Add caching and config for it

build.gradle

@@ -18,5 +18,6 @@ dependencies {
     implementation "com.fasterxml.jackson.core:jackson-core:$jacksonVersion"
     implementation "com.fasterxml.jackson.core:jackson-annotations:$jacksonVersion"
     implementation "com.fasterxml.jackson.core:jackson-databind:$jacksonVersion"
+    implementation 'com.github.ben-manes.caffeine:caffeine:2.8.8'
     testImplementation 'junit:junit:4.13.1'
 }

src/main/java/com/annimon/imagetagger/Main.java

@@ -1,7 +1,7 @@
 package com.annimon.imagetagger;
 
 import com.annimon.imagetagger.beans.Config;
-import com.annimon.imagetagger.logic.FilesProvider;
+import com.annimon.imagetagger.logic.CacheableFilesProvider;
 import com.annimon.imagetagger.logic.ImageProcessor;
 import com.annimon.imagetagger.logic.KeyProcessor;
 import com.annimon.imagetagger.views.ImagePanel;
@@ -34,7 +34,7 @@ public class Main extends JFrame {
 
         final var tagButtons = config.getButtons(config.getProfile());
         final var tagPanel = new TagPanel(tagButtons);
-        final var files = new FilesProvider(config.getDir());
+        final var files = new CacheableFilesProvider(config.getDir(), config.getCache());
         final var imageProcessor = new ImageProcessor(files, config.getFilter(), config.getSort());
         final var imagePanel = new ImagePanel(imageProcessor);
         final var keyProcessor = new KeyProcessor(tagButtons);

src/main/java/com/annimon/imagetagger/beans/CacheConfig.java

@@ -0,0 +1,35 @@
+package com.annimon.imagetagger.beans;
+
+import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
+import java.util.Objects;
+
+@JsonIgnoreProperties(ignoreUnknown = true)
+public class CacheConfig {
+
+    public static final CacheConfig DEFAULT = new CacheConfig(20, 1920, 1080);
+
+    private Integer size;
+    private Integer width;
+    private Integer height;
+
+    public CacheConfig() {
+    }
+
+    public CacheConfig(Integer size, Integer width, Integer height) {
+        this.size = size;
+        this.width = width;
+        this.height = height;
+    }
+
+    public int getSize() {
+        return Objects.requireNonNullElse(size, DEFAULT.size);
+    }
+
+    public int getWidth() {
+        return Objects.requireNonNullElse(width, DEFAULT.width);
+    }
+
+    public int getHeight() {
+        return Objects.requireNonNullElse(height, DEFAULT.height);
+    }
+}

src/main/java/com/annimon/imagetagger/beans/Config.java

@@ -11,6 +11,7 @@ import java.util.Objects;
 public class Config {
 
     private String dir;
+    private CacheConfig cache;
     private String filter;
     private String sort;
     private String profile;
@@ -23,6 +24,10 @@ public class Config {
         return dir;
     }
 
+    public CacheConfig getCache() {
+        return Objects.requireNonNullElse(cache, CacheConfig.DEFAULT);
+    }
+
     public String getFilter() {
         return Objects.requireNonNullElse(filter, "");
     }

src/main/java/com/annimon/imagetagger/logic/CacheableFilesProvider.java

@@ -0,0 +1,52 @@
+package com.annimon.imagetagger.logic;
+
+import com.annimon.imagetagger.beans.CacheConfig;
+import com.annimon.imagetagger.views.ResizableImage;
+import com.github.benmanes.caffeine.cache.Caffeine;
+import com.github.benmanes.caffeine.cache.LoadingCache;
+import java.io.File;
+import java.util.concurrent.Executor;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
+
+public class CacheableFilesProvider extends FilesProvider {
+
+    private final Executor exe;
+    private final LoadingCache<File, ResizableImage> cache;
+    private final int maxWidth, maxHeight;
+
+    public CacheableFilesProvider(String dir, CacheConfig cacheConfig) {
+        super(dir);
+        maxWidth = Math.max(cacheConfig.getWidth(), 100);
+        maxHeight = Math.max(cacheConfig.getHeight(), 100);
+        exe = Executors.newSingleThreadExecutor();
+        cache = Caffeine.newBuilder()
+                .executor(exe)
+                .maximumSize(Math.max(cacheConfig.getSize(), 1))
+                .expireAfterWrite(10, TimeUnit.MINUTES)
+                .softValues()
+                .build(this::loadAndResize);
+    }
+
+    @Override
+    public ResizableImage loadImage(File file) {
+        final var image = cache.get(file);
+        if (image != null) {
+            return image;
+        } else {
+            final var result = loadAndResize(file);
+            cache.put(file, result);
+            return result;
+        }
+    }
+
+    @Override
+    public void preloadImage(File file) {
+        exe.execute(() -> cache.get(file));
+    }
+
+    private ResizableImage loadAndResize(File file) {
+        final var image = super.loadImage(file);
+        return new ResizableImage(image.getResized(maxWidth, maxHeight));
+    }
+}

src/main/java/com/annimon/imagetagger/logic/ImageProcessor.java

@@ -103,6 +103,8 @@ public class ImageProcessor {
         if (imagesCount > 0) {
             index = 0;
             loadImage();
+            preloadImage(1);
+            preloadImage(-1);
         }
     }