Module drop_shadow 

Drop shadow filter implementation.

This implements the feDropShadow primitive from SVG Filter Effects 2. The drop shadow effect is a shorthand for a commonly used sequence of filter operations:

1. Extract alpha channel
2. Offset the alpha
3. Blur the offset alpha
4. Composite shadow color with blurred alpha
5. Composite shadow with original graphic

@see https://drafts.fxtf.org/filter-effects-2/#feDropShadowElement

Functions

apply_drop_shadow 🔒

Apply drop shadow effect.

compose_src_over 🔒

Composite two pixels using Porter-Duff “source over” operator.

norm_to_u8 🔒

Convert a normalized f32 (0.0-1.0) to u8 color component (0-255).

src_over_channel 🔒

Blend a single channel using Porter-Duff “source over” operator.

u8_to_norm 🔒

Convert a u8 color component (0-255) to normalized f32 (0.0-1.0).

write_colored_shadow 🔒

Apply the shadow color and optionally composite with the original.