Fabric js image quality is not getting good after set image height and width dynamically

Question

I have added image into canvas and dynamically I want to change image height and width according to the rectangle height and width. I have done calculation of image height and width according to rectangle height and width and original image height and width.

Using below code I have changed image height and width but image quality is getting very low

var image_height = 200; //For now here image height is dummy
var image_width = 150; //For now here image width is dummy
var obj = canvas.getActiveObject();
obj.setHeight(image_height);
obj.setWidth(image_width);
obj.setCoords();
canvas.renderAll();

Answer 1

I ran into the same problem a few days ago. The solution I found is to not try to set widthand height but rather ask your image to scale up to the canvas dimensions.

Here is how I did it :

var scaleWidth = canvas.getWidth() / img.width;
var scaleHeight = canvas.getHeight() / img.height;
var scale = Math.min(scaleWidth, scaleHeight);
bgImage = new fabric.Image(img, {
    [...]
    scaleX: scale,
    scaleY: scale,
    [...]
  });
canvas.add(bgImage);
canvas.sendToBack(bgImage); // useful in case you want a background but not **needed**
canvas.renderAll();

In the code above I compute width and height ratios, pick the lower one, and then I apply it on the picture using scaleX and scaleY properties.

If it still doesn't work for you, please let me know in the comments.

EDIT : I completed my linked code for more clarity.

2nd EDIT : It appears a method called scaleexists and could be used on your image. Looks cleaner if you want to keep your ratio (aka scaleXand scaleY properties would have the same value).