91 lines
4.0 KiB
Rust
91 lines
4.0 KiB
Rust
//! Freeform gradients in the renderer.
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//!
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//! vello has no freeform shading, so the colour field ([`vectorcraft_color::freeform`]) is
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//! sampled on a grid of cells over the painted box and drawn as an image paint (bilinear, edges
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//! padded): the fill or stroke being painted clips it. The grid is sized from the box's size on
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//! screen (a cell per few device pixels, in power-of-two steps so zooming reuses it) and cached by
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//! the gradient's content, so panning and redraws don't resample it.
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use std::cell::RefCell;
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use std::collections::HashMap;
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use std::hash::{Hash, Hasher};
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use std::sync::Arc;
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use vectorcraft_color::freeform::{grid_size, painted_box, spread_scale};
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use vectorcraft_color::{Color, Freeform, GradientPaint};
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use vectorcraft_geom::{Affine, Rect};
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use vello_cpu::peniko::{Extend, ImageQuality, ImageSampler};
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use vello_cpu::{Pixmap, RenderContext};
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use crate::ink::Ink;
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/// Grids kept before the cache starts over.
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const MAX_GRIDS: usize = 128;
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thread_local! {
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static GRIDS: RefCell<HashMap<u64, Arc<Pixmap>>> = RefCell::new(HashMap::new());
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}
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fn hash_color(c: &Color, h: &mut impl Hasher) {
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match *c {
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Color::Rgb { r, g, b } => (0u8, r.to_bits(), g.to_bits(), b.to_bits()).hash(h),
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Color::Cmyk { c, m, y, k } => (1u8, c.to_bits(), m.to_bits(), y.to_bits(), k.to_bits()).hash(h),
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Color::Gray { k } => (2u8, k.to_bits()).hash(h),
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Color::Lab { l, a, b } => (3u8, l.to_bits(), a.to_bits(), b.to_bits()).hash(h),
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}
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}
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/// Cache key of the grid of `f` on box `b` at `cols` × `rows` painted with `ink` (and the active
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/// colour settings, which turn colours into display RGB or inks).
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fn key(f: &Freeform, b: Rect, cols: u16, rows: u16, ink: Ink) -> u64 {
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let mut h = std::collections::hash_map::DefaultHasher::new();
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for p in &f.points {
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(p.at.x.to_bits(), p.at.y.to_bits(), p.opacity.to_bits(), p.spread.to_bits()).hash(&mut h);
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hash_color(&p.color, &mut h);
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}
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f.lines.hash(&mut h);
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(b.x0.to_bits(), b.y0.to_bits(), b.x1.to_bits(), b.y1.to_bits(), cols, rows).hash(&mut h);
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(Arc::as_ptr(&vectorcraft_color::cms::active()) as usize, ink).hash(&mut h);
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h.finish()
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}
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/// Sample `f` at the centres of a `cols` × `rows` grid over `b` (premultiplied, colours as `ink`
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/// paints them).
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pub(crate) fn rasterize(f: &Freeform, b: Rect, cols: u16, rows: u16, ink: Ink) -> Pixmap {
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let field = f.field_with(spread_scale(b), &|c| ink.rgb(c));
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let data = field
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.grid(b, cols, rows)
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.map(|([r, g, bl], a)| {
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let a = a.clamp(0.0, 1.0);
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let q = |v: f32| (v.clamp(0.0, 1.0) * a * 255.0).round() as u8;
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vello_cpu::color::PremulRgba8 { r: q(r), g: q(g), b: q(bl), a: (a * 255.0).round() as u8 }
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})
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.collect();
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Pixmap::from_parts(data, cols, rows)
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}
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/// Set freeform gradient `g` on box `bounds` (in the paint's space, which the context's current
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/// transform maps to pixels) as the context paint. Returns false for an empty box.
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pub(crate) fn set_freeform_paint(ctx: &mut RenderContext, g: &GradientPaint, bounds: Rect, ink: Ink) -> bool {
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let Some(b) = painted_box(bounds) else { return false };
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let device = b.width().max(b.height()) * ctx.transform().determinant().abs().sqrt();
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let (cols, rows) = grid_size(b, device);
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let f = g.freeform_on(b);
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let k = key(&f, b, cols, rows, ink);
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let pm = GRIDS.with(|c| c.borrow().get(&k).cloned()).unwrap_or_else(|| {
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let pm = Arc::new(rasterize(&f, b, cols, rows, ink));
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GRIDS.with(|c| {
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let mut c = c.borrow_mut();
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if c.len() >= MAX_GRIDS {
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c.clear();
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}
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c.insert(k, pm.clone());
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});
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pm
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});
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let sampler = ImageSampler { x_extend: Extend::Pad, y_extend: Extend::Pad, quality: ImageQuality::Medium, alpha: 1.0 };
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ctx.set_paint(vello_cpu::Image { image: vello_cpu::ImageSource::Pixmap(pm), sampler });
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ctx.set_paint_transform(Affine::translate(b.origin().to_vec2()) * Affine::scale_non_uniform(b.width() / cols as f64, b.height() / rows as f64));
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true
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}
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