how to stretch image size to match fabric.Image object - fabricjs

Question

I am using fabricjs to implement image editing and I try to use a fabric.Image object as the background image of canvas to store the data. And the following is the code:
var canvas = new fabric.Canvas('canvasId');
var imageObject = new fabric.Image($originImage);
canvas.add(imageObject);
but I found the $originImage's size is much larger than canvas' size and also imageObject's size, so the canvas can only show part of the image. I want to know how to stretch the $originImage to adapt the canvas then canvas can display all of the $originImage?
Here what I have done
$canvas.width = $originImage.clientWidth;
$canvas.height = $originImage.clientHeight;
var fabricCanvas = new fabric.Canvas('canvasId');
// canvas.setFabricCanvas(fabricCanvas);
var imageObject = new fabric.Image($originImage);
// fabricCanvas.add(imageObject);
// fabricCanvas.isDrawingMode = true;
fabricCanvas.setBackgroundImage(imageObject, fabricCanvas.renderAll.bind(fabricCanvas), {
scaleX: fabricCanvas.width / $originImage.naturalWidth,
scaleY: fabricCanvas.height / $originImage.naturalHeight
});
the upper is my related code and below is the display:
it is solved, and the previous question is because I resize the $originImage first, so when I input the image src as setBackgroundImage's parameter, it can display normally.

Answer 1

For version 2.0 of fabricjs, they have changed the way to handle width/height compared to previous version. If you apply width/height, then it basically crop the image to that particular size compared to the original image size. In order to resize it to a proper size, you have to switch to use scaleX/scaleY like other people have suggested.
For example, I use image.fromUrl to load an image and set it to be the background:
fabric.Image.fromURL(imgUrl, function(img) {
img.set({
scaleX: currentWidth / img.width,
scaleY: currentHeight / img.height,
top: topPosition,
left: leftPosition
originX: 'left', originY: 'top'
});
canvas.setBackgroundImage(img, canvas.renderAll.bind(canvas));
});
where currentWidth/currentHeight can be your canvas size if you want full background or they can be a specific width/height that you want (in my project, I want to do letter-boxed image instead so I set the width and height based on my letter-boxing algorithm), and top/left is the location that you want to place your image in the canvas (leave it none if you want to be full background image). Do not set any width and height since that will crop the scaled image rather than setting the image to be the exact size.
If this does not work, check the backgroundImage object from the canvas and see if its dimension and scale properties are different compared to a manual calculation. If you take a look, you will see the width and height properties are your natural image width and height, but it will have scaleX and scaleY less than 1 if your canvas size is less than the image size or more than 1 if it is bigger.
Also I see you are loading image directly into an image object. That might be different compared to load the data and set it directly using setBackgroundImage.

Answer 2

canvas.setBackgroundImage(img, canvas.renderAll.bind(canvas), {
scaleX: canvas.width / $originalImg.naturalWidth,
scaleY: canvas.width / $originalImg.naturalHeight
});
use scaleX,scaleY to resize.
(function() {
var $originalImg = $('#originalImage')[0];
console.dir($originalImg)
var canvas = this.__canvas = new fabric.Canvas('c');
var img = new fabric.Image($originalImg);
canvas.setBackgroundImage(img,canvas.renderAll.bind(canvas),{
scaleX:canvas.width/$originalImg.naturalWidth,
scaleY:canvas.width/$originalImg.naturalHeight
});
})();
canvas{
border-width: 1pz;
border-style: solid;
border-color: #000;
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/fabric.js/2.0.0-rc.3/fabric.js"></script>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<img id='originalImage'src='http://fabricjs.com/assets/pug_small.jpg'>
<canvas id='c' width=200 height=200></canvas>

Answer 3

I am using the following script to ensure the image is no larger than the canvas width:
var aspect = image.width / image.height; //Aspect ratio of image
new fabric.Image(image, {
scaleX: canvas.width / image.width,
scaleY: canvas.width / (image.height * aspect)
});