figcraft/crates/pdf/src/raster.rs

//! Rasterised parts: effects (shadows, blurs, noise, texture) drawn by the tiny-skia renderer
//! and placed as images in page space.
//!
//! - Nodes with a layer blur, noise or texture are rendered whole (`figcraft_render`) and placed
//!   as one image.
//! - Drop and inner shadows are computed from a render of the node without its effects (the
//!   renderer's own shadows: spread offsets the outline, blur, tint, offset, knock-out), so the
//!   node itself stays vector: drop shadows go under it, inner shadows over its fills (under its
//!   children and strokes).
//! - Background blur and glass are drawn by the renderer from a render of what lies under the
//!   node on the page, and placed under its content.

use figcraft_color::BlendMode;
use figcraft_doc::{EffectKind, NodeId, NodeKind};
use figcraft_geom::{Affine, Rect};
use figcraft_render::{Alone, Pixmap, View, backdrop, shadow};
use krilla::geom::Size;
use krilla::image::Image;

use crate::print::Ink;
use krilla::surface::Surface;

use crate::draw::{Exporter, MAX_RASTER_SIDE, affine_ok, blend, norm, to_xf};

/// An image covering `rect` (document page coordinates).
pub(crate) struct Raster {
    image: Image,
    rect: Rect,
    px: (u32, u32),
}

#[derive(Default)]
pub(crate) struct Shadows {
    pub drop: Vec<(Raster, BlendMode)>,
    pub inner: Vec<Raster>,
}

impl Raster {
    fn new(p: &Pixmap, rect: Rect, ink: Ink) -> Raster {
        Raster { image: ink.bitmap(figcraft_render::to_rgba8(p), p.width(), p.height()), rect, px: (p.width(), p.height()) }
    }
}

impl Exporter<'_> {
    /// A view of page area `b` (clipped to the page) at the raster scale, at most
    /// [`MAX_RASTER_SIDE`] pixels a side.
    fn raster_view(&self, b: Rect) -> Option<View> {
        let b = b.intersect(self.page_rect);
        if !(b.width() > 0.0 && b.height() > 0.0 && crate::rect_finite(b)) {
            return None;
        }
        let mut k = self.raster_scale();
        let side = b.width().max(b.height()) * k;
        if side > MAX_RASTER_SIDE {
            k *= MAX_RASTER_SIDE / side;
        }
        let (w, h) = ((b.width() * k).ceil().max(1.0), (b.height() * k).ceil().max(1.0));
        Some(View { origin: (b.x0, b.y0), scale: k, width: w as u32, height: h as u32 })
    }

    fn view_rect(v: &View) -> Rect {
        let k = v.scale.max(1e-9);
        Rect::new(v.origin.0, v.origin.1, v.origin.0 + f64::from(v.width) / k, v.origin.1 + f64::from(v.height) / k)
    }

    /// Draw a raster image at its page rectangle.
    pub(crate) fn place_raster(&self, s: &mut Surface, r: &Raster, opacity: f32, b: BlendMode) {
        let (pw, ph) = r.px;
        let Some(size) = Size::from_wh(pw as f32, ph as f32) else { return };
        let t = self.page_origin
            * Affine::translate((r.rect.x0, r.rect.y0))
            * Affine::scale_non_uniform(r.rect.width() / f64::from(pw.max(1)), r.rect.height() / f64::from(ph.max(1)));
        if !affine_ok(t) {
            return;
        }
        let pb = blend(b);
        if let Some(b) = pb {
            s.push_blend_mode(b);
        }
        if opacity < 1.0 {
            s.push_opacity(norm(opacity));
        }
        s.push_transform(&to_xf(t));
        s.draw_image(r.image.clone(), size);
        s.pop();
        if opacity < 1.0 {
            s.pop();
        }
        if pb.is_some() {
            s.pop();
        }
    }

    /// Inner shadow images, over a node's fills.
    pub(crate) fn place_inner(&self, s: &mut Surface, inner: &[Raster]) {
        for r in inner {
            self.place_raster(s, r, 1.0, BlendMode::Normal);
        }
    }

    /// Render node `id` whole (with its effects, opacity and blend) and place it as an image.
    pub(crate) fn raster_node(&mut self, s: &mut Surface, id: NodeId) {
        let doc = self.doc;
        let Some(n) = doc.node(id) else { return };
        // Blurs, shadows and texture reach beyond the painted bounds.
        let Some(view) = figcraft_render::raster_bounds(doc, id).and_then(|b| self.raster_view(b)) else { return };
        // Its backdrop effects are placed separately (see `backdrop`).
        let Some(pix) = figcraft_render::render_alone(doc, id, &view, Alone::WithEffects) else { return };
        // The renderer applied opacity; the blend mode applies against the PDF backdrop.
        self.place_raster(s, &Raster::new(&pix, Self::view_rect(&view), self.ink()), 1.0, n.blend);
    }

    /// Node `id`'s background blurs and glass as an image over its shape, drawn by the renderer
    /// from a render of what lies under the node on this page (everything drawn before it, its
    /// ancestors' own fills included), the way the canvas and PNG export draw them.
    pub(crate) fn backdrop(&mut self, id: NodeId) -> Option<Raster> {
        let (pix, view) = self.backdrop_pixels(id)?;
        Some(Raster::new(&pix, Self::view_rect(&view), self.ink()))
    }

    /// [`Exporter::backdrop`]'s pixels and the page area they cover.
    pub(crate) fn backdrop_pixels(&self, id: NodeId) -> Option<(Pixmap, View)> {
        let view = self.raster_view(backdrop::shape_bounds(self.doc, id)?)?;
        // Nothing is exported past the page's edge (the renderer's export ends there too).
        let fx = backdrop::effects_beneath(self.doc, &self.page_ids, id, &view, Some(self.page_rect))?;
        Some((fx, view))
    }

    /// The drop and inner shadows of node `id`, as images (the renderer's own shadows).
    pub(crate) fn shadows(&mut self, id: NodeId) -> Option<Shadows> {
        let doc = self.doc;
        let n = doc.node(id)?;
        let world = doc.world_transform(id);
        let sc = world.determinant().abs().sqrt();
        let sc = if sc.is_finite() && sc > 0.0 { sc } else { 1.0 };
        let reach = n
            .effects
            .iter()
            .filter(|e| e.visible)
            .map(|e| match &e.kind {
                // Inner shadows need room outside the shape: everything outside casts them.
                EffectKind::DropShadow(sh) | EffectKind::InnerShadow(sh) => {
                    sh.radius.abs() * 2.0 + sh.spread.abs() * figcraft_doc::SPREAD_MITER_LIMIT + sh.offset.0.abs() + sh.offset.1.abs()
                }
                _ => 0.0,
            })
            .filter(|m| m.is_finite())
            .fold(0.0, f64::max)
            * sc;
        let b = doc.world_render_bounds(id)?.inflate(reach + 1.0, reach + 1.0);
        let view = self.raster_view(b)?;
        let rect = Self::view_rect(&view);
        let (w, h) = (view.width, view.height);
        let layer = figcraft_render::render_alone(doc, id, &view, Alone::Plain)?;
        let xf = view.transform() * world;
        let caster = shadow::Caster::new(doc, n, &layer, xf, view.scale);
        let shape = figcraft_render::node_outline(doc, n);
        let mut out = Shadows::default();
        for e in n.effects.iter().filter(|e| e.visible) {
            match &e.kind {
                EffectKind::DropShadow(sh) => {
                    if let Some(p) = shadow::drop_shadow(&caster, sh) {
                        out.drop.push((Raster::new(&p, rect, self.ink()), sh.blend));
                    }
                }
                EffectKind::InnerShadow(sh) => {
                    // A group is no outline: its layers' pixels, together, are what is shaded.
                    let inner = match &shape {
                        Some(o) => shadow::inner_shadow(o, w, h, xf, view.scale, sh),
                        None if matches!(n.kind, NodeKind::Group) => shadow::inner_shadow_of(&layer, view.scale, sh),
                        None => None,
                    };
                    if let Some(p) = inner {
                        out.inner.push(Raster::new(&p, rect, self.ink()));
                    }
                }
                _ => {}
            }
        }
        Some(out)
    }
}