panzoom 
Extensible, mobile friendly pan and zoom framework (supports DOM and SVG).
Demo
- Regular DOM object
- Standalone page - this repository
- SVG Tiger - js fiddle
Usage
Grab it from npm and use with your favorite bundler:
npm install panzoom --save
Or download from CDN:
<script src='https://unpkg.com/[email protected]/dist/panzoom.min.js'></script>
If you download from CDN the library will be available under panzoom global name.
Pan and zoom DOM subtree
// just grab a DOM element
var element = document.querySelector('#scene')
// And pass it to panzoom
panzoom(element)
SVG panzoom example
<!-- this is your html file with svg -->
<body>
<svg>
<!-- this is the draggable root -->
<g id='scene'>
<circle cx='10' cy='10' r='5' fill='pink'></circle>
</g>
</svg>
</body>
// In the browser panzoom is already on the
// window. If you are in common.js world, then
// var panzoom = require('panzoom')
// grab the DOM SVG element that you want to be draggable/zoomable:
var element = document.getElementById('scene')
// and forward it it to panzoom.
panzoom(element)
If require a dynamic behavior (e.g. you want to make an element not
draggable anymore, or even completely delete an SVG element) make sure to call
dispose() method:
var instance = panzoom(element)
// do work
// ...
// then at some point you decide you don't need this anymore:
instance.dispose()
This will make sure that all event handlers are cleared and you are not leaking
memory
Events notification
The library allows to subscribe to transformation changing events. E.g. when
user starts/ends dragging the element, the element will fire panstart/panend
events. Here is example of all supported events:
var instance = panzoom(element);
instance.on('panstart', function(e) {
console.log('Fired when pan is just started ', e);
// Note: e === instance.
});
instance.on('pan', function(e) {
console.log('Fired when the `element` is being panned', e);
});
instance.on('panend', function(e) {
console.log('Fired when pan ended', e);
});
instance.on('zoom', function(e) {
console.log('Fired when `element` is zoomed', e);
});
instance.on('zoomend', function(e) {
console.log('Fired when zoom animation ended', e);
});
instance.on('transform', function(e) {
// This event will be called along with events above.
console.log('Fired when any transformation has happened', e);
});
See JSFiddle console for a demo.
Ignore mouse wheel
Sometimes zooming interferes with scrolling. If you want to alleviate it you
can provide a custom filter, which will allow zooming only when modifier key is
down. E.g.
panzoom(element, {
beforeWheel: function(e) {
// allow wheel-zoom only if altKey is down. Otherwise - ignore
var shouldIgnore = !e.altKey;
return shouldIgnore;
}
});
See JSFiddle for the demo. The tiger will be
zoomable only when Alt key is down.
Ignore mouse down
If you want to disable panning or filter it by pressing a specific key, use the
beforeMouseDown() option. E.g.
panzoom(element, {
beforeMouseDown: function(e) {
// allow mouse-down panning only if altKey is down. Otherwise - ignore
var shouldIgnore = !e.altKey;
return shouldIgnore;
}
});
Note that it only works when the mouse initiates the panning and would not work
for touch initiated events.
Ignore keyboard events
By default, panzoom will listen to keyboard events, so that users can navigate the scene
with arrow keys and +, - signs to zoom out. If you don't want this behavior you can
pass the filterKey() predicate that returns truthy value to prevent panzoom's default
behavior:
panzoom(element, {
filterKey: function(/* e, dx, dy, dz */) {
// don't let panzoom handle this event:
return true;
}
});
Zoom Speed
You can adjust how fast it zooms, by passing optional zoomSpeed argument:
panzoom(element, {
zoomSpeed: 0.065 // 6.5% per mouse wheel event
});
Pinch Speed
On touch devices zoom is achieved by "pinching" and depends on distance between
two fingers. We try to match the zoom speed with pinch, but if you find
that too slow (or fast), you can adjust it:
panzoom(element, {
pinchSpeed: 2 // zoom two times faster than the distance between fingers
});
Get current transform (scale, offset)
To get the current zoom (scale) level use the getTransform() method:
console.log(instance.getTransform()); // prints {scale: 1.2, x: 10, y: 10}
Fixed transform origin when zooming
By default when you use mouse wheel or pinch to zoom, panzoom uses mouse
coordinates to determine the central point of the zooming operation.
If you want to override this behavior and always zoom into center of the
screen pass transformOrigin to the options:
panzoom(element, {
// now all zoom operations will happen based on the center of the screen
transformOrigin: {x: 0.5, y: 0.5}
});
You specify transformOrigin as a pair of {x, y} coordinates. Here are some examples:
// some of the possible values:
let topLeft = {x: 0, y: 0};
let topRight = {x: 1, y: 0};
let bottomLeft = {x: 0, y: 1};
let bottomRight = {x: 1, y: 1};
let centerCenter = {x: 0.5, y: 0.5};
// now let's use it:
panzoom(element, {
transformOrigin: centerCenter
});
To get or set new transform origin use the following API:
let instance = panzoom(element, {
// now all zoom operations will happen based on the center of the screen
transformOrigin: {x: 0.5, y: 0.5}
});
let origin = instance.getTransformOrigin(); // {x: 0.5, y: 0.5}
instance.setTransformOrigin({x: 0, y: 0}); // now it is topLeft
instance.setTransformOrigin(null); // remove transform origin
Min Max Zoom
You can set min and max zoom, by passing optional minZoom and maxZoom argument:
var instance = panzoom(element, {
maxZoom: 1,
minZoom: 0.1
});
You can later get the values using getMinZoom() and getMaxZoom()
assert(instance.getMaxZoom() === 1);
assert(instance.getMinZoom() === 0.1);
Disable Smooth Scroll
You can disable smooth scroll, by passing optional smoothScroll argument:
panzoom(element, {
smoothScroll: false
});
With this setting the momentum is disabled.
Pause/resume the panzoom
You can pause and resume the panzoom by calling the following methods:
var element = document.getElementById('scene');
var instance = panzoom(element);
instance.isPaused(); // returns false
instance.pause(); // Pauses event handling
instance.isPaused(); // returns true now
instance.resume(); // Resume panzoom
instance.isPaused(); // returns false again
Script attachment
If you want to quickly play with panzoom without using javascript, you can configure it via
script tag:
<!-- this is your html file -->
<!DOCTYPE html>
<html>
<head>
<script src='https://unpkg.com/[email protected]/dist/panzoom.min.js'
query='#scene' name='pz'></script>
</head>
<body>
<svg>
<!-- this is the draggable root -->
<g id='scene'>
<circle cx='10' cy='10' r='5' fill='pink'></circle>
</g>
</svg>
</body>
</html>
Most importantly, you can see query attribute that points to CSS selector. Once the element is found
panzoom is attached to this element. The controller will become available under window.pz name. And you
can pass additional options to the panzoom via attributes prefixed with pz-.
Here is a demo: Script based attributes
Adjust Double Click Zoom
You can adjust the double click zoom multiplier, by passing optional zoomDoubleClickSpeed argument.
When double clicking, zoom is multiplied by zoomDoubleClickSpeed, which means that a value of 1 will disable double click zoom completely.
panzoom(element, {
zoomDoubleClickSpeed: 1,
});
Set Initial Position And Zoom
You can set the initial position and zoom, by chaining the zoomAbs function with x position, y position and zoom as arguments:
panzoom(element, {
maxZoom: 1,
minZoom: 0.1,
initialX: 300,
initialY: 500,
initialZoom: 0.5
});
Handling touch events
The library will handle ontouch events very aggressively, it will preventDefault, and
stopPropagation for the touch events inside container. Sometimes this is not a desirable behavior.
If you want to take care about this yourself, you can pass onTouch callback to the options object:
panzoom(element, {
onTouch: function(e) {
// `e` - is current touch event.
return false; // tells the library to not preventDefault.
}
});
Note: if you don't preventDefault yourself - make sure you test the page behavior on iOS devices.
Sometimes this may cause page to bounce undesirably.
Handling double click events
By default panzoom will prevent default action on double click events - this is done to avoid
accidental text selection (which is default browser action on double click). If you prefer to
allow default action, you can pass onDoubleClick() callback to options. If this callback
returns false, then the library will not prevent default action:
panzoom(element, {
onDoubleClick: function(e) {
// `e` - is current double click event.
return false; // tells the library to not preventDefault, and not stop propagation
}
});
Bounds on Panzoom
By default panzoom will not prevent Image from Panning out of the Container. bounds (boolean) and
boundsPadding (number) can be defined so that it doesn't fall out. Default value for boundsPadding is 0.05 .
panzoom(element, {
bounds: true,
boundsPadding: 0.1
});
Triggering Pan
To Pan the object using Javascript use moveTo(<number>,<number>) function. It expects x, y value to where to move.
instance.moveTo(0, 0);
To pan in a smooth way use smoothMoveTo(<number>,<number>):
instance.smoothMoveTo(0, 0);
Triggering Zoom
To Zoom the object using Javascript use zoomTo(<number>,<number>,<number>) function. It expects x, y value as coordinates of where to zoom. It also expects the zoom factor as the third argument. If zoom factor is greater than 1, apply zoom IN. If zoom factor is less than 1, apply zoom OUT.
instance.zoomTo(0, 0, 2);
To zoom in a smooth way use smoothZoom(<number>,<number>,<number>):
instance.smoothZoom(0, 0, 0.5);
Custom UI to trigger zoom
One of the common use case is to have a custom UI to trigger zoom. For example, you can use a button to zoom in/out.
Since this library does not depend on any popular framework (react, vue, etc.) you can implement it yourself
following this example:
- Live demo
- Source code of the demo
license
MIT
