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Place image to alpha channels in canvas

I need to find top, left, max width and max height values of all transparent places in canvas.
http://jsfiddle.net/alperxx/t521jra4/ (fiddle)
I have 4 transparent place in canvas. but i can't detect true places. First alpha channel corners colour must be red. Next is: black, yellow and green. But my groups is not correct.
If I complete the groups truely, every uploading photos will place to alpha places.
My Processes are in comment.
function alphaRatio(ctx) {
var pixelData = ctx.getImageData(0, 0, ctx.canvas.width, ctx.canvas.height);
const data = pixelData.data;
const pixel_groups = [];
var total = 0;
for (let i = 0, dx = 0; dx < data.length; i++, dx = i << 2) {
if (data[dx + 3] == 0) {
//First, I'm catching all transparent pixels.
total++;
var x = (dx / 4) % ctx.canvas.width;
var y = ~~((dx / 4) / ctx.canvas.width);
// if pixel after a last grouped item add to in.
var found = false;
if (pixel_groups.length) {
for (im = 0; im < pixel_groups.length; im++) {
last_pixels = pixel_groups[im][pixel_groups[im].length - 1];
if (
last_pixels.x + 1 == x || last_pixels.x - 1 == x ||
last_pixels.y + 1 == y || last_pixels.y - 1 == y
) {
found = true;
pixel_groups[im].push({
x: x,
y: y
});
break;
}
}
}
if (!found) {
pixel_groups.push([{
x: x,
y: y
}]);
}
}
}
// i grouped all them
if (pixel_groups.length) {
console.debug(pixel_groups);
for (i = 0; i < pixel_groups.length; i++) {
var alphawidth = {};
var alphaheight = {};
for (im = 0; im < pixel_groups[i].length; im++) {
//now lets calculate first pixel left and top for width and height
if (typeof(alphawidth['min']) === 'undefined') {
alphawidth['min'] = pixel_groups[i][im].x;
alphawidth['max'] = pixel_groups[i][im].x;
} else {
if (pixel_groups[i][im].x < alphawidth['min']) {
alphawidth['min'] = pixel_groups[i][im].x;
}
if (pixel_groups[i][im].x > alphawidth['max']) {
alphawidth['max'] = pixel_groups[i][im].x;
}
}
if (typeof(alphaheight['min']) === 'undefined') {
alphaheight['min'] = pixel_groups[i][im].y;
alphaheight['max'] = pixel_groups[i][im].y;
} else {
if (pixel_groups[i][im].y < alphaheight['min']) {
alphaheight['min'] = pixel_groups[i][im].y;
}
if (pixel_groups[i][im].y > alphaheight['max']) {
alphaheight['max'] = pixel_groups[i][im].y;
}
}
}
// update group key for only x y w h
pixel_groups[i] = {
x: pixel_groups[i][0].x,
y: pixel_groups[i][0].y,
w: alphawidth['max'] - alphawidth['min'],
h: alphaheight['max'] - alphaheight['min']
};
}
// for test alpha places put a colour all corners
for (i = 0; i < pixel_groups.length; i++) {
var colour = ['red', 'black', 'yellow', 'green'];
canvas.add(new fabric.Circle({
left: pixel_groups[i].x,
top: pixel_groups[i].y,
radius: 4,
fill: colour[i],
originX: 'center',
originY: 'center',
hasControls: false
}));
canvas.add(new fabric.Circle({
left: pixel_groups[i].x + pixel_groups[i].w,
top: pixel_groups[i].y + pixel_groups[i].h,
radius: 4,
fill: colour[i],
originX: 'center',
originY: 'center',
hasControls: false
}));
canvas.add(new fabric.Circle({
left: pixel_groups[i].x + pixel_groups[i].w,
top: pixel_groups[i].y,
radius: 4,
fill: colour[i],
originX: 'center',
originY: 'center',
hasControls: false
}));
canvas.add(new fabric.Circle({
left: pixel_groups[i].x,
top: pixel_groups[i].y + pixel_groups[i].h,
radius: 4,
fill: colour[i],
originX: 'center',
originY: 'center',
hasControls: false
}));
}
return pixel_groups;
}
return false;
}

Fabric.js - rotate one object the other rotate too

I have an application using HTML5 canvas via Fabric.js. And I would like to do arrow with text. Then moving arrow the text is in correct position, but is problem with rotation:
incorrect text position:
text position have to be:
My code is:
var canvas = new fabric.Canvas('c');
var line = new fabric.Line([10, 50, 200, 50], {
stroke: 'black',
strokeWidth: 3,
strokeDashArray: [10, 5]
});
var line2 = new fabric.Line([199, 50, 180, 60], {
stroke: 'black',
strokeWidth: 3
});
var line3 = new fabric.Line([199, 50, 180, 40], {
stroke: 'black',
strokeWidth: 3
});
var strele = new fabric.Group([line, line2, line3], {});
tekst = new fabric.IText('<<extend>>', {
left: 50,
top: 20,
fontFamily: 'Arial',
fill: '#333',
fontSize: 20
});
canvas.add(strele, tekst);
function onMoving(options) {
if (options.target === strele) {
tekst.left = strele.left + ((strele.width * strele.scaleX) / 2) - (tekst.width * tekst.scaleX) / 2;
tekst.top = strele.top - strele.height * strele.scaleY;
} else if (options.target === tekst) {
strele.left = tekst.left - ((strele.width * strele.scaleX) / 2 - (tekst.width * tekst.scaleX) / 2);
strele.top = tekst.top + strele.height * strele.scaleY;
}
canvas.forEachObject(function(o) {
o.setCoords()
});
}
function onRotating(options) {
if (options.target === strele) {
tekst.angle = strele.angle;
tekst.left = strele.left((strele.width * strele.scaleX) / 2) - (tekst.width * tekst.scaleX) / 2;
tekst.top = strele.top - strele.height * strele.scaleY;
}
}
canvas.on('object:moving', onMoving);
canvas.on('object:rotating', onRotating);
My code in fiddle
How can I fix this?

Here is an approach that closely resembles your image.
To simplify the calculations I changed the objects origin(X & Y) to center, the rest is just some math and conditions for the angles. My approach was to keep the text readable and not overlap the line.
var canvas = new fabric.Canvas('c');
var line = new fabric.Line([160, 100, 350, 100], {stroke: 'black', strokeWidth: 3, strokeDashArray: [10, 5]});
var line2 = new fabric.Line([350, 100, 330, 110], {stroke: 'black', strokeWidth: 3});
var line3 = new fabric.Line([350, 100, 330, 90], {stroke: 'black', strokeWidth: 3});
var strele = new fabric.Group([line, line2, line3], {originX: "center", originY: "center"});
var tekst = new fabric.IText('<<extend>>', {left: 160, top: 70, fontFamily: 'Arial',fill: 'red', fontSize: 20, selectable: false,
originX: "center", originY: "center"
});
canvas.add(strele, tekst);
canvas.setActiveObject(canvas.item(0));
canvas.on('object:moving', onMoving);
canvas.on('object:rotating', onRotating);
function onMoving() {
tekst.left = strele.left + 20 * Math.sin(strele.angle * Math.PI /180);
tekst.top = strele.top - 20 * Math.cos(strele.angle * Math.PI /180);
}
function onRotating() {
var ang = strele.angle % 360;
if (ang < 270) {
if (ang > 180) {
ang = strele.angle % 180;
} else if (ang > 90) {
ang = 180+strele.angle;
}
}
tekst.angle = ang
onMoving()
}
function rotate() {
strele.angle += 22.2;
strele.setCoords()
onRotating()
canvas.renderAll();
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/fabric.js/2.3.4/fabric.min.js"></script>
<button id="rotate" onclick="rotate()">rotate</button>
<canvas id="c" width="600" height="600"></canvas>

Compound Shape Class?

Has anyone ever tried to create a custom shape class for Fabric.js that is a combination of shapes? I want to create something like a ruler, where the left and right ends are vertical lines and is attached to the middle, |---| .
I'd also like to have a text box follow along in the center of this ruler. The ends should also have the ability to reposition.
I've done this without a class, but it won't save or load, since I made my version from multiple shapes.
Anyone have any thoughts if it's possible to create a custom shape like this?
Below is an example of some code that I pulled together from another example I found a while ago. 3 lines are created to make up my ruler. If I export the canvas data I'll get data to recreate as 3 lines, so if I clear the canvas and reload with this data, I'll get my 3 lines, but they will be independent 3 lines. I guess I need to figure out how to save their relationship so they can retain their ruler behavior when reloaded. I was thinking the best approach would be to create a custom shape with a type of "ruler".
window.onload = function() {
var canvas;
var started = false;
var mode = 0;
var lastX = 0;
var lastY = 0;
canvas = new fabric.Canvas('c');
canvas.isDrawingMode = false;
canvas.isTouchSupported = true;
canvas.selection = false;
canvas.on("mouse:down", function(option) {
if (mode === 1) {
var mouse = canvas.getPointer(option.e);
lastX = mouse.x;
lastY = mouse.y;
started = true;
var ln = new fabric.Line([lastX, lastY, lastX, lastY], {
fill: 'red',
stroke: 'red',
strokeWidth: 4,
originX: 'center',
originY: 'center',
lockScalingX: true,
lockScalingY: true,
lockRotation: true,
hasBorders: false,
hasControls: false,
perPixelTargetFind: true
});
var rAnchor = new fabric.Line([lastX - 20, lastY, lastX + 20, lastY], {
fill: 'red',
stroke: 'red',
strokeWidth: 4,
originX: 'center',
originY: 'center',
lockScalingX: true,
lockScalingY: true,
lockRotation: true,
hasBorders: false,
hasControls: false,
perPixelTargetFind: true
});
var tip = new fabric.Line([lastX - 20, lastY, lastX + 20, lastY], {
fill: 'red',
stroke: 'red',
strokeWidth: 4,
originX: 'center',
originY: 'center',
lockScalingX: true,
lockScalingY: true,
lockRotation: true,
hasBorders: false,
hasControls: false,
perPixelTargetFind: true
});
tip.line = ln;
rAnchor.line = ln;
ln.tip = tip;
ln.rAnchor = rAnchor;
canvas.add(ln);
canvas.add(rAnchor);
canvas.add(tip);
canvas.setActiveObject(ln);
canvas.renderAll();
}
});
canvas.on("mouse:move", function(e) {
if (!started) {
return false;
}
var mouse = canvas.getPointer(e.e);
var line = canvas.getActiveObject();
line.set('x2', mouse.x).set('y2', mouse.y);
var tip = line.get('tip');
tip.set('left', mouse.x).set('top', mouse.y);
var rAnchor = line.get('rAnchor');
// Get the angle for pointing the tip at the mouse location.
var rad = Math.atan2((line.y1 - line.y2), (line.x1 - line.x2));
var ang = rad * (180 / Math.PI);
tip.set('angle', (ang - 90));
rAnchor.set('angle', (ang - 90));
line.setCoords();
tip.setCoords();
rAnchor.setCoords();
canvas.renderAll();
});
canvas.on("mouse:up", function() {
if (started) {
started = false;
}
canvas.discardActiveObject();
canvas.renderAll();
});
// Event Handler for Drawn Object move
canvas.on('object:moving', function(e) {
var p = e.target;
// move line
if (p.tip) {
var oldCenterX = (p.x1 + p.x2) / 2;
var oldCenterY = (p.y1 + p.y2) / 2;
var deltaX = p.left - oldCenterX;
var deltaY = p.top - oldCenterY;
p.tip.set({
'left': p.x2 + deltaX,
'top': p.y2 + deltaY
}).setCoords();
p.rAnchor.set({
'left': p.x1 + deltaX,
'top': p.y1 + deltaY
});
p.set({
'x1': p.x1 + deltaX,
'y1': p.y1 + deltaY
});
p.set({
'x2': p.x2 + deltaX,
'y2': p.y2 + deltaY
});
p.set({
'left': (p.x1 + p.x2) / 2,
'top': (p.y1 + p.y2) / 2
});
}
// move tip
if (p.line) {
var tip = p.line.tip;
var rAnchor = p.line.rAnchor;
p.line.set({
'x2': tip.left,
'y2': tip.top,
'x1': rAnchor.left,
'y1': rAnchor.top
});
// Get the angle for pointing the tip at the mouse location.
var rad = Math.atan2((p.line.y1 - p.line.y2), (p.line.x1 - p.line.x2));
var ang = rad * (180 / Math.PI);
tip.set('angle', (ang - 90));
rAnchor.set('angle', (ang - 90));
tip.setCoords();
rAnchor.setCoords();
p.line.setCoords();
}
canvas.renderAll();
});
// Button Event Handlers
document.getElementById("btnEdit").addEventListener("click", function(e) {
mode = 0;
});
document.getElementById("btnArrow").addEventListener("click", function(e) {
mode = 1;
});
};
<script src="https://cdnjs.cloudflare.com/ajax/libs/fabric.js/1.7.17/fabric.min.js"></script>
<canvas style="border: 2px solid; " height="500" width="600" id="c"></canvas>
<button id="btnEdit">Edit</button>
<button id="btnArrow">Ruler</button>

KineticJS: How to Cache a Group of Shapes?

I want to increase mobile drag and drop performance of canvas objects. I have a Group which contains different Shapes (Images, Stars, Recs,...). I want to use caching to increase the performance when I drag and drop or rotate the entire Group.
Here is a JSFiddle I created: http://jsfiddle.net/confile/k4Lsv73d/
function setFPSMeter() {
var RAF = (function () {
return window["requestAnimationFrame"] || window["webkitRequestAnimationFrame"] || window["mozRequestAnimationFrame"] || window["oRequestAnimationFrame"] || window["msRequestAnimationFrame"] || FRAF;
})();
function FRAF(callback) {
window.setTimeout(callback, 1000 / 60);
}
var fpsDiv = document.createElement("div");
fpsDiv.style.position = "absolute";
fpsDiv.style.zIndex="40000";
document.body.appendChild(fpsDiv);
var meter = new window.FPSMeter(fpsDiv, {
position: 'fixed',
zIndex: 10,
right: '5px',
top: '5px',
left: 'auto',
bottom: 'auto',
margin: '0 0 0 0',
interval: 1000,
graph: true,
history: 20,
theme: 'colorful',
heat: true
});
var tick = function () {
meter.tick();
RAF(tick);
};
tick();
}
setFPSMeter();
console.log(!!window.FPSMeter);
Kinetic.pixelRatio = 1;
//console.log(window.requestAnimationFrame);
// http://d3lp1msu2r81bx.cloudfront.net/kjs/js/lib/kinetic-v5.1.0.min.js
var width = $("#container").width();
var height = $("#container").height();
console.log("width: "+width+" height: "+height);
var stage = new Kinetic.Stage({
container: 'container',
width: width,
height: 400
});
var layer = new Kinetic.Layer();
// add the layer to the stage
stage.add(layer);
var blob;
var imageObj = new Image();
imageObj.onload = function () {
var group = new Kinetic.Group({
draggable: true
});
var star = new Kinetic.Star({
innerRadius: 50,
outerRadius: 70,
fill: 'red',
stroke: 'black',
strokeWidth: 5,
numPoints: 20,
x: 200,
y: 100,
shadowOffset: 5,
shadowColor: 'black',
shadowBlur: 5,
shadowOpacity: 0.5
});
blob = new Kinetic.Image({
image: imageObj,
x: 50,
y: 40,
// draggable: true,
width: 300,
height: 300
});
// performance
// blob.transformsEnabled('position');
group.add(blob);
group.add(star);
// setTimeout(function () {
// add the shape to the layer
//layer.add(blob);
layer.add(group);
// blob.cache();
layer.batchDraw();
// }, 50);
loadEvents();
/*
blob.cache({
width: 500,
height: 500,
drawBorder: true
}).offset({
x: 10,
y: 10
});
*/
/*
blob.cache({
drawBorder: true
});
*/
};
imageObj.src = "https://dl.dropboxusercontent.com/u/47067729/sandwich2.svg";
function getDistance(p1, p2) {
return Math.sqrt(Math.pow((p2.x - p1.x), 2) + Math.pow((p2.y - p1.y), 2));
}
function loadEvents() {
var lastDist = 0;
var startScale = 1;
stage.getContent().addEventListener('touchstart', function (evt) {
console.log("touchstart");
blob.clearCache();
blob.cache();
}, false);
stage.getContent().addEventListener('touchmove', function (evt) {
clearCache
var touch1 = evt.touches[0];
var touch2 = evt.touches[1];
if (touch1 && touch2) {
// blob.draggable(false);
var dist = getDistance({
x: touch1.clientX,
y: touch1.clientY
}, {
x: touch2.clientX,
y: touch2.clientY
});
if (lastDist == 0) {
lastDist = dist;
}
console.log("touchmove dist: "+dist);
console.log("touchmove lastDist: "+lastDist);
console.log("blob.getScale().x: "+blob.getScale().x);
// scale
var scale = blob.getScale().x * dist / lastDist;
console.log("scale: "+scale);
blob.setScale(scale);
lastDist = dist;
//// rotate
///
layer.batchDraw();
}
}, false);
stage.getContent().addEventListener('touchend', function (evt) {
console.log("touchend");
// blob.draggable(true);
lastDist = 0;
}, false);
}
How can I use caching on a Group of Shapes in KineticJS?

group.cache({
width: blob.width(),
height: blob.height(),
x : blob.x(),
y : blob.y(),
drawBorder: true
}).offset({
x: 10,
y: 10
});
http://jsfiddle.net/k4Lsv73d/2/
You should better config x, y, width and height attrs for caching.

Kinetic.js: Get MinX, MaxX, MinY, and MaxY of rotated Kinetic.Label

I'm trying to prevent a rotated Label from being dragged off the screen, but I cannot figure out how to get MinX, MaxX, MinY, and MaxY of the object in its rotated state. getHeight & getWidth only return the values prior to the rotation.
Here is an example illustrating the problem:
var stage = new Kinetic.Stage({
container: 'container',
width: window.innerWidth,
height: window.innerHeight
});
var layer = new Kinetic.Layer();
var labelLeft = new Kinetic.Label({
x: 95,
y: 180,
opacity: 1.0,
listening: true,
draggable: true,
rotationDeg: -45,
text: {
text: 'Pointing Arrow',
fontFamily: 'Calibri',
fontSize: 20,
padding: 5,
fill: 'white'
},
rect: {
fill: 'blue',
pointerDirection: 'left',
pointerWidth: 20,
pointerHeight: 38,
stroke: 'black',
strokeWidth: 2
},
dragBoundFunc: function (pos) {
var newY = pos.y < 50 ? 50 : pos.y;
return {
x: pos.x,
y: newY
};
}
});
layer.add(labelLeft);
// add the layer to the stage
stage.add(layer);
http://jsfiddle.net/fSNnA/4/
In this example, I use dragBoundFunc to prevent the label from being dragged above y=50. but since the label is rotated, its actual highest point (MinY) has changed, and therefore you can drag it up and partially out of view.
What I really need is a function that will return the absolute current MinX, MaxX, MinY, and MaxY - taking into account the angle of rotation and length of text will not always be the same.
Can anyone help?

Here's how to calculate the bounding-box size of a rotated rectangle (label).
var w = label.getWidth();
var h = label.getHeight();
var rads = label.getRotation();
var c = Math.abs(Math.cos(rads));
var s = Math.abs(Math.sin(rads));
var newWidth = h * s + w * c;
var newHeight = h * c + w * s;
Then assuming you'll always rotate around the center, the left/top boundaries are:
var centerX = label.getX()+label.getWidth()/2;
var centerY = label.getY()+label.getHeight()/2;
var MinX = centerX - newWidth/2;
var MinY = centerY - newHeight/2;
[ Disclaimer: This is just off the top of my head--review it accordingly! ]