Zoomable

Zoomable is a Compose Multiplatform library that enables the content zoomable by pinch gesture, by double-tap, or by double-tap and drag gesture.

Pinch	Double-tap	Double-tap and drag

Zoomable provides a simple Modifier extension function Modifier.zoomable.

Here is the simplest sample code. You can make image zoomable by just adding one line code.

Image(
    painter = painterResource(id = R.drawable.penguin),
    contentDescription = null,
    modifier = Modifier.zoomable(rememberZoomState()),
)

Zoomable can be used with

• any composable components such as Image, Text, etc.
• asynchronous image composable such as coil's AsyncImage.

Zoomable also can be used in conjunction with HorizontalPager and VerticalPager.

Platforms

Platform	Support
Android	✅ Supported
iOS	✅ Supported
Desktop	⚠️ Experimental Only double-tap zoom is available. Touch gestures and mouse gestures are not available.
Web	🚫 Not supported

API Reference

API Reference🔎

Usage

Download

Zoomable is available on Maven Central.

repositories {
    mavenCentral()
}

dependencies {
    implementation "net.engawapg.lib:zoomable:$version"
}

The latest version:

Basic Usage

You can use Modifier.zoomable to make contents such as an image zoomable. The zoom state is managed in a ZoomState object that can be created via rememberZoomState. If contentSize is set, the range of offset will be optimized for the specified size.

val painter = painterResource(id = R.drawable.penguin)
val zoomState = rememberZoomState(contentSize = painter.intrinsicSize)
Image(
    painter = painter,
    contentDescription = "Zoomable image",
    contentScale = ContentScale.Fit,
    modifier = Modifier
        .fillMaxSize()
        .zoomable(zoomState),
)

Double tap action

By default, every time double tap is detected, zoomable modifier switches the scale between 1.0f and 2.5f.

To change the scale set for double-tap detection, call toggleScale with desired value in onDoubleTap callback.

val targetScale = 5.0f
zoomable(
    zoomState = zoomState,
    onDoubleTap = { position -> zoomState.toggleScale(targetScale, position) }
)

If you want to implement the logic to determine the scale value yourself, you can use the changeScale function. In the example below, the scale is switched in three steps.

zoomable(
    zoomState = zoomState,
    onDoubleTap = { position ->
        val targetScale = when {
            zoomState.scale < 2f -> 2f
            zoomState.scale < 4f -> 4f
            else -> 1f
        }
        zoomState.changeScale(targetScale, position)
    }
)

To disable double tap action, set empty function to onDoubleTap.

zoomable(
    zoomState = zoomState,
    onDoubleTap = {}
)

One finger zoom

By default, one finger zoom action, double tap followed by vertical drag, is enabled. If you want disable it, set false to enableOneFingerZoom.

zoomable(
    zoomState = zoomState,
    enableOneFingerZoom = false,
)

ScrollGesturePropagation

You can choose when to propagate scroll gestures to the parent Pager composable by specifying scrollGesturePropagation.

• ContentEdge: Scroll gesture is propagated when the content is scrolled to the edge and attempts to scroll further.
• NotZoomed: Scroll gesture is propagated when the content is not zoomed.

ContentEdge	NotZoomed

Snap Back Zoom

Modifier.snapBackZoomable allows you to zoom an image with a pinch gesture and automatically return it to its original size when you release your finger. You can easily achieve Instagram-like behavior.

Samples

You can try sample app that contains following samples.

• Standard Image composable
• Asynchronous image loading using Coil library
• Text
• Image on HorizontalPager and VerticalPager

Lisence

Copyright 2022 usuiat

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.