I'm working with PaperJS. When I resize the browser window, I ask the canvas to redraw. However, the graphics do not re-center, as I draw the graphics from view.center:
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title>Demo</title>
<script src="http://code.jquery.com/jquery-latest.min.js"></script>
<script src="js/paper-full.min.js"></script>
<script type="text/paperscript" canvas="paperjs-canvas">
var center = new Path.Circle(view.center, 450);
center.fillColor = '#000000';
function onResize(event) {
// redraw canvas
paper.view.draw();
}
</script>
<style>
html, body {
padding: 0;
margin: 0;
height: 100%;
overflow: hidden; /* avoid Mac / Chrome overscroll */
}
#paperjs-canvas {
width: 100%;
height: 100%;
background-color: #D0E7D1;
}
</style>
</head>
<body>
<canvas id="paperjs-canvas" class="off" data-paper-resize="true"></canvas>
</body>
</html>
I checked from Developer Console that the resize function is called every time I resize the browser, but the paper.view.draw(); does not re-align the graphics.
What did I miss?
Running on Google Chrome 41, Mac OS X 10.10.2
View.center is just a regular coordinate. There's nothing special about it that keeps an object positioned there locked at the "center" of the canvas.
If you want to keep the same point as view.center after resizing the canvas, you can use view.scrollBy(point) to transform the coordinate system. Just keep in mind that the point [0,0] may no longer correspond to the top-left of the canvas.
var center = new Path.Circle(view.center, 240);
center.fillColor = '#000000';
var lastPoint = view.center;
function onResize(event) {
view.scrollBy(lastPoint.subtract(view.center));
lastPoint = view.center;
}
Here's a sketch on paper.js
Related
I am trying to build from scratch a minimalist Pdf.js viewer: I would just need zoom, pan and actual page number/overall pages number.
I am able to set the initial zoom so that the pdf is shown as I want at the beginning, i.e. it fits one of the two dimension of the available screen (for clarity in my code below I directly set the height property supposing the aspect ratio (height / width) of the document is higher than that of the available screen). Here is my code:
<!DOCTYPE html>
<html style="margin: 0; padding: 0; border: 0;
height:100%; width:100%">
<head>
<title>PDF.js Learning</title>
</head>
<body style="background-color:rgba(0, 0, 0, 0.78); margin: 0; padding: 0;
border: 0; height:100%; width:100%">
<div style="position: relative; margin: 0; padding: 0; border: 0;
height:100%; width:100%">
<canvas id="the-canvas" style="position: absolute; margin: 0;
padding: 0; border: 0; top: 50%;
left: 50%;
transform: translate(-50%, -50%);">
</canvas>
</div>
<!-- JQuery libraries -->
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.1.1/jquery.min.js"></script>
<!-- Pdf.js libraries -->
<script type="text/javascript" src="build\pdf.js"></script>
<script type="text/javascript" src="web\compatibility.js></script>
<script>
var url = "your_PDF_url";
// Asynchronous download PDF
function openPdf () {
PDFJS.getDocument(url).then(function(pdf) {
return pdf.getPage(1);
}).then(function(page) {
/* Get viewport (dimensions) and setting scale depending on
the relative aspect ratio of the pdf and window*/
var desiredHeight = $(window).height(); //or width
var viewport = page.getViewport(1);
var scale = desiredHeight / viewport.height; //or width
viewport = page.getViewport(scale);
// Get canvas#the-canvas
var canvas = document.getElementById('the-canvas');
// Fetch canvas' 2d context
var context = canvas.getContext('2d');
// Set dimensions to Canvas
canvas.height = viewport.height;
canvas.width = viewport.width;
// Prepare object needed by render method
var renderContext = {
canvasContext: context,
viewport: viewport
};
// Render PDF page
page.render(renderContext);
});
}
$(document).ready(function() {
(openPdf());
});
$(window).resize(function() {
(openPdf());
});
</script>
</body>
</html>
I can't find anywhere how I should do if I want to resize the pdf document or if I want to zoom it in and out:
should I reload the document and re-render? Should I only re-render it (as, if I haven't misunderstood, the pdf file once loaded, should be already available) with a new scale? Is there a less computation option than the 2 above?
I tried the first one (calling the PDFJS.getDocument() on resize) but it is really consuming and sometimes I get a bad rendering or no render at all.
Is there a reference for this and for pan somewhere? And how to show scroll bar, in the case of multiple pages documents, to change page? Thank you for your help.
First-time posting a question, and I avow up front that my HTML/CSS/Javascript knowledge is ... shall we say scrappy. I usually manage, but I can't seem to figure this out.
All I want to do is display an image centered. Then create a canvas, position the canvas over the image, and draw on it. Then have the canvas stay with the image as the browser is re-sized. Here's what I have so far (I confess, I got much of the Javascript code from another poster, and I'm trying to use it as a learning example):
<!DOCTYPE html>
<html>
<head>
<script>
function myInit()
{
hdc = set_canvas();
hdc.fillRect(0, 0, 50, 50);
}
function set_canvas()
{
var img = document.getElementById('audubon_image');
var x = img.offsetLeft,
y = img.offsetTop,
w = img.clientWidth,
h = img.clientHeight;
var c = document.getElementById('myCanvas');
img.parentNode.appendChild(c);
c.style.zIndex = 1;
c.style.left = x + 'px';
c.style.top = y + 'px';
c.setAttribute('width', w+'px');
c.setAttribute('height', h+'px');
hdc = c.getContext('2d');
return(hdc);
}
</script>
<style>
#container
{
text-align: center;
}
canvas
{
pointer-events: none;
position: absolute;
border: 1px solid black;
}
</style>
</head>
<body onload='myInit()'>
<div id="container">
<img src="http://www.sturtz.org/john/audubon/wp-content/uploads/2015/04/Audubon.jpg" id="audubon_image" />
<canvas id='myCanvas'></canvas> <!-- gets re-positioned in myInit(); -->
</div>
</body>
</html>
What's supposed to happen: The image gets placed. Then the Javascript code determines the position and size of the image, and sets the canvas to match. Then draws on the canvas (for the moment, a lovely elegant block box in the upper left corner).
So far, so good. But since the image centered, if the browser is re-sized (specifically made wider or narrower), the image's position moves relative to the left and right edges of the browser window.
With 'position: absolute' specified for the canvas, the canvas does not move (unsurprisingly; I suppose that's what absolute means). So the image and canvas do not stay aligned.
If I change the canvas CSS to 'position: relative', then when I re-size the window, the image and canvas remain in the same position relative to one another (which is what I want). But then I can't get the canvas over the top of the image.
My gut feel is that this should be possible (easy, even), and my lack of knowledge is causing me not to see it.
I think I'm on to it.
Put the canvas in a div. Wrap that and the img in a container div. Specify 'position: relative' for the outer div, 'position: absolute' for the inner div. That way, the x and y coordinates of the div containing the canvas may simply be specified as (0,0).
<!DOCTYPE html>
<html>
<head>
<script>
function myInit()
{
hdc = set_canvas();
hdc.fillRect(0, 0, 50, 50);
}
function set_canvas()
{
var c = document.getElementById('map_canvas');
c.style.zIndex = 1;
c.setAttribute('width', '650px');
c.setAttribute('height', '300px');
hdc = c.getContext('2d');
return(hdc);
}
</script>
<style>
#image_container
{
margin-left: auto;
margin-right: auto;
width: 650px;
position: relative;
}
#canvas_container
{
position: absolute;
top: 0px;
left: 0px;
}
#map_canvas
{
}
</style>
</head>
<body onload='myInit()'>
<div id="image_container">
<img src="http://www.sturtz.org/john/audubon/wp-content/uploads/2015/04/Audubon.jpg" id="audubon_image" />
<div id="canvas_container">
<canvas id="map_canvas"></canvas>
</div>
</div>
</body>
</html>
How to position the canvas directly over the img with the container horizontally centered.
Keep the canvas directly over the image
Set both #audubon_image and #myCanvas to position:absolute inside the #container that's set to position:relative.
Center the container div
margin:0 auto; to center #container on the page.
CSS
#container{
margin:0 auto;
position:relative;
border:1px solid blue;
}
#audubon_image,#myCanvas{position:absolute; top:0px; left:0px;}
#audubon_image{border:1px solid green;}
#myCanvas{ border:1px solid red;}
Javascript
Set the #container's CSS size and #canvas's element size to equal the img's size. Be sure to set the canvas element size (not css size) or your canvas drawings will be distorted.
// get a reference to #audubon_image
var img=document.getElementById('audubon_image');
// set #container's size to equal the #audubon_image size
var container=document.getElementById('container');
container.style.width=img.width+'px';
container.style.height=img.height+'px';
// set #myCanvas's size to equal the #audubon_image size
var canvas=document.getElementById('myCanvas');
canvas.width=img.width;
canvas.height=img.height;
Note: Once in a great while, browsers will fire window.onload before the image's width & height are set (shame on you browsers!). So in production, you might "defensively" wrap the javascript inside a setTimeout of 1 second to be sure the image's width & height have been set.
Full code and a Demo:
window.onload = (function() {
// get a reference to #audubon_image
var img = document.getElementById('audubon_image');
// set #container's size to equal the #audubon_image size
var container = document.getElementById('container');
container.style.width = img.width + 'px';
container.style.height = img.height + 'px';
// set #myCanvas's size to equal the #audubon_image size
var canvas = document.getElementById('myCanvas');
canvas.width = img.width;
canvas.height = img.height;
});
body {
background-color: ivory;
}
#container {
margin: 0 auto;
position: relative;
border: 1px solid blue;
}
#audubon_image,
#myCanvas {
position: absolute;
top: 0px;
left: 0px;
}
#audubon_image {
border: 1px solid green;
}
#myCanvas {
border: 1px solid red;
}
<div id="container">
<img id="audubon_image" src='https://dl.dropboxusercontent.com/u/139992952/multple/character3.png' />
<canvas id='myCanvas'></canvas>
</div>
im trying to do a css background animation with the Body tag. Here's the code
body
{
animation-name:mymove;
animation-duration:5s;
animation-direction:alternate;
animation-iteration-count:infinite;
-webkit-animation-name:mymove;
-webkit-animation-duration:5s;
-webkit-animation-direction:alternate;
-webkit-animation-iteration-count:infinite;
}
#keyframes mymove
{
from {background-image:url('Space.png');}
to {background:blue;}
}
#-webkit-keyframes mymove
{
from {background-image:url('Space.png');}
to {background:blue;}
}
But when i use it the background just fades from white to blue. Is there a reason why the image wont display? And by the way the image directory is correct and works if i just set it as the background image.
Background image isn't a property that can be animated - you can't tween the property. Thus you cant use it with keyframe animations. Instead try this code-
<!DOCTYPE html>
<html>
<head>
<style type="text/css">
body
{background:url('Space.png');}
#frame
{
position: absolute;
z-index: -1;
top: 0;
left: 0;
height: 100%; /* or the height of webpage is px */
width: 100%; /* or the width of webpage is px */
animation-name:mymove;
animation-duration:5s;
animation-direction:alternate;
animation-iteration-count:infinite;
-webkit-animation-name:mymove;
-webkit-animation-duration:5s;
-webkit-animation-direction:alternate;
-webkit-animation-iteration-count:infinite;
}
#keyframes mymove
{
from {background:transparent;}
to {background:blue;}
}
#-webkit-keyframes mymove
{
from {background:transparent;}
to {background:blue;}
}
</style>
</head>
<body>
<div id="frame">
<--- Webpage contents --->
</div>
</body>
</html>
I have an object and now i want to show the anchor points in order to increase or decrease the width of object on hovering.
How can i achieve this from HTML5 canvas?
How to join the objects by using the canvas library?
A canvas drawing library would give you a shortcut to user-rescaling.
Here is an example of the FabricJS canvas drawing library automatically displaying anchor points. The user can resize and rotate with the anchor points.
You can download the FabricJS canvas library here: https://github.com/kangax/fabric.js
After you download the library, you need to go to the “dist” folder and copy the “all.min.js” file to your scripts folder. Be sure to reference “all.min.js” as a script in your html file.
Here is code and a Fiddle: http://jsfiddle.net/m1erickson/g33Vp/
<!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>
<script type="text/javascript" src="/scripts/all.min.js"></script>
<style>
body{ background-color: ivory; padding:30px; }
canvas{border: 1px solid red; }
</style>
<script>
$(function(){
// tell FabricJS to manage your canvas drawing
var canvas = new fabric.Canvas('canvas');
// draw a Fabric rectangle on the canvas
// the rectangele comes with drag/scale/rotate built in!
var rect = new fabric.Rect({
left: 150,
top: 150,
width: 75,
height: 50,
fill: 'green',
angle: 20,
padding: 10
});
canvas.add(rect);
}); // end $(function(){});
</script>
</head>
<body>
<br/><p>Click on the green rectangle to activate anchor points</p>
<br/><p>Then drag the anchor points to resize / rotate</p><br/>
<canvas id="canvas" width="300" height="300"></canvas>
</body>
</html>
I've been trying to use Kineticjs 4.3.3. to create a graphical image and can be dragged across a parent div, but it will not work if the parent div has scalling set under its style properties ( example provided http://jsfiddle.net/kreavie/MZSE9/). Does anyone have any ideas how to get dragging to work when scalling is previously set?
Thanks,
krlib
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="X-UA-Compatible" content="IE=9">
<script src="http://www.html5canvastutorials.com/libraries/kinetic-v4.3.0-beta2.js"></script>
<script type="text/javascript">
window.onload = function () {
var par = document.getElementById('frame');
var canvas = document.createElement('div');
canvas.id = "canvas1";
par.appendChild(canvas);
var stage = new Kinetic.Stage({
container: 'canvas1',
width: 500,
height: 500
});
var layer = new Kinetic.Layer();
var triangle = new Kinetic.Polygon({
stroke: "red",
strokeWidth: 4,
points: [60, 100, 90, 100, 90, 140],
draggable: true
});
layer.add(triangle);
stage.add(layer);
}
</script>
</head>
<body >
<div id="frame" style="width: 200px; height: 200px; -ms-transform: scale(0.420091);">
</div>
</body>
</html>
See: http://jsfiddle.net/MZSE9/2/
Your object is local to the canvas element, not to another div in which you apply scaling.
if you want to scale an object, layer, or the entire stage just do:
shape.setScale(xAmount, yAmount);
stage.setScale(xAmount, yAmount);
layer.setScale(xAmount, yAmount);