ngx-panzoom

ngx-panzoom

An Angular component for panning and zooming an element or elements using the mouse and mousewheel. Provides rudimentary support for touchscreens (read section on mobile support). It was adapted from the angular-pan-zoom library for AngularJS, but it has been heavily modified. Many thanks go out to Martin Vindahl Olsen for having written it, and for his blessing.

It is built using Angular CLI. It is only tested with the corresponding version of Angular.

This library deliberately parts with certain received Angular wisdom of using only Angular-ish methods to accomplish things. We use native event listeners. We apply CSS transforms directly to the DOM. But as this library doesn't fit the traditional Angular model, as its purpose is only to apply CSS transforms to a certain part of the DOM, without moving or changing anything else, it has no impact on an application's state (except if the app consumes modelChanged observables). By using this approach, it is hoped that performance will be maximised.

End Of Life

There are no plans to support ngx-panzoom beyond version 19. PR's may still be accepted, though.

Version 19 Compatibility

Version 19 is compatible with Angular 18 and up. Assuming Angular's API doesn't significantly change in future releases, this library should continue to function.

Version 19 Breaking Changes

• The PanZoomConfig class has been removed. Configuration options which were previously set using PanZoomConfig should now be bound directly to ngx-panzoom in the template.
• Version 19 adopts a more conventional API approach -- it removes the need to access the API via an observable (this interface has been fully removed). One need only use viewChild or @ViewChild with a PanZoomComponent selector, or a #Hash selector in the template.
• The modelChanged RxJS BehaviorSubject of the PanZoomConfig class has been replaced with a standard modelChange Angular output.

See code example for more details.

Demo

As of version 19, the demo app is part of this repository, under projects/demo-app. Click here

Features

• Zoom using mouse wheel, touch surface, double click, or API controls tied to your own UI.
• Pan using click/touch and drag, or API calls. When releasing the mouse button or touch surface whilst panning, the pan will come to a gradual stop.

Differences From the Original AngularJS Version

• The pan-zoom service has been eliminated.
• Free zoom - zooming is no longer limited to switching between two distinct zoom levels. Zoom can now be smoothly and freely controlled using the mouse wheel or trackpad.
• zoomToFit() animation - using the zoomToFit() function now will animate the view to the a desired rectangle.
• A convenience method resetView() has been provided to animate the view back to its initial settings.
• The zoomIn() and zoomOut() API functions can zoom to either the last zoomed point or to the view's centre point, depending on the value of zoomType (lastPoint or viewCenter).
• New API methods panToPoint(), panDelta(), panDeltaPercent(), panDeltaAbsolute(), and many others have been added.
• Performance improvements.
• The widget has not been migrated from the original project.
• Touchscreen support "works", but not well.

Dependencies

• = Angular 18

Mobile Support -- Actively Soliciting PR's

The library implements some basic support that may work with some mobile devices, though pinch-to-zoom still needs considerable work. As the application that this library was developed for was never intended for use with mobile devices, there are no plans to implement full mobile support. As long as this remains the case, I respecfully ask for no more issues concerning mobile support, please. I realise that this will limit adoption, but for an enterprising developer out there, I can't imagine that adding mobile support would be nearly as big of a challenge as it was to port the library to Angular from AngularJS!

Installation

npm install ngx-panzoom --save

app.module.ts:

import { NgxPanZoomModule } from 'ngx-panzoom';

@NgModule({
  imports: [  ...,
    NgxPanZoomModule
  ],
  ...
})

export class MyAppModule { }

Usage

This library exposes a component called ngx-panzoom, under which you may place any standard Angular template code. Though the events which trigger panning and zooming are run outside of Angular and thus themselves will not trigger change detection, it should not break change detection for any sub-components.

Configuration parameters are set as properties of the ngx-panzoom template element.

The API can be accessed directly on the PanZoomComponent class, which can be obtained either as a template reference (i.e. #PanZoom) or using viewChild or @ViewChild. See below example code.

Top Tip

Be sure to place your pan-zoom component underneath an element with a definite height/width, like an absolute-positioned div. You may not see anything if you don't do this.

Example

import { viewChild, signal } from '@angular/core';
import { PanZoomComponent, PanZoomModel } from 'ngx-panzoom';

@Component({
  selector: 'my-component'
  template: `
    <div style="position: absolute; top: 100px; bottom: 0; left: 0; right: 0;">
      <ngx-panzoom
        #PanZoom
        [zoomLevels]="10"
        [scalePerZoomLevel]="scalePerZoomLevel()"
        [zoomStepDuration]="0.2"
        [freeMouseWheelFactor]="0.01"
        [zoomToFitZoomLevelFactor]="0.9"
        [neutralZoomLevel]="neutralZoomLevel()"
        (modelChange)="panzoomModel.set($event)"
      >
        <div style="position: relative;">
          <img src="/myimage1.jpg">
        </div>
      </ngx-panzoom>
    </div>
    
    <!-- API by template reference -->
    <button (click)="PanZoom.zoomOut('lastPoint')"></button>`
})

export class MyComponent {
  ...
  readonly panZoom = viewChild(PanZoomComponent);
  readonly panzoomModel = signal<PanZoomModel>(undefined!);
  
  myMethod(): void {
    // API by viewChild
    this.panZoom().zoomIn('lastPoint');
  }
}

Configuration

Configuration is set via property bindings on the ngx-panzoom element.

The following attributes are defined:

Name	Type	Default	Description
zoomLevels	number	5	Number of discrete zoom levels, each one representing a scale. The higher the number, the more zoomed in it is.
neutralZoomLevel	number	2	The zoom level at which the contents render at 1:1 scale.
scalePerZoomLevel	number	2.0	The difference in actual scale between two adjacent zoom levels.
initialZoomLevel	number	neutralZoomLevel	The initially selected zoom level.
initialPanX	number	0	The initial pan in the horizontal direction.
initialPanY	number	0	The initial pan in the vertical direction.
initialZoomToFit	Rect	null	When defined, will initially zoom to fit the given rectangle (see API for explanation of zoom to fit). This overrides the initialZoomLevel, initialPanX, and initialPanY values.
zoomToFitZoomLevelFactor	number	0.95	A number to indicate how closely zoom to fit will work. 1.0 is a perfect fit. Lowering the number will reveal a bit of the surrounding contents.
zoomOnDoubleClick	boolean	true	Enable or disable zooming in on double click.
zoomButtonIncrement	number	1.0	The number of zoom levels to zoom on double click.
zoomStepDuration	number	0.2	Number of seconds to animate between two adjacent zoom levels.
zoomOnMouseWheel	boolean	true	Enable or disable zoom in/out on mouse wheel.
invertMouseWheel	boolean	false	Invert the behaviour of the mouse wheel (or two finger trackpad gesture).
freeMouseWheel	boolean	true	By setting this to true, the mouse wheel will freely zoom the view without respect to discreet zoom levels. With false, moving the mouse wheel will zoom the view by zoomButtonIncrement.
freeMouseWheelFactor	number	0.08	How much to zoom the view with every tick of the wheel, if using freeMouseWheel.
friction	number	10.0	Constant which controls the friction when dragging and then letting go. The higher the number, the more quickly the animation will come to a stop.
haltSpeed	number	100.0	Constant which controls when the pan animation has slowed down enough to be terminated. The lower the number, the longer it will take to come to a stop.
panOnClickDrag	boolean	true	Enable or disable pan on clicking and dragging the mouse.
keepInBounds	boolean	false	When true, it will not be possible to pan the contents off the screen -- it will snap back when trying to do so. It will not be possible to zoom further out than the neutral zoom level. REMEMBER that the initial zoom level must either be less than or equal to the neutral zoom level, or weird things will happen.
keepInBoundsRestoreForce	number	0.5	Constant to control how quickly the contents snap back into place after attempting to pan out of bounds.
keepInBoundsDragPullback	number	0.7	Constant to control the perceived force preventing dragging the contents out of bounds.
dragMouseButton	string	'left'	Controls which mouse button drags the view. Valid options are left, middle, and right. NOTE: Using middle and right will disable the default 'auxclick' and 'contextmenu' handlers, respectively. ALSO NOTE: Chrome seems to have a bug that doesn't the permit the 'mousemove' event to fire after middle-click drag until it receives a normal left 'click' event. If anyone can shed any light on this, I'd be happy to hear from you. It's such an edge case, though, that I won't be opening a bug report, but feel free to do so if this affects you.
noDragFromElementClass	string	null	If set, this will prevent click-drag on elements who have a parent element containing a specific class name.
acceleratePan	boolean	true	Controls whether the pan frame will be hardware accelerated.
dynamicContentDimensions	boolean	false	If true, a ResizeObserver will be used to detect changes in the content dimensions. Useful if the content dimensions can't be predicted. Alternatively, the API methods detectContentDimensions() or contentDimensionsChanged() can also be used. ResizeObservers may not work in some older or mobile web browsers. See https://developer.mozilla.org/en-US/docs/Web/API/ResizeObserver for info on browser compatibility.

Events

Name	Type	Description
modelChange	PanZoomModel	Emits changes to the panZoom model.

API

The panzoom library provides an API for interacting with, observing, and controlling it. The following methods and objects are available from the PanZoomAPI:

• changeZoomLevel(newZoomLevel: number, clickPoint: Point) - This method will reset the view to newZoomLevel, with clickPoint as its centre point.

• zoomIn(zoomType: 'lastPoint' | 'viewCenter' = 'lastPoint') - This will zoom the view in to either the last zoomed point (if lastPoint), or to the centre point of the view (viewCenter), by one zoom level. The default zoomType is lastPoint.

• zoomOut(zoomType: 'lastPoint' | 'viewCenter' = 'lastPoint') - This will zoom the view out from either the last zoomed point (if lastPoint), or from the centre point of the view (viewCenter), by one zoom level. The default zoomType is lastPoint.

• zoomToFit(rectangle: Rect, [duration: number]) - Animates the view to focus on a rectangle of the underlying canvas. duration is how long the animation should take (in seconds), and is optional. rectangle is two coordinates on the canvas which the panZoom view is pan/zooming. See the below section on PanZoom Interfaces for its definition.

• resetView() - A shortcut method to reset the pan and zoom back to the initial view.

• getViewPosition(modelPosition: Point) - By passing in x,y coordinates of the original, untransformed content canvas, it will return the current pixel position of this point.

• getModelPosition(viewPosition: Point) - The reverse operation of getViewPosition().

• panToPoint(point: Point, [duration: number]) - Will animate the view so that the centre point of the view is at the point parameter coordinates, relative to the original, unzoomed content width and height.

• panDelta(delta: Point, [duration: number]) - Will pan the view left, right, up, or down, based on a number of pixels relative to the original, unzoomed content.

• panDeltaPercent(deltaPercent: Point, [duration: number]) - Will pan the view up, down, left, or right, based on a percentage of the original, unzoomed content width and height.

• panDeltaAbsolute(delta: Point, [duration: number]) - Will pan the view left, right, up, or down, based on a number of pixels. This method doesn't adjust for scale. I'm not sure why you'd want this, but it's provided just in case.

• centerContent([duration: number]) - Will centre the the content vertically and horizontally at the current scale.

• centerTopLeft([duration: number]) - Will centre the top-left corner of the content at the current scale.

• centerBottomLeft([duration: number]) - Will centre the bottom-left corner of the content at the current scale.

• centerTopRight([duration: number]) - Will centre the top-right corner of the content at the current scale.

• centerBottomRight([duration: number]) - Will centre the bottom-right corner of the content at the current scale.

• centerX([duration: number]) - Will centre the view on its X axis.

• centerY([duration: number]) - Will centre the view on its Y axis.

• detectContentDimensions() - Will trigger a one-time detection of the content dimensions.

• updateContentDimensions([width: number], [height: number]) - Will update the content dimensions with the width and height values passed in. Either parameter is optional.

Interfaces

interface PanZoomModel {
  zoomLevel: number;
  isPanning?: boolean;
  pan: Point; // how far the view has been moved on the x and y axes.  It is not adjusted for scale
}

interface Point {
  x: number;
  y: number;
}

interface Rect {
  x: number; // the x0 (top left) coordinate
  y: number; // the y0 (top left) coordinate
  width: number; // the x1 (bottom right) coordinate
  height: number; // the y1 (bottom right) coordinate
}

Contributing

Pull requests are welcome.

Reference

Martin Vindahl Olsen's original angular-pan-zoom project on GitHub