Develop Reference

Fabric JS: sync position of object after pan/zoom across two instances

Fabric JS question.
SCREENSHOT this is what my Fabric JS app looks like
CODEPEN https://codepen.io/zaynbuksh/pen/VVKRxj?editors=0011 (alt-click-drag to pan, scroll-wheel to zoom)
TLDR; How do I get the line to stick after panning and zooming a few times?
I am developing a Fabric JS app for labeling images of specimens. As part of this, people want to be able to zoom in on what each label is pointing at. I have been asked to make the labels remain visible when the specimen image is zoomed in. From research, people recommend two canvases stacked on top of each other.
I have created two Fabric JS canvas instances, layered on top of each other. The canvas at the bottom holds a background image that can be zoomed and panned, the canvas above it shows a pointer-line/label that is not zoomed (to keep the label visible at all times).
At first everything works - the line stays in sync with the image when I pan and zoom the first time only. I get problems with syncing the line to the image after that.
The problem manifests when I pan then zoom two or more times. The problem repeats each time I pan and then zoom i.e. the line moves when I zoom, but then stays in sync when I pan, moves again when I zoom again, pans normally and so on...
(Pan is handled by alt-click-drag, Zoom is handled by scroll wheel)
/*
"mouse:wheel" event is where zooms are handled
"mouse:move" event is where panning is handled
*/
// create Fabric JS canvas'
var labelsCanvas = new fabric.Canvas("labelsCanvas");
var specimenCanvas = new fabric.Canvas("specimenCanvas");
//set defaults
var startingPositionForLine = 100;
const noZoom = 1;
var wasPanned = false;
var panY2 = startingPositionForLine;
var panX2 = startingPositionForLine;
var zoomY2 = startingPositionForLine;
var zoomX2 = startingPositionForLine;
// set starting zoom for specimen canvas
var specimenZoom = noZoom;
/*
Add pointer, label and background image into canvas
*/
// create a pointer line
var line = new fabric.Line([150, 35, panX2, panY2], {
fill: "red",
stroke: "red",
strokeWidth: 3,
strokeDashArray: [5, 2],
// selectable: false,
evented: false
});
// create text label
var text = new fabric.Text("Label 1", {
left: 100,
top: 0,
// selectable: false,
evented: false,
backgroundColor: "red"
});
// add both into "Labels" canvas
labelsCanvas.add(text);
labelsCanvas.add(line);
// add a background image into Specimen canvas
fabric.Image.fromURL(
"https://upload.wikimedia.org/wikipedia/commons/c/cb/Skull_brain_human_normal.svg",
function(oImg) {
oImg.left = 0;
oImg.top = 0;
oImg.scaleToWidth(300);
oImg.scaleToHeight(300);
specimenCanvas.add(oImg);
}
);
/*
Handle mouse events
*/
// zoom the specimen image canvas via a mouse scroll-wheel event
labelsCanvas.on("mouse:wheel", function(opt) {
// scroll value e.g. 5, 6 -1, -18
var delta = opt.e.deltaY;
// zoom level in specimen
var zoom = specimenCanvas.getZoom();
console.log("zoom ", zoom);
// make zoom smaller
zoom = zoom + delta / 200;
// use sane defaults for zoom
if (zoom > 20) zoom = 20;
if (zoom < 0.01) zoom = 0.01;
// create new zoom value
zoomX2 = panX2 * zoom;
zoomY2 = panY2 * zoom;
// save the zoom
specimenZoom = zoom;
// set the specimen canvas zoom
specimenCanvas.setZoom(zoom);
// move line to sync it with the zoomed image
line.set({
x2: zoomX2,
y2: zoomY2
});
console.log("zoomed line ", line.x2);
// render the changes
this.requestRenderAll();
// block default mouse behaviour
opt.e.preventDefault();
opt.e.stopPropagation();
console.log(labelsCanvas.viewportTransform[4]);
// stuff I've tried to fix errors
line.setCoords();
specimenCanvas.calcOffset();
});
// pan the canvas
labelsCanvas.on("mouse:move", function(opt) {
if (this.isDragging) {
// pick up the click and drag event
var e = opt.e;
// sync the label position with the panning
text.left = text.left + (e.clientX - this.lastPosX);
var x2ToUse;
var y2ToUse;
// UNZOOMED canvas is being panned
if (specimenZoom === noZoom) {
x2ToUse = panX2;
y2ToUse = panY2;
// move the image using the difference between
// the current position and last known position
line.set({
x1: line.x1 + (e.clientX - this.lastPosX),
y1: line.y1,
x2: x2ToUse + (e.clientX - this.lastPosX),
y2: y2ToUse + (e.clientY - this.lastPosY)
});
// set the new panning value
panX2 = line.x2;
panY2 = line.y2;
// stuff I've tried
// zoomX2 = line.x2;
// zoomY2 = line.y2;
}
// ZOOMED canvas is being panned
else
{
x2ToUse = zoomX2;
y2ToUse = zoomY2;
// stuff I've tried
// x2ToUse = panX2;
// y2ToUse = panY2;
// move the image using the difference between
// the current position and last known ZOOMED position
line.set({
x1: line.x1 + (e.clientX - this.lastPosX),
y1: line.y1,
x2: x2ToUse + (e.clientX - this.lastPosX),
y2: y2ToUse + (e.clientY - this.lastPosY)
});
zoomX2 = line.x2;
zoomY2 = line.y2;
}
// hide label/pointer when it is out of view
if (text.left < 0 || line.y2 < 35) {
text.animate("opacity", "0", {
duration: 15,
onChange: labelsCanvas.renderAll.bind(labelsCanvas)
});
line.animate("opacity", "0", {
duration: 15,
onChange: labelsCanvas.renderAll.bind(labelsCanvas)
});
}
// show label/pointer when it is in view
else
{
text.animate("opacity", "1", {
duration: 25,
onChange: labelsCanvas.renderAll.bind(labelsCanvas)
});
line.animate("opacity", "1", {
duration: 25,
onChange: labelsCanvas.renderAll.bind(labelsCanvas)
});
}
specimenCanvas.viewportTransform[4] += e.clientX - this.lastPosX;
specimenCanvas.viewportTransform[5] += e.clientY - this.lastPosY;
this.requestRenderAll();
specimenCanvas.requestRenderAll();
this.lastPosX = e.clientX;
this.lastPosY = e.clientY;
}
console.log(line.x2);
wasPanned = true;
});
labelsCanvas.on("mouse:down", function(opt) {
var evt = opt.e;
if (evt.altKey === true) {
this.isDragging = true;
this.selection = false;
this.lastPosX = evt.clientX;
this.lastPosY = evt.clientY;
}
});
labelsCanvas.on("mouse:up", function(opt) {
this.isDragging = false;
this.selection = true;
});
.canvas-container {
position: absolute!important;
left: 0!important;
top: 0!important;
}
.canvas {
position: absolute;
top: 0;
right: 0;
border: solid red 1px;
}
.label-canvas {
z-index: 2;
}
.specimen-canvas {
z-index: 1;
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/fabric.js/2.4.3/fabric.js"></script>
<h1>
Dual canvas test
</h1>
<div style="position: relative; height: 300px">
<canvas class="canvas specimen-canvas" id="specimenCanvas" width="300" height="300"></canvas>
<canvas class="canvas label-canvas" id="labelsCanvas" width="300" height="300"></canvas>
</div>

As a side note, I think you're overcomplicating things a little bit. You don't really need to store panX/panY and zoomX/zoomY (zoomed pan as I've guessed) separately, they're already there in your line's coordinates. Just saying, because they've probably contributed to the confusion/debugging. The core idea of a fix, however, is that you should multiply your line's coordinates not by the whole zoom value but by the newZoom / previousZoom ratio. I've updated your snippet, it seems to work as expected:
/*
"mouse:wheel" event is where zooms are handled
"mouse:move" event is where panning is handled
*/
// create Fabric JS canvas'
var labelsCanvas = new fabric.Canvas("labelsCanvas");
var specimenCanvas = new fabric.Canvas("specimenCanvas");
//set defaults
var startingPositionForLine = 100;
const noZoom = 1;
var wasPanned = false;
var panY2 = startingPositionForLine;
var panX2 = startingPositionForLine;
var zoomY2 = startingPositionForLine;
var zoomX2 = startingPositionForLine;
// set starting zoom for specimen canvas
var specimenZoom = noZoom;
var prevZoom = noZoom;
/*
Add pointer, label and background image into canvas
*/
// create a pointer line
var line = new fabric.Line([150, 35, panX2, panY2], {
fill: "red",
stroke: "red",
strokeWidth: 3,
strokeDashArray: [5, 2],
// selectable: false,
evented: false
});
// create text label
var text = new fabric.Text("Label 1", {
left: 100,
top: 0,
// selectable: false,
evented: false,
backgroundColor: "red"
});
// add both into "Labels" canvas
labelsCanvas.add(text);
labelsCanvas.add(line);
// add a background image into Specimen canvas
fabric.Image.fromURL(
"https://upload.wikimedia.org/wikipedia/commons/c/cb/Skull_brain_human_normal.svg",
function(oImg) {
oImg.left = 0;
oImg.top = 0;
oImg.scaleToWidth(300);
oImg.scaleToHeight(300);
specimenCanvas.add(oImg);
}
);
window.specimenCanvas = specimenCanvas
/*
Handle mouse events
*/
// zoom the specimen image canvas via a mouse scroll-wheel event
labelsCanvas.on("mouse:wheel", function(opt) {
// scroll value e.g. 5, 6 -1, -18
var delta = opt.e.deltaY;
// zoom level in specimen
var zoom = specimenCanvas.getZoom();
var lastZoom = zoom
// make zoom smaller
zoom = zoom + delta / 200;
// use sane defaults for zoom
if (zoom > 20) zoom = 20;
if (zoom < 0.01) zoom = 0.01;
// save the zoom
specimenZoom = zoom;
// set the specimen canvas zoom
specimenCanvas.setZoom(zoom);
// move line to sync it with the zoomed image
var zoomRatio = zoom / lastZoom
console.log('zoom ratio: ', zoomRatio)
line.set({
x2: line.x2 * zoomRatio,
y2: line.y2 * zoomRatio
});
// console.log("zoomed line ", line.x2);
// render the changes
this.requestRenderAll();
// block default mouse behaviour
opt.e.preventDefault();
opt.e.stopPropagation();
// console.log(labelsCanvas.viewportTransform[4]);
// stuff I've tried to fix errors
line.setCoords();
specimenCanvas.calcOffset();
});
// pan the canvas
labelsCanvas.on("mouse:move", function(opt) {
if (this.isDragging) {
// pick up the click and drag event
var e = opt.e;
// sync the label position with the panning
text.left = text.left + (e.clientX - this.lastPosX);
// UNZOOMED canvas is being panned
if (specimenZoom === noZoom) {
x2ToUse = panX2;
y2ToUse = panY2;
// move the image using the difference between
// the current position and last known position
line.set({
x1: line.x1 + (e.clientX - this.lastPosX),
y1: line.y1,
x2: line.x2 + (e.clientX - this.lastPosX),
y2: line.y2 + (e.clientY - this.lastPosY)
});
// stuff I've tried
// zoomX2 = line.x2;
// zoomY2 = line.y2;
}
// ZOOMED canvas is being panned
else
{
// move the image using the difference between
// the current position and last known ZOOMED position
line.set({
x1: line.x1 + (e.clientX - this.lastPosX),
y1: line.y1,
x2: line.x2 + (e.clientX - this.lastPosX),
y2: line.y2 + (e.clientY - this.lastPosY)
});
}
// hide label/pointer when it is out of view
if (text.left < 0 || line.y2 < 35) {
text.animate("opacity", "0", {
duration: 15,
onChange: labelsCanvas.renderAll.bind(labelsCanvas)
});
line.animate("opacity", "0", {
duration: 15,
onChange: labelsCanvas.renderAll.bind(labelsCanvas)
});
}
// show label/pointer when it is in view
else
{
text.animate("opacity", "1", {
duration: 25,
onChange: labelsCanvas.renderAll.bind(labelsCanvas)
});
line.animate("opacity", "1", {
duration: 25,
onChange: labelsCanvas.renderAll.bind(labelsCanvas)
});
}
specimenCanvas.viewportTransform[4] += e.clientX - this.lastPosX;
specimenCanvas.viewportTransform[5] += e.clientY - this.lastPosY;
this.requestRenderAll();
specimenCanvas.requestRenderAll();
this.lastPosX = e.clientX;
this.lastPosY = e.clientY;
prevZoom = specimenCanvas.getZoom()
}
// console.log(line.x2);
wasPanned = true;
});
labelsCanvas.on("mouse:down", function(opt) {
var evt = opt.e;
if (evt.altKey === true) {
this.isDragging = true;
this.selection = false;
this.lastPosX = evt.clientX;
this.lastPosY = evt.clientY;
}
});
labelsCanvas.on("mouse:up", function(opt) {
this.isDragging = false;
this.selection = true;
});
.canvas-container {
position: absolute!important;
left: 0!important;
top: 0!important;
}
.canvas {
position: absolute;
top: 0;
right: 0;
border: solid red 1px;
}
.label-canvas {
z-index: 2;
}
.specimen-canvas {
z-index: 1;
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/fabric.js/2.4.3/fabric.js"></script>
<h1>
Dual canvas test
</h1>
<div style="position: relative; height: 300px">
<canvas class="canvas specimen-canvas" id="specimenCanvas" width="300" height="300"></canvas>
<canvas class="canvas label-canvas" id="labelsCanvas" width="300" height="300"></canvas>
</div>

Drag, drop and delete objects on FabricJS canvas

I am having issues getting drag, drop and delete to work on a FabricJS using JQuery.
Select an object and click delete is working with no issues.
Here's a demo of my code Fiddle
I can get drag, drop and delete to work outside of FabricJS (Just dragging unrelated elements to delete) but I'm having difficulty combing the two.
Maybe I need to incorporate the delete button inside the canvas in order for the 'drop' to work? When I try this the #delete element disappears.
JS
var canvas = new fabric.Canvas('canvas');
$("#delete").click(function() {
deleteObjects();
});
//Test objects on the canvas
//Circle
var circle = new fabric.Circle({
left: 200,
top: 150,
radius: 30,
fill: "#ff0072"
});
circle.hasRotatingPoint = true;
canvas.add(circle);
// adding triangle
var triangle = new fabric.Triangle({
left: 130,
top: 150,
strokeWidth: 1,
width: 70,
height: 60,
fill: '#00b4ff',
selectable: true,
originX: 'center'
});
triangle.hasRotatingPoint = true;
canvas.add(triangle);
//Select all objects
function deleteObjects() {
var activeObject = canvas.getActiveObject(),
activeGroup = canvas.getActiveGroup();
if (activeObject) {
canvas.remove(activeObject);
}
}
//Drag and drop delete
$(function() {
$('#delete').droppable({
drop: function(event, ui) {
deleteObjects();
}
});
});
HTML
<section class="canvas__container">
<canvas id="canvas" width="400" height="400"></canvas>
<div id="delete">♻</div>
</section>
(I didn't paste my CSS as that's not particularly relevant)

This should get you close:
var bin;
var selectedObject;
fabric.Image.fromURL('data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAADUAAAA1CAIAAABuhDQnAAAAAXNSR0IArs4c6QAAAARnQU1BAACxjwv8YQUAAAAJcEhZcwAADsMAAA7DAcdvqGQAAAPPSURBVGhDzZd9U+IwEIfv+3+2Gxln9PAEcYRBURQVkVeFe9rdC2laIFsK+Pzh2Cab/ZF9Sfpr9bMpr+/r6+v5+fn+/v5vyuXl5e8U/uGx2Wwy9Pr6yjQ1KIVZ32w2e3x8xL2oiYHJmGCoS1gw6MPB7e2t+iwF5laVUfqIEcGq1WrqZw9YhKXig75bHzlUiTIfFmRZdbCVHfrIG13yALC4utnMRn2EYM9siwEX22NdrA8b1y8ODY62SCzWd4Sd88GdOs5RoO+gObeJTbkY6qOs1OLoFFZ0Rh95UHkriQfX+UTM6Ot2uzr3RCBApfxnrY+T54SbJyAgOADX+krX7NnZGTeAm5ub8/NzfbUHQS2rPlTruJFOp7NYLGQR+P7+5vHz8/Pl5eX6+lonGfG3UPWV6ykPDw/L5VJWyIPQcjHxe43qM93nBEz8nSvk4+OD6KtBNKys9qKPqtYRC3d3d/P5XFYRptMpBei/ZGXyUg0suEaT6OOarq/toHI8HrPIZDLhWn91dTUajdKVE4g+tz2dasH16kSfte1Rp29vb71e7+LiQt78SeFRtPqQ7ExmVGZG4hphoo8fra+jQRx7A5QqJeySjJoNgs5jueQW8zL6Wq0WqSb2wnA41LG0gbm6YRqKUW+9rSFJVkj0mYxJsqDFs4s0Gh1OISlJcGJdr9cRR3ytvQZJsniiT9/FQeMVSwe+86240WiQjuDKxXozEiuzPupULB00OR3Lgmg/DTA09UKxMsfX10fuE8cguA6izHGnU9PJ5IaO7SITX1N9uPjijx1CXKFXCpDR4MfEO8rUh6n+3a5QFqQUGSbvaYrtdnswGBBThqghioO6Tr0kUCUyM4ZMfzH1Z3IoSEGksFVPT0/6nELcqQz2TB4R7X5JDJn+bD3fAilsJx0xyDYftDKqxnFkzjfs9XUcHPmYiD0QTQ5ZttDtVkC/31fLaNz6iT6wHkFsuRgKoiB/+ML7+7uprYBLPlB91vspLjFxv1J6L3/JRU5kV0C0RlPaCQX3U9bVQSOcEySftBguCpSwvN8H//xUfVDuLl45yFBBKWt9qP4J35d+5cFaH1gvqpXj2p4jow/tJ9zC/OZBRh9Yb0EV4nqyT6gPyn0L74nfU3wK9MGRazmoWZ9ifeSB9YuhNDjKp52jWB9gc4RdxMUWcbBRn3DQXNyUcz479AFlVXnTYcHCas2zWx8QAjpnJSpZhKW2x9QnSp/AAbhnRmLun/0xGPQJOCBvTPdFJmNiVSaY9TmIETlEsHDP55brR/zDIy8ZYkJ8KAspr+84/Gx9q9U/+FfCZwDz5ogAAAAASUVORK5CYII=', function(img) {
img.set({
left: 174,
top: 329,
selectable: false
});
bin = img;
canvas.add(img, circle, triangle);
});
canvas.on('object:selected', function(evn) {
selectedObject = evn.target;
})
canvas.on('mouse:up', function(evn) {
var x = evn.e.offsetX;
var y = evn.e.offsetY;
if (x > bin.left && x < (bin.left + bin.width) &&
y > bin.top && y < (bin.top + bin.height)) {
canvas.remove(selectedObject);
}
});
Here's your JSFiddle updated, https://jsfiddle.net/rekrah/jgruwse0/.
Let me know if you have any further questions.

JavaScript - Dynamically create SVG and modify for cursor

Say I have a HTML5 canvas (In this case using fabric.js), and I want to change the cursor over the canvas to represent whatever brush size and colour has been selected. I'm thinking there should be a way to do this by changing an SVG's properties (size & colour) dynamically with JS so we don't have to use multiple images. Any ideas on if this is possible?
var canvas = new fabric.Canvas(c, {
isDrawingMode: true,
freeDrawingCursor: 'url("img/cursor.svg"), auto'
});

I think freeDrawingCursor is just looking for normal css property names. Here is an example of how to have a fabric object represent the cursor size and color:
var canvas = new fabric.Canvas('c', {
isDrawingMode: true,
freeDrawingCursor: 'none'
});
canvas.freeDrawingBrush.width = 10;
canvas.freeDrawingBrush.color = '#9f9';
var mousecursor = new fabric.Circle({
left: 0,
top: 0,
radius: canvas.freeDrawingBrush.width / 2,
fill: canvas.freeDrawingBrush.color,
originX: 'right',
originY: 'bottom',
})
canvas.add(mousecursor);
canvas.on('mouse:move', function(obj) {
mousecursor.top = obj.e.y - mousecursor.radius;
mousecursor.left = obj.e.x - mousecursor.radius;
canvas.renderAll()
})
canvas.on('mouse:out', function(obj) {
// put circle off screen
mousecursor.top = -100;
mousecursor.left = -100;
canvas.renderAll()
})
canvas {
border: 1px solid #ccc;
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/fabric.js/1.6.3/fabric.js"></script>
<canvas id="c" width="600" height="600"></canvas>

Existing answers didn't work for me in 2020. Try the following:
this.canvas.isDrawingMode = true;
this.canvas.freeDrawingCursor = 'none';
const mousecursor = new fabric.Circle({
left: 0,
top: 0,
radius: this.canvas.freeDrawingBrush.width / 2,
fill: this.canvas.freeDrawingBrush.color,
originX: 'right',
originY: 'bottom',
});
this.canvas.add(mousecursor);
// Cursor in canvas
this.canvas.on('mouse:move', event => {
mousecursor.top = event.e.layerY + mousecursor.radius;
mousecursor.left = event.e.layerX + mousecursor.radius;
this.canvas.renderAll();
});
// Cursor out of canvas
this.canvas.on('mouse:out', event => {
mousecursor.top = -100;
mousecursor.left = -100;
this.canvas.renderAll();
});
Worked fine with Angular 7.

I was looking for the same and found my way to this question. Unfortunately the solution by STHayden is not working for me. So I've modified it a bit and came up with the code below. It uses two canvas layers, the bottom for drawing, the top for the "cursor". Works pretty well for me now, maybe someone will find it helpful :)
//drawing layer
var canvas = new fabric.Canvas("draw", {
isDrawingMode: true,
freeDrawingCursor: 'none'
});
//mouse cursor layer
var cursor = new fabric.StaticCanvas("cursor");
canvas.freeDrawingBrush.width = 20;
canvas.freeDrawingBrush.color = '#ff0000';
var cursorOpacity = .5;
//create cursor and place it off screen
var mousecursor = new fabric.Circle({
left: -100,
top: -100,
radius: canvas.freeDrawingBrush.width / 2,
fill: "rgba(255,0,0," + cursorOpacity + ")",
stroke: "black",
originX: 'center',
originY: 'center'
});
cursor.add(mousecursor);
//redraw cursor on new mouse position when moved
canvas.on('mouse:move', function (evt) {
var mouse = this.getPointer(evt.e);
mousecursor
.set({
top: mouse.y,
left: mouse.x
})
.setCoords()
.canvas.renderAll();
});
//put cursor off screen again when mouse is leaving
canvas.on('mouse:out', function () {
mousecursor
.set({
top: mousecursor.originalState.top,
left: mousecursor.originalState.left
})
.setCoords()
.canvas.renderAll();
});
//while brush size is changed show cursor in center of canvas
document.getElementById("size").oninput = function () {
var size = parseInt(this.value, 10);
mousecursor
.center()
.set({
radius: size/2
})
.setCoords()
.canvas.renderAll();
};
//after brush size has been changed move offscreen, update brush size
document.getElementById("size").onchange = function () {
var size = parseInt(this.value, 10);
canvas.freeDrawingBrush.width = size;
mousecursor
.set({
left: mousecursor.originalState.left,
top: mousecursor.originalState.top,
radius: size/2
})
.setCoords()
.canvas.renderAll();
};
//change mousecursor opacity
document.getElementById("opacity").onchange = function () {
cursorOpacity = this.value;
var fill = mousecursor.fill.split(",");
fill[fill.length-1] = cursorOpacity + ")";
mousecursor.fill = fill.join(",");
};
//change drawing color
document.getElementById("color").onchange = function () {
canvas.freeDrawingBrush.color = this.value;
var bigint = parseInt(this.value.replace("#", ""), 16);
var r = (bigint >> 16) & 255;
var g = (bigint >> 8) & 255;
var b = bigint & 255;
mousecursor.fill = "rgba(" + [r,g,b,cursorOpacity].join(",") + ")";
};
#cont {
position: relative;
width: 500px;
height: 500px;
}
canvas {
border: 1px solid;
}
#cont canvas, .canvas-container {
position: absolute!important;
left: 0!important;
top: 0!important;
width: 100%!important;
height: 100%!important;
}
#cursor {
pointer-events: none!important;
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/fabric.js/1.6.4/fabric.min.js"></script>
Color: <input id="color" type="color" value="#ff0000"><br/>
Brush size: <input id="size" type="range" min="1" max="100" step="1" value="20"><br/>
Brush opacity: <input id="opacity" type="number" min="0" max="1" step="0.1" value="0.5"><br/>
<div id="cont">
<canvas id="draw" width="500" height="500"></canvas>
<canvas id="cursor" width="500" height="500"></canvas>
</div>

I use fabricJs and want to get mouse position in zooming

I am using fabricJs library to create rectangles and want to get mouse position after zooming
I use this code to start drawing the rectangle, in scale = 1, it works right but after i get zoom in for example and click i get the rectangle start point in the point not i click on, what cause this ?
// Create new rectangle
canvas.on('mouse:down', function (options) {
if (canvas.getActiveObject()) {
return false;
}
started = true;
ex = (posx);
ey = (posy);
var colors = ['#FF8080', '#D5D5E6', '#C0F2C0', '#8080E4', '#CCCCAA'];
var rectangle_color = colors[Math.floor(Math.random() * colors.length)];
var square = new fabric.Rect({
width: 0,
height: 0,
left: ex,
top: ey,
fill: rectangle_color
});
var square = new fabric.Rect({ width: 0, height: 0, left: ex, top: ey, fill: rectangle_color });
canvas.add(square);
canvas.setActiveObject(square);
});

You need your real coordinates of your mouse not some scope declared posx and posy:
canvas.on('mouse:down', function (event) {
if (canvas.getActiveObject()) {
return false;
}
var pointer = canvas.getPointer(event.e);
var posx = pointer.x;
var posy = pointer.y;
//...
//your code
//...
}

Kineticjs - free rotate on image

I need help only having the anchors for rotating. Right now there is five anchors and I don't know how to get rid of all of them except the rotate one. I would also only like the anchors to show when the user hovers over the image
Here is my code
<html>
<head>
<style>
body {
margin: 0px;
padding: 0px;
}
</style>
</head>
<body>
<body onmousedown="return false;">
<div id="container"></div>
<script src="http://d3lp1msu2r81bx.cloudfront.net/kjs/js/lib/kinetic-v4.7.4.min.js">
</script>
<script>
function update(activeAnchor) {
var group = activeAnchor.getParent();
var topLeft = group.get('.topLeft')[0];
var topRight = group.get('.topRight')[0];
var bottomRight = group.get('.bottomRight')[0];
var bottomLeft = group.get('.bottomLeft')[0];
var rotateAnchor = group.get('.rotateAnchor')[0];
var image = group.get('Image')[0];
var anchorX = activeAnchor.getX();
var anchorY = activeAnchor.getY();
var imageWidth = image.getWidth();
var imageHeight = image.getHeight();
var offsetX = Math.abs((topLeft.getX() + bottomRight.getX() + 10) / 2);
var offsetY = Math.abs((topLeft.getY() + bottomRight.getY() + 10) / 2);
// update anchor positions
switch (activeAnchor.getName()) {
case 'rotateAnchor':
group.setOffset(offsetX, offsetY);
break;
case 'topLeft':
topRight.setY(anchorY);
bottomLeft.setX(anchorX);
break;
case 'topRight':
topLeft.setY(anchorY);
bottomRight.setX(anchorX);
break;
case 'bottomRight':
topRight.setX(anchorX);
bottomLeft.setY(anchorY);
break;
case 'bottomLeft':
topLeft.setX(anchorX);
bottomRight.setY(anchorY);
break;
}
rotateAnchor.setX(topRight.getX() + 5);
rotateAnchor.setY(topRight.getY() + 20);
image.setPosition((topLeft.getPosition().x + 20), (topLeft.getPosition().y + 20));
var width = topRight.getX() - topLeft.getX() - 30;
var height = bottomLeft.getY() - topLeft.getY() - 30;
if (width && height) {
image.setSize(width, height);
}
}
function addAnchor(group, x, y, name, dragBound) {
var stage = group.getStage();
var layer = group.getLayer();
var anchor = new Kinetic.Circle({
x: x,
y: y,
stroke: '#666',
fill: '#ddd',
strokeWidth: 2,
radius: 8,
name: name,
draggable: true,
dragOnTop: false
});
if (dragBound == 'rotate') {
anchor.setAttrs({
dragBoundFunc: function (pos) {
return getRotatingAnchorBounds(pos, group);
}
});
}
anchor.on('dragmove', function() {
update(this);
layer.draw();
});
anchor.on('mousedown touchstart', function() {
group.setDraggable(false);
this.moveToTop();
});
anchor.on('dragend', function() {
group.setDraggable(true);
layer.draw();
});
// add hover styling
anchor.on('mouseover', function() {
var layer = this.getLayer();
document.body.style.cursor = 'pointer';
this.setStrokeWidth(4);
layer.draw();
});
anchor.on('mouseout', function() {
var layer = this.getLayer();
document.body.style.cursor = 'default';
this.setStrokeWidth(2);
layer.draw();
});
group.add(anchor);
}
function loadImages(sources, callback) {
var images = {};
var loadedImages = 0;
var numImages = 0;
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];
}
}
function getRotatingAnchorBounds(pos, group) {
var topLeft = group.get('.topLeft')[0];
var bottomRight = group.get('.bottomRight')[0];
var topRight = group.get('.topRight')[0];
var absCenterX = Math.abs((topLeft.getAbsolutePosition().x + 5 + bottomRight.getAbsolutePosition().x + 5) / 2);
var absCenterY = Math.abs((topLeft.getAbsolutePosition().y + 5 + bottomRight.getAbsolutePosition().y + 5) / 2);
var relCenterX = Math.abs((topLeft.getX() + bottomRight.getX()) / 2);
var relCenterY = Math.abs((topLeft.getY() + bottomRight.getY()) / 2);
var radius = distance(relCenterX, relCenterY, topRight.getX() + 5, topRight.getY() + 20);
var scale = radius / distance(pos.x, pos.y, absCenterX, absCenterY);
var realRotation = Math.round(degrees(angle(relCenterX, relCenterY, topRight.getX() + 5, topRight.getY() + 20)));
var rotation = Math.round(degrees(angle(absCenterX, absCenterY, pos.x, pos.y)));
rotation -= realRotation;
group.setRotationDeg(rotation);
return {
y: Math.round((pos.y - absCenterY) * scale + absCenterY),
x: Math.round((pos.x - absCenterX) * scale + absCenterX)
};
}
function radians(degrees) { return degrees * (Math.PI / 180); }
function degrees(radians) { return radians * (180 / Math.PI); }
// Calculate the angle between two points.
function angle(cx, cy, px, py) {
var x = cx - px;
var y = cy - py;
return Math.atan2(-y, -x);
}
// Calculate the distance between two points.
function distance(p1x, p1y, p2x, p2y) {
return Math.sqrt(Math.pow((p2x - p1x), 2) + Math.pow((p2y - p1y), 2));
}
function initStage(images) {
var stage = new Kinetic.Stage({
container: 'container',
width: 578,
height: 400
});
var darthVaderGroup = new Kinetic.Group({
x: 270,
y: 100,
draggable: true
});
var yodaGroup = new Kinetic.Group({
x: 100,
y: 110,
draggable: true
});
var layer = new Kinetic.Layer();
/*
* go ahead and add the groups
* to the layer and the layer to the
* stage so that the groups have knowledge
* of its layer and stage
*/
layer.add(darthVaderGroup);
layer.add(yodaGroup);
stage.add(layer);
// darth vader
var darthVaderImg = new Kinetic.Image({
x: 0,
y: 0,
image: images.darthVader,
width: 200,
height: 138,
name: 'image'
});
darthVaderGroup.add(darthVaderImg);
addAnchor(darthVaderGroup, -20, -20, 'topLeft', 'none');
addAnchor(darthVaderGroup, 220, -20, 'topRight', 'none');
addAnchor(darthVaderGroup, 220, 158, 'bottomRight', 'none');
addAnchor(darthVaderGroup, -20, 158, 'bottomLeft','none');
addAnchor(darthVaderGroup, 225, 0, 'rotateAnchor','rotate');
darthVaderGroup.on('dragstart', function() {
this.moveToTop();
});
stage.draw();
}
var sources = {
darthVader: 'http://www.html5canvastutorials.com/demos/assets/darth-vader.jpg'
};
loadImages(sources, initStage);
</script>
</body>
</html>

You can use each anchors show/hide methods inside the images mouseenter/mouseleave events to display the anchors when the mouse enters the image:
image.on("mouseleave",function(){ anchor1.hide(); }
image.on("mouseenter",function(){ anchor1.show(); layer.draw(); }
Problem is that since your anchors are partly outside your image, so hiding the anchors when the mouse leaves the image might make the anchors "disappear" when the user intends to use them.
The ideal solution would be to listen for mouseenter/mouseleave events on the group which contains the image but also extends to include the outside part of the anchors. Unfortunately, a Kinetic.Group will not respond to mouseenter/mouseleave events.
A workaround is to create a Kinetic.Rect background to the group which includes the images plus the anchors. The rect will listen for mouseenter/mouseleave events and will show/hide the anchors. If you don't want the background rect to be visible, just set it's opacity to .001. The rect will still listen for events, but will be invisible.
groupBackgroundRect.on("mouseleave",function(){ anchor1.hide(); }
groupBackgroundRect.on("mouseenter",function(){ anchor1.show(); layer.draw(); }
A related note:
With KineticJS, combining rotation with resizing is made more difficult than it needs to be because KineticJS uses offsetX/offsetY as both an object's rotation point and as an offset to its position. Your key to making it work will be to re-center the offset point after resizing so that your rotation takes place around the new centerpoint--not the previous centerpoint. (or reset the offset reference point to any other point that you want to rotate around).