I created a new image but I'm trying to resize it and add some transformations to it. How ever, they are not taking effect.
Example: https://jsfiddle.net/chung9ey/3/
img.onload = function(){
img.style.width = "500";
img.style.height = "300";
img.style.transform = "perspective(500px) rotateZ(30deg)";
context.drawImage(img, 0 ,0);
}
Styles change properties, not attributes. In order to change the actual attributes you would need to use
img.height = 300;
//or by native API
img.setAttribute("height",300);
and so on for each attribute you wanted to change. Note that attributes are part of the html element and not necessarily part of the css definition (more on that here: https://www.w3.org/TR/CSS21/cascade.html#preshint).
Try using this.
document.getElementById("imageID").style.height="300px";
document.getElementById("imageID").style.width="500px";
That should change the element's style width and height to what you want.
In the HTML script, it'd be
<img src="source.jog" id="imageID"/>
Based on this Stack Overflow answer, change your JS to:
var img = new Image();
var canvas = document.getElementById("hello");
var context = canvas.getContext("2d");
img.onload = function(){
context.save(); // Saves current canvas state (includes transformations)
context.rotate(30); // This rotates canvas context around its top left corner...
context.translate(-275, 125); // ...so you need to make a correction.
context.drawImage(img, 0, 0, 500, 300);
context.restore(); // Restore canvas state
};
img.src = "https://www.enterprise.com/content/dam/global-vehicle-images/cars/CHRY_200_2015.png";
This essentially rotates the canvas's contents after the image is drawn on it.
Part of the image is off-canvas as a result of this rotation, so you may also want to scale the canvas to fit the rotated image.
https://jsfiddle.net/Lcyksjoz/
i would change the image size in the canvas and then manipulating the canvas through id
var img = new Image(100, 100);
var canvas = document.getElementById("hello");
var context = canvas.getContext("2d");
var width = 500;
var height = 300;
img.onload = function(){
img.style.transform = "perspective(200px) rotateZ(30deg)";
context.drawImage(img, 0 ,0, width,height);
}
img.src = "https://www.enterprise.com/content/dam/global-vehicle-images/cars/CHRY_200_2015.png";
document.getElementById("hello").style.width="300px";
https://jsfiddle.net/chung9ey/27/
Related
I am trying to show previews of uploaded images in a canvas. The preview should be a square version of image.
What I have:
var img = new Image;
img.src = imageSrc;
var c = document.getElementById('file-preview-' + data.response.id);
var ctx = c.getContext("2d");
img.onload = function() {
ctx.drawImage(img, 0, 0);
};
And the preview:
So how can I draw on the canvas a 150x150 square with maintained ratio cropped version of the image?
For example for this image:
I should get:
Here's a method that yields precisely the result you desire, cropped, resized and centered (with commented out lines that yield a left based cropping instead)...
var ctx;
function init(event) {
ctx = document.getElementById('canvas').getContext('2d');
// Your preview is actually 120x120,
// but I've stuck with the textual description of
// your requirements here.
ctx.canvas.width = 150;
ctx.canvas.height = 150;
loadBackground('http://i.stack.imgur.com/PCKEo.png');
}
function loadBackground(path) {
var img = new Image();
img.onload = drawBackground;
img.src = path;
}
function drawBackground(event) {
var img = event.target;
var imgSize = Math.min(img.width, img.height);
// The following two lines yield a central based cropping.
// They can both be amended to be 0, if you wish it to be
// a left based cropped image.
var left = (img.width - imgSize) / 2;
var top = (img.height - imgSize) / 2;
//var left = 0; // If you wish left based cropping instead.
//var top = 0; // If you wish left based cropping instead.
ctx.drawImage(event.target, left, top, imgSize, imgSize, 0, 0, ctx.canvas.width, ctx.canvas.height);
}
window.addEventListener('load', init, false);
<canvas id="canvas"></canvas>
Based on information from this question: SO Question
I was able to modify what was done to create a square cropped image in canvas:
var img = new Image;
img.src = "http://cdn.bmwblog.com/wp-content/uploads/2016/02/M-Performance-Parts-BMW-M2-3.jpg"; //Or whatever image source you have
var c= document.getElementById('file-preview');
var ctx=c.getContext("2d");
img.onload = function(){
ctx.drawImage(img, img.width/2, img.height/2, img.width, img.height, 0, 0, img.width, img.height);
};
You just have to modify the arguments you are passing to the drawImage function as well as add some more.
You can see a fiddle here: https://jsfiddle.net/4d93pkoa/3/
Remember that the first two parameters specify the image's top left coordinates within the canvas element.
Remember to set the width and height of the canvas element in HTML to a square shape.
On load of my image I:
var img = new Image();
img.src = e.target.result;
var canvas = $('#test-canvas')[0];
$('#test-canvas').width(img.width);
$('#test-canvas').height(img.height);
var ctx = canvas.getContext('2d');
ctx.drawImage(img, 0, 0);
But the image is drawn larger than it's original size? I've tried a few images, same problem.
What's the fix?
jQuery will resize the element through CSS, which won't actually change the canvas internal height and width. This will resize the actual canvas element.
var canvas = document.GetElementById('test-canvas');
canvas.width = img.width;
canvas.height = img.height;
jsFiddle (http://jsfiddle.net/L0drfwgL/) just show it drawing it to scale, and resizing the canvas item itself.
It looks like you are pulling the image from an image element on load. You can use the src from the image element rather than recreating an image object and then get the image width/height from the element to draw the image to canvas.
<script>
$(document).ready(function(){
$('#testImg').on('load',function(){
var image = document.getElementById('testImg');
var canvas = document.getElementById('test-canvas');
canvas.width = image.width;
canvas.height = image.height;
var ctx=canvas.getContext("2d");
ctx.drawImage(image,0,0);
})
});
</script>
/** with vue3 -(to fix drawing canvas image is larger than actual image size **/
const captureImage = () => {
let width = video.value.getBoundingClientRect().width;
let height = video.value.getBoundingClientRect().height;
let context = canvas.value.getContext('2d')
canvas.value.width = width
canvas.value.height = height
context.drawImage(video.value, 0, 0, width, height)
}
I'm looking for a way to overlay the visible areas of a transparent black silhouette PNG file with a certain pattern.
Is there a CSS, JavaScript, mixed solution for this?
Example: I have one image of a weapon silhoutte and a set of camo patterns which I want to lay over the weapon.
Demo: In Photoshop the same result is givin when selecting layer mask > overlay.
Ps: my question is similar to this thread: Silhouette a PNG image using CSS except I am looking for the exact opposite.
You can do this using canvas with globalCompositeOperation set to destination-in. For example
var canvas = document.createElement('canvas');
canvas.width = 250;
canvas.height = 250;
var canvas_context = canvas.getContext("2d");
var img = new Image();
img.onload = function(){
var msk = new Image();
msk.onload = function(){
canvas_context.drawImage(img, 0, 0);
canvas_context.globalCompositeOperation = "destination-in";
canvas_context.drawImage(msk, 0, 0);
canvas_context.globalCompositeOperation = "source-over";
};
msk.src = 'silhouette.png';
}
img.src = 'pattern.jpg';
document.body.appendChild(canvas);
I have been trying to get an image drawn on the canvas however have failed to do so. The HTML code simply creates the canvas element "canvas1" with no additional processing.
Here is the JS:
function loadlogo(){
var logo = new Image();
var canvas = document.getElementById('canvas1');
var context = canvas.getContext('2d');
//resize the canvas to the current window
context.canvas.width = window.innerWidth;
context.canvas.height = window.innerHeight / 3;
logo.src = "images/1.png";
logo.onload = function() {context.drawImage(logo,0,0;};
context.shadowOffsetX = 50;
context.shadowOffsetY = 30;
context.shadowColor = "pink";
}
window.addEventListener("load",loadlogo,false);
window.addEventListener("resize",loadlogo,false);
Any help you could give would be awesome!!!
I have tried this many ways and am stuck.
Thanks,
Bryan
Put your onload function for img before you assign img src
Change this part
{context.drawImage(logo,0,0;};
^ Notice the missing end-parenthesis here
to
{context.drawImage(logo,0,0)};
I would as QBM5 also recommend to put the src after setting onload to be sure it's properly initialized.
I'm trying to load an image from a URL into a HTML canvas at a 1:1 scale. I load the image, and set the canvas DOM element to the appropriate dimensions, but for some reason the image in the canvas is significantly upscaled and therefore only the top left hand corner is drawn.
This is demonstrated by the following JSFiddle: http://jsfiddle.net/KdrYr/1/
var img = new Image();
var cv = document.getElementById('thecanvas');
img.src = 'http://www.photographyblogger.net/wp-content/uploads/2009/12/Picture-in-a-picture4.jpg';
img.onload = function() {
var ctx = cv.getContext('2d');
cv.style.width = img.width + 'px';
cv.style.height = img.height + 'px';
ctx.drawImage(img, 0, 0);
};
For example, I'm trying to draw this (sorry about the big images :/)
But end up with this
What could be causing this?
You need to assign the canvas actual width and height, not via its style:
cv.width = img.width;
cv.height = img.height;
Live test case.
As for the why, well, it's explained already here.