bendns' repos / fimg
fast image operations
Diffstat (limited to 'src/pixels/blending.rs')
-rw-r--r--src/pixels/blending.rs95
1 files changed, 95 insertions, 0 deletions
diff --git a/src/pixels/blending.rs b/src/pixels/blending.rs
new file mode 100644
index 0000000..17ce141
--- /dev/null
+++ b/src/pixels/blending.rs
@@ -0,0 +1,95 @@
+//! module for pixel blending ops
+use super::{unfloat, Floatify, PMap, Trunc, Unfloatify};
+use umath::FF32;
+
+/// Trait for blending pixels together.
+pub trait Blend<const W: usize> {
+ /// blends self with another pixel
+ fn blend(&mut self, with: [u8; W]);
+}
+
+impl Blend<4> for [u8; 4] {
+ 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.trunc()
+ // SAFETY: no u8 can possibly become INF / NAN
+ .pmap(bg.trunc(), |f, b| unsafe {
+ (f * fg[3] + b * bg[3] * (FF32::new(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<2> for [u8; 2] {
+ 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 { FF32::new(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]);
+ }
+}