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Clipping mask using fabricjs

I'm currently working on web app for photo editing using FabricJS and one of features I need to implement is something like Clipping masks from Photoshop.
For example I have this assets: frame, mask and image. I need to insert image inside frame and clip it with mask. Most tricky part is in requirements:
User should be able to modify image inside frame, e.g. move, rotate, skew... Frame itself also can be moved inside canvas.
Number of layers is not limited so user can add objects under or above masked image.
Masks, frames and images is not predefined, user should be able to upload and use new assets.
My current solution is this:
Load assets
Set globalCompositeOperation of image to source-out
Set clipTo function for image.
Add assets on canvas as a group
In this solution clipTo function preserve image inside rectangular area of frame and with help of globalCompositeOperation I'm clipping image to actual mask. At first sight it works fine but if I add new layer above this newly added group it will be cutted off because of globalCompositeOperation="source-out" rule. I've created JSFiddle to show this.
So, that else could I try? I've seen some posts on StackOverflow with advices to use SVGs for clipping mask, but if I understand it correctly SVG must contain only one path. This could be a problem because of third requirement of my app.
Any advice in right direction will help, because right now I'm totally stuck with this problem.

You can do this by using ClipPath property of Img Object which you want to mask. With this, you can Mask Any Type of Object. and also you need to add some Ctx Configuration in ClipTo function of Img Object.
check this link https://jsfiddle.net/naimsajjad/8w7hye2v/8/
(function() {
var img01URL = 'http://fabricjs.com/assets/printio.png';
var img02URL = 'http://fabricjs.com/lib/pug.jpg';
var img03URL = 'http://fabricjs.com/assets/ladybug.png';
var img03URL = 'http://fabricjs.com/assets/ladybug.png';
var canvas = new fabric.Canvas('c');
canvas.backgroundColor = "red";
canvas.setHeight(500);
canvas.setWidth(500);
canvas.setZoom(1)
var circle = new fabric.Circle({radius: 40, top: 50, left: 50, fixed: true, fill: '', stroke: '1' });
canvas.add(circle);
canvas.renderAll();
fabric.Image.fromURL(img01URL, function(oImg) {
oImg.scale(.25);
oImg.left = 10;
oImg.top = 10;
oImg.clipPath = circle;
oImg.clipTo = function(ctx) {
clipObject(this,ctx)
}
canvas.add(oImg);
canvas.renderAll();
});
var bili = new fabric.Path('M85.6,606.2c-13.2,54.5-3.9,95.7,23.3,130.7c27.2,35-3.1,55.2-25.7,66.1C60.7,814,52.2,821,50.6,836.5c-1.6,15.6,19.5,76.3,29.6,86.4c10.1,10.1,32.7,31.9,47.5,54.5c14.8,22.6,34.2,7.8,34.2,7.8c14,10.9,28,0,28,0c24.9,11.7,39.7-4.7,39.7-4.7c12.4-14.8-14-30.3-14-30.3c-16.3-28.8-28.8-5.4-33.5-11.7s-8.6-7-33.5-35.8c-24.9-28.8,39.7-19.5,62.2-24.9c22.6-5.4,65.4-34.2,65.4-34.2c0,34.2,11.7,28.8,28.8,46.7c17.1,17.9,24.9,29.6,47.5,38.9c22.6,9.3,33.5,7.8,53.7,21c20.2,13.2,62.2,10.9,62.2,10.9c18.7,6.2,36.6,0,36.6,0c45.1,0,26.5-15.6,10.1-36.6c-16.3-21-49-3.1-63.8-13.2c-14.8-10.1-51.4-25.7-70-36.6c-18.7-10.9,0-30.3,0-48.2c0-17.9,14-31.9,14-31.9h72.4c0,0,56-3.9,70.8,26.5c14.8,30.3,37.3,36.6,38.1,52.9c0.8,16.3-13.2,17.9-13.2,17.9c-31.1-8.6-31.9,41.2-31.9,41.2c38.1,50.6,112-21,112-21c85.6-7.8,79.4-133.8,79.4-133.8c17.1-12.4,44.4-45.1,62.2-74.7c17.9-29.6,68.5-52.1,113.6-30.3c45.1,21.8,52.9-14.8,52.9-14.8c15.6,2.3,20.2-17.9,20.2-17.9c20.2-22.6-15.6-28-16.3-84c-0.8-56-47.5-66.1-45.1-82.5c2.3-16.3,49.8-68.5,38.1-63.8c-10.2,4.1-53,25.3-63.7,30.7c-0.4-1.4-1.1-3.4-2.5-6.6c-6.2-14-74.7,30.3-74.7,30.3s-108.5,64.2-129.6,68.9c-21,4.7-18.7-9.3-44.3-7c-25.7,2.3-38.5,4.7-154.1-44.4c-115.6-49-326,29.8-326,29.8s-168.1-267.9-28-383.4C265.8,13,78.4-83.3,32.9,168.8C-12.6,420.9,98.9,551.7,85.6,606.2z',{top: 0, left: 180, fixed: true, fill: 'white', stroke: '', scaleX: 0.2, scaleY: 0.2 });
canvas.add(bili);
canvas.renderAll();
fabric.Image.fromURL(img02URL, function(oImg) {
oImg.scale(0.5);
oImg.left = 180;
oImg.top = 0;
oImg.clipPath = bili;
oImg.clipTo = function(ctx) {
clipObject(this,ctx)
}
canvas.add(oImg);
canvas.renderAll();
});
function clipObject(thisObj,ctx)
{
if (thisObj.clipPath) {
ctx.save();
if (thisObj.clipPath.fixed) {
var retina = thisObj.canvas.getRetinaScaling();
ctx.setTransform(retina, 0, 0, retina, 0, 0);
// to handle zoom
ctx.transform.apply(ctx, thisObj.canvas.viewportTransform);
thisObj.clipPath.transform(ctx);
}
thisObj.clipPath._render(ctx);
ctx.restore();
ctx.clip();
var x = -thisObj.width / 2, y = -thisObj.height / 2, elementToDraw;
if (thisObj.isMoving === false && thisObj.resizeFilter && thisObj._needsResize()) {
thisObj._lastScaleX = thisObj.scaleX;
thisObj._lastScaleY = thisObj.scaleY;
thisObj.applyResizeFilters();
}
elementToDraw = thisObj._element;
elementToDraw && ctx.drawImage(elementToDraw,
0, 0, thisObj.width, thisObj.height,
x, y, thisObj.width, thisObj.height);
thisObj._stroke(ctx);
thisObj._renderStroke(ctx);
}
}
})();
<script src="https://cdnjs.cloudflare.com/ajax/libs/fabric.js/3.6.3/fabric.min.js"></script>
<canvas id="c" width="400" height="400"></canvas>

Not sure what you want.
If you want the last image loaded (named img2), the one you send to the back to not effect the layers above do the following.
You have mask,frame,img, and img2;
Put them in the following order and with the following comp settings.
img2, source-over
img, source-over
mask, destination-out
frame, source-over
If you want something else you will have to explain it in more detail.
Personally when I provide masking to the client I give them full access to all the composite methods and allow them to work out what they need to do to achieve a desired effect. Providing a UI that allows you to change the comp setting, and layer order makes it a lot easier to sort out the sometimes confusing canvas composite rules.

I'd suggest looking at this solution.
Multiple clipping areas on Fabric.js canvas
You end up with a shape layer that is used to define the mask shape. That shape then gets applied as a clipTo to your image.
The one limitation I can think off though that you might run into is when you start to rotate various shapes. I know I have it working great with a rectangle and a circle, however ran into some issues with polygons from what I recall... This was all setup under and older version of FabricJS however, so there may have been some improvements there that I'm not experienced with.
The other issue I ran into was drop shadows didn't render correctly when passed to a NodeJS server running FabricJS.

FabricJS prevent canvas.clipTo from clipping canvas.backgroundImage

I want to set a global clipTo in my Fabric-powered Canvas that will affect all user-added layers. I want a background image and an overlay image, which are unaffected by this clip mask.
Example:
Here's what's happening in this photo:
A canvas overlay image makes the t-shirt look naturally wrinkled. This overlay image is mostly transparent
A background image in the exact shape of the t-shirt was added, which is supposed to make the t-shirt look blue
A canvas.clipTo function was added, which clips the canvas to a rectangular shape
A user-added image (the famous Fabric pug) was added
I want the user-added image (the pug) to be limited to the rectangular area.
I do not want the background image (the blue t-shirt shape) affected by the clip area.
Is there a simple way to accomplish this? I really don't want to have to add a clipTo on every single user layer rather than one tidy global clipTo.
You can play with a JS fiddle showing the problem here.

I came here with the same need and ultimately found a solution for what I'm working on. Maybe it helps:
For SVG paths, within the clipTo function you can modify the ctx directly prior to calling render(ctx) and these changes apply outside the clipped path o. Like so:
var clipPath = new fabric.Path("M 10 10 L 100 10 L 100 100 L 10 100", {
fill: 'rgba(0,0,0,0)',
});
var backgroundColor = "rgba(0,0,0, 0.2)";
var opts = {
controlsAboveOverlay: true,
backgroundColor: 'rgb(255,255,255)',
clipTo: function (ctx) {
if (typeof backgroundColor !== 'undefined') {
ctx.fillStyle = backgroundColor;
ctx.fillRect(0, 0, 300, 150);
}
clipPath.render(ctx);
}
}
var canvas = new fabric.Canvas('c', opts);
canvas.add(new fabric.Rect({
width: 50,
height: 50,
left: 30,
top: 30,
fill: 'rgb(255,0,0)'
}));
You can of course add an image instead of a color, or whatever else you want done. The trick I've found is to put it in the clipTo function on the ctx directly.
here's a fiddle

One (sorta hacky) solution: set a CSS background image on your canvas element, as shown in https://jsfiddle.net/qpnvo3cL/
<canvas id="c" width="500" height="500"></canvas>
<style>
background: url('http://fabricjs.com/assets/jail_cell_bars.png') no-repeat;
</style>
<script>
var canvas = window._canvas = new fabric.Canvas('c');
canvas.clipTo = function(ctx) {
ctx.rect(100,100,100,100);
}
</script>

Have you tried clipping a fabric Group? You could make the whole shirt one canvas. The center graphics would be one Group which you clip to where you want it. The white t-shirt and the blue overlay would of course not be part of the clipped group.
Here's an example of clipping a group:
var rect = new fabric.Rect({width:100, height: 100, fill: 'red' });
var circle = new fabric.Circle({ radius: 100, fill: 'green' });
var group1 = new fabric.Group([ circle, rect ], { left: 100, top: 100 });
canvas.add(group1);
group1.clipTo = function(ctx) {
ctx.rect(50,50,200,200);
};
See this jsfiddle I made: https://jsfiddle.net/uvepfag5/4/

I find clip rather slow so I tend to use globalCompositeOperation to do masking.
If you really need to use clip then use it in conjunction with save and restore.
// ctx is canvas context 2d
// pug is the image to be clipped
// draw your background
ctx.save(); // save state
ctx.rect(100,100,100,100); // set the clip area
ctx.clip(); // apply the clip
ctx.drawImage(pug,x,y); // draw the clipped image
ctx.restore(); // remove the clipping
// draw the other layers.
or you can
// draw background
ctx.globalCompositeOperation = "xor"; // set up the mask
ctx.fillRect(100,100,100,100); // draw the mask, could be an image.
// Alpha will effect the amount of masking,
// not available with clip
ctx.globalCompositeOperation = "destination-over";
ctx.drawImage(pug,x,y); // draw the image that is masked
ctx.globalCompositeOperation = "source-over";
// draw the stuff that needs to be over everything.
The advantage of composite operations is you have control over the clipping at a per pixel level, including the amount of clipping via the pixel alpha value

Draw on top of an image using javascript

For a certain image I have a list containing the pixel coordinates of all the points in a polygon segmenting all the objects it contains (look at the image below).
For instance, for the person I have a list l1 = [x0,y0,x1,y1,...,xn,yn], for the cat a list l2 = [x0',y0',x1',y1',...,xk',yk'], and similarly for all the objects.
I have 2 questions:
What is the best javascript library to use to draw on top of an image? Given the raw image I would like to obtain the result seen below.
I would like each segmentation to be visualized only when the mouse hovers on top of it. For this I believe I should bind this drawing function to the mouse position.
I'm thinking at something with the structure below but don't know how to fill the gaps, could you please give me some indication?
$(.container).hover( function(e) {
//get coordinates of mouse
//if mouse is over one object
//draw on top of image the segmentation for that object
});
container is the class of the div containing the image so I should be able to get the coordinates of the mouse since the image starts at the top left corner of the container div.

Simply rebuild the polygons from each array and do a hit test using the mouse position.
First: If you have many arrays defining the shapes it could be smarter to approach it in a more general way instead of using variables for each array as this can soon be hard to maintain. Better yet, an object holding the array and for example id could be better.
Using an object you could do - example:
function Shape(id, points, color) {
this.id = id;
this.points = points;
this.color = color;
}
// this will build the path for this shape and do hit-testing:
Shape.prototype.hitTest = function(ctx, x, y) {
ctx.beginPath();
// start point
ctx.moveTo(this.points[0], this.points[1]);
// build path
for(var i = 2, l = this.points.length; i < l; i += 2) {
ctx.lineTo(this.points[i], this.points[i+1]);
}
ctx.closePath();
return ctx.isPointInPath(x, y);
};
Now you can create new instances with the various point arrays like this:
var shapes = [];
shapes.push(new Shape("Cat", [x0,y0,x1,y1, ...], "rgba(255,0,0,0.5)");
shapes.push(new Shape("Woman", [x0,y0,x1,y1, ...], "rgba(0,255,0,0.5)"));
...
When you get a mouse position simply hit-test each shape:
$(".container").hover( function(e) {
//get corrected coordinates of mouse to x/y
// redraw canvas without shapes highlighted
for(var i = 0, shape; shape = shapes[i]; i++) { // get a shape from array
if (shape.hitTest(ctx, x, y)) { // is x/y inside shape?
ctx.fillStyle = shape.color; // we already have a path
ctx.fill(); // when testing so just fill
// other tasks here...
break;
}
}
});

check this Link it might be slow your problem.
Include necessary javascript library files
jquery.min.js,raphael.min.js,json2.min.js,raphael.sketchpad.js
To create an editor
<div id="editor"></div>
<form action="save.php" method="post">
<input type="hidden" name="data" />
<input type="submit" value="Save" />
</form>
<script type="text/javascript">
var sketchpad = Raphael.sketchpad("editor", {
width: 400,
height: 400,
editing: true
});
// When the sketchpad changes, update the input field.
sketchpad.change(function() {
$("#data").val(sketchpad.json());
});
</script>

Using PaperJs to Animate the Drawing of a Line

This is my code:
<!DOCTYPE html>
<html>
<head>
<!-- Load the Paper.js library -->
<script type="text/javascript" src="paper.js"></script>
<!-- Define inlined PaperScript associate it with myCanvas -->
<script type="text/paperscript" canvas="myCanvas">
// Create a Paper.js Path to draw a line into it:
var path = new Path();
// Give the stroke a color
path.strokeColor = 'black';
var start = new Point(100, 100);
// Move to start and draw a line from there
path.moveTo(start);
// Note the plus operator on Point objects.
// PaperScript does that for us, and much more!
function onFrame(event) {
// Your animation code goes in here
for (var i = 0; i < 100; i++) {
path.add(new Point(i, i));
}
}
</script>
</head>
<body style="margin: 0;">
<canvas id="myCanvas"></canvas>
</body>
</html>
When the page is loaded, a line is drawn. But I am trying to animate the drawing of the line from point A to B. My attempt above doesn't seem to do anything... it just draws the line on page load with no animation of the actual line going from A to B.
Ref. http://paperjs.org/download/

Since you are running the for-loop on every frame, you're re-creating the same line segments over and over, all at once. Instead, you need to add one segment per frame:
// Create a Paper.js Path to draw a line into it:
var path = new Path();
// Give the stroke a color
path.strokeColor = 'black';
var start = new Point(100, 100);
// Move to start and draw a line from there
// path.moveTo(start);
// Note the plus operator on Point objects.
// PaperScript does that for us, and much more!
function onFrame(event) {
// Your animation code goes in here
if (event.count < 101) {
path.add(start);
start += new Point(1, 1);
}
}
The if statement serves as a limit for the line's length.
Also note that the path.moveTo(start) command does not mean anything if your path does not yet have any segments.
If you don't want to add points every frame, but only change the length of a line, simply change the position of one of the segments. First create add two segments to your path, then change the position of the second segment's point per frame event:
// Create a Paper.js Path to draw a line into it:
var path = new Path();
// Give the stroke a color
path.strokeColor = 'black';
path.add(new Point(100, 100));
path.add(new Point(100, 100));
// Move to start and draw a line from there
// path.moveTo(start);
// Note the plus operator on Point objects.
// PaperScript does that for us, and much more!
function onFrame(event) {
// Your animation code goes in here
if (event.count < 101) {
path.segments[1].point += new Point(1, 1);
}
}

Dynamic Canvas DrawImage Function

I've got a problem filling 25 canvas elements automatically in a for loop. They are numbered like so: can01 to can25.
I've tried all I knew to draw different images on the canvas and I have spent a lot of time in searching a few articles which are about this problem but I haven't found any.
This is my working code to fill all canvas elements with the same image:
var imageGrass = new Image();
imageGrass.src = 'recources/imagesBG/grass.jpg';
imageGrass.onload = function() {
for (var i = 1; i < 26; i++)
{
if( i < 10 )
{
var task = "can0" + i + "_ctx.drawImage(imageGrass, 0, 0);";
eval(task);
}
else
{
var task = "can" + i + "_ctx.drawImage(imageGrass, 0, 0);";
eval(task);
}
}
}
But I really don't know how to make the imageGrass.src dynamic. For example, the canvas element no. 5 (can05) in this case shall look like stone texture.
I´m really looking forward to read your ideas. I just don't get it.

Here’s how to impliment Dave’s good idea of using arrays to organize your canvases:
Create an array that will hold references to all your 25 canvases (do the same for 25 contexts)
var canvases=[];
var contexts=[];
Next, fill the array with all your canvases and contexts:
for(var i=0;i<25;i++){
var canvas=document.getElementById("can"+(i<10?"0":""));
var context=canvas.getContext("2d");
canvases[i]=canvas;
contexts[i]=context;
}
If you haven't seen it before: i<10?"0":"" is an inline if/else used here to add a leading zero to your lower-numbered canvases.
Then you can fetch your “can05” canvas like this:
var canvas=canvases[4];
Why 4 and not 5? Arrays are zero based, so canvases[0] holds can01. Therefore array element 4 contains your 5th canvas “can05”.
So you can fetch the drawing context for your “can05” like this:
var context=contexts[4];
As Dave says, “evals are evil” so here’s how to fetch the context for “can05” and draw the stone image on it.
var context=contexts[4];
context.drawImage(stoneImage,0,0);
This stone drawing can be shortened to:
contexts[4].drawImage(stoneImage,0,0);
You can even put this shortened code into a function for easy reuse and modification:
function reImage( canvasIndex, newImage ){
contexts[ canvasIndex ].drawImage( newImage,0,0 );
}
Then you can change the image on any of your canvases by calling the function:
reimage( 4,stoneImage );
That’s it!
The evil-evals have been vanquished (warning: never invite them to your computer again!)
Here is example code and a Fiddle: http://jsfiddle.net/m1erickson/ZuU2e/
This code creates 25 canvases dynamically rather than hard-coding 25 html canvas elements.
<!doctype html>
<html>
<head>
<link rel="stylesheet" type="text/css" media="all" href="css/reset.css" /> <!-- reset css -->
<script type="text/javascript" src="http://code.jquery.com/jquery.min.js"></script>
<style>
body{ background-color: ivory; padding:0px; margin:0px;border:0px; }
canvas{vertical-align: top; }
</style>
<script>
$(function(){
var canvases=[];
var contexts=[];
var grass=new Image();
grass.onload=function(){
// the grass is loaded
// now make 25 canvases and fill them with grass
// ALSO !!!
// keep track of them in an array
// so we can use them later!
make25CanvasesFilledWithGrass()
// just a test
// fill canvas#3 with gold
draw(3,"gold");
// fill canvas#14 with red
draw(14,"red");
}
//grass.src="https://dl.dropboxusercontent.com/u/139992952/stackoverflow/grass.jpg";
//grass.src="grass.jpg";
function make25CanvasesFilledWithGrass(){
// get the div that we will fill with 25 canvases
var container=document.getElementById("canvasContainer");
for(var i=0;i<25;i++){
// create a new html canvas element
var canvas=document.createElement("canvas");
// assign the new canvas an id, width and height
canvas.id="can"+(i<10?"0":"")+i;
canvas.width=grass.width;
canvas.height=grass.height;
// get the context for this new canvas
var ctx=canvas.getContext("2d");
// draw the grass image in the new canvas
ctx.drawImage(grass,0,0);
// add this new canvas to the web page
container.appendChild(canvas);
// add this new canvas to the canvases array
canvases[i]=canvas;
// add the context for this new canvas to the contexts array
contexts[i]=ctx;
}
}
// test -- just fill the specified canvas with the specified color
function draw(canvasIndex,newColor){
var canvas=canvases[canvasIndex];
var ctx=contexts[canvasIndex];
ctx.beginPath();
ctx.fillStyle=newColor;
ctx.rect(0,0,canvas.width,canvas.height);
ctx.fill();
}
}); // end $(function(){});
</script>
</head>
<body>
<div id="canvasContainer"></div>
</body>
</html>