Support custom color encodings

2 files changed, 56 insertions, 6 deletions

diff --git a/tvg/src/colors.rs b/tvg/src/colors.rs
index 10bc41c..9f4e7e5 100644
--- a/tvg/src/colors.rs
+++ b/tvg/src/colors.rs
@@ -3,6 +3,8 @@ use std::io::{self, Read};
 use byteorder::{BigEndian, LittleEndian, ReadBytesExt};
 use num_enum::TryFromPrimitive;
 
+use crate::TvgError;
+
 /// The color table encodes the palette for this file.
 ///
 /// It’s binary content is defined by the `color_encoding` field in the header.
@@ -14,12 +16,14 @@ pub struct ColorTable<C: Color> {
 }
 
 impl<C: Color> ColorTable<C> {
-	/// Read in one encoding, and convert it to another
+	/// Read in one encoding, and convert it to another. If `encoding` is
+	/// [`ColorEncoding::Custom`], then return
+	/// [`TvgError::UnsupportedColorEncoding`].
 	pub fn read_from_encoding(
 		reader: &mut impl Read,
 		color_count: u32,
 		encoding: ColorEncoding,
-	) -> io::Result<Self> {
+	) -> Result<Self, TvgError> {
 		Ok(match encoding {
 			ColorEncoding::Rgba8888 => (&ColorTable::<Rgba8888>::read(reader, color_count)?).into(),
 			ColorEncoding::Rgb565 => (&ColorTable::<Rgb565>::read(reader, color_count)?).into(),
@@ -28,6 +32,21 @@ impl<C: Color> ColorTable<C> {
 		})
 	}
 
+	/// Read in one encoding, and convert it into another. If `encoding` is
+	/// [`ColorEncoding::Custom`], then use the given encoding.
+	pub fn read_from_encoding_with_custom<Custom: Color>(
+		reader: &mut impl Read,
+		color_count: u32,
+		encoding: ColorEncoding,
+	) -> io::Result<Self> {
+		Ok(match encoding {
+			ColorEncoding::Rgba8888 => (&ColorTable::<Rgba8888>::read(reader, color_count)?).into(),
+			ColorEncoding::Rgb565 => (&ColorTable::<Rgb565>::read(reader, color_count)?).into(),
+			ColorEncoding::RgbaF32 => (&ColorTable::<RgbaF32>::read(reader, color_count)?).into(),
+			ColorEncoding::Custom => (&ColorTable::<Custom>::read(reader, color_count)?).into(),
+		})
+	}
+
 	/// Parse a color table.
 	fn read(reader: &mut impl Read, color_count: u32) -> io::Result<Self> {
 		let mut colors = Vec::with_capacity(color_count as usize);
@@ -117,7 +136,7 @@ pub trait Color: Sized {
 
 /// Each color value is encoded as a sequence of four bytes.
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
-struct Rgba8888 {
+pub struct Rgba8888 {
 	/// Red color channel between 0 and 100% intensity, mapped to byte values 0
 	/// to 255.
 	red: u8,
@@ -172,7 +191,7 @@ impl Color for Rgba8888 {
 
 /// Each color value is encoded as a sequence of 2 bytes.
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
-struct Rgb565 {
+pub struct Rgb565 {
 	/// Red color channel between 0 and 100% intensity, mapped to integer
 	/// values 0 to 31.
 	red: u8,
@@ -224,7 +243,7 @@ impl Color for Rgb565 {
 
 /// Each color value is encoded as a sequence of 16 bytes.
 #[derive(Debug, Clone, Copy, PartialEq)]
-struct RgbaF32 {
+pub struct RgbaF32 {
 	/// Red color channel, using 0.0 for 0% intensity and 1.0 for 100%
 	/// intensity.
 	red: f32,
diff --git a/tvg/src/lib.rs b/tvg/src/lib.rs
index 5cbe33c..011b5c7 100644
--- a/tvg/src/lib.rs
+++ b/tvg/src/lib.rs
@@ -11,7 +11,7 @@ mod commands;
 mod header;
 mod path;
 
-pub use colors::Rgba16;
+pub use colors::{Rgb565, Rgba16, Rgba8888, RgbaF32};
 pub use header::SUPPORTED_VERSION;
 
 pub struct TvgFile<C: Color> {
@@ -21,6 +21,7 @@ pub struct TvgFile<C: Color> {
 }
 
 impl<C: Color + std::fmt::Debug> TvgFile<C> {
+	/// Read a TinyVG file.
 	pub fn read_from(reader: &mut impl Read) -> Result<Self, TvgError> {
 		let header = TvgHeader::read(reader)?;
 		let color_table =
@@ -42,6 +43,34 @@ impl<C: Color + std::fmt::Debug> TvgFile<C> {
 			commands: commands.into_boxed_slice(),
 		})
 	}
+
+	/// Read a TinyVG file. If a Custom color encoding if found, use the specified encoding.
+	pub fn read_with_custom_encoding<Custom: Color>(
+		reader: &mut impl Read,
+	) -> Result<Self, TvgError> {
+		let header = TvgHeader::read(reader)?;
+		let color_table = ColorTable::read_from_encoding_with_custom::<Custom>(
+			reader,
+			header.color_count(),
+			header.color_encoding(),
+		)?;
+
+		let mut commands = Vec::new();
+		loop {
+			let command = Command::read(reader, &header)?;
+			commands.push(command.clone());
+
+			if command.is_end_of_document() {
+				break;
+			}
+		}
+
+		Ok(Self {
+			header,
+			color_table,
+			commands: commands.into_boxed_slice(),
+		})
+	}
 }
 
 #[derive(Debug, Error)]
@@ -52,6 +81,8 @@ pub enum TvgError {
 	UnsupportedVersion(u8),
 	#[error("Found a coordinate range with an index of 3, which is invalid")]
 	InvalidCoordinateRange,
+	#[error("Found a Custom color encoding, which is unsupported")]
+	UnsupportedColorEncoding,
 	#[error("Found a command with an index of {}, which is invalid", .0)]
 	InvalidCommand(u8),
 	#[error("Found a style kind with an index of 3, which is invalid")]