diff --git a/index.pug b/index.pug
index 89c5249..d161e67 100644
--- a/index.pug
+++ b/index.pug
@@ -63,7 +63,7 @@ html(lang="en-gb")
                                     select#palette
 
                                 label
-                                    input#dither(type="checkbox")
+                                    input#dither(type="checkbox" checked=true)
                                     | dither
                                 br
 
diff --git a/src/lib.rs b/src/lib.rs
index a43cbb7..3456230 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -4,6 +4,8 @@ use bitsy_parser::game::Game;
 use bitsy_parser::image::Image;
 use bitsy_parser::tile::Tile;
 use image::{GenericImageView, Pixel, DynamicImage};
+use image::imageops::ColorMap;
+use image::imageops::FilterType::CatmullRom;
 use lazy_static::lazy_static;
 use std::sync::Mutex;
 use wasm_bindgen::prelude::*;
@@ -83,6 +85,7 @@ pub fn load_image(image_base64: String) -> String {
         Ok(image) => {
             match image::load_from_memory(image.as_ref()) {
                 Ok(image) => {
+                    // todo get rid of magic numbers! what about Bitsy HD?
                     let image = image.resize(128, 128, CatmullRom);
                     state.image = Some(image);
                     "OK"
@@ -162,19 +165,40 @@ fn image_to_base64(image: &DynamicImage) -> String {
 }
 
 fn render_preview(state: &State) -> DynamicImage {
-    let mut buffer =  state.image.as_ref().unwrap().clone().into_rgba();
+    let mut buffer = state.image.as_ref().unwrap().clone().into_rgba();
 
     // todo get actual chosen palette
-    let palette_id = state.palette.as_ref().unwrap();
-    let palette = &state.game.as_ref().unwrap().get_palette(palette_id).unwrap();
+    let palette_id   = state.palette.as_ref().unwrap();
+    let palette     = *&state.game.as_ref().unwrap().get_palette(palette_id).unwrap();
     let colour_map = crate::ColourMap::from(palette);
 
-    image::imageops::brighten(&mut buffer, state.brightness);
+    let mut buffer = image::imageops::brighten(&mut buffer, state.brightness);
 
     if state.dither {
         image::imageops::dither(&mut buffer, &colour_map);
     } else {
-        image::imageops::colorops::index_colors(&mut buffer, &colour_map);
+        // just do colour indexing
+        let indices = image::imageops::colorops::index_colors(&mut buffer, &colour_map);
+
+        // todo get rid of magic numbers! what about Bitsy HD?
+        buffer = image::ImageBuffer::from_fn(128, 128, |x, y| -> image::Rgba<u8> {
+            let p = indices.get_pixel(x, y);
+            colour_map
+                .lookup(p.0[0] as usize)
+                .expect("indexed color out-of-range")
+                .into()
+        });
+        let mut indexed = buffer.clone();
+        for (i, pixel) in buffer.pixels().enumerate() {
+            // todo get rid of magic numbers! what about Bitsy HD?
+            let mut pixel = image::Rgba::from(pixel.0);
+            colour_map.map_color(&mut pixel);
+            indexed.put_pixel(
+                (i % 128) as u32,
+                (i / 128) as u32,
+                pixel
+            );
+        }
     }
 
     image::DynamicImage::ImageRgba8(buffer)