PaperJS has documentation how to setup the canvas in to resize the canvas when the window changes dimensions. The same solution can be found in this SO answer.
The problem with this approach is that it will change the coordinates while drawing, and also it will be resizing the canvas, which can be less performant.
I would like to scale the canvas without changing the width of the element. The problem I found is that PaperJS adds a width and height to the canvas element in runtime, and I could not find a way to stop this behaviour, this will result the calculated value when the setup is done, and could be for instance:
width="817" height="817"
Here is an example of a HTML Canvas that behaves the way I intend, and also the PaperJS version which does not scale. Resize the browser window to see how the example in the bottom will stretch the canvas content, but keeping the circle in the center of the canvas.
I would like to find a way to configure PaperJS that would work in the same way, without having to change the draw coordinates inside a onResize handler.
Is this possible?
const SIZE = 150;
window.onload = () => {
// --- Paperjs ---
const canvas = document.getElementById('paper');
paper.setup(canvas);
// draw circle in the center of the view
const c = new paper.Path.Circle(new paper.Point(SIZE, SIZE), SIZE);
c.strokeColor = 'white';
c.strokeWidth = 3;
// --- END Paperjs ---
// --- Canvas ---
const ctx = document.querySelector("#canvas").getContext("2d");
ctx.strokeStyle = "#FFFFFF";
ctx.fillStyle = "white";
ctx.lineWidth = 3;
ctx.beginPath();
// x, y, width
ctx.arc(SIZE, SIZE, SIZE, 0, 2 * Math.PI);
ctx.stroke();
// --- END Canvas ---
}
.wrapper {
margin-left: 10vw;
width: 80vw;
border: 1px solid cyan;
}
.responsive-canvas {
background-color: silver;
max-width: inherit;
max-height: inherit;
height: inherit !important;
width: inherit !important;
object-fit: contain;
}
* {
margin: 0;
padding: 0;
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/paper.js/0.12.17/paper-full.min.js"></script>
<h2>PaperJS</h2>
<div class="wrapper">
<canvas id="paper" class="responsive-canvas" width="300px" height="300px"></canvas>
</div>
<h2>Canvas</h2>
<div class="wrapper">
<canvas class="responsive-canvas" id="canvas" width="300px" height="300px"></canvas>
</div>
I am practicing javascript and I am trying to make a game. I want the canvas element to be fullscreen, so I used percentages for the height and width attribute, but when I do, it doesn't behave like it normally does. When I run my debug code, it is supposed to make a box that is 50px by 50px, but the graphics look bigger than normal.
I've tried getting the canvas height and width in pixels, but that did not work. It does not report any error messages, but it is still too big.
<!DOCTYPE html>
<html>
<head></head>
<body>
<canvas id="canvas" style="height: 100%; width:100%;"></canvas>
</body>
<style>
html, body {width: 100%;
margin: 0;
height: 100%;
overflow: hidden;
position:fixed;}
</style>
<script>
var canvas = document.getElementById("canvas")
var c = canvas.getContext("2d")
c.fillStyle = "#FFFF00"
c.fillRect(50,50,50,50)
</script>
There are no error messages none appearing, but it is not sized correctly, and I can't figure out why it's not working.
It makes a difference if canvas size is set in CSS or using element attributes.
The canvas element size is set by its width and height attributes (as numbers). This sets the number of addressable pixels used to store the canvas drawing in memory. In the absence of width and height attributes, canvas element dimensions are set to 300 by 150 (pixels) by default.
CSS applied to the canvas can scale its dimensions using software interpolation of the canvas treated as an image. Just as a small image looks bigger when scaled to full screen, both the 300 by 150 pixel canvas and objects drawn within it (using canvas pixel coordinates) appear larger when blown up.
To make canvas coordinates match the screen size in pixels, set its width and height attributes to pixel number values. E.G.
var canvas = document.getElementById("canvas")
var c = canvas.getContext("2d")
c.fillStyle = "#FFFF00"
c.fillRect(50,50,50,50)
console.log( canvas.width, canvas.height);
alert( "fix?" )
canvas.style=""; // remove CSS scaling
canvas.width = document.body.clientWidth;
canvas.height = document.body.clientHeight;
c.fillStyle = "#FFFF00"
c.fillRect(50,50,50,50)
body {
width: 100%;
margin: 0;
height: 100%;
background-color: honeydew;
overflow: hidden;
position:fixed;
}
canvas {
background-color: silver;
}
<canvas id="canvas" style="height: 100%; width:100%;"></canvas>
I'm trying to make the fullscreen option work in html/javascript.
I have placed my canvas and buttons in a div, fullscreen works, But now I want to center my game in the middle of the screen, and I want my canvas height to be equal to the monitor height of the display. And I want my width to be equal to my height. So my canvas has the shape of a square.
I think I need css for this, but I never used it so I don't know where to start.
My html code looks now like this:
<div id="theGame">
<canvas id="canvas" width="500" height="500" style=" position:absolute; top:40px; left:0px; border:6px ridge #FFAB00;"></canvas>
<button buttonSpecs... </button>
<button buttonSpecs... </button>
</div>
Currently when I'm in fullscreen it looks like this:
https://www.dropbox.com/s/ee4bv0cn2tm2nns/fullscreen.jpg
But thats not how I want it, I want it like this:
https://www.dropbox.com/s/cu54fqz0gzap1ul/howIwant.jpg
See the following question: HTML5 Canvas 100% Width Height of Viewport?
(function() {
var canvas = document.getElementById('canvas'),
context = canvas.getContext('2d');
// resize the canvas to fill browser window dynamically
window.addEventListener('resize', resizeCanvas, false);
function resizeCanvas() {
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
/**
* Your drawings need to be inside this function otherwise they will be reset when
* you resize the browser window and the canvas goes will be cleared.
*/
drawStuff();
}
resizeCanvas();
function drawStuff() {
// do your drawing stuff here
}
})();
Okay, I can now stretch the canvas, using
CSS:
#canvas {
width: 100%;
height: 100%;
position: absolute;
left: 0px;
top: 0px;
z-index: 0;
}
I'm looking to make a page that has a background gradient that changes color every few seconds and blends between transitions. Now I want to apply this effect on the to the upper elements that are blocked by a element that has a solid background.
To give you a better example what I mean I have attached a simple mockup and hopefully your understand what I'm attempting to do, I'm open to suggestions.
(source: bybe.net)
The problem is obviously the block that contains the black background which any PNG transparent used would see black not the gradient.
I'll include sample code so far:
<body><!-- A Jquery script will be used to add CSS background, Easy stuff -->
<div class="blackbox">
<div class="logo"><img src="#" alt=""></div>
<hr class="h-line">
<div class="v-line"> </div>
</div>
So what I'm after is either:
A known jQuery method to obtain a background image but it needs to be able to refer of the position of the gradient so its inline with the background.
A better solution to getting this to work, please bare in mind that the page needs to be responsive so I could use other methods but since its responsive I can't think of any.
Since you ask for alternatives to jQuery solutions
You could play a little with margins and box-shadow and keyframe animations.
Something in this direction for the shape (depends on what you want to do with which part - add content ... and in what way you want it to be responsive):
html:
<div class="wrapper">
<div class="header"><img src="http://i.imgur.com/CUbOIxr.png" alt="Company name" /></div>
<div class="content"></div>
</div>
CSS:
body {
background:orange;
width:100%;
height:100%;
}
.wrapper {
width:40%;
height:90%;
border:30px solid #000;
border-right-width:100px;
border-bottom-width:100px;
}
.header {
width:100%;
border-bottom:10px solid transparent;
-webkit-box-shadow: 0 30px 0 #000;
-moz-box-shadow: 0 30px 0 #000;
box-shadow: 0 30px 0 #000;
}
.header img {
width:100%;
}
.content {
width:95%;
height:400px;
background-color:#000;
margin-top:30px;
}
DEMO
This way no javascript is needed. And for the background you can use a linear gradient and do all animations with css transitions or keyframe animations. You also need to play with the lengths and adjust the borders and box-shadows to your needs, maybe add some #media queries for the responsiveness.
Hope this helps you a little in the right direction =)
Update:
I hoped the gradients changing was the smaller problem ;-) Silly me, sorry.
I will elaborate my CSS-only suggestion for the animation, but you can choose a javascript slider for the background animation, if you don't like CSS3 solutions - although this is the hot stuff now ;-)
Ok. So, I would add some more fixed positioned elements with gradient backgrounds (layer1 and layer2).
To have something in this direction in the html now:
<div class="layer layer1"></div>
<div class="layer layer2"></div>
<div class="wrapper">
<div class="header">
<img src="http://newtpond.com/test/company-name.png" alt="Company name" />
</div>
<div class="content"></div>
</div>
and add a keyframe animation on them in CSS (here it is just with the -webkit vendor prefix [probably cause I am a lazy bum], but I hope you can get the idea, and could add the others):
body {
width:100%;
height:100%;
margin:0;
padding:0;
}
/* for the animation */
.layer {
position:fixed;
width:100%;
height:100%;
}
#-webkit-keyframes GoLayer1 {
0% {
opacity:1;
}
50% {
opacity:0;
}
100% {
opacity:1;
}
}
#-webkit-keyframes GoLayer2 {
0% {
opacity:0;
}
50% {
opacity:1;
}
100% {
opacity:0;
}
}
.layer1 {
background: -webkit-linear-gradient(bottom, rgb(43, 70, 94) 29%, rgb(194, 41, 41) 65%, rgb(155, 171, 38) 83%);
-webkit-animation: GoLayer1 5s infinite;
}
.layer2 {
background: -webkit-linear-gradient(bottom, rgb(225, 202, 230) 29%, rgb(39, 163, 194) 65%, rgb(36, 124, 171) 83%);
-webkit-animation: GoLayer2 5s infinite;
}
/* the wrapper shape */
.wrapper {
z-index:999;
opacity:1;
position:relative;
width:40%;
height:90%;
border:30px solid #000;
border-right-width:100px;
border-bottom-width:100px;
}
.header {
width:100%;
border-bottom:10px solid transparent;
-webkit-box-shadow: 0 30px 0 #000;
-moz-box-shadow: 0 30px 0 #000;
box-shadow: 0 30px 0 #000;
}
.header img {
width:100%;
}
.content {
width:95%;
height:400px;
background-color:#000;
margin-top:28px;
}
DEMO (tested in Chrome 26 - looked cool =)
This is now where I can point you according this CSS-only approach. There is still stuff to modify and consider browser compatibility. But it is certainly an alternative ... and a step in the direction where html5 and css3 is going (if you want to be hot and cool ;-), hehe, sorry, too much silliness.
Good luck!
Update 2:
So, I overcame my laziness a tiny bit and added some more vendor prefixes to the top example (and of course you can use any image as background):
DEMO
And here I add another example, that is using a png image for the gradient, and is sliding up and down in the background (as another alternative):
DEMO
There are many ways to do this, CSS3 and images are already suggested, so I'll suggest using a canvas.
The HTML canvas element has everything you need built in. It allows for gradient background fills, and with globalCompositeOperation, masking of shapes and text is possible, creating cut-outs in the background to make real changeable HTML elements truly transparent against a colored background. It also scales well, and can easily be made responsive.
The canvas element is supported in all major browsers except Internet Explorer 8 and below, which means browser support is better than many of the CSS3 methods previously mentioned, like keyframes and background-size.
Using a fallback, like say images that fade in and out if canvas is'nt available, should'nt be very hard to figure out, and in all other browsers except Internet Explorer below version 9, no images would be needed to create the gradient backgrounds and text masks in a canvas, which should make the loading of the page significantly faster.
To detect wether or not canvas is supported, you can use this convenient function :
function isCanvasSupported(){
var elem = document.createElement('canvas');
return !!(elem.getContext && elem.getContext('2d'));
}
used like so :
if ( isCanvasSupported() ) {
// do canvas stuff
}else{
// fall back to images
}
So, lets get to it! To create a "last resort" fallback and some elements we can "clone" into the canvas, we'll create the elements we need in the HTML to get a structure somewhat similar to what you've outlined in your question. This has the added advantage of being able to just change some of the CSS to also make changes in the canvas :
<div id="gradient">
<div class="text">COMPANY NAME</div>
<div class="h_bar"></div>
<div class="v_bar"></div>
</div>
It's just a container with an element for text, and one for each of the bars.
Some styling is neccessary as well, I'll do it the easy way, with position absolute and some really fast positioning, as these elements won't be visible unless someone has disabled javascript anyway :
#gradient {position: absolute;
background: #000;
top: 5%; left: 5%; right: 5%; bottom: 5%;
}
.text {position: absolute;
top: 20px;
left: 100px;
width: 400px;
color: #fff; font-size: 40px; font-weight: bold;
font-family: arial, verdana, sans-serif;
}
.h_bar {position: absolute;
height: 20px;
top: 100px; left: 60px; right: 60px;
background: #fff;
}
.v_bar {position: absolute;
width: 20px;
top: 140px; bottom: 30px; right: 60px;
background: #fff;
}
Without any javascript that would look exactly like THIS FIDDLE, and it should be somewhat responsive and adapt to the window size.
Now we need some javascript to turn those elements into something in a canvas. We'll create two canvas elements, one for the background, as I've decided to animate the background continously between random gradients, and one for the inner black box and the content (the text and the bars).
As the masking of the text and bars can be a little slow, we don't have to redraw everything, just the background canvas, as the foreground is pretty static.
This also avoids a flickering issue in some browsers with high frame rates, and we're going to use requestAnimationFrame for the animation of the background canvas, so flickering in the text mask would be an issue if we did'nt use two canvas elements.
For browsers that does'nt support requestAnimationFrame we'll add this polyfill to make sure it works everywhere.
Time to write some javascript, this of course uses jQuery :
var gradSite = {
init: function() {
var self = this;
self.create().setSizes().events();
(function animationloop(){
requestAnimationFrame(animationloop);
self.draw().colors.generate();
})();
},
create: function() { // creates the canvas elements
this.canvas = document.createElement('canvas');
this.canvas2 = document.createElement('canvas');
this.canvas.id = 'canvas1';
this.canvas2.id = 'canvas2';
this.canvas.style.position = 'absolute';
this.canvas2.style.position = 'absolute';
$('#gradient').after(this.canvas, this.canvas2);
return this;
},
events: function() { //event handlers
$(window).on('resize', this.setSizes);
$('#gradient').on('contentchange', this.draw2);
return this;
},
setSizes: function() { // sets sizes on load and resize
var self = gradSite,
w = $(window),
m = $('#gradient');
self.canvas.height = w.height();
self.canvas.width = w.width();
self.canvas2.bg = m.css('background-color');
self.canvas2.height = m.height();
self.canvas2.width = m.width();
self.canvas2.style.top = m.offset().top + 'px';
self.canvas2.style.left = m.offset().left + 'px';
self.draw2();
return self;
},
colors: {
colors: {
0: [255,255,0],
1: [255,170,0],
2: [255,0,0]
},
map: {
0: [0,0,1],
1: [0,1,1],
2: [0,1,1]
},
generate: function() { // generates the random colors
var self = this;
$.each(self.colors, function(i,color) {
$.each(color, function(j, c) {
var r = Math.random(),
r2 = Math.random(),
val = self.map[i][j] == 0 ? (c-(j+r)) : (c+(j+r2));
if (c > 255) self.map[i][j] = 0;
if (c < 0 ) self.map[i][j] = 1;
self.colors[i][j] = val;
});
});
}
},
raf: (function() { // polyfill for requestAnimationFrame
var lastTime = 0,
vendors = ['webkit', 'moz'];
for(var x = 0; x < vendors.length && !window.requestAnimationFrame; ++x) {
window.requestAnimationFrame = window[vendors[x]+'RequestAnimationFrame'];
window.cancelAnimationFrame = window[vendors[x]+'CancelAnimationFrame'] || window[vendors[x]+'CancelRequestAnimationFrame'];
}
if (!window.requestAnimationFrame)
window.requestAnimationFrame = function(callback, element) {
var currTime = new Date().getTime(),
timeToCall = Math.max(0, 16 - (currTime - lastTime)),
id = window.setTimeout(function() { callback(currTime + timeToCall); }, timeToCall);
lastTime = currTime + timeToCall;
return id;
};
if (!window.cancelAnimationFrame)
window.cancelAnimationFrame = function(id) {
clearTimeout(id);
};
}()),
calculateColor: function(colors) { // returns a rgb color from the array
return 'rgb(' + Math.round(colors[0]) + ',' + Math.round(colors[1]) + ',' + Math.round(colors[2]) + ')';
},
draw: function() { //draws the color background
var self = this,
c = self.canvas || document.getElementById('canvas1'),
ctx = c.getContext('2d'),
grad = ctx.createLinearGradient(0,0,0,self.canvas.height);
c.width = c.width;
grad.addColorStop(0, self.calculateColor(self.colors.colors[0]));
grad.addColorStop(0.5, self.calculateColor(self.colors.colors[1]));
grad.addColorStop(1, self.calculateColor(self.colors.colors[2]));
ctx.fillStyle = grad;
ctx.fillRect(0,0,self.canvas.width, self.canvas.height);
return self;
},
draw2: function() { // draws the black square and content
var self = this,
c = self.canvas2 || document.getElementById('canvas2'),
ctx2 = c.getContext('2d'),
txt = $('.text', '#gradient').first(),
hbar = $('.h_bar', '#gradient').first(),
vbar = $('.v_bar', '#gradient').first();
c.width = c.width;
ctx2.globalCompositeOperation = 'xor';
ctx2.font = txt.css('font');
ctx2.fillStyle = c.bg || '#000';
ctx2.fillText(txt.text(), txt.offset().left, txt.offset().top);
ctx2.fillRect(hbar.position().left, hbar.position().top, hbar.width(),hbar.height());
ctx2.fillRect(vbar.position().left, vbar.position().top, vbar.width(),vbar.height());
ctx2.fillRect(0,0,c.width,c.height);
}
}
The raf function would be the polyfill for requestAnimationFrame, and the two draw functions create the content in the canvas. It's really not that complicated.
We will call the above script inside a DOM ready handler, like so :
$(function() {
gradSite.init(); // starts the canvas stuff
});
Adding all that up into a fiddle, and adding a few elements for demonstration purposes, it would look like THIS FIDDLE, and here's the finished ->
FULL SCREEN DEMO
The only way I can see this working is if your black div has no background and is cut into sections that that each have a background. The company name area would need to have the same foreground color as the background for the rest of the div sections. Depending on your layout needs this might be fine.
For example, you could cut it into three sections and two images:
You can try combinig background-size and background-position with javascript:
setGradientSizes = function (el) {
var width = $(document).width() + 'px', height = $(document).height() + 'px';
$(el || '.gradient:not(body)').each(function () {
var offset = $(this).offset();
$(this).css('background-size', width + ' ' + height);
$(this).css('background-position', (offset.left * -1) + 'px ' + (offset.top * -1) + 'px');
})};
Working example here -> jsbin
NOTES:
this is not 100% cross browser - background-size is supported in FF4.0+, IE9.0+, Opera 10.0+, Chrome 1.0+, Safari 3+.
For some older browsers you can try browser specific prefixes (like -moz-background-size) - my example does not cover that.
To reduce load flickering you can apply calculations at first and then add background gradient
You could make the background of the image with the text black, then set the div's background color to rgba(0,0,0,0) making it transparent
This might be helpful for you according to my understanding
There is inherit to copy a certain value from a parent to its children, but there is no property the other way round (which would involve another selector to decide which style to revert).
You will have to revert style changes manually:
div { color: green; }
form div { color: red; }
form div div.content { color: green; }
If you have access to the markup, you can add several classes to style precisely what you need:
form div.sub { color: red; }
form div div.content { /* remains green */ }
Edit: The CSS Working Group is up to something:
div.content {
all: default;
}
If I was you I'll duplicate the css and jQuery, print it on a div on top of what ever and make the overflow hidden (like masking layers but with z-index).