How to Programming with Canvas

javascript,asp.net,html5,canvas

You have used two different ways to set the lineWidth: lineWidth and strokeWidth. Your problem is solved by adding a row in your function CanvasState.prototype.drawGridLines. Here's a snapshot of the code: CanvasState.prototype.drawGridLines = function (lineOptions, labelOptions) { var iWidth = this.width; var iHeight = this.height; var ctx = this.ctx; ctx.lineWidth...

Context.Arc not drawing on specified coordinates

I managed to figure it out! Instead of drawing circles I drew lines. On mousedown, call moveTo(clientX,clientY) and on mouseMove call lineTo(clientX,clientY) moveTo(clientX,clientY) That way when the user clicks I have the initial position for the line, when he moves, assign the final position and update the initial position. JS:...

How to alter a degree value into an actual x/y position change?

javascript,canvas,radians

Yes, all angles in JavaScript are in radians. In addition, the canvas context has 0° point to the right so you need to subtract 90° from all angles if you want 0° to be straight up: var angle = (movement.degrees - 90) / 180 * Math.PI; // compensate angle -90°,...

Change a straight line into a curved line when length is overtaken

javascript,html,canvas

I would probably do something like this: Define a holding array with number of entries based on a resolution Map the lines into that array setting 1's very there would be a line range, 0's for the gap. Define a target shape such as an oval (can be any shape...

Javascript Canvas clear/ redraw

javascript,android,cordova,canvas,fabricjs

You need to add a beginPath() in there. rect() will accumulate rectangles to the path, clearRect() won't clear those. Also reset comp. mode and alpha as they are sticky. You could avoid beginPath() if you use fillRect() instead of rect() + fill() (added example below) as fillRect() does not add...

fabric.js resize canvas to fit screen

1. Use css to set your right resolution for canvas: var canvas = document.getElementById("canvas"), ctx = canvas.getContext("2d"); canvas.width = 800; canvas.height = 600; css: /* media query 1 */ #canvas{ width: 400px; height: 250px; } /* media query 2 */ #canvas{ width: 200px; height: 120px; } pros: All the resolution...

Spawning multiple Balls in array js

javascript,canvas,fabricjs

You've got a lot of syntax errors in your code, that's why it doesn't work: It will work if you remove the animframe() call out of the for loop because that's whats making it only push one ball and stopping the for loop. You have also defined the animframe() function...

Fabric.js copy paste of selected group

Thanks to Nistor for helping to get me started. I had to do some additional work to get the result I wanted. Here is my paste function (note that I am using Angular but others can adapt as necessary). Objects must be copied to the clipboard array prior to this...

Using destination-over to save background and actual sketch

javascript,jquery,canvas,sketchjs

Assume you have a SketchJS canvas on top of an image containing a background: #wrapper{positon:relative;} #bk,#myCanvas{position:absolute;} <div id='wrapper'> <img crossOrigin='anonymous' id=bk src='yourImage.png'> <canvas id="myCanvas" width=500 height=300></canvas> </div> Then when you want to combine the Sketch with the background and save it as an image you can use destination-over compositing to...

How to create infinite raphael canvas

javascript,canvas,raphael

One solution is to perform a check on all your objects to see if they're inside or outside your current canvas size. If it's outside, you give the canvas new width/height. Here's a working example (although not using dragable objects) just to show the idea: var c = document.getElementById("canvas"); var...

Highchart Polar chart multiple background colors to SVG

javascript,jquery,canvas,svg,highcharts

The problem is you that created backgrounds are not part of the chart. In fact, add them in the chart.events.load event, and will be included in the exported SVG: http://jsfiddle.net/9eqh0xrj/5/ chart: { polar: true, renderTo: 'container', events: { load: modelMe } }, And example for function: function modelMe() { var...

Javascript Canvas, can't draw multiple images

The reason for only seeing 1 enemy is becuase you're using the wrong variable to the x and y coordinates. You were using the variable enemy that you used to make the enemies. Change the last row in your moveEnemy function from images.enemy.draw(CONTEXT, enemy.posX, enemy.posY); to images.enemy.draw(CONTEXT, myEnemy.posX, myEnemy.posY); ...

Create a cone with shadows

javascript,canvas,drag-and-drop,easeljs,createjs

There is unfortunately no gradient type in canvas which allow you to specify a radiant gradient. You have to provide a mechanism to do so manually. You could use a shadow approach drawing the object off-screen while offsetting the shadow so it overlapped the cone base. One for light and...

Why WebGL slower than Canvas?

javascript,html5,canvas,webgl

The short answer is that webgl/opengl is not meant for drawing a SINGLE quad at a time. GPUs are designed to be massively parallel and thus to gain the most out of webgl you have to draw in batches. You should be comparing drawing 10k images in canvas versus drawing...

Easeljs snap to grid

This is pretty straightforward: Loop over each point, and get the distance to the mouse If the item is closer than the others, set the object to its position Otherwise snap to the mouse instead Here is a quick sample with the latest EaselJS: http://jsfiddle.net/lannymcnie/qk1gs3xt/ The distance check looks like...

How to display button over a Ad Mediator in windows phone 8?

c#,xaml,button,windows-phone-8,canvas

Just embed it in a panel like Grid so it just follows the DOM. Something like (in pseudo); <Grid> <AdMediator/> <Button/> </Grid> ...

Converting Text view to bitmap returns null

java,android,canvas,bitmap,textview

You did not add the text view to the the screen. Once you add it, the view height and width will be calculated for rendering and then only view will be drawn and you can get the bitmap out of it. Do the three things, Add the textview to the...

Displaying tooltips on mouse hover on shapes/position(coordinates) on canvas

html5,canvas,tooltip

You can test if the mouse is over one of your circular hot-spots like this: var hotspots=[ {x:100,y:100,radius:20,tip:'You are over 100,100'}, {x:100,y:200,radius:20,tip:'You are over 100,200'}, ]; var dx=mouseX-hotspot[0].x; var dy=mouseY-hotspot[0].y; if(dx*dx+dy*dy<hotspot[0].radius*hotspot[0].radius){ // it's over hotspot[0] } Here's example code and a Demo: Note: you don't need to show the circular...

Randomly appearing text in html page

javascript,html5,css3,canvas,html5-canvas

Here's one way to animate words into a final sentence: https://jsfiddle.net/m1erickson/q7tpsnmv/ Define some word objects in an array: var words=[]; words.push({ text:'Welcome', // starting x,y of the word offscreen x0:Math.random()*cw, y0:(Math.random()*100)+ch, // ending position of the word onscreen x1:20, y1:50, // font-size size:10, // delay before starting to animate this...

Android Bitmap on Canvas from External File

android,canvas,bitmap,drawable

How about something like: Bitmap bitmap = BitmapFactory.decodeFile(pathToFile); canvas.drawBitmap(bitmap, ...); ...

Drawing rectangles on android canvas

android,canvas

Assuming that you only want this to be for this specific pattern and not expandable then the following should work. Though it is unlikely that it will look right because it is unlikely that a screen will be 1:2 aspect ratio, so you might need to make your canvas a...

Saving an html object to firebase

javascript,canvas,ember.js,firebase,emberfire

You have to serialize and deserialize the image: function serialize(canvas) { return canvas.toDataURL(); } function deserialize(data, canvas) { var img = new Image(); img.onload = function() { canvas.width = img.width; canvas.height = img.height; canvas.getContext("2d").drawImage(img, 0, 0); }; img.src = data; } Based on this answer. Update 1 The canvas.toDataURL() method...

slowly animate a simple line

javascript,animation,canvas

That's actually not what you want to do: computers don't do things "slowly", especially not in a context that is single-threaded. What you want to do instead is draw lots of lines, over and over, where each next line is a little longer than the previous one. That way, it...

How to select particular area in canvas? [closed]

javascript,jquery,html5,canvas

You can define the area you want to fill using an image mask that fits on top of your image - this step is something for Photoshop/GIMP. For example, having your shoe as-is: Create a mask for it leaving the heal in the original position (it makes it easier to...

HTML Canvas Width

So it take some delay to resize image? So don't init it when canvas not resize yet. canvas.width = width; canvas.height = height; canvas.style.backgroundImage = "...." Hope this help....

I'm trying to call a method in a constructer every second for 15 seconds but setInterval doesn't seem to work

javascript,canvas,bezier,quadratic

You need to pass a bound reference to bob.update var intervalID = setInterval(bob.update.bind(bob), 1000); ...

Calculating a concentric arc in canvas

The question as it stands is a bit unclear about requirements. Here is in any case an approach that does not require much calculations, but takes advantage of draw operations to visualize about the same as shown in the codepen. The main steps are: At an off-screen canvas: Define a...

Add metadata (Exif) to base64

javascript,canvas,upload,exif

There is no easy way to do this. Canvas will only save out the JPEG file, then encode it as either a Data-URL or a Blob depending on the method you chose with the most basic chunks. There is no mechanism to insert custom or additional chunks into the file...

Canvas fillRect has wrong X coordinate

javascript,jquery,html,canvas

in the console i am getting the x coordinate as NaN their is no "event.x" you need to do "event.clientX" to get the X coordinate And one more thing you are first definig a var x where the value is stored, next right below it you are running a for...

JavaScript objects: 'addEventListener is not a function'

javascript,html,object,canvas,mapping

Your specific error: 'Uncaught TypeError: elements[i].addEventListener is not a function' is because elements[i].addEventListener is undefined and thus is not a function. The reason it is undefined is because your elements array contains regular Javascript objects. Those objects do not have a .addEventListener() method. That is a method on DOM objects...

AngularJS - ReferenceError: $ is not defined

javascript,angularjs,canvas,reference

try this: var fbcanvas = document.getElementById('fbcanvas'); instead of: var fbcanvas = $('#fbcanvas'); check if data is undefined too...

a border where you can not go through (canvas game)

javascript,css,html5,canvas

You need a concept called "clamping". Clamping is limiting a value within a specified range. You want to clamp your ship's horizontal position to be no less than 0 and no greater than the canvas width. You want to clamp your ship's vertical position to be no less than 0...

Equivalent of canvas quadraticCurveTo in SVG

javascript,jquery,canvas,svg,bezier-curve

It's just a bug in your code. You are not updating lastPoint in your SVG version. http://jsfiddle.net/67haj4nt/4/ And if you update the SVG version to match the canvas version, you get identical curves. http://jsfiddle.net/67haj4nt/5/...

Finding non transparent filled areas in images on javascript canvas

javascript,image,canvas

Here's an outline to get you started: Use context.getImageData to get the pixel data from the canvas, Scan the pixel data for the first non-transparent pixel, Use the "marching squares" algorithm to find the border path points around the circle or rectangle: Draw border around nontransparent part of image on...

Canvas borders c# ( Windows Phone 7)

c#,windows-phone-7,canvas

I`ve fixed this problem. I had just to create another canvas below and set ZIndex to higher paremeter For the bottom Canvas Canvas.ZIndex = 1 For the top Canvas Canvas.ZIndex = 0 Its just about the priority of ZIndex...

Canvas image not loading correctly in Firefox unless cached

javascript,canvas,html5-canvas,automatic-ref-counting,trigonometry

Thank you, K3N! By only calling generateRGBKs once and adding a callback to its imgComp, the issue was resolved. function loadFontColours() { console.log("loading font colours"); console.log(font); var start = new Date().getTime(); var rgbks = generateRGBKs(font, function() { colourLookupTable[0].fontBuf = generateTintImage(rgbks, font, 240, 240, 240); colourLookupTable[1].fontBuf = generateTintImage(rgbks, font, 242, 178,...

Pass an image to a canvas with dataurl

html5,canvas,data-url

The reason nothing shows is that the provided Data-URI contains no data, that is, it is 300x150 fully transparent: data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAASwAAACWCAYAAABkW7XSAAAAxUlEQVR4nO3BMQEAAADCoPVPbQhfoAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAOA1v9QAATX68/0AAAAASUVORK5CYII= My guess is that you along the way saved an empty...

Facebook Canvas login - session not created?

php,facebook,canvas

Well, I decided to take a leap of faith, and now things have progressed. I: a) set up a FacebookRedirectLoginHelper at the top of my app b) get the loginUrl from that, using a pointer to my app (mydomain.com/myapp), and present that for authorization c) user clicks on that link,...

Aligning StackPanel to top-center in Canvas

c#,wpf,xaml,canvas

If you don't want any input or hit testing on a certain element you should set the IsHitTestVisible property to false: <Grid> <Canvas Name="Canvas" Background="#EFECCA"> <DockPanel VerticalAlignment="Stretch" HorizontalAlignment="Stretch" Width="{Binding ActualWidth, ElementName=Canvas}" Height="{Binding ActualHeight, ElementName=Canvas}" MouseLeftButtonDown="DockPanel_MouseLeftButtonDown" TouchDown="DockPanel_TouchDown" Panel.ZIndex="2" Background="Transparent"> </DockPanel> <Button Width="50" Height="50"...

Draw arc on canvas from two x,y points and a center x,y point

The arc() method works only with angles so points has to be converted based on their location and distance to center (distance, representing the radius, has to be the same for both in this case). The signature of arc() is: void arc(unrestricted double x, unrestricted double y, unrestricted double radius,...

How to get the value for one function to another?

javascript,canvas,drag-and-drop

You could call check(num) inside the setInterval() function with a condition: if(i < 30){ draw(num); i++; } else { check(num); } You should also then end your loop as this will keep running indefinitely. To do this assign the interval to a variable: var myInterval = setInterval(function() { And then...

How can I make different shapes of a canvas draggable and particular area of it droppable in the same canvas

Drag and drop in specifik area UPDATE: Copy of box remains at original position while it's being moved. First you need to be able to detect your rectangles. You do this by making then into objects in your code: function box(x,y,w,h,rgb) { this.x = x, this.y = y; this.xS =...

Html5 canvas animation. How to reset rectangle when it hits the end

javascript,html5,canvas,sigma.js

Using your variables y, you can simply check if it is below the height of the canvas height. if( y > c.height ){ // use the canvas height, not the context height y = 0; } Also, the way you're currently calling the timer is a bit inefficient. Instead of...

http://sigmajs.org/ les mis tutorial - why are my canvases 0 height?

Because your CSS code is false. Replace it with this : #sigma-container { position :absolute; width :500px; height :500px; } ...

Snake Game with Mobile Button Controls

javascript,jquery,jquery-mobile,canvas,html5-canvas

AND TIME So basically you have some errors going on. Your first one is your styling. You really need to make your styles more flexible, but this will solve the right button problem I was having. .button-pad > div { z-index: 9999; width: 50px; } http://jsfiddle.net/34oeacnm/8/ $(document).on('click', '.button-pad .button', function(e)...

How to know whether the mousedown event is occured on where we want in canvas?

javascript,html5,canvas,viewport

An explanation of what your code is testing. This part of your code... ((dx * dx) + (dy * dy) < circleRadius * circleRadius) ...uses the Pythagorean Theorem to mathematically test if the mouse is inside the circumference of a circle. (dx * dx) + (dy * dy) measures the...

I want to make a viewport for a canvas game

Try storing the view port in a variable. var view = {x: 0, y: 0}; Then, at the beginning of your draw loop / render function, save the canvas state and translate to the view port. ctx.save(); ctx.translate(view.x, view.y); If you want view.x and view.y to represent the center of...

HTML5: Center text within rectangle

This works (fiddle): var rects = [ [a, 20, w, h, 'Day of the week'], [a, 130, w, h, 'Final'], [a, 240, w, h, 'Direction'], [a, 350, w, h, 'GoSS'], [a, 460, w, h, 'Cyber'], [a, 570, w, h, 'Ultumate77'], [a, 680, w, h, 'Ami'], [a, 790, w, h, 'TestFasePartTwo'],...

How to move a canvas element up and down for a certain amount of time with javascript

Here, I made a small example of a vibrating guitar string. It waits 2 seconds then strums the string, which vibrates for half a second. The problem you have in your code is that you're adding a time-variable to your clearInterval, which isn't possible. If you want a delay on...

HTML canvas breaking when keyboard is shown at landscape orientation

javascript,android,css,html5,canvas

Try using fixed position for it: canvas { position: fixed; left:0; top:0; height: 100%; width: 100%; z-index: -1; /* place in background */ } ...

Canvas - Rotate line

You can use transformations to rotate a line or any shape drawn to canvas. To rotate: Translate to pivot point, ie. point of rotation Apply rotation transform Translate back Draw shape In your case, if we say rotate around the middle of the line: var cd; var ctx2; var startPoint;...

Determine shape drawn on canvas from stored coordinates in an array

Heres how i solved my problem finally :) var newLine = new myLine(startX, startY, endX, endY,type); myLines.push(newLine); function myLine(xStart, yStart, xEnd, yEnd,type) { this.xS = xStart; this.yS = yStart; this.xE = xEnd; this.yE = yEnd; this.type=type } And then looped through the array for (i = 0; i < myLines.length;...

Redraw text over clearRect HTML5 Canvas

jquery,html5,canvas

One possible solution is that you move all your clearRect()'s out from the else-statements to the top and clear it from the start. Then you add text in a second step. That way you can also group the if-statements together to form a if-else if relationship (crappy explanation, just look...

Draw triangle by the intersect of 3 circles

javascript,canvas,draw

Finding the intersection points which are on the circumference of all three circles Here's how to do it: Define 3 circles: var A={x:0,y:0,r:200,color:"rgba(52, 152, 219,0.5)"}; var B={x:0,y:400,r:250,color:"rgba(46, 204, 113,0.5)"}; var C={x:300,y:200,r:280,color:"rgba(241, 196, 15,0.5)"}; Calculate the intersection points of the 3 circles vs each other (AB,BC,CA): var intersections=[]; var AB=circleIntersections(A,B); //...

Text in canvas to show in timed sequences using jQuery?

javascript,canvas,charts,rotation

There are several issues with this code. As @Jackson suggest, you have used wrong jquery function toggle() instead of toggleClass(). Secondly, your footer has margin-top property set to -700px which cause this element to disappear since your canvas and "No" button in summary have about 400px height. So your footer...

Rotating charts in Chart JS

There's no way to rotate the chartJS but not rotate the tips :-\ On the bright side, it's easy enough to code yourself from previous Stackoverflow posts! A polar chart is a set of concentric wedges as shown in this Stackoverflow post: Creating Polar Area Chart using Canvas Tooltips are...

HTML5 canvas slow native function getImageData() on Mac OS

javascript,html5,canvas,getimagedata

I Highly recommend sending such works (image and or other intense data manipulations for example) to a web worker you you won't clog your call stack and your application's responsiveness. Web Workers on HTML5 Rocks helped me figure out how to use web workers for image transformations without making your...

Safari on Mobile blocks window.open [closed]

javascript,html5,canvas,drawimage

It looks to me like you're calling window.open indirectly, not in direct response to a user event. Most browsers will block those calls (I'm surprised Chrome isn't, but I don't know a lot basically anything about canvas rendering). You may have to break up your logic into two buttons: One...

DrawImage is not drawing in a canvas

In your function function loadImg() { var loadTile = new Image(); loadTile.src = 'Top/x+y+/' + tileToLoad + ".png"; loadTile.onload = function() { ctx.drawImage(loadTile, tileToLoadX, tileToLoadY); }; console.log("Successfully loaded tile " + tileToLoad); }; The variables tileToLoad, tileToLoadX and tileToLoadY belong to the function imageSearch() as local variables and would be...

How do I clearRect in my JS canvas?

javascript,html5,canvas,html5-canvas

You are missing a beginPath() in the code to clear the path. This will cause all rectangles to be redraw each time (and will eventually slow down the whole process). var canvas = document.getElementById('myCanvas'); var ctx = canvas.getContext('2d'); var angle = 0; setInterval(function() { angle++; ctx.clearRect(0, 0, canvas.width, canvas.height); ctx.save();...

Image array won't draw to canvas

javascript,canvas,setinterval

It's hard to say exactly where you made a misstake. It seems like ALL your images are added at the same time the first time loadImg is called. In order for your example to draw the images with a delay, you need to put a delay on adding the actual...

How to map tapped event for a single object in a canvas control in XAML?

c#,xaml,canvas,foreach

I think you should try something like this: foreach (UIElement ball in playArea.Children) { if(ball is ContentControl) ball.Tapped += ball_Tapped; } } void ball_Tapped(object sender, TappedRoutedEventArgs e) { ContentControl ball = sender as ContentControl; double top = Canvas.GetTop(ball); animateBall(ball, top, playArea.ActualHeight, "(Canvas.Top)"); } ...

Detect mouse clicks on circles on HTML5 canvas

javascript,html5,canvas,click,mouseevent

With SVG, it would be easy - a circle is an element, and can have a click handler, and has fill that you can manipulate to change colour. With Canvas, you need to: save the data for each circle you draw (center and radius) capture click on canvas as cx,...

How can I make a button who draws a line

javascript,html,button,canvas,htmlbutton

This is how I did it - https://jsfiddle.net/jadeallencook/wnhmgya7/ HTML <center> <div id="myLine"></div> <br /> <button id="myButton"> Draw Line </button> </center> <script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script> CSS #myLine { height: 1px; width: 0px; background: black; margin-top: 25px; } .animate { -webkit-animation: myfirst 5s; animation: myfirst 5s; } @keyframes myfirst { 0% {width: 0px;} 100%...

Java - Show multiple canvases in container

java,canvas,containers

Container Layout is not set. Set the layout by like: container.setLayout(new GridLayout(1,2)); ...

Creating a click event in Javascript Canvas

You can have your canvas listen for mouse clicks on itself like this: // get a reference to the canvas element var canvas=document.getElementById('ctx'); // tell canvas to listen for clicks and call "handleMouseClick" canvas.onclick=handleMouseClick; In the click handler, you'll need to know the position of your canvas relative to the...

Continuous gradient along a HTML5 canvas path

You can do a simple approach interpolating two colors along a line. If you need smooth/shared gradients where two lines joins at steeper angles, you would need to calculate and basically implement a line drawing algorithm from (almost) scratch. This would be out of scope for SO, so here is...

Resize function canvas loaded on shrinked browser and expanded

javascript,css,canvas,html2canvas

You just need to change the canvas to c in the event listener; http://jsbin.com/zigoto/1/edit?js,output var c = document.getElementById('c'), largeHeader = document.getElementById('h'); var w = c.width = window.innerWidth, h = c.height = window.innerHeight, ctx = c.getContext('2d'), spawnProb = 1, numberOfMoves = [8, 16], //[min, max] distance = [50, 200], attenuator =...

Circle div in CSS doesn't show in canvas properly

The border-radius must be the half of the width/height. So setting it to 10px – or even better 50% will render a smooth circle: div { width: 20px; height: 20px; border-radius: 50%; background: red; } http://jsfiddle.net/hmjqLz3p/...

JavaFX 8 Canvas Fonts always Bold

canvas,fonts,javafx-8

I am going to answer my own question. Instead of using: strokeText() in the GraphicsContext, I should use:fillText(). If I do that it works fine....

HTML5 Canvas Base64 Error [closed]

javascript,html,canvas,base64

You gave imgObj1 time to load with imgObj1.onload, but you must also give img time to load by adding img.onload https://jsfiddle.net/m1erickson/tf0y1pL9/ BTW, errors are easier to spot if you format your code. ;-) var can = document.getElementById('canvas1'); var ctx = can.getContext('2d'); // create and load the first image var imgObj1...

What is difference between fillRect(0,0,0,1) and clearRect()

javascript,html5,audio,canvas,html5-canvas

(Updated to correspond to OPs changes in question:) fillRect() with ctx.fillStyle = "rgba(0, 0, 0, 1)"; will fill the region with opaque pixels, in this case black (note alpha is a normalized value [0,1]). clearRect() does the opposite, "clearing" all pixels so that the bitmap becomes transparent (technically the region...

How do I calculate logrithmic labels for a VU meter scale?

I suppose you have a value-to pixel function. What you need to write is the inverse function of that. When you have the inverse function, you just divide the screen area to N equal parts (in the picture you have 6 regions). One region will be X pixels in width....

How can I implement a zoom function in a 2D canvas?