I'm struggling to get an image of a deck of small cards into spritesheet form using javascript. I need to get them into an array so as to shuffle them. Here's what I've got so far. Only the canvas shows up light blue against a dark blue background.
<html>
<head>
<style>
canvas#game-canvas {
position: absolute;
top: 5%;
left: 5%;
background: lightblue;
height: 281px;
width: 500px;
}
body {
background: darkblue;
}
</style>
<script type="text/javascript" src="jquery1_10_2_min.js"></script>
<script>
var canvas = document.getElementById("game-canvas");
var ctx = canvas.getContext("2d");
function SpriteSheet(path, frameWidth, frameHeight) {
this.image = new Image();
this.frameHeight = frameHeight;
this.frameWidth = frameWidth;
// calculate the number of frames in a row after the image loads
var self = this;
this.image.onload = function() {
self.framesPerRow = Math.floor(this.image.width / frameWidth);
};
this.image.src = path;
}
var spritesheet = new SpriteSheet('small_playing_cards.png', 54, 65);
</script>
</head>
<body>
<canvas id="game-canvas"></canvas>
</body>
</html>
That's an duplicated answer, anyway you can do it by creating one new canvas and drawing it on the main.
PS: that's not my costume code, so I'll do somethings I'd not do, as create variables, etc.
1. Create canvas element asigned as value from one variable;
var Area=document.createElement("canvas")
2. Set the frame size to this canvas;
Area.width=FrameWidth,
Area.height=FrameHeight
3. Draw the spritesheet in this canvas in the x/y (negative) where the frame you want is located;
var AContext=Area.getContext("2d");
AContext.drawImage(SpriteSheet,0-FrameX,0-FrameY);
4. Draw this canvas as image in the main canvas, but with x/y preference;
MainCanvas.drawImage(Area,PreferenceX,PreferenceY)
It's like these steps you can draw one frame from an spritesheet image. I'm not sure if it's that you want, I can't understand your question as well.
Related
I am working on a simple JS/HTML/CSS project. I have a box that's very big (400vw, 400vh) and it acts like a map. What I want to do is a mini-map for that huge thing on the top left corner.
What I understand is that it has to be done with canvas by getting the whole page, put it in canvas and then display it in another box that's just for example 10 times smaller. If my logic is correct, then what is wrong in the code?
<html>
<head>
<script defer src="js/main.js"></script>
<link rel="stylesheet" href="css/main.css">
<style>
#minimapCanvas {
position: absolute;
top: 0;
left: 0;
}
</style>
<script>
window.onload = function() {
// Get the canvas element and its context
var canvas = document.getElementById("myCanvas");
var context = canvas.getContext("2d");
// Draw something on the main canvas
context.fillRect(0, 0, canvas.width, canvas.height);
saveCanvas();
}
function saveCanvas() {
// Get the canvas element and its context
var canvas = document.getElementById("myCanvas");
var context = canvas.getContext("2d");
// Get the image data from the canvas
var imageData = context.getImageData(0, 0, canvas.width, canvas.height);
// Create a new canvas for the minimap
var minimapCanvas = document.getElementById("minimapCanvas");
minimapCanvas.width = 100;
minimapCanvas.height = 100;
var minimapContext = minimapCanvas.getContext("2d");
// Draw the image data on the minimap canvas
minimapContext.putImageData(imageData, 0, 0, 0, 0, minimapCanvas.width, minimapCanvas.height);
}
</script>
</head>
<body>
<div class="box">
<canvas id="myCanvas" width="500" height="500"></canvas>
<canvas id="minimapCanvas" width="100" height="100"></canvas>
</div>
</body>
</html>
and after I run the application I get a big black box instead of the minimap -
I have been trying to search every possible topic about JS mini-map in stackoverflow but couldn't find my solution. I also tried Chat GPT (which usually helps me).
EDIT:
Here is a github link to my repository (NOTE: you have to run it with a live server for example in VSCode, in order for the character's image to work properly) -
https://github.com/ApooBG/minimap
I am trying to draw a textbox on canvas that contains an image and some drawing over it. now I am trying to draw a textbox over it.
When I am trying to initialize canvas object using fabricJS it's making canvas empty first. like..
var canvas = new fabric.Canvas('mycanvas')
after this code, it makes canvas empty. but if I initialize this code in the very beginning just after canvas initialized and then I try to add a textbox to that canvas object like...
var text = new fabric.Textbox('A Computer Science Portal',
{
width: 450,
height: 10,
top: 100,
left: 100,
});
this.canvas.add(text);
Then the textbox is not visible. I think it went in the background of the image.
I have already written lots of code for drawing over the canvas not want to draw textbox on the canvas after with all existing drawing and image that is developed in javascript only.
On Fabric you have bringToFront use that to keep the text on top.
Here is the official documentation:
http://fabricjs.com/docs/fabric.Canvas.html#bringToFront
Sample code:
var image;
var canvas = new fabric.Canvas('canvas');
var url = "http://swagger-net-test.azurewebsites.net/api/SvgImage?"
var text = new fabric.Textbox('TEST', { width: 90, height: 10, top: 30, left: 50 });
this.canvas.add(text);
function loadSVG(url) {
fabric.loadSVGFromURL(url, function(objects, options) {
if (image) canvas.remove(image);
image = fabric.util.groupSVGElements(objects, options);
image.name = 'sticker';
canvas.add(image);
image.scaleToHeight(100);
image.center();
image.setCoords();
canvas.renderAll();
canvas.bringToFront(text)
});
}
loadSVG(url + "color=red")
setTimeout(function() {
loadSVG(url + "color=blue")
}, 3000);
<canvas id="canvas" width="200" height="200"></canvas>
<script src="https://cdnjs.cloudflare.com/ajax/libs/fabric.js/2.3.4/fabric.min.js"></script>
Started using fabric.js and trying to add a canvas inside another canvas, so that the top canvas stays constant and I'll add objects to inner canvas.
Here is the snippet of adding a canvas to another canvas.
canvas = new fabric.Canvas('artcanvas');
innerCanvas = new fabric.Canvas("innerCanvas");
canvas.add(innerCanvas);
and my html looks like this
<canvas id="artcanvas" width="500" height="500"></canvas>
<canvas id="innerCanvas" width="200" height="200" ></canvas>
Once adding these successfully, what I am going to do is , add the coordinates to the inner canvas, so that it looks like one on another to the end user.
However, ran into the below error for the tried code
Uncaught TypeError: obj.setCoords is not a function
at klass._onObjectAdded (fabric.js:6894)
at klass.add (fabric.js:231)
at main.js:60
at fabric.js:19435
at HTMLImageElement.fabric.util.loadImage.img.onload (fabric.js:754)
_onObjectAdded # fabric.js:6894
add # fabric.js:231
(anonymous) # main.js:60
(anonymous) # fabric.js:19435
fabric.util.loadImage.img.onload # fabric.js:754
Looking at the error message, just went to the line of error and here is what I found in chrome console
Can someone point the mistake in my codes ?
After going through no.of discussions and internet solutions, for time being I am using Fabric Rectangle as a clipper and setting it's boundaries so user can be able to drop/play with in that particular clipper.
Dotted red(image below) is my clipper and now I can bound the dropping and below is the code to add an image with a clipper.
function addImageToCanvas(imgSrc) {
fabric.Object.prototype.transparentCorners = false;
fabric.Image.fromURL(imgSrc, function(myImg) {
var img1 = myImg.set({
left: 20,
top: 20,
width: 460,
height: 460
});
img1.selectable = false;
canvas.add(img1);
var clipRectangle = new fabric.Rect({
originX: 'left',
originY: 'top',
left: 150,
top: 150,
width: 200,
height: 200,
fill: 'transparent',
/* use transparent for no fill */
strokeDashArray: [10, 10],
stroke: 'red',
selectable: false
});
clipRectangle.set({
clipFor: 'layer'
});
canvas.add(clipRectangle);
});
}
Now while appending any image/layer to the canvas, I bind that image/layer/text to the clipper I created.
function addLayerToCanvas(laImg) {
var height = $(laImg).height();
var width = $(laImg).width();
var clickedImage = new Image();
clickedImage.onload = function(img) {
var pug = new fabric.Image(clickedImage, {
width: width,
height: height,
left: 150,
top: 150,
clipName: 'layer',
clipTo: function(ctx) {
return _.bind(clipByName, pug)(ctx)
}
});
canvas.add(pug);
};
clickedImage.src = $(laImg).attr("src");
}
And the looks like, after restriction of bounds,
Here is the fiddle I have created with some static image url.
https://jsfiddle.net/sureshatta/yxuoav39/
So I am staying with this solution for now and I really feel like this is hacky and dirty. Looking for some other clean solutions.
As far as I know you can't add a canvas to another canvas - you're getting that error as it tries to call setCoords() on the object you've added, but in this case it's another canvas and fabric.Canvas doesn't contain that method (see docs). I think a better approach would be to have two canvases and position them relatively using CSS - see this simple fiddle
HTML
<div class="parent">
<div class="artcanvas">
<canvas id="artcanvas" width="500" height="500"></canvas>
</div>
<div class="innerCanvas">
<canvas id="innerCanvas" width="200" height="200" ></canvas>
</div>
</div>
CSS
.parent {
position: relative;
background: black;
}
.artcanvas {
position: absolute;
left: 0;
top: 0;
}
.innerCanvas {
position: absolute;
left: 150px;
top: 150px;
}
JS
$(document).ready(function() {
canvas = new fabric.Canvas('artcanvas');
innerCanvas = new fabric.Canvas("innerCanvas");
var rect = new fabric.Rect({
fill: 'grey',
width: 500,
height: 500
});
canvas.add(rect);
var rect2 = new fabric.Rect({
fill: 'green',
width: 200,
height: 200
});
innerCanvas.add(rect2);
})
To handle the object serialization, you can do something like this:
var innerObjs = innerCanvas.toObject();
console.dir(innerObjs);
var outerObjs = canvas.toObject();
innerObjs.objects.forEach(function (obj) {
obj.left += leftOffset; // offset of inner canvas
obj.top += topOffset;
outerObjs.objects.push(obj);
});
var json = JSON.stringify(outerObjs);
This will then give you the JSON for all objects on both canvases
I have no understanding why you want to do this thing, but to put a canvas inside another canvas, you have one simple way:
canvas = new fabric.Canvas('artcanvas');
innerCanvas = new fabric.Canvas("innerCanvas");
imageContainer = new fabric.Image(innerCanvas.lowerCanvasEl);
canvas.add(imageContainer);
Then depending what you want to do, you may need additional tweaks, but this should work out of the box.
Don't create a canvas
Most objects in fabric (from my limited experience) are at some point converted to a canvas. Creating an additional fabric canvas to manage a group of objects is kind of pointless as you are just adding overhead and mimicking fabrics built in groups object.
Fabric objects are basically DOM canvases wrappers.
The following example shows how fabric uses a canvas to store the content of a group. The demo creates a group and adds it to the fabric canvas, then gets the groups canvas and adds it to the DOM. Clicking on the group's canvas will add a circle. Note how it grows to accommodate the new circles.
const radius = 50;
const fill = "#0F0";
var pos = 60;
const canvas = new fabric.Canvas('fCanvas');
// create a fabric group and add two circles
const group = new fabric.Group([
new fabric.Circle({radius, top : 5, fill, left : 20 }),
new fabric.Circle({radius, top : 5, fill, left : 120 })
], { left: 0, top: 0 });
// add group to the fabric canvas;
canvas.add(group);
// get the groups canvas and add it to the DOM
document.body.appendChild(group._cacheContext.canvas);
// add event listener to add circles to the group
group._cacheContext.canvas.addEventListener("click",(e)=>{
group.addWithUpdate(
new fabric.Circle({radius, top : pos, fill : "blue", left : 60 })
);
canvas.renderAll();
pos += 60;
});
canvas {
border : 2px solid black;
}
div {
margin : 10px;
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/fabric.js/1.7.13/fabric.min.js"></script>
<div>Fabric's canvas "canvas = new fabric.Canvas('fCanvas');"</div>
<canvas id="fCanvas" width="256" height="140"></canvas>
<div>Fabric group canvas below. Click on it to add a circle.</div>
Use a group rather than a new instance of a fabric canvas.
As you can see a canvas is generated for you. Adding another fabric canvas (Note that a fabric canvas is not the same as a DOM canvas) will only add more work for fabric to do, which already has a lot of work to do.
You are best of to use a group and have that hold the content of the other fabric object you wish to shadow. That would also contain its content in a group.
Just an image
And just a side not, a DOM canvas is an image and can be used by fabric just as any other image. It is sometimes better to do the rendering directly to the canvas rather than via fabric so you can avoid rendering overheads that fabric needs to operate.
To add a DOM canvas to fabric just add it as an image. The border and text are not fabric object, and apart from the code to render them take up no memory, and no additional CPU overhead that would be incurred if you used a fabric canvas and objects.
const canvas = new fabric.Canvas('fCanvas');
// create a standard DOM canvas
const myImage = document.createElement("canvas");
// size it add borders and text
myImage.width = myImage.height = 256;
const ctx = myImage.getContext("2d");
ctx.fillRect(0,0,256,256);
ctx.fillStyle = "white";
ctx.fillRect(4,4,248,248);
ctx.fillStyle = "black";
ctx.font = "32px arial";
ctx.textAlign = "center";
ctx.textBaseline = "middle";
ctx.fillText("The DOM canvas!",128,128);
// use the canvas to create a fabric image and add it to fabrics canvas.
canvas.add( new fabric.Image(myImage, {
left: (400 - 256) / 2,
top: (400 - 256) / 2,
}));
canvas {
border : 2px solid black;
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/fabric.js/1.7.13/fabric.min.js"></script>
<canvas id="fCanvas" width="400" height="400"></canvas>
innerCanvas.setCoords(); ìs a function, but you need it only after you set the coordinates. Or more precise, set these four elements:
innerCanvas.scaleX = 1;
innerCanvas.scaleY = 1;
innerCanvas.left = 150;
innerCanvas.top = 150;
innerCanvas.setCoords();
canvas.renderAll();
I am using two images in a canvas, now i want to bring one image over another, ie. i want to bring the plane over the sky, how can i do that?
here is my code
var canvas = document.getElementById('canvas');
var skyContext = canvas.getContext('2d');
var planeContext = canvas.getContext('2d');
var sky = new Image();
sky.src = './images/m35.jpeg';
sky.onload = function () {
skyContext.drawImage(sky, 0, 0, 250, 250, 50, 50, 250, 250);
}
var plane = new Image();
plane.src = './images/space-ship.png';
plane.onload = function () {
planeContext.drawImage(plane, 0, 0, 70, 80, 50, 250, 70, 80);
}
In the above code, the sky is coming at the front of the plane making the plane invisible.
I also tried to use the same context like this but i am not able to bring the image at the top of another.
The most effective way to do this (especially as it looks like you're creating a game) is to use two separate canvas elements, positioned on top of each other using CSS.
For example:
var canvasMain = document.getElementById('canvasMain');
var canvasBackground = document.getElementById('canvasBackground');
var skyContext = canvasMain.getContext('2d');
var sky = new Image();
sky.src = 'https://i.stack.imgur.com/xjj19.jpg';
sky.onload = function () {
skyContext.drawImage(sky, 0, 0, 250, 250, 50, 50, 250, 250);
}
var planeContext = canvasBackground.getContext('2d');
var plane = new Image();
plane.src = 'https://i.stack.imgur.com/nHugQ.png';
plane.onload = function () {
planeContext.drawImage(plane, 0, 0, 70, 80, 50, 250, 70, 80);
}
.canvas {
position: absolute;
top: 0;
left: 0;
}
<canvas id="canvasMain" class="canvas" width="700" height="500"></canvas>
<canvas id="canvasBackground" class="canvas" width="700" height="500"></canvas>
The issue with your code is that the images are drawn once loaded and I would suspect that because the sky image is larger than the plane image it takes longer to load so the sky image is being drawn second.
Drawing things on canvas works like layers in photoshop with whatever is drawn last overwriting things drawn before it.
It is possible to use the same canvas for both the sky and the plane, you just need to wait until both images have loaded then draw them in the correct order to the sky is drawn first, then the plane on top.
You can use the same canvas context for both objects if the are on the same canvas, no need to create multiple contexts (2 just point to the same place anyway). Usually when I work with canvases I just create one context variable called ctx as its a lot quicker than typing context.etc all the time.
almcd answer is one way to do it, though to me the background and main are reversed; I would put the sky / galaxy on the background and draw the plane on the main canvas, but there is a better way...
If the sky never changes, 2 canvases is not even needed, just one canvas with a background image behind it; the sky. When it comes time to animate the plane, this method of having the background a static image means there is less to draw each frame of the game loop, so you will get better FPS.
In terms of a solution for you, I think 1 canvas with the sky as a background image positioned by CSS, and only the plane being drawn on the canvas is the best, here is the code for that...
<!doctype HTML>
<html>
<head>
<style>
#canvasContainer {
background-image: url('https://i.stack.imgur.com/xjj19.jpg');
background-repeat: no-repeat;
}
</style>
</head>
<body>
<div id="canvasContainer">
<canvas id="canvas" width="1200" height="600"></canvas>
</div>
<script>
var canvas = document.getElementById('canvas');
var ctx = canvas.getContext('2d');
// Load the plane and draw it.
var plane = new Image();
plane.src = 'https://i.stack.imgur.com/nHugQ.png';
plane.onload = function () {
ctx.drawImage(plane, 100, 100);
}
</script>
</body>
</html>
You can move the plane by changing the 100, 100 parameters sent to draw image, as these are the left and top used to position the plane image.
Kind regards,
DouG.
Creator of Winwheel.js a feature packed JavaScript library for making spinning prize wheels on HTML canvas. See http://dougtesting.net
I am trying to learn about fabricjs and noticed that when i create a new fabric.Canvas object it changes the position of my canvas.
HTML
<canvas id="c"></canvas>
Css
#c {
border: thin red solid;
position: absolute;
top: 50px;
left: 100px;
}
Javascript
var c = document.getElementById("c");
var ctx = c.getContext("2d");
var img = new Image();
img.src = 'cheese.jpg';
img.onload = function() {
ctx.drawImage(img, 0, 0);
};
// applying the below line shifts the canvas element back to 0,0 position
var cFabric = new fabric.Canvas('c');
Hoping you guys know what i am doing wrong.
You are not doing anything wrong. Calling the fabric.Canvas constructor on your native canvas element will result in your native canvas getting wrapped by a .canvas-container div. The original canvas gets an added .lower-canvas class and its left, right css styles are set to 0px. Other then that, a sibling canvas is added below your original canvas, with a class of upper-canvas. These two canvases act like layers, managed by the inner workings of Fabric.js (magic :O).
If you need to position and style your canvas, I recommend you wrap your html canvas with a wrapper div.
<div id="canvas-wrapper">
<canvas id="c"></canvas>
</div>
Next transfer your css rules to the wrapper
#canvas-wrapper {
position: absolute;
top: 50px;
left: 100px;
}
Here's a simple fiddle that I made by updating #Mullainathan's sample fiddle: https://jsfiddle.net/eo7vdg1t/1/