What is the method for obtaining the angle in a CSS3 rotate transformation?

Question

What is the method for obtaining the angle in a CSS3 rotate transformation?

In my current code, I am setting the rotational angle of an element using the following:

$('#1-link-2')
                .css('height', length)
                .css('-webkit-transform', 'rotate(' + angle + 'deg)')
                .css('-moz-transform', 'rotate(' + angle + 'deg)')
                .css('-o-transform', 'rotate(' + angle + 'deg)')
                .css('-ms-transform', 'rotate(' + angle + 'deg)')
                .css('transform', 'rotate(' + angle + 'deg)');

The angle is calculated dynamically based on the mouse position.

Now, I want to retrieve the angle. I attempted this:

var angle= $("#1-link-2").css('-webkit-transform');
    $('#node-title').html(angle);   //displaying it on the screen

The output I received was:

matrix(0.5425908601788315, -0.839997118120292, 0.839997118120292, 0.5425908601788315, 0, 0)

How do I extract the angle in degrees from this?

javascript jquery css

Answer 1

Answer №1

When dealing with rotation angles, the first value corresponds to the cosine, and the second value corresponds to the sine - provided there are no additional transforms applied to the element. Utilize your preferred mathematical library to compute inverse sine and cosine functions.

For instance, the inverse cosine of .54 equates to around 54 or 306 degrees. Similarly, the inverse sine of -0.83 is approximately 234 or 306 degrees.

It seems like the correct answer consistently amounts to 306 degrees.

If you need a geometry refresher, you can find one here.

Answer 2

When dealing with rotation angles, the first value corresponds to the cosine, and the second value corresponds to the sine - provided there are no additional transforms applied to the element. Utilize your preferred mathematical library to compute inverse sine and cosine functions.

For instance, the inverse cosine of .54 equates to around 54 or 306 degrees. Similarly, the inverse sine of -0.83 is approximately 234 or 306 degrees.

It seems like the correct answer consistently amounts to 306 degrees.

If you need a geometry refresher, you can find one here.

Answer 3

Answer №2

Take a look at this helpful article:

const element = document.getElementById("elementID");
const styles = window.getComputedStyle(element, null);
const transformValue = styles.getPropertyValue("-webkit-transform") ||
         styles.getPropertyValue("-moz-transform") ||
         styles.getPropertyValue("-ms-transform") ||
         styles.getPropertyValue("-o-transform") ||
         styles.getPropertyValue("transform") ||
         "FAIL";

// Example with rotate(30deg)...
// matrix(0.866025, 0.5, -0.5, 0.866025, 0px, 0px)
console.log('Matrix: ' + transformValue);

// Extracting values from the matrix
const matrixValues = transformValue.split('(')[1].split(')')[0].split(',');
const a = matrixValues[0];
const b = matrixValues[1];
const c = matrixValues[2];
const d = matrixValues[3];

const scaleValue = Math.sqrt(a*a + b*b);

console.log('Scale: ' + scaleValue);

// Calculating the rotation angle
const sinValue = b/scaleValue;
const angle = Math.round(Math.atan2(b, a) * (180/Math.PI));

console.log('Rotation Angle: ' + angle + 'deg');

Answer 4

Take a look at this helpful article:

const element = document.getElementById("elementID");
const styles = window.getComputedStyle(element, null);
const transformValue = styles.getPropertyValue("-webkit-transform") ||
         styles.getPropertyValue("-moz-transform") ||
         styles.getPropertyValue("-ms-transform") ||
         styles.getPropertyValue("-o-transform") ||
         styles.getPropertyValue("transform") ||
         "FAIL";

// Example with rotate(30deg)...
// matrix(0.866025, 0.5, -0.5, 0.866025, 0px, 0px)
console.log('Matrix: ' + transformValue);

// Extracting values from the matrix
const matrixValues = transformValue.split('(')[1].split(')')[0].split(',');
const a = matrixValues[0];
const b = matrixValues[1];
const c = matrixValues[2];
const d = matrixValues[3];

const scaleValue = Math.sqrt(a*a + b*b);

console.log('Scale: ' + scaleValue);

// Calculating the rotation angle
const sinValue = b/scaleValue;
const angle = Math.round(Math.atan2(b, a) * (180/Math.PI));

console.log('Rotation Angle: ' + angle + 'deg');

Answer 5

Answer №3

const calculateRotation = (element) => {
  const matrix = element.css("-webkit-transform") ||
                 element.css("-moz-transform") ||
                 element.css("-ms-transform") ||
                 element.css("-o-transform") ||
                 element.css("transform");
  
  if (matrix !== 'none') {
    const values = matrix.split('(')[1].split(')')[0].split(',');
    const a = values[0];
    const b = values[1];
    let angle = Math.round(Math.atan2(b, a) * (180/Math.PI));
    return (angle < 0) ? angle + 360 : angle;
  } else {
    return 0;
  }
}

let angle1 = calculateRotation($('#1-link-2'));

Answer 6

const calculateRotation = (element) => {
  const matrix = element.css("-webkit-transform") ||
                 element.css("-moz-transform") ||
                 element.css("-ms-transform") ||
                 element.css("-o-transform") ||
                 element.css("transform");
  
  if (matrix !== 'none') {
    const values = matrix.split('(')[1].split(')')[0].split(',');
    const a = values[0];
    const b = values[1];
    let angle = Math.round(Math.atan2(b, a) * (180/Math.PI));
    return (angle < 0) ? angle + 360 : angle;
  } else {
    return 0;
  }
}

let angle1 = calculateRotation($('#1-link-2'));

What is the method for obtaining the angle in a CSS3 rotate transformation?

Answer №1

Answer №2

Answer №3

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