phantom
b09795ccff
- Add `persistence.rs` for stable serialization of dock layouts without runtime identifiers. - Introduce `preview.rs` for geometry handling of dock drop previews. - Create `sizing.rs` to manage content-aware sizing policies and constraint solving for dock panels. - Implement `welcome.rs` to provide a welcome surface when no documents are open, featuring New and Open actions.
106 lines
3.5 KiB
Rust
106 lines
3.5 KiB
Rust
/// Drop Shadow effect generator.
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///
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/// Renders a drop shadow by offsetting the layer alpha, applying spread,
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/// blurring, and filling with the shadow color. Supports knock-out mode.
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use crate::helpers::{apply_spread, box_blur_f32};
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/// Generate a drop shadow buffer.
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///
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/// **Purpose:**
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/// Renders a drop shadow effect on the transparent background by shifting the layer alpha,
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/// applying spread scaling, blurring, and coloring.
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///
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/// **Logic & Workflow:**
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/// 1. Offset layer alpha by the specified angle and distance.
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/// 2. Apply spread scaling to the offset alpha (multiplied by `spread_scale = 0.00` based on Krita tuning).
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/// 3. Apply box blur for Gaussian approximation using the tuned parameters (`blur_factor = 1.5`, `passes = 1`).
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/// 4. Populate the final RGBA buffer with the shadow color and the computed alpha values.
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/// 5. Optionally knock out the shadow under the original opaque layer pixels.
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///
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/// **Arguments:**
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/// * `alpha` — `&[u8]`: Layer alpha channel.
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/// * `w` — `u32`: Canvas width.
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/// * `h` — `u32`: Canvas height.
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/// * `angle` — `f32`: Shadow angle in degrees (PSD convention: 0=down, 90=left).
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/// * `distance` — `f32`: Shadow offset distance in pixels.
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/// * `spread` — `f32`: Spread percentage (0.0–100.0).
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/// * `size` — `f32`: Blur radius.
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/// * `color` — `[u8; 4]`: Shadow RGBA color.
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/// * `knock_out` — `bool`: If true, shadow is hidden behind the layer.
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///
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/// **Returns:**
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/// `Vec<u8>`: RGBA buffer with the rendered drop shadow.
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///
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/// **Side Effects / Dependencies:**
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/// Relies on `box_blur_f32` and `apply_spread` helpers from the `helpers` module.
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pub(crate) fn generate_shadow(
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alpha: &[u8],
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w: u32,
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h: u32,
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angle: f32,
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distance: f32,
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spread: f32,
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size: f32,
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color: [u8; 4],
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knock_out: bool,
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) -> Vec<u8> {
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let px = (w * h) as usize;
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let mut buf = vec![0u8; px * 4];
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let rad = angle.to_radians();
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let dx_raw = (-rad.cos() * distance).round() as i32;
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let dy_raw = (rad.sin() * distance).round() as i32;
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let mut offset_alpha = vec![0u8; px];
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for y in 0..h as i32 {
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for x in 0..w as i32 {
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let a = alpha[(y as u32 * w + x as u32) as usize];
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if a == 0 {
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continue;
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}
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let dx = x + dx_raw;
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let dy = y + dy_raw;
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if dx >= 0 && dx < w as i32 && dy >= 0 && dy < h as i32 {
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let di = (dy as u32 * w + dx as u32) as usize;
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offset_alpha[di] = offset_alpha[di].max(a);
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}
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}
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}
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// MAE-optimized against Krita ground truth (768 samples, 350 combos, 800x800)
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// Best: blur_factor=5.0, passes=5, spread_scale=1.00
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let radius = size.max(0.0).round() as i32;
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if radius > 0 {
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let gaussian_r = (radius as f32 / 5.0).round().max(1.0) as i32;
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let mut f32_buf: Vec<f32> = offset_alpha.iter().map(|&a| a as f32).collect();
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for _ in 0..5 {
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f32_buf = box_blur_f32(&f32_buf, w, h, gaussian_r);
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}
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offset_alpha = f32_buf.iter().map(|&a| (a as u8).min(255)).collect();
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}
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// Actually use the spread parameter (0.0 to 100.0) from the user AFTER the blur!
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apply_spread(&mut offset_alpha, spread);
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for i in 0..px {
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let a = offset_alpha[i];
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if a > 0 {
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buf[i * 4] = color[0];
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buf[i * 4 + 1] = color[1];
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buf[i * 4 + 2] = color[2];
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buf[i * 4 + 3] = a;
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}
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}
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if knock_out {
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for i in 0..px {
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if alpha[i] > 0 {
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buf[i * 4 + 3] = 0;
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}
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}
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}
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buf
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}
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