diff --git a/melatonin/cached_blur.cpp b/melatonin/cached_blur.cpp
index 0b6e95c..4873871 100644
--- a/melatonin/cached_blur.cpp
+++ b/melatonin/cached_blur.cpp
@@ -1,6 +1,6 @@
 #include "cached_blur.h"
-#include "internal/rendered_single_channel_shadow.h"
 #include "internal/implementations.h"
+#include "internal/rendered_single_channel_shadow.h"
 
 namespace melatonin
 {
@@ -12,24 +12,35 @@ namespace melatonin
 
     void CachedBlur::update (const juce::Image& newSource)
     {
-        if (newSource != src)
-        {
-            jassert (newSource.isValid());
-            src = newSource;
-
-            // the first time the blur is created, a copy is needed
-            // so we are passing correct dimensions, etc to the blur algo
-            dst = src.createCopy();
-            melatonin::blur::argb (src, dst, radius);
-        }
+        jassert (newSource.isValid());
+        src = newSource;
+
+        // the first time the blur is created, a copy is needed
+        // so we are passing correct dimensions, etc to the blur algo
+        dst = src.createCopy();
+        blur::argb (src, dst, radius);
     }
 
-    juce::Image& CachedBlur::render (juce::Image& newSource)
+    juce::Image& CachedBlur::render (const juce::Image& newSource)
     {
-        update (newSource);
+        // TODO: This doesn't check if image contents have changed
+        // Only that a new image is being passed in.
+        // This is problematic for juce::ImageEffectFilter::applyEffect
+        // because the image passed in will always be the same image.
+        // In that case, you can directly call update
+        if (needsRedraw || newSource != src)
+            update (newSource);
+
         return dst;
     }
 
+    void CachedBlur::setRadius (size_t newRadius)
+    {
+        radius = newRadius;
+        needsRedraw = true;
+    }
+
+
     juce::Image& CachedBlur::render()
     {
         // You either need to have called update or rendered with a src!
diff --git a/melatonin/cached_blur.h b/melatonin/cached_blur.h
index c432efc..c82505b 100644
--- a/melatonin/cached_blur.h
+++ b/melatonin/cached_blur.h
@@ -7,19 +7,25 @@ namespace melatonin
     public:
         explicit CachedBlur (size_t r);
 
-        // we are passing the source by value here
+        // we are passing the source by reference here
         // (but it's a value object of sorts since its reference counted)
         void update (const juce::Image& newSource);
 
-        juce::Image& render (juce::Image& newSource);
+        // Render and potentially update the image
+        juce::Image& render (const juce::Image& newSource);
+
+        // Render the image from cache
         juce::Image& render();
 
+        void setRadius (size_t newRadius);
+
     private:
         // juce::Images are value objects, reference counted behind the scenes
         // We want to store a reference to the src so we can compare on render
         // And we actually are the owner of the dst
         size_t radius = 0;
-        juce::Image src;
-        juce::Image dst;
+        juce::Image src {};
+        juce::Image dst {};
+        bool needsRedraw = false;
     };
-}
\ No newline at end of file
+}