Subsampling Scale Image View

This library is forked from Fossify SubsamplingScaleImageView project, specifically adapted for use with my version of Fossify Gallery.

• See What's New in Release 1.0.0 for a list of functional and build related changes.
• See Quickstart for instructions on how to add the library to your project

A custom image view for Android, designed for photo galleries and displaying huge images (e.g. maps and building plans) without OutOfMemoryErrors. Includes pinch to zoom, panning, rotation and animation support, and allows easy extension so you can add your own overlays and touch event detection.

The view optionally uses subsampling and tiles to support very large images - a low resolution base layer is loaded and as you zoom in, it is overlaid with smaller high resolution tiles for the visible area. This avoids holding too much data in memory. It's ideal for displaying large images while allowing you to zoom in to the high resolution details. You can disable tiling for smaller images and when displaying a bitmap object. There are some advantages and disadvantages to disabling tiling so to decide which is best, see the wiki.

What's New in Release 1.0.0

This is a list of changes compared to Fossify SubsamplingScaleImageView project.

Features & UI Improvements

Enhanced Scaling & Zoom Logic:

• Full-screen fit: image stretches to match screen width (landscape) or height (portrait), cropping edges as needed. Aspect ratio is maintained.
• Double-Tap Zoom: On each double tap, the zoom level increases in 25% steps until 1:1 scale is reached. Once at 1:1 scale, the next double tap resets to fully zoomed out.

Project Maintenance & Build System

Modernized Build Setup:

• Updated to the latest version of Gradle.
• Migrated build scripts to Kotlin.
• Removed obsolete plugins and settings from gradle.properties to eliminate build warnings.

New Publishing Identity:

• Changed the library's groupId to com.github.gm-h28669 to prevent naming conflicts and support JitPack publishing.
• Formally set library version to 1.0.0

Guides

• Installation and setup
• Image display notes & limitations
• Using preview images
• Handling orientation changes
• Advanced configuration
• Event handling
• Animation
• Extension
• Reference (Javadocs)

Features

Image display

• Display images from assets, resources, the file system or bitmaps
• Automatically rotate images from the file system (e.g. the camera or gallery) according to EXIF
• Manually rotate images in 90° increments
• Display a region of the source image
• Use a preview image while large images load
• Swap images at runtime
• Use a custom bitmap decoder

With tiling enabled:

• Display huge images, larger than can be loaded into memory
• Show high resolution detail on zooming in
• Tested up to 20,000x20,000px, though larger images are slower

Gesture detection

• One finger pan
• Two finger pinch to zoom
• Quick scale (one finger zoom)
• Pan while zooming
• Seamless switch between pan and zoom
• Fling momentum after panning
• Double tap to zoom in and out
• Options to disable pan and/or zoom gestures

Animation

• Public methods for animating the scale and center
• Customizable duration and easing
• Optional uninterruptible animations

Overridable event detection

• Supports OnClickListener and OnLongClickListener
• Supports interception of events using GestureDetector and OnTouchListener
• Extend to add your own gestures

Easy integration

• Use within a ViewPager to create a photo gallery
• Easily restore scale, center and orientation after screen rotation
• Can be extended to add overlay graphics that move and scale with the image
• Handles view resizing and wrap_content layout

Quick start

Step 1. Add the JitPack repository to your build file.

Add it in your settings.gradle.kts at the end of repositories:

dependencyResolutionManagement {
  repositoriesMode.set(RepositoriesMode.FAIL_ON_PROJECT_REPOS)
  repositories {
    mavenCentral()
    maven { url = uri("https://jitpack.io") }
  }
}

Step 2. Add this dependency in your app's build.gradle.kts file.

Release build

dependencies {
  implementation("com.github.gm-h28669.subsampling-scale-image-view:subsampling-scale-image-view:1.0.0")
}

Debug build

dependencies {
  implementation("com.github.gm-h28669.subsampling-scale-image-view:subsampling-scale-image-view-debug:1.0.0")
}

Step 3. Add the view to your layout XML.

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >

    <com.davemorrissey.labs.subscaleview.SubsamplingScaleImageView
        android:id="@+id/imageView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>
</LinearLayout>

Step 3a. Now, in your fragment or activity, set the image resource, asset name or file path.

SubsamplingScaleImageView imageView = (SubsamplingScaleImageView)findViewById(id.imageView);
imageView.setImage(ImageSource.resource(R.drawable.monkey));
// ... or ...
imageView.setImage(ImageSource.asset("map.png"))
// ... or ...
imageView.setImage(ImageSource.uri("/sdcard/DCIM/DSCM00123.JPG"));

Step 3b. Or, if you have a Bitmap object in memory, load it into the view. This is unsuitable for large images because it bypasses subsampling - you may get an OutOfMemoryError.

SubsamplingScaleImageView imageView = (SubsamplingScaleImageView)findViewById(id.imageView);
imageView.setImage(ImageSource.bitmap(bitmap));

Photo credits

• San Martino by Luca Bravo, via unsplash.com
• Swiss Road by Ludovic Fremondiere, via unsplash.com

About

Copyright 2018 David Morrissey, and licensed under the Apache License, Version 2.0. No attribution is necessary, but it's very much appreciated. Star this project if you like it!