CODEWITHSUNDEEP
javascriptmousewheelzooming
wantToBeAProgrammer
wantToBeAProgrammer

Reputation: 179

mouse point zoom image - wheel event

Here is zoom working example. I'd like the image to be zoomed on actual mouse position over image. How to achieve this? No libraries.

const image = document.querySelector('img');
const zoom = {
    min: 1,
    max: 3,
    value: 1,
    step: 0.1
};

image.addEventListener('wheel', event => {
   event.preventDefault();

   if (event.deltaY < 0) {
     zoom.value = zoom.value >= zoom.max ? zoom.max : zoom.value + zoom.step;
     
     } else  if (event.deltaY > 0) {
      zoom.value = zoom.value <= zoom.min ? zoom.min : zoom.value - zoom.step;
   }
  
  image.style.transform = `scale(${zoom.value})`
	}
)
div {
  width: 500px;
  overflow: hidden;
}

img {
  width: 100%;
}
<div>
  <img src="https://picjumbo.com/wp-content/uploads/free-stock-photos-san-francisco-1080x720.jpg">
</div>

egzample

Upvotes: 3

Views: 1173

Answers (3)

Kostas
Kostas

Reputation: 1903

const image = document.querySelector('img');
const zoom = {
    min: 1,
    max: 3,
    value: 1,
    step: 0.1
};

var div = document.querySelector('div');

div.addEventListener('wheel', event => {
   event.preventDefault();

   if (event.deltaY < 0) {
     zoom.value = zoom.value >= zoom.max ? zoom.max : zoom.value + zoom.step;
     
     } else  if (event.deltaY > 0) {
      zoom.value = zoom.value <= zoom.min ? zoom.min : zoom.value - zoom.step;
   }
  
  image.style.transform = `scale(${zoom.value})`
  var xPerc = (x * 100) / image.width;
  var yPerc = (y * 100) / image.height;
    image.style.transformOrigin = xPerc + '%' + ' ' + yPerc + '%';
    }
)

var x, y;

div.addEventListener('mousemove', e => {
    x = e.clientX - div.offsetLeft;
  y = e.clientY - div.offsetTop;
})
div {
  width: 500px;
  overflow: hidden;
}

img {
  width: 100%;
}
<div>
  <img src="https://picsum.photos/200">
</div>

Played a little bit with your example and found out transform-origin might do the trick. Added coordinates x,y relative to image's container and converted them to a percentage in order to set image's tranform-origin style property.

Upvotes: 2

Kamil Kiełczewski
Kamil Kiełczewski

Reputation: 92427

Change you image.style.transform... to (500x337 is div-image size)

let x = (-event.offsetX+500/2)*(zoom.value-1);
let y = (-event.offsetY+337/2)*(zoom.value-1);

image.style.transform = `translate(${x}px,${y}px) scale(${zoom.value}) `


const image = document.querySelector('img');
const zoom = {
  min: 1,
  max: 3,
  value: 1,
  step: 0.1
};

image.addEventListener('wheel', event => {
  event.preventDefault();

  if (event.deltaY < 0) {
    zoom.value = zoom.value >= zoom.max ? zoom.max : zoom.value + zoom.step;

  } else if (event.deltaY > 0) {
    zoom.value = zoom.value <= zoom.min ? zoom.min : zoom.value - zoom.step;
  }

  let x = (-event.offsetX+500/2)*(zoom.value-1);
  let y = (-event.offsetY+337/2)*(zoom.value-1);
  
  image.style.transform = `translate(${x}px,${y}px) scale(${zoom.value}) `
})
div {
  width: 500px;
  overflow: hidden;
}

img {
  width: 100%;
}
<div>
  <img src="https://picjumbo.com/wp-content/uploads/free-stock-photos-san-francisco-1080x720.jpg">
</div>

Upvotes: 0

Yosef Tukachinsky
Yosef Tukachinsky

Reputation: 5895

add 

image.style.transformOrigin = `${event.x}px ${event.y}px`


const image = document.querySelector('img');
const zoom = {
    min: 1,
    max: 3,
    value: 1,
    step: 0.1,
    originX: 0,
    originY: 0
};

image.addEventListener('wheel', event => {
   event.preventDefault();
   zoom.originX += (event.x-zoom.originX)/zoom.value;
   zoom.originY += (event.y-zoom.originY)/zoom.value;
   image.style.transformOrigin = zoom.originX+'px '+zoom.originY+'px';

   if (event.deltaY < 0) {
     zoom.value = zoom.value >= zoom.max ? zoom.max : zoom.value + zoom.step;
     
     } else  if (event.deltaY > 0) {
      zoom.value = zoom.value <= zoom.min ? zoom.min : zoom.value - zoom.step;
   }
  image.style.transformOrigin = `${event.x}px ${event.y}px`
  image.style.transform = `scale(${zoom.value})`
	}
)
div {
  width: 500px;
  overflow: hidden;
}

img {
  width: 100%;
}
<div>
  <img src="https://picjumbo.com/wp-content/uploads/free-stock-photos-san-francisco-1080x720.jpg">
</div>

Upvotes: 0

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