rectangular region for image
context.beginPath();
context.rect(rectX, rectY, challengerImg.width, challengerImg.height);
context.closePath();
this.addRegionEventListener("mousedown", function(){
draggingRect = true;
var mousePos = events.getMousePos();
draggingRectOffsetX = mousePos.x - rectX;
draggingRectOffsetY = mousePos.y - rectY;
});
this.addRegionEventListener("mouseup", function(){
draggingRect = false;
});
this.addRegionEventListener("mouseover", function(){
document.body.style.cursor = "pointer";
});
this.addRegionEventListener("mouseout", function(){
document.body.style.cursor = "default";
});
this.closeRegion();
});
}

context.save and context.restore only works for state of the context (transformation, globalAlpha,...), but not for what is rendered inside.
When you clear your context, it makes it empty.
What you have to do is to :
catch mouse events and change position variables
clear the canvas
redraw all images at their new position

save(), restore() do not handle bitmap data at all :).
To drag stuff around, basically you need to have an offscreen canvas which doesn't contain the element you are drawing, and after each update draw the offscreen canvas plus the element being dragged.
It's probably simpler to use a library that already does it, most do, like http://www.html5canvastutorials.com/labs/html5-canvas-interactive-scatter-plot-with-20000-nodes-using-kineticjs/

The canvas is a flat object - once you draw an image onto it, the image has no more context as it renders as part of the canvas. You can either create an array of rectangle objects with their coordinates to keep track of what's already on the canvas or test the mouse position for the background color to determine whether there is an image or not. Then you can remove the item where the event happened by clearing the canvas and redrawing all the other items again.
Hope this helps!

creating a hierarchical tree structure of images in html5 canvas tag?

There is a tree hierarchical relation between a group of images, I want images to be represented as a tree structure in canvas tag with child node images smaller than parent node images and all the images should scale up with some value on mouseover.
The setscale and translate javascript functions let me do the scaling effect all right but I cannot get mouse event listener functions working right, mouseover and mouseout are not being detected although the images are displayed. I do not get the alert messages I have used for debugging. This is just a test code:-
function loadImages(sources, callback){
var images = {};
var loadedImages = 0;
var numImages = 0;
// get num of sources
for (var src in sources) {
numImages++;
}
for (var src in sources) {
images[src] = new Image();
images[src].onload = function(){
if (++loadedImages >= numImages) {
callback(images);
}
};
images[src].src = sources[src];
}
}
window.onload = function(){
var canvas = document.getElementById("myCanvas");
var context = canvas.getContext("2d");
var destX = 20;
var destY = 20;
var destWidth = 200;
var destHeight = 137;
var sources = new Array();
sources[0]="darth-vader.jpg";
sources[1]="darth-vader.jpg";
var imageObj = new Image();
loadImages(sources, function(images){
context.drawImage(images[0], destX, destY, destWidth, destHeight);
images[0].onmouseover=function()
{
alert('1');
}
images[0].onmouseout=function()
{
alert('2');
}
context.drawImage(images[1], destX+200,destY, destWidth, destHeight);
images[1].onmouseover=function()
{
alert('3');
}
images[1].onmouseout=function()
{
alert('4');
}
});
};

Events are triggered on dom elements not on images painted on a canvas. If you want to simulate those events try to set a mousemove event on the canvas and then if the mouse is inside the area where you have drawn the image trigger the mouseover.

You can only put mouse events on the canvas itself, not on the images drawn to it.
You're going to have to start keeping track of the size and location of images drawn so you can do relevant things when the user clicks on the canvas. See A Gentle Introduction to Making Canvas Useful for examples of how to keep track of multiple selectable objects on a canvas.