9 files changed, 569 insertions, 0 deletions
diff --git a/gifed/src/block/colortable.rs b/gifed/src/block/colortable.rs
new file mode 100644
index 0000000..01fe00b
--- /dev/null
+++ b/gifed/src/block/colortable.rs
@@ -0,0 +1,117 @@
+pub use crate::Color;
+use crate::EncodingError;
+use std::{
+	convert::{TryFrom, TryInto},
+	ops::Deref,
+};
+
+#[derive(Clone, Debug)]
+pub struct ColorTable {
+	table: Vec<Color>,
+}
+
+impl ColorTable {
+	pub fn new() -> Self {
+		Self { table: vec![] }
+	}
+
+	/// Returns the number of colors in the color table as used by the packed
+	/// fields in the Logical Screen Descriptor and Image Descriptor. You can
+	/// get the actual size with the [`len`](struct.ColorTable.html#method.len) method.
+	pub fn packed_len(&self) -> u8 {
+		((self.table.len() as f32).log2().ceil() - 1f32) as u8
+	}
+
+	/// Returns the number of items in the table
+	pub fn len(&self) -> usize {
+		self.table.len()
+	}
+
+	/// Pushes a color on to the end of the table
+	pub fn push(&mut self, color: Color) {
+		self.table.push(color);
+	}
+
+	pub fn get(&self, index: u8) -> Option<Color> {
+		self.table.get(index as usize).map(|v| v.clone())
+	}
+
+	pub fn from_color(&self, color: Color) -> Option<u8> {
+		for (i, &c) in self.table.iter().enumerate() {
+			if c == color {
+				return Some(i as u8);
+			}
+		}
+		None
+	}
+}
+
+impl Deref for ColorTable {
+	type Target = [Color];
+
+	fn deref(&self) -> &Self::Target {
+		&self.table
+	}
+}
+
+impl From<&ColorTable> for Box<[u8]> {
+	fn from(table: &ColorTable) -> Self {
+		let mut vec = vec![];
+
+		for color in table.iter() {
+			vec.extend_from_slice(&[color.r, color.g, color.b]);
+		}
+
+		let packed_len = 2usize.pow(table.packed_len() as u32 + 1);
+		let padding = (packed_len as usize - table.len()) * 3;
+		if padding > 0 {
+			vec.extend_from_slice(&vec![0; padding]);
+		}
+
+		vec.into_boxed_slice()
+	}
+}
+
+//TODO: TryFrom Vec<u8> (must be multiple of 3 len) and From Vec<Color>
+impl TryFrom<&[u8]> for ColorTable {
+	type Error = ();
+
+	fn try_from(value: &[u8]) -> Result<Self, Self::Error> {
+		if value.len() % 3 != 0 {
+			return Err(());
+		} else {
+			Ok(Self {
+				table: value
+					.chunks(3)
+					.map(|slice| Color::from(TryInto::<[u8; 3]>::try_into(slice).unwrap()))
+					.collect::<Vec<Color>>(),
+			})
+		}
+	}
+}
+
+impl TryFrom<Vec<Color>> for ColorTable {
+	type Error = EncodingError;
+
+	fn try_from(value: Vec<Color>) -> Result<Self, Self::Error> {
+		if value.len() > 256 {
+			Err(EncodingError::TooManyColors)
+		} else {
+			Ok(Self { table: value })
+		}
+	}
+}
+
+impl TryFrom<Vec<(u8, u8, u8)>> for ColorTable {
+	type Error = EncodingError;
+
+	fn try_from(value: Vec<(u8, u8, u8)>) -> Result<Self, Self::Error> {
+		if value.len() > 256 {
+			Err(EncodingError::TooManyColors)
+		} else {
+			Ok(Self {
+				table: value.into_iter().map(|c| c.into()).collect(),
+			})
+		}
+	}
+}
diff --git a/gifed/src/block/extension/application.rs b/gifed/src/block/extension/application.rs
new file mode 100644
index 0000000..9ec1814
--- /dev/null
+++ b/gifed/src/block/extension/application.rs
@@ -0,0 +1,15 @@
+pub struct Application {
+	pub(crate) identifier: String, // max len 8
+	pub(crate) authentication_code: [u8; 3],
+	pub(crate) data: Vec<u8>,
+}
+
+impl Application {
+	pub fn identifier(&self) -> &str {
+		&self.identifier
+	}
+
+	pub fn authentication_code(&self) -> &[u8] {
+		&self.authentication_code
+	}
+}
diff --git a/gifed/src/block/extension/graphiccontrol.rs b/gifed/src/block/extension/graphiccontrol.rs
new file mode 100644
index 0000000..b595554
--- /dev/null
+++ b/gifed/src/block/extension/graphiccontrol.rs
@@ -0,0 +1,116 @@
+use std::{convert::TryInto, fmt};
+
+#[derive(Clone, Debug)]
+pub struct GraphicControl {
+	pub(crate) packed: u8,
+	pub(crate) delay_time: u16,
+	pub(crate) transparency_index: u8,
+}
+
+impl GraphicControl {
+	pub fn new(
+		disposal_method: DisposalMethod,
+		user_input_flag: bool,
+		transparency_flag: bool,
+		delay_time: u16,
+		transparency_index: u8,
+	) -> Self {
+		let mut ret = Self {
+			packed: 0,
+			delay_time,
+			transparency_index,
+		};
+
+		ret.set_disposal_method(disposal_method);
+		ret.user_input(user_input_flag);
+		ret.transparency(transparency_flag);
+
+		ret
+	}
+
+	pub fn disposal_method(&self) -> Option<DisposalMethod> {
+		match self.packed & 0b000_111_00 {
+			0b000_000_00 => Some(DisposalMethod::NoAction),
+			0b000_100_00 => Some(DisposalMethod::DoNotDispose),
+			0b000_010_00 => Some(DisposalMethod::RestoreBackground),
+			0b000_110_00 => Some(DisposalMethod::RestorePrevious),
+			_ => None,
+		}
+	}
+
+	pub fn set_disposal_method(&mut self, method: DisposalMethod) {
+		match method {
+			DisposalMethod::NoAction => self.packed &= 0b111_000_1_1,
+			DisposalMethod::DoNotDispose => self.packed |= 0b000_100_0_0,
+			DisposalMethod::RestoreBackground => self.packed |= 0b000_010_0_0,
+			DisposalMethod::RestorePrevious => self.packed |= 0b000_110_0_0,
+		};
+	}
+
+	pub fn transparency_index(&self) -> u8 {
+		self.transparency_index
+	}
+
+	pub fn user_input(&mut self, flag: bool) {
+		if flag {
+			self.packed |= 0b000_000_1_0;
+		} else {
+			self.packed &= 0b111_111_0_1;
+		}
+	}
+
+	pub fn transparency(&mut self, flag: bool) {
+		if flag {
+			self.packed |= 0b000_000_0_1;
+		} else {
+			self.packed &= 0b111_111_1_0;
+		}
+	}
+
+	pub fn delay_time(&self) -> u16 {
+		self.delay_time
+	}
+
+	pub fn delay_time_mut(&mut self) -> &mut u16 {
+		&mut self.delay_time
+	}
+
+	pub fn is_transparent(&self) -> bool {
+		self.packed & 0b000_000_0_1 > 0
+	}
+}
+
+impl From<[u8; 4]> for GraphicControl {
+	fn from(arr: [u8; 4]) -> Self {
+		let packed = arr[0];
+		let delay_time = u16::from_le_bytes(arr[1..3].try_into().unwrap());
+		let transparency_index = arr[3];
+
+		Self {
+			packed,
+			delay_time,
+			transparency_index,
+		}
+	}
+}
+
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub enum DisposalMethod {
+	NoAction,
+	DoNotDispose,
+	RestoreBackground,
+	RestorePrevious,
+}
+
+impl fmt::Display for DisposalMethod {
+	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+		let st = match self {
+			DisposalMethod::NoAction => "Dispose as Normal",
+			DisposalMethod::DoNotDispose => "No Dispose",
+			DisposalMethod::RestoreBackground => "Restore to background",
+			DisposalMethod::RestorePrevious => "Restore previous image",
+		};
+
+		write!(f, "{}", st)
+	}
+}
diff --git a/gifed/src/block/extension/mod.rs b/gifed/src/block/extension/mod.rs
new file mode 100644
index 0000000..fb5eb20
--- /dev/null
+++ b/gifed/src/block/extension/mod.rs
@@ -0,0 +1,49 @@
+mod application;
+mod graphiccontrol;
+
+pub use graphiccontrol::{DisposalMethod, GraphicControl};
+
+pub use self::application::Application;
+
+pub enum Extension {
+	GraphicControl(GraphicControl),
+	Looping(u16),
+	Comment(Vec<u8>), // Plain Text
+	Application(Application),
+}
+
+impl From<&Extension> for Box<[u8]> {
+	fn from(ext: &Extension) -> Self {
+		let mut vec = vec![];
+		vec.push(0x21); // Push the extension introducer
+
+		match ext {
+			Extension::GraphicControl(gc) => {
+				vec.push(0xF9); // Graphic control label
+				vec.push(0x04); // Block size for this extension is always 4
+				vec.push(gc.packed);
+				vec.extend_from_slice(&gc.delay_time.to_le_bytes());
+				vec.push(gc.transparency_index);
+			}
+			Extension::Looping(count) => {
+				vec.push(0xFF); // Application extension label
+				vec.push(0x0B); // 11 bytes in this block
+				vec.extend_from_slice(b"NETSCAPE2.0"); // App. ident. and "auth code"
+				vec.push(0x03); // Sub-block length
+				vec.push(0x01); // Identifies netscape looping extension
+				vec.extend_from_slice(&count.to_le_bytes());
+			}
+			Extension::Comment(_) => todo!(),
+			Extension::Application(_) => todo!(),
+		}
+
+		vec.push(0x00); // Zero-length data block indicates end of extension
+		vec.into_boxed_slice()
+	}
+}
+
+impl From<GraphicControl> for Extension {
+	fn from(gce: GraphicControl) -> Self {
+		Extension::GraphicControl(gce)
+	}
+}
diff --git a/gifed/src/block/imagedescriptor.rs b/gifed/src/block/imagedescriptor.rs
new file mode 100644
index 0000000..25567b2
--- /dev/null
+++ b/gifed/src/block/imagedescriptor.rs
@@ -0,0 +1,73 @@
+use std::convert::TryInto;
+
+pub struct ImageDescriptor {
+	// Image Seperator 0x2C is the first byte //
+	pub left: u16,
+	pub top: u16,
+	pub width: u16,
+	pub height: u16,
+	pub packed: u8,
+}
+
+impl ImageDescriptor {
+	pub fn set_color_table_present(&mut self, is_present: bool) {
+		if is_present {
+			self.packed |= 0b1000_0000;
+		} else {
+			self.packed &= 0b0111_1111;
+		}
+	}
+
+	pub fn set_color_table_size(&mut self, size: u8) {
+		// GCT size is calulated by raising two to this number plus one,
+		// so we have to work backwards.
+		let size = (size as f32).log2().ceil() - 1f32;
+		self.packed |= size as u8;
+	}
+
+	//TODO: Setter for sort flag in packed field
+	//TODO: Setter for interlace flag in packed field
+
+	pub fn color_table_present(&self) -> bool {
+		self.packed & 0b1000_0000 != 0
+	}
+
+	pub fn color_table_size(&self) -> usize {
+		crate::packed_to_color_table_length(self.packed & 0b0000_0111)
+	}
+}
+
+impl From<&ImageDescriptor> for Box<[u8]> {
+	fn from(desc: &ImageDescriptor) -> Self {
+		let mut vec = vec![];
+
+		vec.push(0x2C); // Image Seperator
+		vec.extend_from_slice(&desc.left.to_le_bytes());
+		vec.extend_from_slice(&desc.top.to_le_bytes());
+		vec.extend_from_slice(&desc.width.to_le_bytes());
+		vec.extend_from_slice(&desc.height.to_le_bytes());
+		vec.push(desc.packed);
+
+		vec.into_boxed_slice()
+	}
+}
+
+impl From<[u8; 9]> for ImageDescriptor {
+	fn from(arr: [u8; 9]) -> Self {
+		let left = u16::from_le_bytes(arr[0..2].try_into().unwrap());
+		let top = u16::from_le_bytes(arr[2..4].try_into().unwrap());
+		let width = u16::from_le_bytes(arr[4..6].try_into().unwrap());
+		let height = u16::from_le_bytes(arr[6..8].try_into().unwrap());
+		let packed = arr[8];
+
+		Self {
+			left,
+			top,
+			width,
+			height,
+			packed,
+		}
+	}
+}
+
+//TODO: Impl to allow changing the packed field easier
diff --git a/gifed/src/block/indexedimage.rs b/gifed/src/block/indexedimage.rs
new file mode 100644
index 0000000..8ed0319
--- /dev/null
+++ b/gifed/src/block/indexedimage.rs
@@ -0,0 +1,70 @@
+use std::convert::TryFrom;
+
+use super::{ColorTable, ImageDescriptor};
+use crate::LZW;
+
+pub struct IndexedImage {
+	pub image_descriptor: ImageDescriptor,
+	pub local_color_table: Option<ColorTable>,
+	pub indicies: Vec<u8>,
+}
+
+impl IndexedImage {
+	pub fn left(&self) -> u16 {
+		self.image_descriptor.left
+	}
+
+	pub fn top(&self) -> u16 {
+		self.image_descriptor.left
+	}
+
+	pub fn width(&self) -> u16 {
+		self.image_descriptor.width
+	}
+
+	pub fn height(&self) -> u16 {
+		self.image_descriptor.height
+	}
+
+	pub fn as_boxed_slice(&self, minimum_code_size: u8) -> Box<[u8]> {
+		let mut out = vec![];
+
+		let mut boxed: Box<[u8]> = (&self.image_descriptor).into();
+		out.extend_from_slice(&*boxed);
+
+		// Get the mcs while we write out the color table
+		let mut mcs = if let Some(lct) = &self.local_color_table {
+			boxed = lct.into();
+			out.extend_from_slice(&*boxed);
+
+			lct.packed_len()
+		} else {
+			minimum_code_size + 1
+		};
+
+		if mcs < 2 {
+			mcs = 2; // Must be true: 0 <= mcs <= 8
+		}
+
+		// First write out the MCS
+		out.push(mcs);
+
+		let compressed = LZW::encode(mcs, &self.indicies);
+
+		for chunk in compressed.chunks(255) {
+			out.push(chunk.len() as u8);
+			out.extend_from_slice(chunk);
+		}
+		// Data block length 0 to indicate an end
+		out.push(0x00);
+
+		out.into_boxed_slice()
+	}
+}
+
+pub struct CompressedImage {
+	pub image_descriptor: ImageDescriptor,
+	pub local_color_table: Option<ColorTable>,
+	pub lzw_minimum_code_size: u8,
+	pub blocks: Vec<Vec<u8>>,
+}
diff --git a/gifed/src/block/mod.rs b/gifed/src/block/mod.rs
new file mode 100644
index 0000000..e35224b
--- /dev/null
+++ b/gifed/src/block/mod.rs
@@ -0,0 +1,25 @@
+mod colortable;
+pub mod extension;
+mod imagedescriptor;
+mod indexedimage;
+mod screendescriptor;
+mod version;
+
+pub use colortable::ColorTable;
+pub use imagedescriptor::ImageDescriptor;
+pub use indexedimage::CompressedImage;
+pub use indexedimage::IndexedImage;
+pub use screendescriptor::ScreenDescriptor;
+pub use version::Version;
+
+use crate::writer::ImageBuilder;
+
+pub enum Block {
+	IndexedImage(IndexedImage),
+	Extension(extension::Extension),
+}
+
+enum WriteBlock {
+	ImageBuilder(ImageBuilder),
+	Block(Block),
+}
diff --git a/gifed/src/block/screendescriptor.rs b/gifed/src/block/screendescriptor.rs
new file mode 100644
index 0000000..dc0257d
--- /dev/null
+++ b/gifed/src/block/screendescriptor.rs
@@ -0,0 +1,79 @@
+use std::convert::TryInto;
+
+pub struct ScreenDescriptor {
+	pub width: u16,
+	pub height: u16,
+	pub packed: u8,
+	pub background_color_index: u8,
+	pub pixel_aspect_ratio: u8,
+}
+
+impl ScreenDescriptor {
+	pub fn new(width: u16, height: u16) -> Self {
+		Self {
+			width,
+			height,
+			packed: 0,
+			background_color_index: 0,
+			pixel_aspect_ratio: 0,
+		}
+	}
+
+	pub fn set_color_table_present(&mut self, is_present: bool) {
+		if is_present {
+			self.packed |= 0b1000_0000;
+		} else {
+			self.packed &= 0b0111_1111;
+		}
+	}
+
+	pub fn set_color_table_size(&mut self, size: u8) {
+		println!("scts: {}", size);
+		// GCT size is calulated by raising two to this number plus one,
+		// so we have to work backwards.
+		let size = (size as f32).log2().ceil() - 1f32;
+		self.packed |= size as u8;
+	}
+
+	//TODO: Setter for sort flag in packed field
+	//TODO: Setter for color resolution in packed field
+
+	pub fn color_table_present(&self) -> bool {
+		self.packed & 0b1000_0000 != 0
+	}
+
+	pub fn color_table_len(&self) -> usize {
+		crate::packed_to_color_table_length(self.packed & 0b0000_0111)
+	}
+}
+
+impl From<&ScreenDescriptor> for Box<[u8]> {
+	fn from(lsd: &ScreenDescriptor) -> Self {
+		let mut vec = vec![];
+		vec.extend_from_slice(&lsd.width.to_le_bytes());
+		vec.extend_from_slice(&lsd.height.to_le_bytes());
+		vec.push(lsd.packed);
+		vec.push(lsd.background_color_index);
+		vec.push(lsd.pixel_aspect_ratio);
+
+		vec.into_boxed_slice()
+	}
+}
+
+impl From<[u8; 7]> for ScreenDescriptor {
+	fn from(arr: [u8; 7]) -> Self {
+		let width = u16::from_le_bytes(arr[0..2].try_into().unwrap());
+		let height = u16::from_le_bytes(arr[2..4].try_into().unwrap());
+		let packed = arr[4];
+		let background_color_index = arr[5];
+		let pixel_aspect_ratio = arr[6];
+
+		Self {
+			width,
+			height,
+			packed,
+			background_color_index,
+			pixel_aspect_ratio,
+		}
+	}
+}
diff --git a/gifed/src/block/version.rs b/gifed/src/block/version.rs
new file mode 100644
index 0000000..0171ad4
--- /dev/null
+++ b/gifed/src/block/version.rs
@@ -0,0 +1,25 @@
+use std::fmt;
+
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub enum Version {
+	Gif87a,
+	Gif89a,
+}
+
+impl From<&Version> for &[u8] {
+	fn from(version: &Version) -> Self {
+		match version {
+			Version::Gif87a => b"GIF87a",
+			Version::Gif89a => b"GIF89a",
+		}
+	}
+}
+
+impl fmt::Display for Version {
+	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+		match self {
+			Version::Gif87a => write!(f, "GIF87a"),
+			Version::Gif89a => write!(f, "GIF89a"),
+		}
+	}
+}