diff --git a/src/app/commands/cmd_color_quantization.cpp b/src/app/commands/cmd_color_quantization.cpp
index a45d85e7b..4a02ab9ea 100644
--- a/src/app/commands/cmd_color_quantization.cpp
+++ b/src/app/commands/cmd_color_quantization.cpp
@@ -64,7 +64,7 @@ void ColorQuantizationCommand::onExecute(Context* context)
       int n = entries.picks();
 
       Palette palette(frame, n);
-      render::create_palette_from_rgb(sprite, frame, &palette);
+      render::create_palette_from_rgb(sprite, 0, sprite->lastFrame(), &palette);
 
       Palette newPalette(*get_current_palette());
 
diff --git a/src/app/file/file.cpp b/src/app/file/file.cpp
index dcc35845c..380dff397 100644
--- a/src/app/file/file.cpp
+++ b/src/app/file/file.cpp
@@ -706,18 +706,18 @@ void fop_post_load(FileOp* fop)
     return;
   }
 
-  if (fop->document->sprite() != NULL) {
+  Sprite* sprite = fop->document->sprite();
+  if (sprite) {
     // Creates a suitable palette for RGB images
-    if (fop->document->sprite()->pixelFormat() == IMAGE_RGB &&
-        fop->document->sprite()->getPalettes().size() <= 1 &&
-        fop->document->sprite()->palette(frame_t(0))->isBlack()) {
-      base::SharedPtr<Palette> palette
-        (render::create_palette_from_rgb(
-          fop->document->sprite(),
-          frame_t(0), NULL));
+    if (sprite->pixelFormat() == IMAGE_RGB &&
+        sprite->getPalettes().size() <= 1 &&
+        sprite->palette(frame_t(0))->isBlack()) {
+      base::SharedPtr<Palette> palette(
+        render::create_palette_from_rgb(
+          sprite, frame_t(0), sprite->lastFrame(), nullptr));
 
-      fop->document->sprite()->resetPalettes();
-      fop->document->sprite()->setPalette(palette.get(), false);
+      sprite->resetPalettes();
+      sprite->setPalette(palette.get(), false);
     }
   }
 
diff --git a/src/render/quantization.cpp b/src/render/quantization.cpp
index 4f8511581..e6ae3cafe 100644
--- a/src/render/quantization.cpp
+++ b/src/render/quantization.cpp
@@ -43,43 +43,30 @@ static Image* ordered_dithering(
 
 Palette* create_palette_from_rgb(
   const Sprite* sprite,
-  frame_t frameNumber,
+  frame_t fromFrame,
+  frame_t toFrame,
   Palette* palette)
 {
+  PaletteOptimizer optimizer;
+
   if (!palette)
-    palette = new Palette(frame_t(0), Palette::MaxColors);
+    palette = new Palette(fromFrame, Palette::MaxColors);
 
-  bool has_background_layer = (sprite->backgroundLayer() != NULL);
-
-  ImagesCollector images(
-    sprite->folder(),           // All layers
-    frameNumber,                // Ignored, we'll use all frames
-    true,                       // All frames,
-    false);                     // forWrite=false, read only
+  bool has_background_layer = (sprite->backgroundLayer() != nullptr);
 
   // Add a flat image with the current sprite's frame rendered
-  ImageRef flat_image(Image::create(sprite->pixelFormat(),
+  ImageRef flat_image(Image::create(IMAGE_RGB,
       sprite->width(), sprite->height()));
 
-  render::Render().renderSprite(flat_image.get(), sprite, frameNumber);
-
-  // Create an array of images
-  std::vector<Image*> image_array;
-  std::map<ObjectId, Image*> used_images;
-
-  for (auto it=images.begin(); it!=images.end(); ++it) {
-    Image* image = it->image();
-    ObjectId imageId = image->id();
-
-    if (used_images.find(imageId) == used_images.end()) {
-      used_images.insert(std::make_pair(imageId, image));
-      image_array.push_back(image);
-    }
+  // Feed the optimizer with all rendered frames
+  render::Render render;
+  for (frame_t frame=fromFrame; frame<=toFrame; ++frame) {
+    render.renderSprite(flat_image.get(), sprite, frame);
+    optimizer.feedWithImage(flat_image.get());
   }
-  image_array.push_back(flat_image.get());
 
-  // Generate an optimized palette for all images
-  create_palette_from_images(image_array, palette, has_background_layer);
+  // Generate an optimized palette
+  optimizer.calculate(palette, has_background_layer);
 
   return palette;
 }
diff --git a/src/render/quantization.h b/src/render/quantization.h
index 04778b1c5..1a53119f2 100644
--- a/src/render/quantization.h
+++ b/src/render/quantization.h
@@ -1,5 +1,5 @@
 // Aseprite Rener Library
-// Copyright (c) 2001-2014 David Capello
+// Copyright (c) 2001-2015 David Capello
 //
 // This file is released under the terms of the MIT license.
 // Read LICENSE.txt for more information.
@@ -43,7 +43,8 @@ namespace render {
   // Creates a new palette suitable to quantize the given RGB sprite to Indexed color.
   Palette* create_palette_from_rgb(
     const Sprite* sprite,
-    frame_t frameNumber,
+    frame_t fromFrame,
+    frame_t toFrame,
     Palette* newPalette);     // Can be NULL to create a new palette
 
   // Changes the image pixel format. The dithering method is used only