bendn's repos / fimg
fast image operations
Diffstat (limited to 'src/pixels/blending.rs')
-rw-r--r--src/pixels/blending.rs127
1 files changed, 127 insertions, 0 deletions
diff --git a/src/pixels/blending.rs b/src/pixels/blending.rs
new file mode 100644
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+++ b/src/pixels/blending.rs
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+//! module for pixel blending ops
+#![allow(redundant_semicolons)]
+use super::{Floatify, Unfloatify, convert::PFrom, float, unfloat};
+use atools::prelude::*;
+
+/// Trait for blending pixels together.
+pub trait Blend<const W: usize> {
+ /// blends self with another pixel
+ fn blend(&mut self, with: [u8; W]);
+}
+
+pub(crate) fn blend_alpha_and_color(a: u8, color: [u8; 3], onto: &mut [u8; 3]) {
+ if a == 0 {
+ return;
+ }
+ if a == 255 {
+ *onto = color;
+ return;
+ }
+
+ let [br, bg, bb] = *onto;
+ let [fr, fg, fb] = color;
+
+ onto[0] = lerp(br, fr, a);
+ onto[1] = lerp(bg, fg, a);
+ onto[2] = lerp(bb, fb, a);
+
+ // onto.copy_from_slice(&fg.zip(bg).map(|(f, b)| a * (f - b) + b));
+}
+
+fn lerp(ba: u8, fo: u8, a: u8) -> u8 {
+ ((fo as i32 - ba as i32) * a as i32 / 256 + ba as i32) as u8
+}
+
+impl Blend<4> for [u8; 4] {
+ #[lower::apply(algebraic)]
+ fn blend(&mut self, fg: [u8; 4]) {
+ if fg[3] == 0 {
+ return;
+ }
+ if fg[3] == 255 {
+ *self = fg;
+ return;
+ }
+ let fg = fg.float();
+ let bg = self.float();
+ let a = bg[3] + fg[3] - bg[3] * fg[3];
+ if a == 0.0 {
+ return;
+ };
+ self[..3].copy_from_slice(
+ &fg.init()
+ .zip(bg.init())
+ .map(|(f, b)| (f * fg[3] + b * bg[3] * (1.0 - fg[3])) / a)
+ .unfloat(),
+ );
+ self[3] = unfloat(a)
+ }
+}
+
+impl Blend<3> for [u8; 3] {
+ fn blend(&mut self, with: [u8; 3]) {
+ *self = with;
+ }
+}
+
+impl Blend<4> for [u8; 3] {
+ fn blend(&mut self, with: [u8; 4]) {
+ let mut us: [u8; 4] = PFrom::pfrom(*self);
+ us.blend(with);
+ *self = PFrom::pfrom(us);
+ }
+}
+
+impl Blend<2> for [u8; 2] {
+ #[lower::apply(algebraic)]
+ fn blend(&mut self, with: [u8; 2]) {
+ let bg = self.float();
+ let fg = with.float();
+
+ let a = bg[1] + fg[1] - bg[1] * fg[1];
+ if a == 0.0 {
+ return;
+ }
+ *self = [
+ // SAFETY: no u8 can do transform bad
+ (fg[0] * fg[1] + bg[0] * bg[1] * (unsafe { (1.0) } - fg[1])) / a,
+ a,
+ ]
+ .unfloat()
+ }
+}
+
+impl Blend<1> for [u8; 1] {
+ fn blend(&mut self, with: [u8; 1]) {
+ *self = with;
+ }
+}
+
+#[cfg(test)]
+mod blend {
+ use super::*;
+
+ macro_rules! blend {
+ ([$($a:literal),+] + [$($b:literal),+] = $what:expr) => {
+ let mut a = [$($a,)+];
+ a.blend([$($b,)+]);
+ assert_eq!(a, $what);
+ };
+}
+
+ #[test]
+ fn test_blend_rgba() {
+ blend!([255, 255, 255, 255] + [255, 255, 255, 255] = [255, 255, 255, 255]);
+ blend!([255, 255, 255, 0] + [255, 255, 255, 255] = [255, 255, 255, 255]);
+ blend!([255, 255, 255, 255] + [255_u8, 255, 255, 0] = [255, 255, 255, 255]);
+ blend!([255, 255, 255, 0] + [255_u8, 255, 255, 0] = [255, 255, 255, 0]);
+ }
+
+ #[test]
+ fn test_blend_ya() {
+ blend!([255, 255] + [255, 255] = [255, 255]);
+ blend!([255, 0] + [255, 255] = [255, 255]);
+ blend!([255, 255] + [255, 0] = [255, 255]);
+ blend!([255, 0] + [255, 0] = [255, 0]);
+ }
+}