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Add support for matrix transformations
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Co-authored-by: Matteo Bertini <matteo@naufraghi.net>
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@dbrgn @naufraghi
dbrgn and naufraghi committed Aug 20, 2022
1 parent 097c27b commit 7be9a30
Showing 1 changed file with 150 additions and 26 deletions.
176 changes: 150 additions & 26 deletions src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -34,14 +34,17 @@ use std::{
};

use log::trace;
use lyon_geom::{euclid::Point2D, CubicBezierSegment, QuadraticBezierSegment};
use quick_xml::{events::attributes::Attribute, events::Event};
use lyon_geom::{
euclid::{Point2D, Transform2D},
CubicBezierSegment, QuadraticBezierSegment,
};
use quick_xml::events::Event;
use svgtypes::{PathParser, PathSegment};

#[cfg(feature = "serde")]
use serde::{Deserialize, Serialize};

/// A `CoordinatePair` consists of an x and y coordinate.
/// A pair of x and y coordinates.
#[derive(Debug, PartialEq, Copy, Clone)]
#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
#[repr(C)]
Expand All @@ -54,6 +57,13 @@ impl CoordinatePair {
pub fn new(x: f64, y: f64) -> Self {
Self { x, y }
}

/// Apply a 2D transformation.
pub fn transform(&mut self, t: Transform2D<f64, f64, f64>) {
let Point2D { x, y, .. } = t.transform_point(Point2D::new(self.x, self.y));
self.x = x;
self.y = y;
}
}

impl From<(f64, f64)> for CoordinatePair {
Expand Down Expand Up @@ -82,6 +92,14 @@ impl Polyline {
Polyline(vec)
}

/// Apply a transformation to all coordinate pairs
fn transform(mut self, t: Transform2D<f64, f64, f64>) -> Self {
for p in &mut self.0 {
p.transform(t);
}
self
}

/// Push a [`CoordinatePair`] to the end of the polyline.
fn push(&mut self, val: CoordinatePair) {
self.0.push(val);
Expand Down Expand Up @@ -213,8 +231,9 @@ impl CurrentLine {
}
}

/// Parse an SVG string, return vector of path expressions.
fn parse_xml(svg: &str) -> Result<Vec<String>, String> {
/// Parse an SVG string, return vector of `(path expression, transform
/// expression)` tuples.
fn parse_xml(svg: &str) -> Result<Vec<(String, Option<String>)>, String> {
trace!("parse_xml");

let mut reader = quick_xml::Reader::from_str(svg);
Expand All @@ -228,21 +247,23 @@ fn parse_xml(svg: &str) -> Result<Vec<String>, String> {
trace!("parse_xml: Matched start of {:?}", e.name());
match e.name() {
b"path" => {
trace!("parse_xml: Found path attribute");
let path_expr: Option<String> = e
.attributes()
.filter_map(Result::ok)
.find_map(|attr: Attribute| {
if attr.key == b"d" {
attr.unescaped_value()
.ok()
.and_then(|v| str::from_utf8(&v).map(str::to_string).ok())
} else {
None
}
});
trace!("parse_xml: Found path element");
let mut path_expr: Option<String> = None;
let mut transform_expr: Option<String> = None;
for attr in e.attributes().filter_map(Result::ok) {
let extract = || {
attr.unescaped_value()
.ok()
.and_then(|v| str::from_utf8(&v).map(str::to_string).ok())
};
match attr.key {
b"d" => path_expr = extract(),
b"transform" => transform_expr = extract(),
_ => {}
}
}
if let Some(expr) = path_expr {
paths.push(expr);
paths.push((expr, transform_expr));
}
}
_ => {}
Expand Down Expand Up @@ -717,7 +738,50 @@ fn parse_path_segment(
Ok(())
}

/// Parse an SVG string into a vector of polylines.
/// Parse an SVG transformation into a ``Transform2D``.
///
/// Only matrix transformations are supported at the moment. (This shouldn't be
/// an issue, because usvg converts all transformations into matrices.)
#[allow(clippy::many_single_char_names)]
fn parse_transform(transform: &str) -> Result<Transform2D<f64, f64, f64>, String> {
// Extract matrix elements from SVG string
let transform = transform.trim();
if !transform.starts_with("matrix(") {
return Err(format!(
"Only 'matrix' transform supported in transform '{}'",
transform
));
}
if !transform.ends_with(')') {
return Err(format!(
"Missing closing parenthesis in transform '{}'",
transform
));
}
let matrix = transform
.strip_prefix("matrix(")
.expect("checked before")
.strip_suffix(')')
.expect("checked to be there");

// Convert elements to floats
let elements = matrix
.split_whitespace()
.map(str::parse)
.collect::<Result<Vec<f64>, _>>()
.map_err(|_| format!("Invalid matrix coefficients in transform '{}'", transform))?;

// Convert floats into Transform2D
let [a, b, c, d, e, f]: [f64; 6] = elements.as_slice().try_into().map_err(|_| {
format!(
"Invalid number of matrix coefficients in transform '{}'",
transform
)
})?;
Ok(Transform2D::new(a, b, c, d, e, f))
}

/// Parse an SVG string into a vector of [`Polyline`]s.
///
/// ## Flattening tolerance
///
Expand Down Expand Up @@ -752,8 +816,14 @@ pub fn parse(svg: &str, tol: f64, preprocess: bool) -> Result<Vec<Polyline>, Str
let mut polylines: Vec<Polyline> = Vec::new();

// Process path expressions
for expr in path_exprs {
polylines.extend(parse_path(&expr, tol)?);
for (path_expr, transform_expr) in path_exprs {
let path = parse_path(&path_expr, tol)?;
if let Some(e) = transform_expr {
let t = parse_transform(&e)?;
polylines.extend(path.into_iter().map(|polyline| polyline.transform(t)));
} else {
polylines.extend(path);
}
}

trace!("parse: This results in {} polylines", polylines.len());
Expand Down Expand Up @@ -1159,7 +1229,7 @@ mod tests {
let result = parse_xml(input).unwrap();
assert_eq!(
result,
vec!["M 10,100 40,70 h 10 m -20,40 10,-20".to_string()]
vec![("M 10,100 40,70 h 10 m -20,40 10,-20".to_string(), None)]
);
}

Expand All @@ -1178,8 +1248,8 @@ mod tests {
assert_eq!(
result,
vec![
"M 10,100 40,70 h 10 m -20,40 10,-20".to_string(),
"M 20,30".to_string(),
("M 10,100 40,70 h 10 m -20,40 10,-20".to_string(), None),
("M 20,30".to_string(), None),
]
);
}
Expand All @@ -1196,7 +1266,31 @@ mod tests {
"#
.trim();
let result = parse_xml(input).unwrap();
assert_eq!(result, vec!["M 20,30".to_string()]);
assert_eq!(result, vec![("M 20,30".to_string(), None)]);
}

#[test]
fn test_parse_xml_with_transform() {
let _ = env_logger::try_init();
let input = r#"
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<svg xmlns="http://www.w3.org/2000/svg" version="1.1">
<path d="M 20,30" transform="matrix(1 0 0 1 0 0)"/>
<path d="M 30,40"/>
</svg>
"#
.trim();
let result = parse_xml(input).unwrap();
assert_eq!(
result,
vec![
(
"M 20,30".to_string(),
Some("matrix(1 0 0 1 0 0)".to_string())
),
("M 30,40".to_string(), None)
],
);
}

#[test]
Expand Down Expand Up @@ -1310,4 +1404,34 @@ mod tests {
])
);
}

#[test]
fn test_parse_transform_matrix() {
// Identity matrix:
// |1 0 0|
// |0 1 0|
// |0 0 1|
assert_eq!(
parse_transform("matrix(1 0 0 1 0 0)"),
Ok(Transform2D::identity())
);

// Scaling matrix (expand in X, compress in Y)
// |2 0 0|
// |0 .5 0|
// |0 0 1|
assert_eq!(
parse_transform("matrix(2 0 0 0.5 0 0)"),
Ok(Transform2D::scale(2.0, 0.5))
);

// Translation matrix
// |1 0 3|
// |0 1 -5|
// |0 0 1|
assert_eq!(
parse_transform("matrix(1 0 0 1 3 -5.0)"),
Ok(Transform2D::translation(3.0, -5.0))
);
}
}

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