Resizing window to maintain aspect ratio - javascript

I have an interesting problem for a little program I have been developing.
Basically what I wish to create is a window which I can resize but still maintain a 16:9 aspect ratio (note this is for a native application using NWJS). I am also using the easelJS libraries to manipulate the canvas.
The program below basically resizes the canvas to be the same size as the window and does it's job perfectly. But I've been stuck trying to figure out exactly how to maintain the aspect ratio of the window itself.
var stage, w, h;
window.addEventListener('resize', resizeCanvas);
function resizeCanvas() {
w = window.innerWidth;
h = window.innerHeight;
stage.canvas.width = w;
stage.canvas.height = h;
Exactly what sort of calculations do I need to do to force this setting? I'm not as knowledgeable when it comes to things such as aspect ratios.

You should base your calculation on one axis only, and get the new height and width from it.
For a 16/9 ratio
w = window.innerWidth;
h = 9*window.innerWidth/16;

Related

Resizing canvas size gives advantage to larger screens. Not sure how to keep the functionality while making it fair

So I am trying to learn javascript by making a game where you click on a canvas to move a circle and you have to dodge multiple other circles coming in your direction. I am close to the final result but I just realized that the larger your screen is, the easier it is for you to play.
The reason is that the enemies spawn at the edges of the canvas, so if the canvas is bigger, you have more time to react to them since their speed doesn't change. The game is supposedly refreshing around 60fps and each time it resizes the canvas depending on if you change your window size. The only thing I can think of is increasing the speed of enemies with the size increase but I don't know if there's any other way to go about this. Maybe I could increase the size of the of the player and the enemies to accommodate the change in window size but I don't know which is better or how to make sure I am consistent with the ratio increase.
Any suggestions would be much appreciated. Thanks for your time
Here's my full code: https://jsfiddle.net/r2f6eb89/2/
It doesn't actually run on this site so it's just a reference for my logic.
Here are the resizing functions:
/*
function setCanvasSize() {
//c.width = window.innerWidth-100;
//c.height = window.innerHeight-100;
if (window.innerWidth < window.innerHeight) {
c.width = window.innerWidth - 150;
c.height = window.innerWidth - 150;
} else {
c.width = window.innerHeight - 150;
c.height = window.innerHeight - 150;
}
}
*/
function setCanvasSize() {
c.width = 600;
c.height = 600;
}
There's actually two kinds of "width" and "height" property. One is the width and height you can actually see in your website, that is, the one you can change by the property on your html file element. The other one is the width and height you set in the javascript file, for setting the coordinate you use to print image or draw in the canvas.
Example for first type of the width/height property:
<canvas id="my_canvas" width="500" height="200"></canvas>
Example for second type of the width/height property:
var canvas = document.getElementById("my_canvas");
canvas.width=500;
canvas.height=200;
It seems like you are changing the second type of the width/height property each refresh. If that's not what you want, try modifying the first type of width/height. It seems like a simpler solution to your question. To modify the first type of property, the CSS property in javascript, here's the code:
canvas.style.width="500px";
canvas.style.height="200px";
Hope that helps :)

Make canvas responsive only when resizing window and not when zooming

I have a 960px width and 960px height html5 canvas game. I use Javascript to resize the canvas and rescale its content proportionally to always fit the window vertically (and horizontally too) so the bottom is never cut off since many screens are less than 960px high and some users don't even know they can zoom out with a desktop browser to fit the content. The code is:
var w = stage.canvas.width;
var h = stage.canvas.height;
var scaleFactor;
window.addEventListener('resize', resizeCanvas, false);
function resizeCanvas() {
scaleFactor = Math.min(window.innerWidth / w, window.innerHeight / h);
stage.canvas.width = scaleFactor * w;
stage.canvas.height = scaleFactor * h;
stage.scaleY = scaleFactor;
stage.scaleX = scaleFactor;
}
My problem is the game also resizes itself when I zoom either in a desktop or in a mobile browser since zooming also changes window.innerWidth and window.innerHeight values. HOWEVER, I want the game to only resize itself when the window is resized but still be able to be zoomed (especially in small mobile screens) for people whose eyes are not so perfect.
I've been searching and trying different methods for weeks now, but I still haven't found any solutions. I would be very happy if someone could come up with a not-so-complicated solution since I'm relatively a beginner.
When zooming in and out, the devicePixelRatio value does change.
So you can save this value at init and check if it has changed in the resize event to determine if the event was triggered by an actual resizing of the window, or by zooming.
let dpr = window.devicePixelRatio;
onresize = e => {
if(window.devicePixelRatio !== dpr){
log.textContent = 'zoom event';
dpr = window.devicePixelRatio
}
else{
log.textContent = 'resize event';
}
};
<pre id="log">Please see in full-page.
Then, either zoom or resize the window</pre>
Or as a fiddle.

How to scale my canvas in reason, with the zoom scale?

I am working on a multiple web game using JavaScript. My canvas is currently set to the width and the height of my screen.
html
<canvas id = "canvas"></canvas>
javascript
var c=document.getElementById("canvas");
var ctx = c.getContext("2d");
//Making canvas scale;
c.width = window.innerWidth;
c.height = window.innerHeight;
function resize(){
//Add some code
}
My problem is, I do not want my players to zoom out, well not by default. It will make the game look bad and give the players an edge over everyone else. So I need to add some code to go into the resize method, that regardless of scale, the canvas will not be zoomed out. If the end result is something blurry at 300%+ that is fine.
IMPORTANT: the resize function cannot remove or reset the canvas back to default.
There are various ways to scale a canvas.
First off, there are 2 main parameters for the canvas size:
-Canvas Pixel Count. Set via canvas.width = 1000
-Canvas Display Pixel Size. Set via canvas.style.width = '1000px'
If you want all players to see a 1000x1000 region but displaying it fullscreen:
canvas.width = 1000;
canvas.height = 1000;
canvas.style.width = window.innerWidth + 'px';
canvas.style.height = window.innerHeight + 'px';
There is also another option with canvas.style.transform = 'scale(2,2)'.
This method is the closest thing to the browser zoom done via Ctrl+ or Ctrl-.
The big advantage of transform is that the scaling is applied to all DOM children elements. If your game is using HTML for its interface, then this is the way to go. (By applying the scaling on the div containing the canvas + HTML interface.

Resizing the canvas

I'm trying to design a web using flex-boxes in order to fit it to any kind of screen size. My main screen has a canvas, so... which is the best way to resize the canvas during the inizialitation?
I have tried these two ways. My first way was to use CSS and set a percentage for its size. For example, width=100% and height=100%. Despite the design worked, I found that there were a lot of issues when playing with the coords of my canvas. For example, when dragging an item, my mouse coords where amplified by ten times or so.
Despite I could manage that, I think it's not the best approach.
The second way was to set a fixed size when the onload and onresize events when they are fired. I was doing something like this:
window.initHeight = window.screen.height;
window.initWidth = window.screen.width;
/*The height of the navbar.*/
navbar.height = document.getElementById('navbar').offsetHeight;
canvas = document.getElementById('canvasStage');
canvas.width = window.initWidth;
canvas.height = window.initHeight - navbar.height;
canvas.setAttribute("width", canvas.width);
canvas.setAttribute("height", canvas.height);
The problem is that the height seems to be too big:
http://i.imgur.com/WI0jGH2.png
How could I fit the screen exactly through this way?
The third way, but I'll try to avoid it, is to set a fixed size and let the small screens to scroll on the page.
Thanks!
UPDATED:
This is my JSFiddle:
http://i.imgur.com/NRTykLv.png
window.screen.width and window.screen.height returns the width and height of the screen which includes all bars (evrything you see on your screen).So you have to use window.innerHeight and window.innerWidth in order to get the view port height and width
Replace
window.initHeight = window.screen.height;
window.initWidth = window.screen.width;
with
window.initHeight = window.innerHeight;
window.initWidth = window.innerWidth;

Update non-retina canvas app to retina display

I have an iPad 2 canvas app (game) and would like to get it to run on the new iPad retina display.
Simply put, what is the best method to stretch/shrink my iPad2 image for retina iPad models?
From the googling I've done, I've seen various methods but many include starting with retina sized images and scaling done.
I've also heard the performance of pushing retina quality sized pixels to the screen is slow, and that it is better to use iPad size images at the expense of some quality.
As it is right now, on the new iPad I see the top left quarter of my app, which makes sense, but performance is shocking compared to iPad 2.
Techniques I've seen include CSS media queries, using the pixel density, and CSS transforms - which are apparently quite fast.
Thanks
I've put together a simple function to handle this problem. Basically, it takes the current canvas size and scales it by the device-pixel-ratio, shrinking it back down using CSS. It then scales the context by the ratio so all your original functions work as usual.
You can give it a shot and see how performance fares. If it isn't what you hoped for, you can just remove it.
function enhanceContext(canvas, context) {
var ratio = window.devicePixelRatio || 1,
width = canvas.width,
height = canvas.height;
if (ratio > 1) {
canvas.width = width * ratio;
canvas.height = height * ratio;
canvas.style.width = width + "px";
canvas.style.height = height + "px";
context.scale(ratio, ratio);
}
}

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