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Copy pathpath.rs
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298 lines (273 loc) · 11.3 KB
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//! Path records: saved paths (image resources 2000–2997), the work path
//! (resource 1025) and vector masks (`vmsk` / `vsms` layer blocks).
//!
//! Implemented from the public Adobe "Photoshop File Formats Specification",
//! section "Path resource format": a path is a list of 26-byte records, each a
//! 2-byte selector followed by 24 bytes of data. Knot coordinates are signed
//! 8.24 fixed-point fractions of the document height (vertical) and width
//! (horizontal), stored vertical first.
//!
//! Undocumented detail (as documented by the MIT-licensed psd-tools): bytes
//! 2–3 of a subpath length record's data (after the knot count) hold the
//! *path operation* of the subpath (`-1` or `1` combine/or, `2` subtract,
//! `3` intersect, `0` exclude/xor). Everything else is kept raw, so parsing
//! and writing a record list is byte-exact.
use crate::error::{PsdError, Result};
/// Length of one path record in bytes (selector + data).
pub const RECORD_LEN: usize = 26;
/// Record selectors (spec table "Path data record types").
pub mod selector {
/// Closed subpath length record.
pub const CLOSED_LENGTH: u16 = 0;
/// Closed subpath Bézier knot, linked.
pub const CLOSED_KNOT_LINKED: u16 = 1;
/// Closed subpath Bézier knot, unlinked.
pub const CLOSED_KNOT_UNLINKED: u16 = 2;
/// Open subpath length record.
pub const OPEN_LENGTH: u16 = 3;
/// Open subpath Bézier knot, linked.
pub const OPEN_KNOT_LINKED: u16 = 4;
/// Open subpath Bézier knot, unlinked.
pub const OPEN_KNOT_UNLINKED: u16 = 5;
/// Path fill rule record.
pub const FILL_RULE: u16 = 6;
/// Clipboard record.
pub const CLIPBOARD: u16 = 7;
/// Initial fill rule record.
pub const INITIAL_FILL: u16 = 8;
}
/// One 26-byte path record, kept raw.
#[derive(Clone, Debug, PartialEq, Eq)]
pub struct PathRecord {
/// Record type (see [`selector`]).
pub selector: u16,
/// The 24 data bytes.
pub data: [u8; 24],
}
impl PathRecord {
fn u16_at(&self, at: usize) -> u16 {
u16::from_be_bytes([self.data[at], self.data[at + 1]])
}
fn i32_at(&self, at: usize) -> i32 {
i32::from_be_bytes([self.data[at], self.data[at + 1], self.data[at + 2], self.data[at + 3]])
}
/// Whether this is a (closed or open) subpath length record.
pub fn is_length(&self) -> bool {
matches!(self.selector, selector::CLOSED_LENGTH | selector::OPEN_LENGTH)
}
/// Whether this is a Bézier knot record.
pub fn is_knot(&self) -> bool {
matches!(self.selector, 1 | 2 | 4 | 5)
}
}
/// A Bézier knot as fractions of the document size: `(x, y)` pairs.
#[derive(Clone, Copy, Debug, PartialEq)]
pub struct PsdKnot {
/// Linked (smooth) knot: the control points move together.
pub linked: bool,
/// Control point preceding the anchor (`(x, y)` fractions).
pub pre: (f64, f64),
/// Anchor point.
pub anchor: (f64, f64),
/// Control point leaving the anchor.
pub post: (f64, f64),
}
/// A subpath: its knots, closed flag and path operation.
#[derive(Clone, Debug, PartialEq)]
pub struct PsdSubpath {
/// Closed subpath.
pub closed: bool,
/// Path operation (bytes 2–3 of the length record data): `-1`/`1`
/// combine, `2` subtract, `3` intersect, `0` exclude.
pub operation: i16,
/// Knots in order.
pub knots: Vec<PsdKnot>,
}
/// Fixed 8.24 → fraction.
pub fn fixed_to_f64(v: i32) -> f64 {
f64::from(v) / 16_777_216.0
}
/// Fraction → fixed 8.24 (rounded, saturating).
pub fn f64_to_fixed(v: f64) -> i32 {
(v * 16_777_216.0).round().clamp(f64::from(i32::MIN), f64::from(i32::MAX)) as i32
}
/// A parsed path record list.
#[derive(Clone, Debug, Default, PartialEq, Eq)]
pub struct PathData {
/// Records in file order.
pub records: Vec<PathRecord>,
}
impl PathData {
/// Parses path records. Trailing bytes shorter than a record are ignored.
pub fn from_bytes(data: &[u8]) -> Result<Self> {
if data.len() / RECORD_LEN > 4_000_000 {
return Err(PsdError::LimitExceeded("path records"));
}
let records = data
.as_chunks::<RECORD_LEN>()
.0
.iter()
.map(|c| {
let mut d = [0u8; 24];
d.copy_from_slice(&c[2..]);
PathRecord { selector: u16::from_be_bytes([c[0], c[1]]), data: d }
})
.collect();
Ok(PathData { records })
}
/// Serializes the records.
pub fn to_bytes(&self) -> Vec<u8> {
let mut out = Vec::with_capacity(self.records.len() * RECORD_LEN);
for r in &self.records {
out.extend_from_slice(&r.selector.to_be_bytes());
out.extend_from_slice(&r.data);
}
out
}
/// Initial fill rule: `true` when the path starts with all pixels filled
/// (inverted path).
pub fn initial_fill(&self) -> bool {
self.records.iter().find(|r| r.selector == selector::INITIAL_FILL).is_some_and(|r| r.u16_at(0) != 0)
}
/// Subpaths with their knots. Knot records not preceded by a length
/// record, or beyond a length record's count, start/extend a subpath
/// leniently instead of failing.
pub fn subpaths(&self) -> Vec<PsdSubpath> {
let mut out: Vec<PsdSubpath> = Vec::new();
let mut remaining = 0usize;
for r in &self.records {
if r.is_length() {
remaining = usize::from(r.u16_at(0));
out.push(PsdSubpath {
closed: r.selector == selector::CLOSED_LENGTH,
operation: r.u16_at(2) as i16,
knots: Vec::with_capacity(remaining.min(4096)),
});
} else if r.is_knot() {
let closed = r.selector <= 2;
if remaining == 0 && out.last().is_none_or(|s| s.closed != closed) {
out.push(PsdSubpath { closed, operation: -1, knots: Vec::new() });
}
remaining = remaining.saturating_sub(1);
let pt = |i: usize| (fixed_to_f64(r.i32_at(i * 8 + 4)), fixed_to_f64(r.i32_at(i * 8)));
if let Some(s) = out.last_mut() {
s.knots.push(PsdKnot { linked: matches!(r.selector, 1 | 4), pre: pt(0), anchor: pt(1), post: pt(2) });
}
}
}
out
}
/// Builds a record list: a fill rule record, an initial fill record,
/// then each subpath's length record and knots.
pub fn from_subpaths(subpaths: &[PsdSubpath], initial_fill: bool) -> Self {
let mut records = vec![PathRecord { selector: selector::FILL_RULE, data: [0; 24] }, PathRecord { selector: selector::INITIAL_FILL, data: [0; 24] }];
records[1].data[..2].copy_from_slice(&u16::from(initial_fill).to_be_bytes());
for s in subpaths {
let mut data = [0u8; 24];
data[..2].copy_from_slice(&(s.knots.len().min(u16::MAX as usize) as u16).to_be_bytes());
data[2..4].copy_from_slice(&s.operation.to_be_bytes());
// Photoshop writes 1 here (psd-tools default); meaning unknown.
data[4..6].copy_from_slice(&1u16.to_be_bytes());
records.push(PathRecord { selector: if s.closed { selector::CLOSED_LENGTH } else { selector::OPEN_LENGTH }, data });
for k in s.knots.iter().take(u16::MAX as usize) {
let sel = match (s.closed, k.linked) {
(true, true) => selector::CLOSED_KNOT_LINKED,
(true, false) => selector::CLOSED_KNOT_UNLINKED,
(false, true) => selector::OPEN_KNOT_LINKED,
(false, false) => selector::OPEN_KNOT_UNLINKED,
};
let mut d = [0u8; 24];
for (i, p) in [k.pre, k.anchor, k.post].iter().enumerate() {
d[i * 8..i * 8 + 4].copy_from_slice(&f64_to_fixed(p.1).to_be_bytes());
d[i * 8 + 4..i * 8 + 8].copy_from_slice(&f64_to_fixed(p.0).to_be_bytes());
}
records.push(PathRecord { selector: sel, data: d });
}
}
PathData { records }
}
}
/// A vector mask block (`vmsk` / `vsms`): version, flags and path records.
#[derive(Clone, Debug, PartialEq, Eq)]
pub struct VectorMaskBlock {
/// Version (3).
pub version: u32,
/// Flags: bit 0 invert, bit 1 not linked, bit 2 disabled.
pub flags: u32,
/// The path.
pub path: PathData,
}
impl VectorMaskBlock {
/// Invert flag.
pub const FLAG_INVERT: u32 = 1;
/// Not-linked flag.
pub const FLAG_NOT_LINKED: u32 = 2;
/// Disabled flag.
pub const FLAG_DISABLED: u32 = 4;
/// Parses the block data.
pub fn from_bytes(data: &[u8]) -> Result<Self> {
if data.len() < 8 {
return Err(PsdError::UnexpectedEof { offset: 0, needed: 8 - data.len() });
}
let version = u32::from_be_bytes([data[0], data[1], data[2], data[3]]);
let flags = u32::from_be_bytes([data[4], data[5], data[6], data[7]]);
Ok(VectorMaskBlock { version, flags, path: PathData::from_bytes(&data[8..])? })
}
/// Serializes the block data.
pub fn to_bytes(&self) -> Vec<u8> {
let mut out = Vec::with_capacity(8 + self.path.records.len() * RECORD_LEN);
out.extend_from_slice(&self.version.to_be_bytes());
out.extend_from_slice(&self.flags.to_be_bytes());
out.extend_from_slice(&self.path.to_bytes());
out
}
}
#[cfg(test)]
mod tests {
use super::*;
fn sample() -> Vec<PsdSubpath> {
vec![
PsdSubpath {
closed: true,
operation: 1,
knots: vec![
PsdKnot { linked: false, pre: (0.25, 0.25), anchor: (0.25, 0.25), post: (0.25, 0.25) },
PsdKnot { linked: true, pre: (0.625, 0.125), anchor: (0.75, 0.25), post: (0.875, 0.375) },
PsdKnot { linked: false, pre: (0.5, 0.75), anchor: (0.5, 0.75), post: (0.5, 0.75) },
],
},
PsdSubpath { closed: false, operation: 2, knots: vec![PsdKnot { linked: false, pre: (-0.5, 1.5), anchor: (0.0, 1.0), post: (0.0625, 0.9375) }] },
]
}
#[test]
fn subpaths_roundtrip_and_bytes_are_stable() {
let p = PathData::from_subpaths(&sample(), true);
let bytes = p.to_bytes();
assert_eq!(bytes.len(), (2 + 2 + 4) * RECORD_LEN);
let q = PathData::from_bytes(&bytes).unwrap();
assert_eq!(q.to_bytes(), bytes);
assert_eq!(q.subpaths(), sample());
assert!(q.initial_fill());
}
#[test]
fn vector_mask_block_roundtrip() {
let b = VectorMaskBlock { version: 3, flags: VectorMaskBlock::FLAG_INVERT, path: PathData::from_subpaths(&sample(), false) };
let bytes = b.to_bytes();
assert_eq!(VectorMaskBlock::from_bytes(&bytes).unwrap(), b);
assert!(VectorMaskBlock::from_bytes(&[0; 4]).is_err());
}
#[test]
fn fixed_point_conversion() {
assert_eq!(f64_to_fixed(1.0), 1 << 24);
assert_eq!(fixed_to_f64(-(1 << 23)), -0.5);
assert_eq!(f64_to_fixed(1e12), i32::MAX);
}
#[test]
fn lenient_knots_without_length_record() {
let mut p = PathData::from_subpaths(&sample(), false);
p.records.retain(|r| !r.is_length());
let s = p.subpaths();
assert_eq!(s.len(), 2);
assert_eq!(s[0].knots.len(), 3);
}
}