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-rw-r--r--src/writer/gifbuilder.rs238
1 files changed, 238 insertions, 0 deletions
diff --git a/src/writer/gifbuilder.rs b/src/writer/gifbuilder.rs
new file mode 100644
index 0000000..ff98ba7
--- /dev/null
+++ b/src/writer/gifbuilder.rs
@@ -0,0 +1,238 @@
+use crate::common::{Color, Version};
+use super::OutVec;
+use super::ImageBuilder;
+
+pub struct GifBuilder {
+	version: Version,
+	width: u16,
+	height: u16,
+	global_color_table: Option<Vec<Color>>,
+	background_color_index: u8,
+	imagebuilders: Vec<ImageBuilder>
+}
+
+impl GifBuilder {
+	pub fn new(version: Version, width: u16, height: u16) -> Self {
+		Self {
+			version,
+			width,
+			height,
+			global_color_table: None,
+			background_color_index: 0,
+			imagebuilders: vec![]
+		}
+	}
+
+	pub fn global_color_table(mut self, vec: Vec<Color>) -> Self {
+		if vec.len() == 0 || vec.len() > 256 {
+			//TODO: Throw error instead of panic
+			panic!("GCT has to be less than or 256 colors in size, and at least one");
+		}
+
+		self.global_color_table = Some(vec);
+
+		self
+	}
+
+	pub fn background_color_index(mut self, ind: u8) -> Self {
+		if self.global_color_table.is_none() {
+			//TODO: Throw error or let it go by, who knows
+			panic!("Setting background color index with noGCT!");
+		}
+
+		self.background_color_index = ind;
+		self
+	}
+
+	pub fn image(mut self, ib: ImageBuilder) -> Self {
+		self.imagebuilders.push(ib);
+		self
+	}
+
+	pub fn write_to_vec(&self) -> Vec<u8> {
+		let mut out = OutVec::new();
+
+		self
+			.write_header(&mut out)
+			.write_logical_screen_descriptor(&mut out)
+			.write_global_color_table(&mut out)
+			.write_images(&mut out)
+			.write_trailer(&mut out);
+
+		out.vec()
+	}
+
+	fn write_header(&self, out: &mut OutVec) -> &Self {
+		out.push_slice(b"GIF");
+
+		//TODO: Automatically detect version
+		match self.version {
+			Version::Gif87a => out.push_slice(b"87a"),
+			Version::Gif89a => out.push_slice(b"89a")
+		};
+
+		self
+	}
+
+	fn write_logical_screen_descriptor(&self, out: &mut OutVec) -> &Self {
+		out.push_u16(self.width).push_u16(self.height);
+
+		let mut packed: u8 = 0;
+
+		if let Some(gct) = &self.global_color_table {
+			packed |= 0b1000_0000; // Set the GCT flag
+
+			// GCT size is calulated by raising two to this number plus one,
+			// so we have to work backwards.
+			let size = (gct.len() as f32).log2().ceil() - 1f32;
+			
+			packed |= size as u8;
+		}
+		//TODO: Color Resolution and Sort Flag fields in packed.
+		out.push_u8(packed);
+
+		out.push_u8(self.background_color_index)
+			.push_u8(0x00); //TOOD: Allow setting pixel aspect ratio
+
+		self
+	}
+
+	fn write_global_color_table(&self, out: &mut OutVec) -> &Self {
+		if let Some(gct) = &self.global_color_table {
+			out.push_colors(&gct);
+		}
+
+		self
+	}
+
+	fn write_images(&self, out: &mut OutVec) -> &Self {
+		//TODO: Deduplicate color table size code
+		let mcs = if let Some(gct) = &self.global_color_table {
+			((gct.len() as f32).log2().ceil() - 1f32) as u8
+		} else {
+			0
+		};
+
+		for ib in &self.imagebuilders {
+			let image = ib.write_to_vec(mcs);
+			out.push_slice(&image);
+		}
+
+		self
+	}
+
+	fn write_trailer(&self, out: &mut OutVec) {
+		/*
+			"This block is a single-field block indicating the end of the GIF Data Stream. 
+			It contains the fixed value 0x3B."
+		*/
+		out.push_u8(0x3B);
+	}
+}
+
+#[cfg(test)]
+pub mod gifbuilder_test {
+	use super::*;
+
+	#[test]
+	pub fn writer_header() {
+		let mut out = OutVec::new();
+		GifBuilder::new(Version::Gif87a, 0, 0).write_header(&mut out);
+
+		assert_eq!(out.vec(), b"GIF87a");
+	}
+
+	#[test]
+	pub fn write_logical_screen_descriptor() {
+		let mut out = OutVec::new();
+		GifBuilder::new(Version::Gif87a, 4, 4).write_logical_screen_descriptor(&mut out);
+
+		assert_eq!(out.vec(), vec![0x04, 0x00, 0x04, 0x00, 0x00, 0x00, 0x00]);
+
+		let mut out = OutVec::new();
+		let gct = vec![
+			Color::new(0, 0, 0), Color::new(0, 0, 0), Color::new(0, 0, 0),
+			Color::new(0, 0, 0), Color::new(0, 0, 0)
+		];
+		GifBuilder::new(Version::Gif87a, 4, 4).global_color_table(gct).write_logical_screen_descriptor(&mut out);
+
+		assert_eq!(out.vec(), vec![0x04, 0x00, 0x04, 0x00, 0b1000_0010, 0x00, 0x00]);
+	}
+
+	#[test]
+	pub fn write_global_color_table() {
+		let mut out = OutVec::new();
+		let gct = vec![
+			Color::new(1, 2, 3), Color::new(253, 254, 255)
+		];
+		GifBuilder::new(Version::Gif87a, 4, 4).global_color_table(gct).write_global_color_table(&mut out);
+
+		assert_eq!(out.vec(), vec![1, 2, 3, 253, 254, 255]);
+	}
+
+	#[test]
+	fn write_images() {
+		let gct = vec![
+			Color::new(1, 2, 3), Color::new(253, 254, 255)
+		];
+		let colortable = vec![
+			Color::new(0, 0, 0), Color::new(128, 0, 255)
+		];
+		let indicies = vec![0, 0, 0, 0, 0, 1, 1, 0, 0, 1, 1, 0, 0, 0, 0, 0];
+
+		let expected_out = vec![
+			0x2C, 0x00, 0x00, 0x00, 0x00, 0x04, 0x00, 0x04, 0x00, 0b1000_0000, // Image Descriptor 1
+			0, 0, 0, 128, 0, 255, // Color Table
+			0x02, 0x05, 0x84, 0x1D, 0x81, 0x7A, 0x50, 0x00, // Image Data 1
+			0x2C, 0x00, 0x00, 0x00, 0x00, 0x04, 0x00, 0x04, 0x00, 0b0000_0000, // Image Descriptor 2
+			0x02, 0x05, 0x84, 0x1D, 0x81, 0x7A, 0x50, 0x00 // Image Data 2
+		];
+
+		let mut out = OutVec::new();
+		GifBuilder::new(Version::Gif87a, 4, 4)
+			.global_color_table(gct)
+			.image(ImageBuilder::new(4, 4)
+				.color_table(colortable)
+				.indicies(indicies.clone())
+			).image(ImageBuilder::new(4, 4)
+				.indicies(indicies)
+			).write_images(&mut out);
+
+		assert_eq!(out.vec(), expected_out);
+	}
+
+	#[test]
+	fn write_to_vec() {
+		let gct = vec![
+			Color::new(1, 2, 3), Color::new(253, 254, 255)
+		];
+		let colortable = vec![
+			Color::new(0, 0, 0), Color::new(128, 0, 255)
+		];
+		let indicies = vec![0, 0, 0, 0, 0, 1, 1, 0, 0, 1, 1, 0, 0, 0, 0, 0];
+
+		let expected_out = vec![
+			0x47, 0x49, 0x46, 0x38, 0x37, 0x61, // Version - GIF87a
+			0x04, 0x00, 0x04, 0x00, 0b1000_0000, 0x00, 0x00, // Logical Screen Descriptor
+			1, 2, 3, 253, 254, 255, // Global Color Table
+			0x2C, 0x00, 0x00, 0x00, 0x00, 0x04, 0x00, 0x04, 0x00, 0b1000_0000, // Image Descriptor 1
+			0, 0, 0, 128, 0, 255, // Color Table
+			0x02, 0x05, 0x84, 0x1D, 0x81, 0x7A, 0x50, 0x00, // Image Data 1
+			0x2C, 0x00, 0x00, 0x00, 0x00, 0x04, 0x00, 0x04, 0x00, 0b0000_0000, // Image Descriptor 2
+			0x02, 0x05, 0x84, 0x1D, 0x81, 0x7A, 0x50, 0x00, // Image Data 2
+			0x3B // Trailer
+		];
+
+		let mut out = OutVec::new();
+		let actual_out = GifBuilder::new(Version::Gif87a, 4, 4)
+			.global_color_table(gct)
+			.image(ImageBuilder::new(4, 4)
+				.color_table(colortable)
+				.indicies(indicies.clone())
+			).image(ImageBuilder::new(4, 4)
+				.indicies(indicies)
+			).write_to_vec();
+
+		assert_eq!(actual_out, expected_out);
+	}
+}
\ No newline at end of file
generated by cgit-pink 1.4.1-3-g733a5 (git 2.37.1) at 2025-01-18 23:05:09 +0000