diff --git a/openbr/plugins/io/write.cpp b/openbr/plugins/io/write.cpp
index 67f9d11..7b88966 100644
--- a/openbr/plugins/io/write.cpp
+++ b/openbr/plugins/io/write.cpp
@@ -10,6 +10,11 @@ namespace br
  * \ingroup transforms
  * \brief Write all mats to disk as images.
  * \author Brendan Klare \cite bklare
+ * \br_property QString outputDirectory Top level directory to write images to.
+ * \br_property QString underscore
+ * \br_property QString imgExtension Extension to save images as.
+ * \br_property int padding Zero pad the image filenames.
+ * \br_property QString subDir Optional group images by a metadata key in subdirectories.
  */
 class WriteTransform : public TimeVaryingTransform
 {
@@ -18,12 +23,15 @@ class WriteTransform : public TimeVaryingTransform
     Q_PROPERTY(QString underscore READ get_underscore WRITE set_underscore RESET reset_underscore STORED false)
     Q_PROPERTY(QString imgExtension READ get_imgExtension WRITE set_imgExtension RESET reset_imgExtension STORED false)
     Q_PROPERTY(int padding READ get_padding WRITE set_padding RESET reset_padding STORED false)
+    Q_PROPERTY(QString subDir READ get_subDir WRITE set_subDir RESET reset_subDir STORED false)
     BR_PROPERTY(QString, outputDirectory, "Temp")
     BR_PROPERTY(QString, underscore, "")
     BR_PROPERTY(QString, imgExtension, "jpg")
     BR_PROPERTY(int, padding, 5)
+    BR_PROPERTY(QString, subDir, "")
 
     int cnt;
+    QMap<QString, int> numImages;
 
     void init() {
         cnt = 0;
@@ -34,10 +42,18 @@ class WriteTransform : public TimeVaryingTransform
     void projectUpdate(const Template &src, Template &dst)
     {
         dst = src;
-        QString path = QString("%1/image%2%3.%4").arg(outputDirectory).arg(cnt++, padding, 10, QChar('0')).arg(underscore.isEmpty() ? "" : "_" + underscore).arg(imgExtension);
-        OpenCVUtils::saveImage(dst.m(), path);
+        if (!subDir.isEmpty()) {
+            QString dir = src.file.get<QString>(subDir, "Temp");
+            QString path = QString("%1/%2/").arg(outputDirectory, dir);
+            int value = numImages.value(dir, 0);
+            path += QString("%1_%2.%3").arg(src.file.get<QString>(subDir, "Image")).arg(value, padding, 10, QChar('0')).arg(imgExtension);
+            numImages[dir] = ++value;
+            OpenCVUtils::saveImage(dst.m(), path);
+        } else {
+            QString path = QString("%1/image%2%3.%4").arg(outputDirectory).arg(cnt++, padding, 10, QChar('0')).arg(underscore.isEmpty() ? "" : "_" + underscore).arg(imgExtension);
+            OpenCVUtils::saveImage(dst.m(), path);
+        }
     }
-
 };
 
 BR_REGISTER(Transform, WriteTransform)