TODOs complete. More TODOs?

TODO.md

@@ -1,9 +1,19 @@
+TODO:
+I still think we can interleave layers to get better progressive loading. But we need FC, FD, FE, and FF commands for "rerun 4/3/2/1 tiles ago."
+Make a super simple one corresponding to quality 3 or so, controlled by constants?
+Generally improve code quality.
+
+
+Done:
+Actually support terminating early for "progressive" loads
 Support an alpha channel.
 Improve the PNG interface.
+Interleave layers instead of having them consecutively. (Bad idea, breaks RLE. Skipping)
 Global parameters to control encoder settings:
 - Quantization level: quant 0
 - Quantization level: quants 1-63
   - Constant term
   - Linear term
 - Number of quants to keep, per tile.
-- Whether to use wide or packed representation for the thumbnail block
+- Whether to use wide or packed representation for the thumbnail block
+Maybe have a second instance of the global parameters block for the alpha channel.

src/compression.rs

@@ -1,48 +1,53 @@
 use std::io::Write;
 
-use crate::{constants::{MAGIC, TILE_SZ, TILE_SZ2}, protocol::{self, ProtocolWriter, ProtocolWriterResult}, quantization, transform};
+use crate::{constants::{MAGIC, TILE_SZ, TILE_SZ2}, image::Image, protocol::{self, ProtocolWriter, ProtocolWriterResult}, quality_settings::{self, QualitySettings}, quantization, transform};
 
 
 struct PixelTile {
-    // i32: representation that supports Walsh-Hadamard
+    quality: QualitySettings,
     pixels: [i16; TILE_SZ2]
 }
 struct CoefTile {
+    quality: QualitySettings,
     coefs: [i16; TILE_SZ2]
 }
 
 #[derive(Clone, Copy)]
 struct QuantTile {
+    quality: QualitySettings,
     quants: [i16; TILE_SZ2]
 }
 
 
 pub fn compress<W: Write>(
-    width: u32,
-    height: u32,
-    // n_components: u16,
-    layers: &[&[u8]],
+    image: Image,
     writer: &mut protocol::ProtocolWriter<W>
 ) -> ProtocolWriterResult<()> {
 
     // validation
-    for l in 0..layers.len() {
-        assert!(layers[l].len() == width as usize * height as usize);
+    for l in 0..image.layers.len() {
+        assert!(image.layers[l].1.len() == image.width as usize * image.height as usize);
     }
 
     // write header
     writer.write_header(MAGIC)?;
-    writer.write_u32_wide(width)?;
-    writer.write_u32_wide(height)?;
-    writer.write_u32_wide(layers.len() as u32)?;
+    writer.write_u32_wide(image.width as u32)?;
+    writer.write_u32_wide(image.height as u32)?;
+    writer.write_u32_wide(image.layers.len() as u32)?;
 
+    // write quality settings for each layout
+    for (quality, _) in image.layers.iter() {
+        writer.write_quality_settings(*quality)?;
+    }
+
+    // build list of tiles
     let mut tiles = vec![];
-    for layer in layers.iter() {
-        for x0 in (0..width).step_by(TILE_SZ) {
-            for y0 in (0..height).step_by(TILE_SZ) {
+    for (quality, layer) in image.layers.iter() {
+        for y0 in (0..image.height).step_by(TILE_SZ) {
+            for x0 in (0..image.width).step_by(TILE_SZ) {
                 let pixel_tile = PixelTile::from_layer(
-                    x0 as usize, y0 as usize, layer, 
-                    width as usize, height as usize
+                    x0 as usize, y0 as usize, *quality, layer, 
+                    image.width as usize, image.height as usize
                 );
                 let coef_tile = CoefTile::from_pixel_tile(&pixel_tile);
                 let quant_tile = QuantTile::from_coef_tile(&coef_tile);
@@ -51,13 +56,16 @@ pub fn compress<W: Write>(
         }
     }
 
+    // write the thumbnail block
     for t in tiles.iter() {
         t.write_zero(writer)?;
     }
-    for ti in 0..tiles.len() {
-        let prev = if ti > 0 { Some(tiles[ti - 1]) } else { None };
-        let t = tiles[ti];
+
+    // write the tiles
+    let mut prev: Option<QuantTile> = None;
+    for t in tiles {
         t.write_rest(prev, writer)?;
+        prev = Some(t);
     }
 
     Ok(())
@@ -67,13 +75,14 @@ impl PixelTile {
     fn from_layer(
         x0: usize,
         y0: usize,
+        quality: QualitySettings,
         layer: &[u8],
         width: usize,
         height: usize
     ) -> PixelTile {
         let mut pixels = [0; TILE_SZ2];
-        for x in 0..TILE_SZ {
-            for y in 0..TILE_SZ {
+        for y in 0..TILE_SZ {
+            for x in 0..TILE_SZ {
                 let src_x = x0 + x;
                 let src_y = y0 + y;
                 pixels[y * TILE_SZ + x] = 
@@ -85,7 +94,7 @@ impl PixelTile {
             }
         }
 
-        return PixelTile { pixels };
+        return PixelTile { quality, pixels };
     }
 }
 
@@ -103,19 +112,24 @@ impl CoefTile {
             transform::encode(&mut coefs, x, 8);
         }
 
-        return CoefTile { coefs }
+        return CoefTile { quality: pt.quality, coefs }
     }
 }
 
 impl QuantTile {
     fn from_coef_tile(pt: &CoefTile) -> QuantTile {
         QuantTile {
-            quants: quantization::to_quantized(pt.coefs)
+            quality: pt.quality,
+            quants: quantization::to_quantized(pt.quality, pt.coefs)
         }
     }
 
     fn write_zero<W: Write>(&self, writer: &mut ProtocolWriter<W>) -> ProtocolWriterResult<()> {
-        writer.write_i16_wide(self.quants[0])?;
+        if self.quality.values[quality_settings::THUMBNAIL_IS_WIDE] != 0 {
+            writer.write_i16_wide(self.quants[0])?;
+        } else {
+            writer.write_i16_packed(self.quants[0])?;
+        }
         Ok(())
     }
 

src/decompression.rs

@@ -1,9 +1,8 @@
-use std::io::Read;
+use std::io::{ErrorKind, Read};
 
-use crate::{constants::{MAGIC, TILE_SZ, TILE_SZ2}, protocol::{ProtocolReader, ProtocolReaderError, ProtocolReaderResult}, quantization, transform};
+use crate::{constants::{MAGIC, TILE_SZ, TILE_SZ2}, image::Image, protocol::{ProtocolReader, ProtocolReaderError, ProtocolReaderResult}, quality_settings::{self, QualitySettings}, quantization, transform};
 
 struct PixelTile {
-    // i32: representation that supports Walsh-Hadamard
     pixels: [i16; TILE_SZ2]
 }
 
@@ -14,46 +13,102 @@ struct CoefTile {
 
 #[derive(Clone, Copy)]
 struct QuantTile {
+    quality: QualitySettings,
     quants: [i16; TILE_SZ2]
 }
 
+pub enum ProgressiveImage {
+    Present { image: Image, complete: bool },
+    NotHereYet
+}
+
 pub fn decompress<R: Read>(
     reader: &mut ProtocolReader<R>
-) -> ProtocolReaderResult<(u32, u32, Vec<Vec<u8>>)> {
+) -> ProtocolReaderResult<ProgressiveImage> {
     // read header
-    let header = reader.read_header()?;
-    if header.bytes != MAGIC.bytes {
-        return Err(ProtocolReaderError::WrongHeader);
-    }
-    if header.version != MAGIC.version {
-        return Err(ProtocolReaderError::WrongVersion);
-    }
+    let read_header_and_stuff: Result<_, ProtocolReaderError> = (|| {
+        let header = reader.read_header()?;
+        if header.bytes != MAGIC.bytes {
+            return Err(ProtocolReaderError::WrongHeader);
+        }
+        if header.version != MAGIC.version {
+            return Err(ProtocolReaderError::WrongVersion);
+        }
 
-    let width = reader.read_u32_wide()?;
-    let height = reader.read_u32_wide()?;
-    let n_layers = reader.read_u32_wide()?;
+        let width = reader.read_u32_wide()?;
+        let height = reader.read_u32_wide()?;
+        let n_layers = reader.read_u32_wide()?;
+
+        // read quality settings for each layout
+        let mut quality_settings = vec![];
+        for _ in 0..n_layers {
+            quality_settings.push(reader.read_quality_settings()?);
+        }
+        Ok((width, height, n_layers, quality_settings))
+    })();
+
+    let Ok((width, height, n_layers, quality_settings)) = read_header_and_stuff else {
+        match read_header_and_stuff {
+            Ok(_) => unreachable!(),
+            Err(ProtocolReaderError::Io(io)) => {
+                if io.kind() == ErrorKind::UnexpectedEof {
+                    return ProtocolReaderResult::Ok(ProgressiveImage::NotHereYet)
+                }
+                return Err(ProtocolReaderError::Io(io))
+            }
+            Err(e) => return Err(e),
+        }
+
+    };
 
     let width_in_tiles = (width as usize + TILE_SZ - 1) / TILE_SZ;
     let height_in_tiles = (height as usize + TILE_SZ - 1) / TILE_SZ;
 
-    let n_tiles = width_in_tiles * height_in_tiles * (n_layers as usize);
-    let mut tiles = vec![QuantTile::new(); n_tiles];
-    for i in 0..n_tiles {
-        tiles[i].load_zero(reader)?;
-    }
-    for i in 0..n_tiles {
-        let prev = if i > 0 { Some(tiles[i - 1]) } else { None };
-        tiles[i].load_rest(
-            prev,
-            reader
-        )?;
-    }
+    let n_tiles_per_layer = width_in_tiles * height_in_tiles;
+
+    let mut tiles = vec![QuantTile::new(); n_tiles_per_layer * n_layers as usize];
+    let read_tiles_and_stuff: Result<(), ProtocolReaderError> = (|tiles: &mut [QuantTile]| {
+        // read thumbnail block
+        for l in 0..n_layers {
+            for i in 0..n_tiles_per_layer {
+                tiles[l as usize * n_tiles_per_layer + i].load_zero(
+                    quality_settings[l as usize], reader
+                )?;
+            }
+        }
+
+        // read remaining tiles
+        let mut prev: Option<QuantTile> = None;
+        for i in 0..n_tiles_per_layer * n_layers as usize {
+            tiles[i].load_rest(
+                prev,
+                reader
+            )?;
+            prev = Some(tiles[i]);
+        }
+        Ok(())
+    })(&mut tiles);
+
+    let complete;
+    match read_tiles_and_stuff {
+        Err(ProtocolReaderError::Io(i)) => {
+            if i.kind() == ErrorKind::UnexpectedEof {
+                complete = false
+            } else {
+                return Err(ProtocolReaderError::Io(i))
+            }
+        }
+        Err(e) => return Err(e),
+        Ok(()) => {
+            complete = true;
+        }
+    };
 
     let mut tile_i = 0;
     let mut layers = vec![vec![0; width as usize * height as usize]; n_layers as usize];
     for layer in 0..n_layers {
-        for x0 in (0..width).step_by(TILE_SZ) {
-            for y0 in (0..height).step_by(TILE_SZ) {
+        for y0 in (0..height).step_by(TILE_SZ) {
+            for x0 in (0..width).step_by(TILE_SZ) {
                 let pixel_tile = tiles[tile_i].to_coef_tile().to_pixel_tile();
                 tile_i += 1;
                 pixel_tile.to_layer(
@@ -63,7 +118,13 @@ pub fn decompress<R: Read>(
             }
         }
     }
-    return Ok((width, height, layers))
+
+    let mut image = Image::new(width as usize, height as usize);
+    for (l, layer) in layers.into_iter().enumerate() {
+        image.add(quality_settings[l], layer).expect("by construction, this layer should be OK");
+    }
+
+    return Ok(ProgressiveImage::Present { image: image, complete });
 }
 
 impl CoefTile {
@@ -86,8 +147,8 @@ impl CoefTile {
 
 impl PixelTile {
     fn to_layer(&self, x0: usize, y0: usize, layer: &mut [u8], width: usize, height: usize) {
-        for x in 0..TILE_SZ {
-            for y in 0..TILE_SZ {
+        for y in 0..TILE_SZ {
+            for x in 0..TILE_SZ {
                 let dst_x = x0 + x;
                 let dst_y = y0 + y;
                 if dst_x < width && dst_y < height { 
@@ -110,17 +171,29 @@ impl PixelTile {
 
 impl QuantTile {
     fn new() -> QuantTile {
-        QuantTile { quants: [0; TILE_SZ2] }
+        QuantTile { 
+            quality: QualitySettings { values: [0, 0, 0, 0, 0, 0, 0, 0] },
+            quants: [0; TILE_SZ2] 
+        }
     }
     
     fn to_coef_tile(&self) -> CoefTile {
         CoefTile {
-            coefs: quantization::from_quantized(self.quants)
+            coefs: quantization::from_quantized(self.quality, self.quants)
         }
     }
 
-    fn load_zero<R: Read>(&mut self, reader: &mut ProtocolReader<R>) -> ProtocolReaderResult<()> {
-        self.quants[0] = reader.read_i16_wide()?;
+    fn load_zero<R: Read>(
+        &mut self, 
+        quality: QualitySettings, 
+        reader: &mut ProtocolReader<R>
+    ) -> ProtocolReaderResult<()> {
+        self.quality = quality;
+        if quality.values[quality_settings::THUMBNAIL_IS_WIDE] != 0 {
+            self.quants[0] = reader.read_i16_wide()?;
+        } else {
+            self.quants[0] = reader.read_i16_packed()?;
+        }
         Ok(())
     }
 

src/image.rs

@@ -0,0 +1,47 @@
+use std::io;
+
+use png::ColorType;
+use thiserror::Error;
+
+use crate::quality_settings::QualitySettings;
+
+#[derive(Error, Debug)]
+pub enum ImageError {
+    #[error("can't make the layer fit {0}x{1}")]
+    WrongSize(usize, usize),
+    #[error("unsupported color type {0:?}")]
+    InvalidInputColorType(ColorType),
+    #[error("can't save an image with {0} layers as png")]
+    WrongNumberOfLayersToSave(usize),
+
+    #[error("general IO error")]
+    IoError(#[from] io::Error),
+    #[error("error in encoding PNG")]
+    PngEncodingError(#[from] png::EncodingError),
+    #[error("error in decoding PNG")]
+    PngDecodingError(#[from] png::DecodingError),
+}
+
+pub struct Image {
+    pub width: usize,
+    pub height: usize,
+    pub layers: Vec<(QualitySettings, Vec<u8>)>
+}
+
+impl Image {
+    pub fn new(width: usize, height: usize) -> Self {
+        Image {
+            width, height, 
+            layers: vec![]
+        }
+    }
+
+    pub fn add(&mut self, quality: QualitySettings, pixels: Vec<u8>) -> Result<(), ImageError> {
+        if pixels.len() != self.width * self.height {
+            return Err(ImageError::WrongSize(self.width, self.height));
+        }
+        self.layers.push((quality, pixels));
+
+        Ok(())
+    }
+}

src/main.rs

@@ -1,100 +1,60 @@
 use std::{fs::File, io::{Cursor, Write}};
 
-use png::{BitDepth, ColorType};
-
-use crate::protocol::{ProtocolReader, ProtocolWriter};
+use crate::{protocol::{ProtocolReader, ProtocolWriter}, quality_settings::QualitySettings};
 
 mod compression;
 mod constants;
 mod decompression;
+mod png_utils;
 mod protocol;
+mod quality_settings;
 mod quantization;
 mod transform;
+mod image;
 
 
 fn main() {
-    for chunk in vec![
-        [0, 0, 0, 0, 0, 0, 0, 0],
-        [0, 1, 2, 3, 4, 5, 6, 7],
-        [255, 255, 255, 255, 255, 255, 255, 80],
-        [255, 255, 255, 255, 255, 255, 255, 0],
-        [255, 253, 254, 252, 251, 252, 255, 254]
-    ] {
-        let orig = chunk;
-        let mut enc = chunk.clone();
-        transform::encode(&mut enc, 0, 1);
-        let mut dec = enc.clone();
-        transform::decode(&mut dec, 0, 1);
-        dbg!(orig, enc, dec);
-    }
-
-    hard_main();
+    // run_for("zonked".to_string(), 9, 2, Some(330000));
+    run_for("zonked".to_string(), 9, 2, Some(37000));
+    run_for("avatar2".to_string(), 9, 2, Some(100000));
 }
-fn hard_main() {
-    let (width, height, r, g, b) = load_image();
+fn run_for(name: String, quality_rgb: u8, quality_alpha: u8, bytes_to_chop: Option<usize>) {
+    let image = png_utils::load_image(
+        format!("inputs/{}.png", name),
+        QualitySettings::new(quality_rgb),
+        QualitySettings::new(quality_alpha),
+    ).unwrap();
     let mut writer = ProtocolWriter::new(vec![]);
+
     compression::compress(
-        width as u32, height as u32, &[&r, &g, &b],
+        image,
         &mut writer
     ).unwrap();
-    let compressed = writer.destroy();
+    let mut compressed = writer.destroy();
 
-    let mut output_file = File::create("outputs/avatar2.rxi").unwrap();
+    if let Some(b2c) = bytes_to_chop {
+        compressed.drain(b2c..);
+    }
+
+    let mut output_file = File::create(format!("outputs/{}.rxi", name)).unwrap();
     output_file.write_all(&compressed).unwrap();
 
     let mut reader = ProtocolReader::new(Cursor::new(compressed));
-    let (width2, height2, decompressed) = 
-        decompression::decompress(&mut reader).unwrap();
+    let decompressed = decompression::decompress(&mut reader).unwrap();
 
-    assert_eq!(3, decompressed.len());
-    save_image(width2 as usize, height2 as usize, decompressed);
-}
-
-
-fn load_image() -> (usize, usize, Vec<u8>, Vec<u8>, Vec<u8>) {
-    let decoder = png::Decoder::new(File::open("inputs/avatar2.png").unwrap());
-    let mut reader = decoder.read_info().unwrap();
-
-    let mut buf = vec![0; reader.output_buffer_size()];
-    let info = reader.next_frame(&mut buf).unwrap();
-    let bytes = &buf[..info.buffer_size()];
-
-    let width = reader.info().width;
-    let height = reader.info().height;
-    assert_eq!(BitDepth::Eight, reader.info().bit_depth);
-    assert_eq!(3, reader.info().bytes_per_pixel());
-    assert_eq!(ColorType::Rgb, reader.info().color_type);
-
-    let r: Vec<u8> = bytes[0..].iter().cloned().step_by(3).collect();
-    let g: Vec<u8> = bytes[1..].iter().cloned().step_by(3).collect();
-    let b: Vec<u8> = bytes[2..].iter().cloned().step_by(3).collect();
-
-    assert_eq!(r.len(), (width * height) as usize);
-    assert_eq!(g.len(), (width * height) as usize);
-    assert_eq!(b.len(), (width * height) as usize);
-
-    (width as usize, height as usize, r, g, b)
-}
-
-fn save_image(width: usize, height: usize, image: Vec<Vec<u8>>) {
-    assert_eq!(image.len(), 3);
-
-    let mut encoder = png::Encoder::new(
-        File::create("outputs/avatar2_out.png").unwrap(),
-        width as u32, height as u32, 
-    );
-    encoder.set_color(ColorType::Rgb);
-
-    let mut idata: Vec<u8> = vec![0; width * height * 3];
-    for i in [0, 1, 2] {
-        for (dst, src) in 
-            idata[i..].iter_mut().step_by(3).zip(image[i].iter()) 
-        {  
-            *dst = *src;
+    let decompressed_image = match decompressed {
+        decompression::ProgressiveImage::Present { image, complete: _ } => {
+            image
         }
-    }
+        decompression::ProgressiveImage::NotHereYet => {
+            // image not here yet
+            println!("not here yet: {}", name);
+            return
+        }
+    };
 
-    let mut writer = encoder.write_header().unwrap();
-    writer.write_image_data(&idata).unwrap();
-
-}
+    png_utils::save_image(
+        format!("outputs/{}_out.png", name), 
+        decompressed_image
+    ).unwrap();
+}

src/png_utils.rs

@@ -0,0 +1,83 @@
+use std::fs::File;
+
+use png::{BitDepth, ColorType};
+
+use crate::{image::{Image, ImageError}, quality_settings::QualitySettings};
+
+pub fn load_image(filename: String, quality_rgb: QualitySettings, quality_alpha: QualitySettings) -> Result<Image, ImageError> {
+    let decoder = png::Decoder::new(File::open(filename).unwrap());
+    let mut reader = decoder.read_info().unwrap();
+
+    let mut buf = vec![0; reader.output_buffer_size()];
+    let info = reader.next_frame(&mut buf).unwrap();
+    let bytes = &buf[..info.buffer_size()];
+
+    assert_eq!(BitDepth::Eight, reader.info().bit_depth);
+    assert_eq!(ColorType::Rgb, reader.info().color_type);
+
+    let width = reader.info().width;
+    let height = reader.info().height;
+
+    match reader.info().color_type {
+        ColorType::Rgb => {
+            assert_eq!(3, reader.info().bytes_per_pixel());
+
+            let r: Vec<u8> = bytes[0..].iter().cloned().step_by(3).collect();
+            let g: Vec<u8> = bytes[1..].iter().cloned().step_by(3).collect();
+            let b: Vec<u8> = bytes[2..].iter().cloned().step_by(3).collect();
+
+            let mut image = Image::new(width as usize, height as usize);
+            image.add(quality_rgb, r)?;
+            image.add(quality_rgb, g)?;
+            image.add(quality_rgb, b)?;
+            return Ok(image);
+        }
+        ColorType::Rgba => {
+            assert_eq!(4, reader.info().bytes_per_pixel());
+
+            let r: Vec<u8> = bytes[0..].iter().cloned().step_by(4).collect();
+            let g: Vec<u8> = bytes[1..].iter().cloned().step_by(4).collect();
+            let b: Vec<u8> = bytes[2..].iter().cloned().step_by(4).collect();
+            let a: Vec<u8> = bytes[3..].iter().cloned().step_by(4).collect();
+
+            let mut image = Image::new(width as usize, height as usize);
+            image.add(quality_rgb, r)?;
+            image.add(quality_rgb, g)?;
+            image.add(quality_rgb, b)?;
+            image.add(quality_alpha, a)?;
+            return Ok(image);
+        }
+        ct => {
+            return Err(ImageError::InvalidInputColorType(ct))
+        }
+    }
+}
+
+pub fn save_image(filename: String, image: Image) -> Result<(), ImageError> {
+    let n_layers = image.layers.len();
+
+    let color_type = match n_layers {
+        3 => ColorType::Rgb,
+        4 => ColorType::Rgba,
+        _ => return Err(ImageError::WrongNumberOfLayersToSave(n_layers)),
+    };
+
+    let mut encoder = png::Encoder::new(
+        File::create(filename)?,
+        image.width as u32, image.height as u32, 
+    );
+    encoder.set_color(color_type);
+
+    let mut idata: Vec<u8> = vec![0; image.width * image.height * n_layers];
+    for i in 0..n_layers {
+        for (dst, src) in 
+            idata[i..].iter_mut().step_by(n_layers).zip(image.layers[i].1.iter()) 
+        {  
+            *dst = *src;
+        }
+    }
+
+    let mut writer = encoder.write_header()?;
+    writer.write_image_data(&idata)?;
+    Ok(())
+}

src/protocol.rs

@@ -1,7 +1,9 @@
-use std::io::{self, ErrorKind, Read, Write};
+use std::io::{self, Read, Write};
 
 use thiserror::Error;
 
+use crate::quality_settings::QualitySettings;
+
 #[derive(Clone, Copy)]
 pub struct Header {
     pub bytes: [u8; 3],
@@ -23,10 +25,6 @@ pub struct ProtocolWriter<W: Write> {
 
 #[derive(Error, Debug)]
 pub enum ProtocolReaderError {
-    // this is explicitly supported: rxi images are progressive
-    #[error("EOF before end of image")]  
-    EarlyEof,
-
     #[error("wrong header")]
     WrongHeader,
 
@@ -57,6 +55,12 @@ impl<W: Write> ProtocolWriter<W> {
         self.writer.write_all(&[value.version])?;
         Ok(())
     }
+    
+    pub fn write_quality_settings(&mut self, quality: QualitySettings) -> ProtocolWriterResult<()> {
+        self.writer.write_all(&quality.values)?;
+        Ok(())
+    }
+
     pub fn write_u32_wide(&mut self, value: u32) -> ProtocolWriterResult<()> {
         self.writer.write_all(&value.to_le_bytes())?;
         Ok(())
@@ -89,10 +93,10 @@ impl<R: Read> ProtocolReader<R> {
 
     pub fn read_header(&mut self) -> ProtocolReaderResult<Header> {
         let mut bytes_buf = [0; 3];
-        self.read_exact(&mut bytes_buf)?;
+        self.reader.read_exact(&mut bytes_buf)?;
 
         let mut version_buf = [0; 1];
-        self.read_exact(&mut version_buf)?;
+        self.reader.read_exact(&mut version_buf)?;
 
         Ok(Header {
             bytes: bytes_buf,
@@ -100,50 +104,43 @@ impl<R: Read> ProtocolReader<R> {
         })
     }
 
+    pub fn read_quality_settings(&mut self) -> ProtocolReaderResult<QualitySettings> {
+        let mut qsettings_buf = [0; 8];
+        self.reader.read_exact(&mut qsettings_buf)?;
+
+        Ok(QualitySettings { values: qsettings_buf })
+    }
+
     pub fn read_u32_wide(&mut self) -> ProtocolReaderResult<u32> {
         let mut u32_buf = [0; 4];
-        self.read_exact(&mut u32_buf)?;
+        self.reader.read_exact(&mut u32_buf)?;
 
         Ok(u32::from_le_bytes(u32_buf))
     }
 
     pub fn read_i16_wide(&mut self) -> ProtocolReaderResult<i16> {
         let mut i16_buf = [0; 2];
-        self.read_exact(&mut i16_buf)?;
+        self.reader.read_exact(&mut i16_buf)?;
 
         Ok(i16::from_le_bytes(i16_buf))
     }
 
     pub fn read_u8_wide(&mut self) -> ProtocolReaderResult<u8> {
         let mut u8_buf = [0; 1];
-        self.read_exact(&mut u8_buf)?;
+        self.reader.read_exact(&mut u8_buf)?;
 
         Ok(u8::from_le_bytes(u8_buf))
     }
 
     pub fn read_i16_packed(&mut self) -> ProtocolReaderResult<i16> {
         let mut i8_buf = [0; 1];
-        self.read_exact(&mut i8_buf)?;
+        self.reader.read_exact(&mut i8_buf)?;
         let i8_value = i8::from_le_bytes(i8_buf);
         if i8_value != i8::MAX { return Ok(i8_value as i16) }
 
         let mut i16_buf = [0; 2];
-        self.read_exact(&mut i16_buf)?;
+        self.reader.read_exact(&mut i16_buf)?;
         let i16_value = i16::from_le_bytes(i16_buf);
         Ok(i16_value as i16) 
     }
-
-    // wrap UnexpectedEof, since that's an error for other Io clients,
-    // but it's specifically not an error for us
-    fn read_exact(&mut self, buf: &mut [u8]) -> ProtocolReaderResult<()> {
-        match self.reader.read_exact(buf) {
-            Ok(_) => Ok(()),
-            Err(e) => {
-                if e.kind() == ErrorKind::UnexpectedEof {
-                    return Err(ProtocolReaderError::EarlyEof)
-                }
-                return Err(ProtocolReaderError::Io(e));
-            }
-        }
-    }
 }

src/quality_settings.rs

@@ -0,0 +1,40 @@
+#[derive(Clone, Copy)]
+pub struct QualitySettings {
+    pub values: [u8; 8],
+}
+
+pub const QUANTIZATION_QUANT0_DIVISOR: usize = 0;
+pub const QUANTIZATION_CONSTANT: usize = 1;
+pub const QUANTIZATION_LINEAR: usize = 2;
+pub const QUANTIZATION_N_QUANTS_TO_KEEP: usize = 3;
+pub const THUMBNAIL_IS_WIDE: usize = 4;
+// 5, 6, 7: reserved
+
+
+impl QualitySettings {
+    pub fn new(level: u8) -> Self {
+        // Concept: 
+        // Levels 0, 1, and 2 are incredibly deep fried
+        // Levels 3, 4, 5, 6 are usable with artifacting 
+        // Levels 7, 8, 9 are above what you would seriously use
+        if level == 0 {
+            return QualitySettings { values: [255, 255, 32, 1, 0, 0, 0, 0] };
+        } else if level == 1 {
+            return QualitySettings { values: [192, 192, 24, 2, 0, 0, 0, 0] };
+        } else if level == 2 {
+            return QualitySettings { values: [128, 128, 16, 3, 0, 0, 0, 0] };
+        } else if level == 3 {
+            return QualitySettings { values: [96, 96, 12, 4, 0, 0, 0, 0] };
+
+            // TODO: Levels 4, 5, 6
+
+
+        } else if level == 7 {
+            return QualitySettings { values: [1, 24, 8, 24, 1, 0, 0, 0] };
+        } else if level == 8 {
+            return QualitySettings { values: [1, 12, 4, 48, 1, 0, 0, 0] };
+        } else { // level >= 9
+            return QualitySettings { values: [1, 1, 1, 96, 1, 0, 0, 0] };
+        }
+    }
+}

src/quantization.rs

@@ -1,4 +1,4 @@
-use crate::constants::TILE_SZ2;
+use crate::{constants::TILE_SZ2, quality_settings::{self, QualitySettings}};
 
 const ZIGZAG: [u8; TILE_SZ2] = [
     0 , 1 , 5 , 6 , 14, 15, 27, 28,
@@ -12,12 +12,13 @@ const ZIGZAG: [u8; TILE_SZ2] = [
 ];
 
 pub fn to_quantized(
+    quality_settings: QualitySettings,
     coefs: [i16; TILE_SZ2]
 ) -> [i16; TILE_SZ2] {
     let mut quant: [i16; TILE_SZ2] = [0; TILE_SZ2];
 
     for cf_ix in 0..TILE_SZ2 {
-        let div = divisor(cf_ix);
+        let div = divisor(quality_settings, cf_ix);
         let qval = (coefs[cf_ix] + div / 2) / div;
         quant[ZIGZAG[cf_ix] as usize] = qval
     }
@@ -27,7 +28,7 @@ pub fn to_quantized(
         indices[i] = i;
     }
     indices.sort_by_key(|i| -quant[*i].abs());
-    for i in 4..indices.len() {
+    for i in (quality_settings.values[quality_settings::QUANTIZATION_N_QUANTS_TO_KEEP] as usize)..indices.len() {
         quant[indices[i]] = 0;
     }
 
@@ -35,21 +36,30 @@ pub fn to_quantized(
 }
 
 pub fn from_quantized(
+    quality_settings: QualitySettings,
     quant: [i16; TILE_SZ2]
 ) -> [i16; TILE_SZ2] {
     let mut coefs: [i16; TILE_SZ2] = [0; TILE_SZ2];
     for cf_ix in 0..TILE_SZ2 {
-        let div = divisor(cf_ix);
+        let div = divisor(quality_settings, cf_ix);
         coefs[cf_ix] = quant[ZIGZAG[cf_ix] as usize].wrapping_mul(div);
     }
     coefs
 }
 
-pub fn divisor(cf_ix: usize) -> i16 {
-    if cf_ix == 0 { return 1; }
+pub fn divisor(
+    quality_settings: QualitySettings,
+    cf_ix: usize
+) -> i16 {
+    if cf_ix == 0 { return quality_settings.values[quality_settings::QUANTIZATION_QUANT0_DIVISOR] as i16; }
     let x = cf_ix % 8;
     let y = cf_ix / 8;
-    let div = 32 + (x as i16 + y as i16) * 12;
+    let div = 
+        (quality_settings.values[quality_settings::QUANTIZATION_CONSTANT] as i16).wrapping_add(
+            (x as i16 + y as i16).wrapping_mul(
+                quality_settings.values[quality_settings::QUANTIZATION_LINEAR] as i16
+            )
+        );
     if div==32 && cf_ix != 0 {
         dbg!(cf_ix, x, y, div);
     }