[api] Standardizes CV output format

api/src/main/java/ai/djl/modality/Classifications.java

@@ -18,14 +18,8 @@
 import ai.djl.util.JsonSerializable;
 import ai.djl.util.JsonUtils;
 
-import com.google.gson.Gson;
 import com.google.gson.JsonElement;
-import com.google.gson.JsonSerializationContext;
-import com.google.gson.JsonSerializer;
 
-import java.lang.reflect.Type;
-import java.nio.ByteBuffer;
-import java.nio.charset.StandardCharsets;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
@@ -42,11 +36,6 @@ public class Classifications implements JsonSerializable, Ensembleable<Classific
 
     private static final long serialVersionUID = 1L;
 
-    private static final Gson GSON =
-            JsonUtils.builder()
-                    .registerTypeAdapter(Classifications.class, new ClassificationsSerializer())
-                    .create();
-
     @SuppressWarnings("serial")
     protected List<String> classNames;
 
@@ -210,31 +199,25 @@ public <T extends Classification> T get(String className) {
 
     /** {@inheritDoc} */
     @Override
-    public String toJson() {
-        return GSON.toJson(this) + '\n';
-    }
-
-    /** {@inheritDoc} */
-    @Override
-    public String getAsString() {
-        return toJson();
-    }
-
-    /** {@inheritDoc} */
-    @Override
-    public ByteBuffer toByteBuffer() {
-        return ByteBuffer.wrap(toJson().getBytes(StandardCharsets.UTF_8));
+    public JsonElement serialize() {
+        return JsonUtils.GSON.toJsonTree(topK());
     }
 
     /** {@inheritDoc} */
     @Override
     public String toString() {
         StringBuilder sb = new StringBuilder();
-        sb.append('[').append(System.lineSeparator());
-        for (Classification item : topK(topK)) {
-            sb.append('\t').append(item).append(System.lineSeparator());
+        sb.append("[\n");
+        List<Classification> list = topK();
+        int index = 0;
+        for (Classification item : list) {
+            sb.append('\t').append(item);
+            if (++index < list.size()) {
+                sb.append(',');
+            }
+            sb.append('\n');
         }
-        sb.append(']');
+        sb.append("]\n");
         return sb.toString();
     }
 
@@ -306,7 +289,7 @@ public double getProbability() {
         @Override
         public String toString() {
             StringBuilder sb = new StringBuilder(100);
-            sb.append("{\"class\": \"").append(className).append("\", \"probability\": ");
+            sb.append("{\"className\": \"").append(className).append("\", \"probability\": ");
             if (probability < 0.00001) {
                 sb.append(String.format("%.1e", probability));
             } else {
@@ -317,15 +300,4 @@ public String toString() {
             return sb.toString();
         }
     }
-
-    /** A customized Gson serializer to serialize the {@code Classifications} object. */
-    public static final class ClassificationsSerializer implements JsonSerializer<Classifications> {
-
-        /** {@inheritDoc} */
-        @Override
-        public JsonElement serialize(Classifications src, Type type, JsonSerializationContext ctx) {
-            List<?> list = src.topK();
-            return ctx.serialize(list);
-        }
-    }
 }

api/src/main/java/ai/djl/modality/cv/output/CategoryMask.java

@@ -18,15 +18,11 @@
 import ai.djl.util.JsonUtils;
 import ai.djl.util.RandomUtils;
 
-import com.google.gson.Gson;
 import com.google.gson.JsonElement;
-import com.google.gson.JsonSerializationContext;
-import com.google.gson.JsonSerializer;
+import com.google.gson.JsonObject;
 
-import java.lang.reflect.Type;
-import java.nio.ByteBuffer;
-import java.nio.charset.StandardCharsets;
 import java.util.List;
+import java.util.stream.Collectors;
 
 /**
  * A class representing the segmentation result of an image in an {@link
@@ -38,12 +34,7 @@ public class CategoryMask implements JsonSerializable {
 
     private static final int COLOR_BLACK = 0xFF000000;
 
-    private static final Gson GSON =
-            JsonUtils.builder()
-                    .registerTypeAdapter(CategoryMask.class, new SegmentationSerializer())
-                    .create();
-
-    private transient List<String> classes;
+    private List<String> classes;
     private int[][] mask;
 
     /**
@@ -77,14 +68,22 @@ public int[][] getMask() {
 
     /** {@inheritDoc} */
     @Override
-    public ByteBuffer toByteBuffer() {
-        return ByteBuffer.wrap(toJson().getBytes(StandardCharsets.UTF_8));
+    public JsonElement serialize() {
+        JsonObject ret = new JsonObject();
+        ret.add("classes", JsonUtils.GSON.toJsonTree(classes));
+        ret.add("mask", JsonUtils.GSON.toJsonTree(mask));
+        return ret;
     }
 
     /** {@inheritDoc} */
     @Override
-    public String toJson() {
-        return GSON.toJson(this) + '\n';
+    public String toString() {
+        StringBuilder sb = new StringBuilder(4096);
+        String list = classes.stream().map(s -> '"' + s + '"').collect(Collectors.joining(", "));
+        sb.append("{\n\t\"classes\": [").append(list).append("],\n\t\"mask\": ");
+        sb.append(JsonUtils.GSON_COMPACT.toJson(mask));
+        sb.append("\n}");
+        return sb.toString();
     }
 
     /**
@@ -195,14 +194,4 @@ private int[] generateColors(int background, int opacity) {
         }
         return colors;
     }
-
-    /** A customized Gson serializer to serialize the {@code Segmentation} object. */
-    public static final class SegmentationSerializer implements JsonSerializer<CategoryMask> {
-
-        /** {@inheritDoc} */
-        @Override
-        public JsonElement serialize(CategoryMask src, Type type, JsonSerializationContext ctx) {
-            return ctx.serialize(src.getMask());
-        }
-    }
 }

api/src/main/java/ai/djl/modality/cv/output/DetectedObjects.java

@@ -13,9 +13,6 @@
 package ai.djl.modality.cv.output;
 
 import ai.djl.modality.Classifications;
-import ai.djl.util.JsonUtils;
-
-import com.google.gson.Gson;
 
 import java.util.List;
 
@@ -27,11 +24,6 @@ public class DetectedObjects extends Classifications {
 
     private static final long serialVersionUID = 1L;
 
-    private static final Gson GSON =
-            JsonUtils.builder()
-                    .registerTypeAdapter(DetectedObjects.class, new ClassificationsSerializer())
-                    .create();
-
     @SuppressWarnings("serial")
     private List<BoundingBox> boundingBoxes;
 
@@ -69,12 +61,6 @@ public int getNumberOfObjects() {
         return boundingBoxes.size();
     }
 
-    /** {@inheritDoc} */
-    @Override
-    public String toJson() {
-        return GSON.toJson(this) + '\n';
-    }
-
     /** A {@code DetectedObject} represents a single potential detected Object for an image. */
     public static final class DetectedObject extends Classification {
 
@@ -106,15 +92,15 @@ public BoundingBox getBoundingBox() {
         public String toString() {
             double probability = getProbability();
             StringBuilder sb = new StringBuilder(200);
-            sb.append("{\"class\": \"").append(getClassName()).append("\", \"probability\": ");
+            sb.append("{\"className\": \"").append(getClassName()).append("\", \"probability\": ");
             if (probability < 0.00001) {
                 sb.append(String.format("%.1e", probability));
             } else {
                 probability = (int) (probability * 100000) / 100000f;
                 sb.append(String.format("%.5f", probability));
             }
-            if (getBoundingBox() != null) {
-                sb.append(", \"bounds\": ").append(getBoundingBox());
+            if (boundingBox != null) {
+                sb.append(", \"boundingBox\": ").append(boundingBox);
             }
             sb.append('}');
             return sb.toString();

api/src/main/java/ai/djl/modality/cv/output/Joints.java

@@ -12,6 +12,8 @@
  */
 package ai.djl.modality.cv.output;
 
+import ai.djl.util.JsonUtils;
+
 import java.io.Serializable;
 import java.util.List;
 
@@ -48,19 +50,7 @@ public List<Joint> getJoints() {
     /** {@inheritDoc} */
     @Override
     public String toString() {
-        StringBuilder sb = new StringBuilder(4000);
-        sb.append("\n[\n\t");
-        boolean first = true;
-        for (Joint joint : joints) {
-            if (first) {
-                first = false;
-            } else {
-                sb.append(",\n\t");
-            }
-            sb.append(joint);
-        }
-        sb.append("\n]");
-        return sb.toString();
+        return JsonUtils.GSON_PRETTY.toJson(this) + "\n";
     }
 
     /**
@@ -69,7 +59,9 @@ public String toString() {
      * @see Joints
      */
     public static class Joint extends Point {
+
         private static final long serialVersionUID = 1L;
+
         private double confidence;
 
         /**
@@ -92,13 +84,5 @@ public Joint(double x, double y, double confidence) {
         public double getConfidence() {
             return confidence;
         }
-
-        /** {@inheritDoc} */
-        @Override
-        public String toString() {
-            return String.format(
-                    "{\"Joint\": {\"x\"=%.3f, \"y\"=%.3f}, \"confidence\": %.4f}",
-                    getX(), getY(), getConfidence());
-        }
     }
 }

api/src/main/java/ai/djl/modality/cv/output/Landmark.java

@@ -12,6 +12,10 @@
  */
 package ai.djl.modality.cv.output;
 
+import ai.djl.util.JsonUtils;
+
+import com.google.gson.JsonObject;
+
 import java.util.List;
 
 /** {@code Landmark} is the container that stores the key points for landmark on a single face. */
@@ -41,4 +45,12 @@ public Landmark(double x, double y, double width, double height, List<Point> poi
     public Iterable<Point> getPath() {
         return points;
     }
+
+    /** {@inheritDoc} */
+    @Override
+    public JsonObject serialize() {
+        JsonObject ret = super.serialize();
+        ret.add("landmarks", JsonUtils.GSON.toJsonTree(points));
+        return ret;
+    }
 }

api/src/main/java/ai/djl/modality/cv/output/Mask.java

@@ -14,6 +14,10 @@
 
 import ai.djl.ndarray.NDArray;
 import ai.djl.ndarray.types.Shape;
+import ai.djl.util.JsonUtils;
+
+import com.google.gson.JsonObject;
+import com.google.gson.JsonPrimitive;
 
 /**
  * A mask with a probability for each pixel within a bounding rectangle.
@@ -79,6 +83,17 @@ public boolean isFullImageMask() {
         return fullImageMask;
     }
 
+    /** {@inheritDoc} */
+    @Override
+    public JsonObject serialize() {
+        JsonObject ret = super.serialize();
+        if (fullImageMask) {
+            ret.add("fullImageMask", new JsonPrimitive(true));
+        }
+        ret.add("mask", JsonUtils.GSON.toJsonTree(probDist));
+        return ret;
+    }
+
     /**
      * Converts the mask tensor to a mask array.
      *

api/src/main/java/ai/djl/modality/cv/output/Point.java

@@ -12,6 +12,8 @@
  */
 package ai.djl.modality.cv.output;
 
+import ai.djl.util.JsonUtils;
+
 import java.io.Serializable;
 
 /**
@@ -20,6 +22,7 @@
 public class Point implements Serializable {
 
     private static final long serialVersionUID = 1L;
+
     private double x;
     private double y;
 
@@ -52,4 +55,10 @@ public double getX() {
     public double getY() {
         return y;
     }
+
+    /** {@inheritDoc} */
+    @Override
+    public String toString() {
+        return JsonUtils.GSON_COMPACT.toJson(this);
+    }
 }