Rework ColorSpace to match the latest spec (0 | 1)

src/colorspace.rs

@@ -1,70 +1,53 @@
-use std::fmt::{self, Debug};
+use std::convert::TryFrom;
 
-#[derive(Copy, Clone, PartialEq, Eq, Hash)]
-pub struct ColorSpace {
-    pub r_linear: bool,
-    pub g_linear: bool,
-    pub b_linear: bool,
-    pub a_linear: bool,
+use crate::error::{Error, Result};
+use crate::utils::unlikely;
+
+/// Image color space.
+///
+/// Note: the color space is purely informative. Although it is saved to the
+/// file header, it does not affect encoding/decoding in any way.
+#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
+#[repr(u8)]
+pub enum ColorSpace {
+    /// sRGB with linear alpha
+    Srgb = 0,
+    /// All channels are linear
+    Linear = 1,
 }
 
 impl ColorSpace {
-    pub const SRGB: Self = Self::new(false, false, false, false);
-    pub const LINEAR: Self = Self::new(true, true, true, true);
-    pub const SRGB_LINEAR_ALPHA: Self = Self::new(false, false, false, true);
-
-    pub const fn new(r_linear: bool, g_linear: bool, b_linear: bool, a_linear: bool) -> Self {
-        Self { r_linear, g_linear, b_linear, a_linear }
-    }
-
     pub const fn is_srgb(self) -> bool {
-        !self.r_linear && !self.g_linear && !self.b_linear && !self.a_linear
+        matches!(self, Self::Srgb)
     }
 
     pub const fn is_linear(self) -> bool {
-        self.r_linear && self.g_linear && self.b_linear && self.a_linear
-    }
-
-    pub const fn is_srgb_linear_alpha(self) -> bool {
-        !self.r_linear && !self.g_linear && !self.b_linear && self.a_linear
-    }
-
-    pub const fn to_u8(self) -> u8 {
-        (self.r_linear as u8) << 3
-            | (self.g_linear as u8) << 2
-            | (self.b_linear as u8) << 1
-            | (self.a_linear as u8)
-    }
-
-    pub const fn from_u8(bits: u8) -> Self {
-        Self::new(bits & 0x08 != 0, bits & 0x04 != 0, bits & 0x02 != 0, bits & 0x01 != 0)
+        matches!(self, Self::Linear)
     }
 }
 
 impl Default for ColorSpace {
     fn default() -> Self {
-        Self::SRGB
-    }
-}
-
-impl From<u8> for ColorSpace {
-    fn from(value: u8) -> Self {
-        Self::from_u8(value)
+        Self::Srgb
     }
 }
 
 impl From<ColorSpace> for u8 {
-    fn from(value: ColorSpace) -> Self {
-        value.to_u8()
+    #[inline]
+    fn from(colorspace: ColorSpace) -> Self {
+        colorspace as u8
     }
 }
 
-impl Debug for ColorSpace {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        write!(
-            f,
-            "ColorSpace({}{}{}{})",
-            self.r_linear as u8, self.g_linear as u8, self.b_linear as u8, self.a_linear as u8
-        )
+impl TryFrom<u8> for ColorSpace {
+    type Error = Error;
+
+    #[inline]
+    fn try_from(colorspace: u8) -> Result<Self> {
+        if unlikely(colorspace | 1 != 1) {
+            Err(Error::InvalidColorSpace { colorspace })
+        } else {
+            Ok(if colorspace == 0 { Self::Srgb } else { Self::Linear })
+        }
     }
 }

src/decode.rs

@@ -123,8 +123,7 @@ pub fn qoi_decode_to_vec(
     data: impl AsRef<[u8]>, channels: impl MaybeChannels,
 ) -> Result<(Header, Vec<u8>)> {
     let data = data.as_ref();
-    let header = qoi_decode_header(data)?;
-    header.validate()?;
+    let header = Header::decode(data)?;
     let channels = channels.maybe_channels().unwrap_or(header.channels);
     match (channels, header.channels) {
         (3, 3) => Ok((header, qoi_decode_impl::<3, false>(data, header.n_pixels())?)),
@@ -137,11 +136,5 @@ pub fn qoi_decode_to_vec(
 
 #[inline]
 pub fn qoi_decode_header(data: impl AsRef<[u8]>) -> Result<Header> {
-    let data = data.as_ref();
-    if unlikely(data.len() < QOI_HEADER_SIZE) {
-        return Err(Error::InputBufferTooSmall { size: data.len(), required: QOI_HEADER_SIZE });
-    }
-    let mut bytes = [0_u8; QOI_HEADER_SIZE];
-    bytes.copy_from_slice(&data[..QOI_HEADER_SIZE]);
-    Ok(Header::from_bytes(bytes))
+    Header::decode(data)
 }

src/encode.rs

@@ -1,3 +1,5 @@
+use std::convert::TryInto;
+
 use crate::colorspace::ColorSpace;
 use crate::consts::{
     QOI_HEADER_SIZE, QOI_OP_DIFF, QOI_OP_INDEX, QOI_OP_LUMA, QOI_OP_RGB, QOI_OP_RGBA, QOI_OP_RUN,
@@ -66,7 +68,7 @@ where
 
     let header =
         Header { width, height, channels: CHANNELS as u8, colorspace, ..Header::default() };
-    buf = buf.write(header.to_bytes());
+    buf = buf.write(header.encode());
 
     let mut index = [Pixel::new(); 256];
     let mut px_prev = Pixel::new().with_a(0xff);
@@ -129,13 +131,18 @@ where
 }
 
 #[inline]
-pub fn qoi_encode_to_buf(
-    mut out: impl AsMut<[u8]>, data: impl AsRef<[u8]>, width: u32, height: u32, channels: u8,
-    colorspace: impl Into<ColorSpace>,
-) -> Result<usize> {
+pub fn qoi_encode_to_buf<O, D, C>(
+    mut out: O, data: D, width: u32, height: u32, channels: u8, colorspace: C,
+) -> Result<usize>
+where
+    O: AsMut<[u8]>,
+    D: AsRef<[u8]>,
+    C: TryInto<ColorSpace>,
+    Error: From<C::Error>,
+{
     let out = out.as_mut();
     let data = data.as_ref();
-    let colorspace = colorspace.into();
+    let colorspace = colorspace.try_into()?;
     match channels {
         3 => qoi_encode_impl::<3>(out, data, width, height, colorspace),
         4 => qoi_encode_impl::<4>(out, data, width, height, colorspace),
@@ -144,12 +151,14 @@ pub fn qoi_encode_to_buf(
 }
 
 #[inline]
-pub fn qoi_encode_to_vec(
-    data: impl AsRef<[u8]>, width: u32, height: u32, channels: u8,
-    colorspace: impl Into<ColorSpace>,
-) -> Result<Vec<u8>> {
-    let data = data.as_ref();
-    let colorspace = colorspace.into();
+pub fn qoi_encode_to_vec<D, C>(
+    data: D, width: u32, height: u32, channels: u8, colorspace: C,
+) -> Result<Vec<u8>>
+where
+    D: AsRef<[u8]>,
+    C: TryInto<ColorSpace>,
+    Error: From<C::Error>,
+{
     let size = encode_size_required(width, height, channels);
     let mut out = vec![0; size]; // note: we could save time here but that won't be safe anymore
     let size = qoi_encode_to_buf(&mut out, data, width, height, channels, colorspace)?;

src/error.rs

@@ -15,7 +15,7 @@ pub enum Error {
     OutputBufferTooSmall { size: usize, required: usize },
     InvalidMagic { magic: u32 },
     UnexpectedBufferEnd,
-    // TODO: invalid colorspace
+    InvalidColorSpace { colorspace: u8 },
 }
 
 pub type Result<T> = StdResult<T, Error>;
@@ -48,6 +48,9 @@ impl Display for Error {
             Self::UnexpectedBufferEnd => {
                 write!(f, "unexpected input buffer end while decoding")
             }
+            Self::InvalidColorSpace { colorspace } => {
+                write!(f, "invalid color space: {} (expected 0 or 1)", colorspace)
+            }
         }
     }
 }

src/header.rs

@@ -43,12 +43,12 @@ const fn u32_from_be(v: &[u8]) -> u32 {
 impl Header {
     #[inline]
     pub const fn new(width: u32, height: u32, channels: u8) -> Self {
-        Self { magic: QOI_MAGIC, width, height, channels, colorspace: ColorSpace::from_u8(0) }
+        Self { magic: QOI_MAGIC, width, height, channels, colorspace: ColorSpace::Srgb }
     }
 
     #[inline]
-    pub fn with_colorspace(mut self, colorspace: impl Into<ColorSpace>) -> Self {
-        self.colorspace = colorspace.into();
+    pub fn with_colorspace(mut self, colorspace: ColorSpace) -> Self {
+        self.colorspace = colorspace;
         self
     }
 
@@ -58,7 +58,7 @@ impl Header {
     }
 
     #[inline]
-    pub(crate) fn to_bytes(&self) -> [u8; QOI_HEADER_SIZE] {
+    pub(crate) fn encode(&self) -> [u8; QOI_HEADER_SIZE] {
         let mut out = [0; QOI_HEADER_SIZE];
         out[..4].copy_from_slice(&u32_to_be(self.magic));
         out[4..8].copy_from_slice(&u32_to_be(self.width));
@@ -69,32 +69,30 @@ impl Header {
     }
 
     #[inline]
-    pub(crate) fn from_bytes(v: [u8; QOI_HEADER_SIZE]) -> Self {
-        Self {
-            magic: u32_from_be(&v[..4]),
-            width: u32_from_be(&v[4..8]),
-            height: u32_from_be(&v[8..12]),
-            channels: v[12],
-            colorspace: v[13].into(),
+    pub(crate) fn decode(data: impl AsRef<[u8]>) -> Result<Self> {
+        let data = data.as_ref();
+        if unlikely(data.len() < QOI_HEADER_SIZE) {
+            return Err(Error::InputBufferTooSmall { size: data.len(), required: QOI_HEADER_SIZE });
         }
+        let magic = u32_from_be(&data[..4]);
+        let width = u32_from_be(&data[4..8]);
+        let height = u32_from_be(&data[8..12]);
+        let channels = data[12];
+        let colorspace = ColorSpace::try_from(data[13])?;
+        if unlikely(magic != QOI_MAGIC) {
+            return Err(Error::InvalidMagic { magic });
+        } else if unlikely(height == 0 || width == 0) {
+            return Err(Error::EmptyImage { width, height });
+        } else if unlikely((width as usize) * (height as usize) > QOI_PIXELS_MAX) {
+            return Err(Error::ImageTooLarge { width, height });
+        } else if unlikely(channels != 3 && channels != 4) {
+            return Err(Error::InvalidChannels { channels });
+        }
+        Ok(Self { magic, width, height, channels, colorspace })
     }
 
     #[inline]
     pub const fn n_pixels(&self) -> usize {
         (self.width as usize).saturating_mul(self.height as usize)
     }
-
-    #[inline]
-    pub const fn validate(&self) -> Result<()> {
-        if unlikely(self.magic != QOI_MAGIC) {
-            return Err(Error::InvalidMagic { magic: self.magic });
-        } else if unlikely(self.height == 0 || self.width == 0) {
-            return Err(Error::EmptyImage { width: self.width, height: self.height });
-        } else if unlikely((self.height as usize) * (self.width as usize) > QOI_PIXELS_MAX) {
-            return Err(Error::ImageTooLarge { width: self.width, height: self.height });
-        } else if unlikely(self.channels < 3 || self.channels > 4) {
-            return Err(Error::InvalidChannels { channels: self.channels });
-        }
-        Ok(())
-    }
 }