HTML5 canvas rectangles using easeljs - javascript

I am creating a multiple choice quiz on a canvas.
Naturally for the options I used squares as checkBoxes. Now I have put an event Listener on clicking a checkbox, it should get colored. However the listener doesnt work on entire square only the border. May I know how can the problem be resolved and also I wanted to know how to know if a square is filled with a color.
Function for loading options with oIndex from 0,1, till numberOfOptions
pHeight is a a global variable, optionChecks- the checkbox and optionsClick- the invisible rectangle for clicking on
function loadOption(oIndex){
optionChecks[oIndex] = new createjs.Shape();
optionChecks[oIndex].graphics.beginStroke("blue");
optionChecks[oIndex].graphics.setStrokeStyle(2);
optionChecks[oIndex].graphics.drawRect( canvas2.width*0.05 ,pHeight+20 ,20 ,20);
stage.addChild(optionChecks[oIndex] );
stage.update();
var y1 = pHeight+15;
var ht = y1;
var maxWidth = canvas2.width *0.8;
var text = problemOptions[oIndex];
var lineHeight = 25;
var x = (canvas2.width - maxWidth) / 2;
var y = y1;//pHeight+15;
//function for wrapping text
wrapText(ctx2, text, x, y, maxWidth, lineHeight);
ht = wHeight +10;
stage.update();
optionClicks[oIndex] = new createjs.Shape();
optionClicks[oIndex].graphics.beginStroke("black");
optionClicks[oIndex].graphics.setStrokeStyle(2);
optionClicks[oIndex].graphics.drawRect( canvas2.width*0.05,y1,maxWidth-500 ,pHeight-y1+10);
optionClicks[oIndex].addEventListener("click", handleOption);
stage.addChild(optionClicks[oIndex] );
}
Thanks in advance.

You could draw another opaque rect and use the button's hitArea - http://createjs.com/Docs/EaselJS/classes/DisplayObject.html#property_hitArea

Related

getting proper mouse position inside a zoomable iframe

I have a project on svg-edit where i have to create polygon on mouse-click , the svg-canvas (not HTML5 canvas suppose as drawing board) is zoomable, i can create polygon on 100% zoom but when i zoomin or zoomout i can't, actually i am unable to get right x and y position after zoom.as you can see in image.
I had tried this method to get points--
//Container 1440*1920
var svgcanvas = document.getElementById("svgcanvas");
//zoom
var initialZoom = 1440 * 1920;
zoomWidth = parseFloat(svgcanvas.style.width);
zoomHeight = parseFloat(svgcanvas.style.height);
currentZoom = zoomHeight * zoomWidth;
zoom = currentZoom / initialZoom;
//points
var rect = event.target.getBoundingClientRect();
var x1 = ((event.clientX) / zoom) - rect.left;
var y1 = ((eevent.clientY) / zoom) - rect.top;
and my task is
It seems you are not interacting with the svg-edit API at all. Things get much easier if you do.
// do not interact with the DOM element, but with the API object
var svgcanvas = svgEditor.canvas;
// your event listener function
function listener (event) {
var rect = svgcanvas.getBBox(event.target);
var x1 = rect.x;
var y = rect.y;
...
}
No need to handle zooming; the SvgCanvas instance does that for you.

Moving dynamically created grouped object within contained area? (html5canvas - fabric.js)

What I'm trying to create is a small canvas widget that would allow a user to dynamically create a shape onto an image and then place it above an area that caught their interest, effectively it is a highlighter.
The problem is with adding a zoom function, as when I zoom onto the image I would like to ensure that;
There is no possible way for the dynamically created shape to be
dragged anywhere outside the image area. (completed - ish, relies on 2nd step)
You cannot drag the image out of the page view, the canvas area cannot show white space. Part of the image must always be shown, and fill the entire canvas area. (problem)
Here are two examples that I've drawn up, neither of which work correctly;
First example - getBoundingRect does not update and is bound to the image
Second example - getBoundingRect does update and is bound to the grouped object
From the link description you can see that I think I've narrowed the problem down, or at least noticed a key difference between the scripts with how the getBoundingRect behaves.
The first plunk seems to work fine, until you try to zoom in multiple times and at a greater zoom level, then it seems to start bugging out (may take a few clicks and a bit of messing around, it is very inconsistent). The second plunk is very jittery and doesn't work very well.
I've been stuck on this for a week or so now, and I'm at breaking point! So really hoping someone can point out what I'm doing wrong?
Code snippet below for first plunk;
// creates group
var objs = canvas.getObjects();
var group = new fabric.Group(objs, {
status: 'moving'
});
// sets grouped object position
var originalX = active.left,
originalY = active.top,
mouseX = evt.e.pageX,
mouseY = evt.e.pageY;
active.on('moving', function(evt) {
group.left += evt.e.pageX - mouseX;
group.top += evt.e.pageY - mouseY;
active.left = originalX;
active.top = originalY;
originalX = active.left;
originalY = active.top;
mouseX = evt.e.pageX;
mouseY = evt.e.pageY;
// sets boundary area for image when zoomed
// THIS IS THE PART THAT DOESN'T WORK
active.setCoords();
// SET BOUNDING RECT TO 'active'
var boundingRect = active.getBoundingRect();
var zoom = canvas.getZoom();
var viewportMatrix = canvas.viewportTransform;
// scales bounding rect when zoomed
boundingRect.top = (boundingRect.top - viewportMatrix[5]) / zoom;
boundingRect.left = (boundingRect.left - viewportMatrix[4]) / zoom;
boundingRect.width /= zoom;
boundingRect.height /= zoom;
var canvasHeight = canvas.height / zoom,
canvasWidth = canvas.width / zoom,
rTop = boundingRect.top + boundingRect.height,
rLeft = boundingRect.left + boundingRect.width;
// checks top left
if (rTop < canvasHeight || rLeft < canvasWidth) {
group.top = Math.max(group.top, canvasHeight - boundingRect.height);
group.left = Math.max(group.left, canvasWidth - boundingRect.width);
}
// checks bottom right
if (rTop > 0 || rLeft > 0) {
group.top = Math.min(group.top, canvas.height - boundingRect.height + active.top - boundingRect.top);
group.left = Math.min(group.left, canvas.width - boundingRect.width + active.left - boundingRect.left);
}
});
// deactivates all objects on mouseup
active.on('mouseup', function() {
active.off('moving');
canvas.deactivateAll().renderAll();
})
// sets group
canvas.setActiveGroup(group.setCoords()).renderAll();
}
EDIT:
I've added comments and tried to simplify the code in the plunks.
The relevant code starts within the if (active.id == "img") { code block.
I've put irrelevant code as functions at the bottom, they can largely be ignored. ( createNewRect() + preventRectFromLeaving() )
I've removed one of the plunks to avoid confusion.
Let me know if it helps, or If I should try to simplify further.
Thanks!
I think that the grouping was messing with the position of the background image. So, I tried removing the group when the image is moving and manually updating the position of the rect instead.
It sets the last position of the image before moving
var lastLeft = active.left,
lastTop = active.top;
And then it updates those and the position of the rect every time the image moves
rect.left += active.left - lastLeft;
rect.top += active.top - lastTop;
// I think this is needed so the rectangle can be re-selected
rect.setCoords();
lastLeft = active.left;
lastTop = active.top;
Since the image has to stay within the canvas, the rect stays inside the canvas, too, whenever the image moves. The rest of the code you wrote seemed to work fine.
http://plnkr.co/edit/6GGcUxGC7CjcyQzExMoK?p=preview

Mouse Proximity to object Javascript

I'm struggling with this for a while now. I'm drawing a grid on the canvas. I add a mousemove eventHandler and track the mouseX and mouseY positions. I would like to be able to calculate the distance from the mouse position to the item in the grid. I can't seem to get this right, I've tried a few different solutions, like adding a loop in the mousemove handler and using requestAnimationFrame, but both solutions are very slow.
Here's my code below:
function setupCanvas(){
canvas = document.getElementById('canvas');
ctx = canvas.getContext('2d');
width = canvas.width = window.innerWidth;
height = canvas.height = window.innerHeight;
blockWidth = width/2 - 150;
blockHeight = height/2 - 100;
gridArray = [];
gridWidthArray = [];
ctx.fillRect(0,0,width,height);
//drawGrid();
drawInitGrid();
canvas.addEventListener('mousemove',onMouseMoveHandler);
}
function drawInitGrid(){
for(x = 0; x<16; x++){
for(y = 0; y<11; y++){
var gridBlock = new GridBlock((blockWidth) + x*20, (blockHeight) + y*20, blockWidth, blockHeight);
gridBlock.render(ctx);
gridArray.push(gridBlock);
//gridWidthArray.push(gridBlock.xPos)
}
}
}
function onMouseMoveHandler(e){
if(containerBounds(e)){
mouseX = e.offsetX;
mouseY = e.offsetY;
console.log(mouseX, mouseY);
//console.log(gridWidthArray);
for(var grid in gridArray){
//console.log(gridArray[grid].xPos)
}
}
}
I've also tried adding a mouseevent in the GridBlock object, but that also doesn't seem to work.
You can calculate the distance between any 2 points like this:
var dx=point2.x-point1.x;
var dy=point2.y-point1.y;
var distance=Math.sqrt(dx*dx+dy*dy);
Also in your fiddle your mouse position calculation should account for the offset position of the canvas within the window:
var BB=canvas.getBoundingClientRect();
var offsetX=BB.left;
var offsetY=BB.top;
function onMouseMoveHandler(e){
var mouseX=parseInt(e.clientX-offsetX);
var mouseY=parseInt(e.clientY-offsetY);
}
[ Finding nearest point in grid ]
Assume you have a mouse position [mx,my] and assume you have a grid with its top-left at [0,0] and with its cell size at cellWidth X cellHeight.
Then you can calculate the grid cell closest to the mouse like this:
var cellX=parseInt((mx+cellWidth/2)/cellWidth)*cellWidth;
var cellY=parseInt((my+cellHeight/2)/cellHeight)*cellHeight;
Of course, if the grid's top-left is not at [0,0], you will have to adjust for the gridss offset.

How to add the vertical parallel lines in the rectangle?

I want to add the vertical lines when I draw rectangle. The no of lines is dependent on the user and can be read from the text box.
I know the logic but somehow I am not able to get the answer.
I am calculating the width of the rectangle and then diving the width on the basis of no of vertical lines.
Click the checkbox near rectangle and draw using mouse down events
Please let me know where I am going wrong.
function PlotPitch()
{
var iPatches = document.getElementById('txtPatchCount').value;
var iTop = mySel.y;
var iBottom = mySel.y + mySel.h;
var iLeft = mySel.x;
var iX = iLeft;
canvas = document.getElementById('canvas2');
context = canvas.getContext('2d');
for (var iPatch=1; iPatch<iPatches; ++iPatch) {
iX = iLeft + iPatch*mySel.w/iPatches;
context.moveTo(iX, iTop);
context.lineTo(iX, iBottom);
}
context.lineWidth=0.25;
context.stroke();
}
http://jsfiddle.net/K5wcs/4/
If I am adding this the code is breaking and I am not able to draw anything.
What you should do if you have 'strange' behaviour is to separate concerns, so in this case that could be by creating a function that you test separately, which draws the lines, then once it's tested ok, plug it in code by just calling the function. You should find quickly.
So begin by testing this :
function drawLines(Context, mySel, iPatches) {
var iTop = mySel.y;
var iBottom = mySel.y + mySel.h;
var iLeft = mySel.x;
var iX = iLeft;
var colWidth = mySel.w/iPatches ;
for (var iPatch=1; iPatch<iPatches; ++iPatch) {
iX += colWidth;
Context.moveTo(iX, iTop);
Context.lineTo(iX, iBottom);
}
Context.lineWidth=0.25;
Context.stroke();
}
Good luck.

Drawing predefined number of dots inside a canvas

I am trying achieve the following:
-Given two variables numberColumns/numberRows I want to draw a grid of rectangles or dots in a set width canvas for example 800x400
I have tried several things, but I fail at getting the rectangles/dots the right size with the right spacing
This is an example I tried to draw one row. I am trying to get to work on any given number of rows/columns
function draw(){
var width = 800;
var height = 400;
var nrow = 32;
var ncol = 48;
var canvas = document.getElementById('tutorial');
if (canvas.getContext){
var ctx = canvas.getContext('2d');
//Have a border so drawing starts at 20,20
var spacew = width - 40;
var x = Math.floor(spacew/ncol);
var currCol = 20;
for(i = 1; i<ncol; i++){
ctx.beginPath();
ctx.arc(currCol, 20, x, 0, Math.PI*2, true);
ctx.closePath();
ctx.fill();
currCol = currCol + x*2;
}
}
}
Any idea on how I would go about this, maybe an example?
Thanks
I have created an example here http://jsfiddle.net/J9MLq/7/. Each circle has a diameter that is a 2*radius. i have put it when calculating the radius dynamically depending on the width of canvas in var x = width/ncol/2; (You don't need any Math.floor/Math.ceil, otherwise you will have gaps between circles and also borders). Also, now canvas element is resizable, your function accepts parameters draw(width, height). Now you can play with the rows by yourself. You can extend the function to accept rows and columns amount as well. Just try it there...

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