How to get Text object font-size after modifying object

Question

How can I get Text object font size after modifying object in fabric.js?

Below is my code.

var text = new fabric.Text(imgText, {
                left: 10,
                top: 5,
                fontSize: 15,
                fontFamily: 'Verdana',
                fill: 'white'
            });
            text.scaleToWidth(canvas.width * 0.5);
            text.setControlsVisibility(canvasConfig);
            canvas.add(text);
            canvas.renderAll();
var objects = canvas.getActiveObject();

            var obj = objects;
            if (!obj) {
                return;
            }
            //console.log(obj.get('fontSize') *= obj.scaleX); 
            var angle = obj.get('angle');

            var objWidth = obj.get('width') * obj.scaleX;
            var objWidthPercent = objWidth / canvas.width * 100;

            var objHeight = obj.get('height') * obj.scaleY;
            var objHeightPercent = objHeight / canvas.height * 100;

            var bound = obj.getBoundingRect();
            var objLeft = obj.get('left') / canvas.width * 100;
            var objTop = obj.get('top') / canvas.height * 100;

            var newfontsize = obj.fontSize * obj.scaleX;

Above I set default FontSize to 15. then I modify object I can get proper Height, Width, Left, Top, but I am not able to get FontSize.

In backend i set image and text like below screenshot.

In frontend what i get like below screenshot.

Below style for image & text on frontend.

element.style {
    left: 64.37%;
    top: 14.54%;
    width: 28.25%;
    height: 14.37%;
    font-size: 63.58px;
    color: #E346FF;
    font-family: Times New Roman;
    position: absolute;
    max-width: 100%;
    z-index: 996;
    max-height: 100%;
}

element.style {
    left: 56.5%;
    top: 0.81%;
    width: 42.86%;
    height: 42.86%;
    max-width: 100%;
    max-height: 100%;
    position: absolute;
    z-index: 995;
    display: block;
    background-image: url(http://10.16.16.101/LabelExtension/pub/media/labelimageuploader/images/image/o/r/orange_38.png);
    background-position: center;
    background-repeat: no-repeat;
    background-size: contain;
}

When i add below code it working perfect but in backend object is getting blur.

this.canvas.setHeight(300);
this.canvas.setWidth(240);
this.canvas.backgroundColor = '#E8EEF1';
this.canvas.setDimensions({width: '480px', height: '600px'}, {cssOnly: true});

Answer 1

Here is the way to match Fabric.js font transforms to CSS transforms: https://jsfiddle.net/mmalex/evpky3tn/

The solution is to match transformations of texts, not trying to adjust font size.

---

Step 1 - Prepare scene, compose canvas, group text with rectangle, let user manipulate this group, rotate and scale it.

var canvas = new fabric.Canvas(document.getElementById('c'));

var rect = new fabric.Rect({
    width: 50,
    height: 50,
    left: 90,
    top: 120,
    fill: 'rgba(255,0,0,0.25)'
});

var text = new fabric.Text("123", {
    left: rect.left,
    top: rect.top,
    fontSize: 15,
    fontFamily: 'Verdana',
    fill: 'black'
});

text.scaleToWidth(rect.width);
canvas.add(text);

var group = new fabric.Group([rect, text], {
    originX: 'center',
    originY: 'center',
    angle: 25,
    scaleY: 1.7
});

canvas.add(group);
canvas.renderAll();

Step 2 - prepare DIV style for scaling

.scaled {  // this style is applied to DIV element with text
    ...
    font-size: 15px; // Fabric.js text is also 15px size
    transform: scale(1, 1); // define initial transform
    transition: all 0.25s linear; // let it animate
    ...
}

Step 3 - Evaluate Fabric.js transforms and apply CSS on DIV element, for example:

element.style {
    transform: rotate(25deg) scale(1.74774, 2.97116); 
}

The solution (aka button handler) converts Fabric.js transform to CSS transform:

function matchCssTransform() {
    let textScale = text.getTotalObjectScaling();
    let pixelRatio = window.devicePixelRatio;
    let styleStr = `rotate(${group.angle}deg) scale(${textScale.scaleX / pixelRatio}, ${textScale.scaleY / pixelRatio}) `;
    document.getElementById("scaled").style.transform = styleStr;
}

Answer 2

getHeightOfLine(lineIndex) → {Number} : Computes height of character at given position and return fontSize of the character. Is it? tell me. It's a method of text class. http://fabricjs.com/docs/fabric.Text.html#getHeightOfLine