diff --git a/vitrivr-engine-index/src/main/kotlin/org/vitrivr/engine/index/aggregators/CenterContentAggregator.kt b/vitrivr-engine-index/src/main/kotlin/org/vitrivr/engine/index/aggregators/CenterContentAggregator.kt
new file mode 100644
index 00000000..1bc8fcb0
--- /dev/null
+++ b/vitrivr-engine-index/src/main/kotlin/org/vitrivr/engine/index/aggregators/CenterContentAggregator.kt
@@ -0,0 +1,46 @@
+package org.vitrivr.engine.index.aggregators
+
+import org.vitrivr.engine.core.context.IndexContext
+import org.vitrivr.engine.core.model.content.element.AudioContent
+import org.vitrivr.engine.core.model.content.element.ContentElement
+import org.vitrivr.engine.core.model.content.element.ImageContent
+import org.vitrivr.engine.core.model.content.element.TextContent
+import org.vitrivr.engine.core.model.retrievable.Retrievable
+import org.vitrivr.engine.core.operators.Operator
+import org.vitrivr.engine.core.operators.ingest.Aggregator
+import org.vitrivr.engine.core.operators.ingest.AggregatorFactory
+import org.vitrivr.engine.core.operators.ingest.Segmenter
+
+/**
+ * A [Aggregator] that returns the middle [ContentElement] of each type.
+ *
+ * @version 1.0.0
+ */
+class CenterContentAggregator : AggregatorFactory {
+
+    /**
+     * Returns an [CenterContentAggregator.Instance].
+     *
+     * @param input The [Segmenter] to use as input.
+     * @param context The [IndexContext] to use.
+     * @param parameters Optional set of parameters.
+     * @return [AllContentAggregator.Instance]
+     */
+    override fun newOperator(input: Segmenter, context: IndexContext, parameters: Map<String, String>): Aggregator = Instance(input, context)
+
+    /**
+     * The [Instance] returns by the [AggregatorFactory]
+     */
+    private class Instance(override val input: Operator<Retrievable>, context: IndexContext) : AbstractAggregator(input, context) {
+        override fun aggregate(content: List<ContentElement<*>>): List<ContentElement<*>> {
+            val imageContent = content.filterIsInstance<ImageContent>()
+            val audioContent = content.filterIsInstance<AudioContent>()
+            val textContent = content.filterIsInstance<TextContent>()
+            return listOfNotNull(
+                imageContent.let { if (it.isNotEmpty()) it[it.size / 2] else null },
+                audioContent.let { if (it.isNotEmpty()) it[it.size / 2] else null },
+                textContent.let { if (it.isNotEmpty()) it[it.size / 2] else null }
+            )
+        }
+    }
+}
\ No newline at end of file
diff --git a/vitrivr-engine-index/src/main/kotlin/org/vitrivr/engine/index/aggregators/image/RepresentativeImageContentAggregator.kt b/vitrivr-engine-index/src/main/kotlin/org/vitrivr/engine/index/aggregators/image/RepresentativeImageContentAggregator.kt
index e0d42b9c..50c69d66 100644
--- a/vitrivr-engine-index/src/main/kotlin/org/vitrivr/engine/index/aggregators/image/RepresentativeImageContentAggregator.kt
+++ b/vitrivr-engine-index/src/main/kotlin/org/vitrivr/engine/index/aggregators/image/RepresentativeImageContentAggregator.kt
@@ -1,6 +1,8 @@
 package org.vitrivr.engine.index.aggregators.image
 
 import org.vitrivr.engine.core.context.IndexContext
+import org.vitrivr.engine.core.model.color.MutableRGBFloatColorContainer
+import org.vitrivr.engine.core.model.color.RGBByteColorContainer
 import org.vitrivr.engine.core.model.content.element.ContentElement
 import org.vitrivr.engine.core.model.content.element.ImageContent
 import org.vitrivr.engine.core.model.retrievable.Retrievable
@@ -8,6 +10,7 @@ import org.vitrivr.engine.core.operators.Operator
 import org.vitrivr.engine.core.operators.ingest.Aggregator
 import org.vitrivr.engine.core.operators.ingest.AggregatorFactory
 import org.vitrivr.engine.core.operators.ingest.Segmenter
+import org.vitrivr.engine.core.util.extension.getRGBArray
 import org.vitrivr.engine.index.aggregators.AbstractAggregator
 
 /**
@@ -27,18 +30,52 @@ class RepresentativeImageContentAggregator : AggregatorFactory {
      * @param parameters Optional set of parameters.
      * @return [RepresentativeImageContentAggregator.Instance]
      */
-    override fun newOperator(input: Segmenter, context: IndexContext, parameters: Map<String, String>): Aggregator = Instance(input, context)
+    override fun newOperator(input: Segmenter, context: IndexContext, parameters: Map<String, String>): Aggregator =
+        Instance(input, context)
 
     /**
      * The [Instance] returns by the [AggregatorFactory]
      */
-    private class Instance(override val input: Operator<Retrievable>, context: IndexContext) : AbstractAggregator(input, context) {
+    private class Instance(override val input: Operator<Retrievable>, context: IndexContext) :
+        AbstractAggregator(input, context) {
         override fun aggregate(content: List<ContentElement<*>>): List<ContentElement<*>> {
             val images = content.filterIsInstance<ImageContent>()
             if (images.isEmpty()) {
                 return emptyList()
             }
-            TODO()
+
+            if (images.size == 1) {
+                return images
+            }
+
+            /* Compute average image. */
+            val firstImage = images.first()
+            val height = firstImage.height
+            val width = firstImage.width
+            val colors = List(firstImage.width * firstImage.height) { MutableRGBFloatColorContainer() }
+            images.forEach { imageContent ->
+                require(imageContent.height == height && imageContent.width == width) { "Unable to aggregate images! All images must have same dimension." }
+                imageContent.content.getRGBArray().forEachIndexed { index, color ->
+                    colors[index] += RGBByteColorContainer.fromRGB(color)
+                }
+            }
+
+            /* normalize */
+            val div = images.size.toFloat()
+            colors.forEach { it /= div }
+
+            /* find image with smallest pixel-wise distance */
+            val mostRepresentative = images.minBy { imageContent ->
+
+                imageContent.content.getRGBArray().mapIndexed { index, color ->
+                    RGBByteColorContainer.fromRGB(color).toFloatContainer().distanceTo(colors[index])
+                }.sum()
+
+            }
+
+            return listOf(mostRepresentative)
+
+
         }
     }
 }
\ No newline at end of file