rasterrocket_render/pipe/

simple.rs

//! Simple pipe: `a_input == 255`, `BlendMode::Normal`, no soft mask, no shape.
//!
//! Equivalent to `Splash::pipeRunSimple{Mono8,RGB8,XBGR8,BGR8,CMYK8,DeviceN8}`.
//! Mono1 is excluded: 1-bit packed bitmaps require bit-level addressing that
//! belongs in the fill/stroke caller, not a generic span function.

use std::cell::RefCell;

use crate::pipe::{self, PipeSrc, PipeState};
#[cfg(all(target_arch = "x86_64", feature = "simd-avx2"))]
use crate::simd;
use crate::types::BlendMode;
use color::Pixel;

// Per-thread scratch buffer for pattern spans — grow-never-shrink.
thread_local! {
    static PAT_BUF: RefCell<Vec<u8>> = const { RefCell::new(Vec::new()) };
}

/// Write `x1 - x0 + 1` pixels of solid source colour directly into the
/// destination row, applying the transfer function.  Destination alpha is
/// set to 255 (fully opaque).
///
/// # Preconditions (checked via `debug_assert!` in `render_span`)
///
/// - `pipe.no_transparency(false) && pipe.blend_mode == BlendMode::Normal`
/// - `dst_pixels.len() == count * P::BYTES`
/// - `P::BYTES > 0` (Mono1 handled by caller)
pub(crate) fn render_span_simple<P: Pixel>(
    pipe: &PipeState<'_>,
    src: &PipeSrc<'_>,
    dst_pixels: &mut [u8],
    dst_alpha: Option<&mut [u8]>,
    x0: i32,
    x1: i32,
    y: i32,
) {
    debug_assert_eq!(pipe.blend_mode, BlendMode::Normal);
    debug_assert_eq!(pipe.a_input, 255);

    #[expect(
        clippy::cast_sign_loss,
        reason = "x1 >= x0 is a precondition, so x1 - x0 + 1 >= 1 > 0"
    )]
    let count = (x1 - x0 + 1) as usize;
    let ncomps = P::BYTES;

    match src {
        PipeSrc::Solid(color) => {
            debug_assert_eq!(color.len(), ncomps, "solid color length must match ncomps");
            // Apply transfer to the source colour once, then fill.
            let mut applied = [0u8; 8]; // DeviceN8 is the largest: 8 bytes.
            debug_assert!(
                ncomps <= 8,
                "ncomps {ncomps} > 8; only modes up to DeviceN8 supported"
            );
            pipe::apply_transfer_pixel(pipe, color, &mut applied[..ncomps]);
            let applied = &applied[..ncomps];

            #[cfg(all(target_arch = "x86_64", feature = "simd-avx2"))]
            {
                match ncomps {
                    1 => simd::blend_solid_gray8(dst_pixels, applied[0], count),
                    3 => simd::blend_solid_rgb8(
                        dst_pixels,
                        [applied[0], applied[1], applied[2]],
                        count,
                    ),
                    _ => {
                        for chunk in dst_pixels.chunks_exact_mut(ncomps) {
                            chunk.copy_from_slice(applied);
                        }
                    }
                }
            }
            #[cfg(not(all(target_arch = "x86_64", feature = "simd-avx2")))]
            {
                for chunk in dst_pixels.chunks_exact_mut(ncomps) {
                    chunk.copy_from_slice(applied);
                }
            }
        }
        PipeSrc::Pattern(pat) => {
            PAT_BUF.with(|cell| {
                let mut buf = cell.borrow_mut();
                buf.resize(count * ncomps, 0);
                pat.fill_span(y, x0, x1, &mut buf);
                for chunk in buf.chunks_exact_mut(ncomps) {
                    pipe::apply_transfer_in_place(pipe, chunk);
                }
                dst_pixels.copy_from_slice(&buf);
            });
        }
    }

    // Overprint: excluded by no_transparency(); this branch is unreachable in
    // a correct caller.  Panic loudly rather than silently dropping overprint.
    debug_assert_eq!(
        pipe.overprint_mask, 0xFFFF_FFFF,
        "simple pipe reached with overprint_mask {:#010x}; route through render_span_general",
        pipe.overprint_mask,
    );

    // Set destination alpha to fully opaque.
    if let Some(alpha) = dst_alpha {
        debug_assert_eq!(alpha.len(), count);
        for a in alpha.iter_mut() {
            *a = 255;
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::state::TransferSet;
    use color::{Rgb8, TransferLut};

    fn opaque_normal_pipe() -> PipeState<'static> {
        PipeState {
            blend_mode: BlendMode::Normal,
            a_input: 255,
            overprint_mask: 0xFFFF_FFFF,
            overprint_additive: false,
            transfer: TransferSet::identity_rgb(),
            soft_mask: None,
            alpha0: None,
            knockout: false,
            knockout_opacity: 255,
            non_isolated_group: false,
        }
    }

    #[test]
    fn solid_fills_all_pixels() {
        let pipe = opaque_normal_pipe();
        let color = [100u8, 150, 200];
        let src = PipeSrc::Solid(&color);
        let count = 5usize;
        let mut dst = vec![0u8; count * 3];
        let mut alpha = vec![0u8; count];

        render_span_simple::<Rgb8>(&pipe, &src, &mut dst, Some(&mut alpha), 0, 4, 0);

        for i in 0..count {
            assert_eq!(&dst[i * 3..i * 3 + 3], &color, "pixel {i}");
            assert_eq!(alpha[i], 255, "alpha {i}");
        }
    }

    #[test]
    fn transfer_applied_to_solid() {
        // Inverting transfer (T[v] = 255 − v) used for all RGB channels; the
        // identity tables are used for the gray / CMYK / device_n slots that
        // aren't exercised here.
        static DN: [[u8; 256]; 8] = [TransferLut::IDENTITY.0; 8];
        let id = TransferLut::IDENTITY.as_array();
        let inv = TransferLut::INVERTED.as_array();

        let transfer = TransferSet {
            rgb: [inv; 3],
            gray: id,
            cmyk: [id; 4],
            device_n: &DN,
        };

        let pipe = PipeState {
            blend_mode: BlendMode::Normal,
            a_input: 255,
            overprint_mask: 0xFFFF_FFFF,
            overprint_additive: false,
            transfer,
            soft_mask: None,
            alpha0: None,
            knockout: false,
            knockout_opacity: 255,
            non_isolated_group: false,
        };

        let color = [100u8, 150, 200];
        let src = PipeSrc::Solid(&color);
        let mut dst = vec![0u8; 3];
        let mut alpha = vec![0u8; 1];
        render_span_simple::<Rgb8>(&pipe, &src, &mut dst, Some(&mut alpha), 0, 0, 0);

        assert_eq!(dst[0], 255 - 100, "R transfer inverted");
        assert_eq!(dst[1], 255 - 150, "G transfer inverted");
        assert_eq!(dst[2], 255 - 200, "B transfer inverted");
    }

    #[test]
    fn no_alpha_plane_works() {
        let pipe = opaque_normal_pipe();
        let color = [10u8, 20, 30];
        let src = PipeSrc::Solid(&color);
        let mut dst = vec![0u8; 3];
        render_span_simple::<Rgb8>(&pipe, &src, &mut dst, None, 0, 0, 0);
        assert_eq!(&dst, &[10, 20, 30]);
    }
}