diff --git a/src/main/java/jp/riken/neurodata/tools/BioFormatsImageException.java b/src/main/java/jp/riken/neurodata/tools/BioFormatsImageException.java
index 1aee081..db0dda5 100644
--- a/src/main/java/jp/riken/neurodata/tools/BioFormatsImageException.java
+++ b/src/main/java/jp/riken/neurodata/tools/BioFormatsImageException.java
@@ -6,7 +6,7 @@ public class BioFormatsImageException extends Exception {
         super(message);
     }
 
-    public BioFormatsImageException(Throwable cause) {
+    public BioFormatsImageException(Exception cause) {
         super(cause.getMessage());
     }
 }
diff --git a/src/main/java/jp/riken/neurodata/tools/BioFormatsImageInfo.java b/src/main/java/jp/riken/neurodata/tools/BioFormatsImageInfo.java
index aaee5cf..db9cc80 100644
--- a/src/main/java/jp/riken/neurodata/tools/BioFormatsImageInfo.java
+++ b/src/main/java/jp/riken/neurodata/tools/BioFormatsImageInfo.java
@@ -2,7 +2,7 @@ package jp.riken.neurodata.tools;
 
 import java.io.IOException;
 import java.util.ArrayList;
-import java.util.Hashtable;
+import java.util.HashMap;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
@@ -16,7 +16,6 @@ import loci.formats.FormatException;
 import loci.formats.FormatTools;
 import loci.formats.IFormatReader;
 import loci.formats.ImageReader;
-import loci.formats.MetadataTools;
 import loci.formats.Modulo;
 import loci.formats.meta.MetadataRetrieve;
 import loci.formats.meta.MetadataStore;
@@ -25,7 +24,7 @@ import loci.formats.tools.ImageInfo;
 public class BioFormatsImageInfo {
 
     protected static Map<String, Object> readImages(final IFormatReader reader) throws FormatException, IOException {
-        final Map<String, Object> metadata = new LinkedHashMap<String, Object>();
+        final Map<String, Object> metadata = new LinkedHashMap<>();
 
         // read basic metadata
         final int seriesCount = reader.getSeriesCount();
@@ -35,7 +34,7 @@ public class BioFormatsImageInfo {
 
             // read basic metadata for series #j
             reader.setSeries(j);
-            final Map<String, Object> seriesMetadata = new LinkedHashMap<String, Object>();
+            final Map<String, Object> seriesMetadata = new LinkedHashMap<>();
 
             final int imageCount = reader.getImageCount();
             final int resolutionCount = reader.getResolutionCount();
@@ -46,7 +45,7 @@ public class BioFormatsImageInfo {
 
             // resolutions
             if (resolutionCount > 1) {
-                final Map<String, Object> resolutionsMetadata = new LinkedHashMap<String, Object>();
+                final Map<String, Object> resolutionsMetadata = new LinkedHashMap<>();
                 for (int i = 0; i < resolutionCount; i++) {
                     reader.setResolution(i);
                     resolutionsMetadata.put(String.format("resolution[%d]", i),
@@ -62,7 +61,7 @@ public class BioFormatsImageInfo {
 
             // indexed
             {
-                final List<Object> indexed = new ArrayList<Object>();
+                final List<Object> indexed = new ArrayList<>();
                 indexed.add(reader.isIndexed());
                 indexed.add(String.format("%b color", !reader.isFalseColor()));
                 final byte[][] table8 = reader.get8BitLookupTable();
@@ -115,7 +114,7 @@ public class BioFormatsImageInfo {
                 for (int i = 0; i < indices.length; i++) {
                     zct[i] = reader.getZCTCoords(indices[i]);
                     indices2[i] = reader.getIndex(zct[i][0], zct[i][1], zct[i][2]);
-                    final Map<String, Object> planeMetadata = new LinkedHashMap<String, Object>();
+                    final Map<String, Object> planeMetadata = new LinkedHashMap<>();
                     planeMetadata.put("Z", zct[i][0]);
                     planeMetadata.put("C", zct[i][1]);
                     planeMetadata.put("T", zct[i][2]);
@@ -132,22 +131,21 @@ public class BioFormatsImageInfo {
     }
 
     protected static Map<String, Object> readAnnotations(final IFormatReader reader) {
-        final Map<String, Object> metadata = new LinkedHashMap<String, Object>();
+        final Map<String, Object> metadata = new LinkedHashMap<>();
         // global metadata
-        final Hashtable<String, Object> globalMetadata = reader.getGlobalMetadata();
-        for (String key : MetadataTools.keys(globalMetadata)) {
-            metadata.put(key, globalMetadata.get(key));
+        final HashMap<String, Object> globalMetadata = new HashMap<>(reader.getGlobalMetadata());
+        for (Map.Entry<String, Object> entry : globalMetadata.entrySet()) {
+            metadata.put(entry.getKey(), entry.getValue());
         }
         // original metadata
         final int seriesCount = reader.getSeriesCount();
         for (int j = 0; j < seriesCount; j++) {
             reader.setSeries(j);
-            final Hashtable<String, Object> seriesMetadata = reader.getSeriesMetadata();
+            final HashMap<String, Object> seriesMetadata = new HashMap<>(reader.getSeriesMetadata());
             if (!seriesMetadata.isEmpty()) {
-                final Map<String, Object> originalMetadata = new LinkedHashMap<String, Object>();
-                final String[] keys = MetadataTools.keys(seriesMetadata);
-                for (int i = 0; i < keys.length; i++) {
-                    originalMetadata.put(keys[i], seriesMetadata.get(keys[i]));
+                final Map<String, Object> originalMetadata = new LinkedHashMap<>();
+                for (Map.Entry<String, Object> entry : seriesMetadata.entrySet()) {
+                    originalMetadata.put(entry.getKey(), entry.getValue());
                 }
                 metadata.put(String.format("series[%d]", j), originalMetadata);
             }
@@ -161,7 +159,7 @@ public class BioFormatsImageInfo {
         if (size == effSize && mLength == 1) {
             return size;
         }
-        final List<Object> ret = new ArrayList<Object>();
+        final List<Object> ret = new ArrayList<>();
         ret.add(size);
         if (size != effSize) {
             ret.add(String.format("(effectively %d)", effSize));
@@ -174,7 +172,7 @@ public class BioFormatsImageInfo {
     }
 
     protected static Map<String, Object> makeRectangle(final int width, final int height) {
-        final Map<String, Object> ret = new LinkedHashMap<String, Object>();
+        final Map<String, Object> ret = new LinkedHashMap<>();
         ret.put("width", width);
         ret.put("height", height);
 
@@ -185,9 +183,8 @@ public class BioFormatsImageInfo {
         final ObjectMapper mapper = new ObjectMapper();
         String json = null;
         try {
-            // json = mapper.writerWithDefaultPrettyPrinter().writeValueAsString(map);
             json = mapper.writeValueAsString(map);
-        } catch (final Throwable e) {
+        } catch (final Exception e) {
             // return "null" if conversion error occurred
             json = "null";
         }
@@ -197,15 +194,13 @@ public class BioFormatsImageInfo {
 
     public static String readMetadata(final String path, final Map<String, Object> metadata)
             throws BioFormatsImageException {
-        if (FilenameUtils.getExtension(path).toLowerCase().equals("zip")) {
+        if (FilenameUtils.getExtension(path).equalsIgnoreCase("zip")) {
             // ignore if file is zip archive
             throw new BioFormatsImageException("Zip is not supported");
         }
         String format = "";
         final ImageInfo info = new ImageInfo();
-        final IFormatReader reader = new ImageReader();
-        try {
-            // info.parseArgs(new String[] { path, "-nopix", "-noflat", "-omexml" });
+        try (final IFormatReader reader = new ImageReader()) {
             info.parseArgs(new String[] { path, "-nopix", "-noflat" });
             info.setReader(reader);
             info.mapLocation();
@@ -216,28 +211,17 @@ public class BioFormatsImageInfo {
             format = reader.getFormat();
             info.configureReaderPostInit();
             info.checkWarnings();
-            // info.printOMEXML();
-            // info.readCoreMetadata();
             metadata.put("images", readImages(reader));
             info.initPreMinMaxValues();
             reader.setSeries(0);
             reader.setResolution(0);
-            // info.printGlobalMetadata();
-            // info.printOriginalMetadata();
+
             final Map<String, Object> annotations = readAnnotations(reader);
             if (!annotations.isEmpty()) {
                 metadata.put("annotations", annotations);
             }
-        } catch (final Throwable e) {
+        } catch (final Exception e) {
             throw new BioFormatsImageException(e);
-        } finally {
-            if (reader != null) {
-                try {
-                    reader.close();
-                } catch (final IOException e) {
-                    throw new BioFormatsImageException(e);
-                }
-            }
         }
 
         return format;
@@ -251,8 +235,8 @@ public class BioFormatsImageInfo {
         boolean metadataON = true;
         boolean thumbnailON = true;
         String path = "";
-        final Map<String, Object> metadata = new LinkedHashMap<String, Object>();
-        final Map<String, Object> thumbnail = new LinkedHashMap<String, Object>();
+        final Map<String, Object> metadata = new LinkedHashMap<>();
+        final Map<String, Object> thumbnail = new LinkedHashMap<>();
         if (args.length == 1) {
             path = args[0];
         } else if (args.length == 2) {
@@ -276,15 +260,15 @@ public class BioFormatsImageInfo {
                 if (thumbnailON) {
                     BioFormatsImageThumbnail.readThumbnail(path, thumbnail);
                 }
-            } catch (Throwable t) {
+            } catch (final Exception e) {
                 status = false;
-                message = t.getMessage();
+                message = e.getMessage();
                 metadata.clear();
                 thumbnail.clear();
             }
         }
 
-        final Map<String, Object> results = new LinkedHashMap<String, Object>();
+        final Map<String, Object> results = new LinkedHashMap<>();
         results.put("status", status);
         results.put("message", message);
         results.put("format", format);
diff --git a/src/main/java/jp/riken/neurodata/tools/BioFormatsImageThumbnail.java b/src/main/java/jp/riken/neurodata/tools/BioFormatsImageThumbnail.java
index a820c85..46bb3e4 100644
--- a/src/main/java/jp/riken/neurodata/tools/BioFormatsImageThumbnail.java
+++ b/src/main/java/jp/riken/neurodata/tools/BioFormatsImageThumbnail.java
@@ -47,8 +47,8 @@ public class BioFormatsImageThumbnail {
         Image resizeImage = image;
         if (scale != 1.0) {
             // resize image if dimension is different with requested dimension.
-            resizeWidth = (int) (scale * (double) imageWidth);
-            resizeHeight = (int) (scale * (double) imageHeight);
+            resizeWidth = (int) (scale * imageWidth);
+            resizeHeight = (int) (scale * imageHeight);
             resizeImage = image.getScaledInstance(resizeWidth, resizeHeight, Image.SCALE_AREA_AVERAGING);
         }
         final int type = hasAlpha ? BufferedImage.TYPE_INT_ARGB : BufferedImage.TYPE_INT_RGB;
@@ -57,10 +57,6 @@ public class BioFormatsImageThumbnail {
         final Color c = new Color(image.getRGB(0, 0), hasAlpha);
         final int offsetX = (width - resizeWidth) / 2;
         final int offsetY = (height - resizeHeight) / 2;
-        // System.out.println("original:" + imageWidth + "," + imageHeight);
-        // System.out.println("resize:" + resizeWidth + "," + resizeHeight);
-        // System.out.println("target:" + width + "," + height);
-        // System.out.println("offset:" + offsetX + "," + offsetY);
         g.setColor(c);
         g.fillRect(0, 0, width, height);
         g.drawImage(resizeImage, offsetX, offsetY, resizeWidth, resizeHeight, null);
@@ -141,26 +137,18 @@ public class BioFormatsImageThumbnail {
         if (bytes.length == 0) {
             throw new BioFormatsImageException("Failed to convert to " + mimeType + " format");
         }
-        final String dataUri = "data:" + mimeType + ";base64," + Base64.getEncoder().encodeToString(bytes);
 
-        return dataUri;
+        return "data:" + mimeType + ";base64," + Base64.getEncoder().encodeToString(bytes);
     }
 
     public static BufferedImage getImageFromBioFormatsFile(final String path) throws BioFormatsImageException {
         BufferedImage ret = null;
-        final BufferedImageReader reader = new BufferedImageReader(new ImageReader());
-        reader.setFlattenedResolutions(false);
-        reader.setNormalized(true);
-        reader.setOriginalMetadataPopulated(false);
-        reader.setMetadataFiltered(true);
-        try {
+        try (final BufferedImageReader reader = new BufferedImageReader(new ImageReader())) {
+            reader.setFlattenedResolutions(false);
+            reader.setNormalized(true);
+            reader.setOriginalMetadataPopulated(false);
+            reader.setMetadataFiltered(true);
             reader.setId(path);
-        } catch (FormatException | IOException e) {
-            throw new BioFormatsImageException("unsupported file: " + path);
-        } catch (Throwable t) {
-            throw new BioFormatsImageException(t);
-        }
-        try {
             int series = 0;
             final int seriesCount = reader.getSeriesCount();
             for (int i = 0; i < seriesCount; i++) {
@@ -175,10 +163,7 @@ public class BioFormatsImageThumbnail {
             final int t = reader.getSizeT() / 2; // middle of frames
             final int c = 0; // first channel
             final int no = reader.getIndex(z, c, t);
-            // System.out.println("series count: " + seriesCount);
-            // System.out.println("image count: " + reader.getImageCount());
-            // System.out.println("resolution: " + reader.getResolutionCount());
-            // System.out.println("thumbnail series: " + series);
+
             ret = reader.openThumbImage(no);
             final boolean is16bit = reader.getBitsPerPixel() > 8;
             final boolean isGrayScale = ret.getSampleModel().getNumBands() == 1;
@@ -186,19 +171,12 @@ public class BioFormatsImageThumbnail {
                 // perform auto scaling if 16bit or gray scale thumbnail image.
                 ret = AWTImageTools.autoscale(ret);
             }
-        } catch (final Throwable t) {
-            for (Throwable e = t; e != null; e = e.getCause()) {
-                if (e instanceof OutOfMemoryError) {
-                    throw new BioFormatsImageException("out of memory");
-                }
-            }
-            throw new BioFormatsImageException(t);
-        } finally {
-            try {
-                reader.close();
-            } catch (final IOException e) {
-                throw new BioFormatsImageException(e);
-            }
+        } catch (final OutOfMemoryError e) {
+            throw new BioFormatsImageException("out of memory");
+        } catch (final FormatException | IOException e) {
+            throw new BioFormatsImageException("unsupported file: " + path);
+        } catch (final Exception e) {
+            throw new BioFormatsImageException(e);
         }
 
         return ret;
@@ -222,7 +200,7 @@ public class BioFormatsImageThumbnail {
         if (!matcher.find()) {
             throw new BioFormatsImageException("Unsupported data URI format");
         }
-        final byte[] bytes = matcher.group(2) == "utf8" ? matcher.group(3).getBytes()
+        final byte[] bytes = "utf8".equals(matcher.group(2)) ? matcher.group(3).getBytes()
                 : Base64.getDecoder().decode(matcher.group(3));
         try (final FileOutputStream fos = new FileOutputStream(path);) {
             fos.write(bytes);
@@ -243,7 +221,7 @@ public class BioFormatsImageThumbnail {
             thumbnail.put("height", height);
             thumbnail.put("mimeType", mimeType);
             thumbnail.put("url", dataUri);
-        } catch (final Throwable t) {
+        } catch (final Exception e) {
             // ignore
             ret = false;
         }
@@ -261,13 +239,12 @@ public class BioFormatsImageThumbnail {
             DebugTools.enableLogging("OFF");
             BufferedImage image = getImageFromBioFormatsFile(path);
             final String format = image.getColorModel().hasAlpha() ? "png" : "jpeg";
-            // image = resize(image, 160, 160);
             final String dataUri = getDataUri(image, "image/" + format);
             System.out.println(dataUri);
-            // saveFile(dataUri, "/var/tmp/thumbnail." + format);
-        } catch (final Throwable t) {
-            // t.printStackTrace();
-            System.out.println(t.getMessage());
+            saveFile(dataUri, "/var/tmp/thumbnail." + format);
+        } catch (final Exception e) {
+            e.printStackTrace();
+            System.out.println(e.getMessage());
             System.exit(1);
         }
     }