I am making the simple canvas application.
I want to use image for background of canvas.
I have found out that I should use drawImage(img,x,y).
This is my codes ,but drummap.img doesn't appear.
Where is wrong?
Test
<canvas id="leap-overlay"></canvas>
<script src="leap.js"></script>
<script>
var canvas = document.getElementById("leap-overlay");
// fullscreen
canvas.width = document.body.clientWidth;
canvas.height = document.body.clientHeight;
// create a rendering context
var ctx = canvas.getContext("2d");
ctx.translate(canvas.width/2,canvas.height);
var img = new Image();
img.src = "drummap.jpg";
ctx.drawImage(img,0,0,100,100);
Assuming that your image drummap.jpg is located in said directory, create the image, set the onload to use the new image, and then set the src (see):
var img = new Image();
img.onload = function () {
ctx.drawImage(img, 0, 0, 100, 100);
};
img.src = 'drummap.jpg';
I'm not sure how you're clearing your canvas or what your drawing, but remember your canvas is inherently transparent so feel free to give the canvas a css style background:
<canvas style = "background-image: url(pathtoyourimage.jpg);"></canvas>
Hope that helps.
Related
supposed i have an image /site/image1.jpg upon drawing this to the canvas it would be something like this.
var image = new Image();
image.src = "/site/image1.jpg";
image.onload = function(){
context.drawImage(image,x,y);
}
Assuming my internet connection is so slow how would i know that the image was already drawn on the canvas?
Thanks.
To workout if the image has been draw keep a flag or mark the image.
var image = new Image();
image.src = "blah.foo";
image.drawn = false; // Add a property to indicate if the image has been drawn
image.onload = function(){
ctx.drawImage(image,0,0);
image.drawn = true; // flag it as drawn
}
// then later you if you want to know if its been drawn
if(image.drawn){
console.log("Yes its been drawn.");
}
I am trying to make an image being passed to a canvas from a weburl.
The code has been taken from this [question][1] which is accepted but for some reason it does not work on me on firefox or chrome.
Any ideas?
EDIT:
Here you are:
var myCanvas = document.getElementById('my_canvas_id');
var ctx = myCanvas.getContext('2d');
var img = new Image;
img.onload = function(){
ctx.drawImage(img,0,0); // Or at whatever offset you like
};
img.src = 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAASwAAACWCAYAAABkW7XSAAAAxUlEQVR4nO3BMQEAAADCoPVPbQhfoAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAOA1v9QAATX68/0AAAAASUVORK5CYII=';
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 canvas as Data-URI using toDataURL() and is now using that for loading an image.
Try this URL instead and you will see it works (red image of 300x150):
data:image/png;base64,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
var myCanvas = document.getElementById('my_canvas_id');
var ctx = myCanvas.getContext('2d');
var img = new Image;
img.onload = function(){
ctx.drawImage(img,0,0); // Or at whatever offset you like
};
img.src = "data:image/png;base64,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";
<canvas id="my_canvas_id"></canvas>
var ctx=c.getContext("2d");
ctx.fillStyle="red";
ctx.fillRect(0,0,300,150);
document.write(c.toDataURL());
<canvas id="c"></canvas>
I've been having some trouble drawing an svg onto a canvas with javascript. I would like this to work...
HTML
<canvas class="buttonCanvas" id="handCanvas" height="60px" width="60px" />
Javascript
function drawHandCanvas(){
var canvas = document.getElementById('handCanvas');
var ctx = canvas.getContext('2d');
var img= document.createElement('img');
img.src='images/handCursor.svg';
img.width = 60; img.height = 60;
ctx.drawImage(img,0,0);
}
drawHandCanvas();
But it doesn't.
If I add an SVG element I can get this to work.
HTML
<canvas class="buttonCanvas" id="handCanvas" height="60px" width="60px" />
<img id="handSVG" src="images/handCursor.svg"/>
Javascript
function drawHandCanvas(){
var canvas = document.getElementById('handCanvas');
var ctx = canvas.getContext('2d');
var img=document.getElementById('handSVG');
img.width = 60; img.height = 60;
setTimeout(function(){
ctx.drawImage(img,0,0);
img.hidden='true';
}, 10);
}
drawHandCanvas();
Note that in this 2nd method of doing it I have to use a setTimeout method to get it to work and add an img element at the end of my down, which I hide after drawing on the canvas. Super hacky! If I just use window.onload instead of setTimeout, it doesn't work. It will hide img, but the drawImage() does nothing, presumably because the canvas isn't ready when the window is already done loading. Any thoughts?
I don't have your svg file, but that being said you have to typically wait till the image is loaded before it will load to canvas. It is like drawing something that isn't there. I think this should work for you.
function drawHandCanvas(){
var canvas = document.getElementById('handCanvas');
var ctx = canvas.getContext('2d');
var img= document.createElement('img');
img.onload = function(){
ctx.drawImage(this,0,0);
}
img.src='images/handCursor.svg';
img.width = 60; img.height = 60;
}
drawHandCanvas();
I have an idea of making a canvas the background with an image. The reason why I want the canvas element to be the background is because I would like to blur the image when the user is logged in. I think that would be a nice effect. And since I don't refresh the page I like it to animate a blurring effect. I am going to have multiple questions in here because they all rely on each other.
I have 2 ideas of how to make this. the first one will have a simple div tag with the background image set. then, when the user have logged in - a canvas element will be created by the script with the background image placed as in the div, then blur it and let it fade in over the div tag.
Another way would be to build the canvas element from the beginning and then let the image be set from the beginning.
This is how I make a background image.
var canvas = document.getElementById('bg_canvas');
var context = canvas.getContext('2d');
var imageObj = new Image();
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
imageObj.onload = function() {
context.drawImage(imageObj, 0, 0);
};
imageObj.src = '2.jpg';
Okay.. thats the easy part.. I need a way to make the height or width in the drawImage function set to auto. if the width is bigger than the height I want the height to be set to auto. I don't want the image to be stretched over the screen. How should I do that?
Now problem number 2. When the user resizes the screen, I would like to resize the image inside the canvas element as well. blurred or not blurred.
i assume it would be set to something like this:
$(document).ready(function() {
winResize();
$(window).resize(function() {
winResize());
}
});
function winResize() {
var canvas = document.getElementById('bg_canvas');
var context = canvas.getContext('2d');
var imageObj = new Image();
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
imageObj.onload = function() {
context.drawImage(imageObj, 0, 0, canvas.height, canvas.width);
};
imageObj.src = '2.jpg';
}
Now I still need the auto mechanism for the height or width of the image.
I am not going to ask for the blur effect, since it should be able to find online somewhere, but what i would like to know is what you would recommend for me to do, when fading in the blurred version. I don't remember there should be a way to fade inside a canvas element, so perhaps I have to duplicate the already existing canvas and then blur and then fade in.
Load the plain image, use a canvas to create a blurred version of the image, then turn that into a real image again for use in an <img> or css background:
function blurImage(imgURL) {
var img = new Image();
img.onload = function() {
var canvas = document.createElement("canvas");
canvas.width = img.width;
canvas.height = img.height;
var context = canvas.getContext("2d");
context.drawImage(img,0,0);
/*
code that actually blurs the image goes here
*/
var dataURI = canvas.toDataUrl("image/png");
setBlurredImage(dataURI);
};
img.src = imgURL;
}
with a set handler:
function setBlurredImage(dataURI) {
whateverElement.style.background = "url(" + dataURI + ")";
}
And now you have a background image that is blurred.
I have a question !
In a html5 canvas, I create an "x" number of images. The last image created is always above the other. Is it possible to swap the depths of the images without the need for libraries? (I do not intend to reverse the order of the variables)
I want somethin like this (without kinetic):
http://www.html5canvastutorials.com/kineticjs/html5-canvas-shape-layering-with-kineticjs/
so, here is the code I'm using:
var canvas = document.getElementById("myCanvas");
var context = canvas.getContext("2d");
var imageObj = new Image();
imageObj.onload = function() {
context.drawImage(imageObj, 69, 50);
};
imageObj.src = "image1.png";
var imageObj2 = new Image();
imageObj2.onload = function() {
context.drawImage(imageObj2, 40, 30);
};
imageObj2.src = "image2.png";
/* I want to put "Image1.png" over "Image2.png" dynamically, for example, pressing a button, all this after render on the canvas */
Draw the furtherest images first. It might help to put the images in an array so you can just loop through them.
Otherwise, in the case of your example, this will fix it as you are drawing context.drawImage(imageObj, 69, 50); last. Think of it as if you would draw it on paper; what you draw last is above what you have already drawn.
var canvas = document.getElementById("myCanvas");
var context = canvas.getContext("2d");
var imageObj2 = new Image();
imageObj2.onload = function() {
context.drawImage(imageObj2, 40, 30);
};
imageObj2.src = "image2.png";
var imageObj = new Image();
imageObj.onload = function() {
context.drawImage(imageObj, 69, 50);
};
imageObj.src = "image1.png";
The order you draw the images matters. You will need to draw the images in the back first, then draw the closer ones.
Why don't you create a canvas object for every image and either show / hide them or adjust the z-index?