Add pixel-transform

crates/lib/pixel-transform/src/transformers/mod.rs

@@ -0,0 +1,165 @@
+use image::{DynamicImage, ImageFormat};
+use std::fmt;
+use std::fmt::{Debug, Display};
+use std::str::FromStr;
+
+mod crop;
+pub use crop::*;
+
+mod maxdim;
+pub use maxdim::*;
+
+pub trait ImageTransformer
+where
+	Self: PartialEq,
+	Self: Sized + Clone,
+	Self: Display + Debug,
+{
+	/// Transform the given image in place
+	fn transform(&self, input: &mut DynamicImage);
+
+	/// Parse an arg string.
+	///
+	/// `name({arg_string})`
+	fn parse_args(args: &str) -> Result<Self, String>;
+}
+
+use serde::{Deserialize, Deserializer};
+
+/// An enum of all [`ImageTransformer`]s
+#[derive(Debug, Clone, PartialEq)]
+pub enum TransformerEnum {
+	/// Usage: `maxdim(w, h)`
+	///
+	/// Scale the image so its width is smaller than `w`
+	/// and its height is smaller than `h`. Aspect ratio is preserved.
+	///
+	/// To only limit the size of one dimension, use `vw` or `vh`.
+	/// For example, `maxdim(50,100vh)` will not limit width.
+	MaxDim(MaxDimTransformer),
+
+	/// Usage: `crop(w, h, float)`
+	///
+	/// Crop the image to at most `w` by `h` pixels,
+	/// floating the crop area in the specified direction.
+	///
+	/// Directions are one of:
+	/// - Cardinal: n,e,s,w
+	/// - Diagonal: ne,nw,se,sw,
+	/// - Centered: c
+	///
+	/// Examples:
+	/// - `crop(100vw, 50)` gets the top 50 pixels of the image \
+	///   (or fewer, if the image's height is smaller than 50)
+	///
+	/// To only limit the size of one dimension, use `vw` or `vh`.
+	/// For example, `maxdim(50,100vh)` will not limit width.
+	Crop(CropTransformer),
+
+	/// Usage: `format(format)`
+	///
+	/// Transcode the image to the given format.
+	/// This step must be last, and cannot be provided
+	/// more than once.
+	///
+	/// Valid formats:
+	/// - bmp
+	/// - gif
+	/// - ico
+	/// - jpeg or jpg
+	/// - png
+	/// - qoi
+	/// - webp
+	///
+	/// Example:
+	/// - `format(png)`
+	///
+	/// When transcoding an animated gif, the first frame is taken
+	/// and all others are thrown away. This happens even if we
+	/// transcode from a gif to a gif.
+	Format { format: ImageFormat },
+}
+
+impl FromStr for TransformerEnum {
+	type Err = String;
+
+	fn from_str(s: &str) -> Result<Self, Self::Err> {
+		let s = s.trim();
+
+		let (name, args) = {
+			let name_len = match s.find('(') {
+				Some(x) => x + 1,
+				None => {
+					return Err(format!(
+						"invalid transformation {s}. Must look like name(args)."
+					));
+				}
+			};
+
+			let mut balance = 1;
+			let mut end = name_len;
+			for i in s[name_len..].bytes() {
+				match i {
+					b')' => balance -= 1,
+					b'(' => balance += 1,
+					_ => {}
+				}
+
+				if balance == 0 {
+					break;
+				}
+
+				end += 1;
+			}
+
+			if balance != 0 {
+				return Err(format!("mismatched parenthesis in {s}"));
+			}
+
+			let name = s[0..name_len - 1].trim();
+			let args = s[name_len..end].trim();
+			let trail = s[end + 1..].trim();
+			if !trail.is_empty() {
+				return Err(format!(
+					"invalid transformation {s}. Must look like name(args)."
+				));
+			}
+
+			(name, args)
+		};
+
+		match name {
+			"maxdim" => Ok(Self::MaxDim(MaxDimTransformer::parse_args(args)?)),
+			"crop" => Ok(Self::Crop(CropTransformer::parse_args(args)?)),
+
+			"format" => Ok(TransformerEnum::Format {
+				format: ImageFormat::from_extension(args)
+					.ok_or(format!("invalid image format {args}"))?,
+			}),
+
+			_ => Err(format!("unknown transformation {name}")),
+		}
+	}
+}
+
+impl<'de> Deserialize<'de> for TransformerEnum {
+	fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+	where
+		D: Deserializer<'de>,
+	{
+		let s = String::deserialize(deserializer)?;
+		s.parse().map_err(serde::de::Error::custom)
+	}
+}
+
+impl Display for TransformerEnum {
+	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+		match self {
+			TransformerEnum::MaxDim(x) => Display::fmt(x, f),
+			TransformerEnum::Crop(x) => Display::fmt(x, f),
+			TransformerEnum::Format { format } => {
+				write!(f, "format({})", format.extensions_str()[0])
+			}
+		}
+	}
+}