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perf(desktop-gpui): presize flattened RGB buffer #2718

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52 changes: 52 additions & 0 deletions apps/desktop-gpui/kernels/benches/frame_export.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -27,6 +27,19 @@ fn mixed_rgba(pixels: usize) -> Vec<u8> {
rgba
}

fn transparent_rgba(pixels: usize) -> Vec<u8> {
let mut rgba = Vec::with_capacity(pixels * 4);
for i in 0..pixels {
rgba.extend_from_slice(&[
(i & 0xFF) as u8,
((i >> 8) & 0xFF) as u8,
(i.wrapping_mul(17) & 0xFF) as u8,
0,
]);
}
rgba
}

fn fused_two_step(rgba: &[u8]) -> Vec<u8> {
baseline::rgba_to_rgb(&baseline::flatten_onto_white(rgba))
}
Expand Down Expand Up @@ -73,6 +86,20 @@ fn run_fused(name: &str, rgba: &[u8]) {
);
}

fn run_presized(name: &str, rgba: &[u8]) {
assert_eq!(
baseline::flatten_rgba_to_rgb_over_white(rgba),
candidate_codec::flatten_rgba_to_rgb_over_white(rgba),
"{name}"
);
emit(
name,
baseline::flatten_rgba_to_rgb_over_white,
candidate_codec::flatten_rgba_to_rgb_over_white,
rgba,
);
}

fn emit<T>(name: &str, before: fn(T) -> Vec<u8>, after: fn(T) -> Vec<u8>, input: T)
where
T: Copy,
Expand Down Expand Up @@ -103,13 +130,17 @@ where
fn main() {
let hd = opaque_rgba(1920 * 1080);
let uhd_opaque = opaque_rgba(3840 * 2160);
let uhd_transparent = transparent_rgba(3840 * 2160);
let uhd_mixed = mixed_rgba(3840 * 2160);
println!("workload,sample,before_ns,after_ns");
run_flatten("flatten-opaque-1080p", &hd);
run_flatten("flatten-opaque-4k", &uhd_opaque);
run_flatten("flatten-mixed-4k", &uhd_mixed);
run_strip("rgba-strip-4k", &uhd_opaque);
run_fused("export-fused-4k", &uhd_mixed);
run_presized("flatten-rgb-opaque-4k", &uhd_opaque);
run_presized("flatten-rgb-transparent-4k", &uhd_transparent);
run_presized("flatten-rgb-mixed-4k", &uhd_mixed);
}

mod baseline {
Expand All @@ -130,4 +161,25 @@ mod baseline {
}
rgba
}

pub fn flatten_rgba_to_rgb_over_white(rgba: &[u8]) -> Vec<u8> {
let mut rgb = Vec::with_capacity(rgba.len() / 4 * 3);
for px in rgba.chunks_exact(4) {
let alpha = px[3];
if alpha == 255 {
rgb.extend_from_slice(&[px[0], px[1], px[2]]);
} else if alpha == 0 {
rgb.extend_from_slice(&[255, 255, 255]);
} else {
let a = u32::from(alpha);
let inv = 255 - a;
rgb.extend_from_slice(&[
((u32::from(px[0]) * a + 255 * inv + 127) / 255) as u8,
((u32::from(px[1]) * a + 255 * inv + 127) / 255) as u8,
((u32::from(px[2]) * a + 255 * inv + 127) / 255) as u8,
]);
}
}
rgb
}
}
84 changes: 75 additions & 9 deletions apps/desktop-gpui/kernels/src/codec.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -28,24 +28,29 @@ pub fn rgba_to_rgb(rgba: &[u8]) -> Vec<u8> {
}

pub fn flatten_rgba_to_rgb_over_white(rgba: &[u8]) -> Vec<u8> {
let mut rgb = Vec::with_capacity(rgba.len() / 4 * 3);
let mut dst = vec![0u8; rgba.len() / 4 * 3];
let mut i = 0;
for px in rgba.chunks_exact(4) {
let alpha = px[3];
let out = &mut dst[i..i + 3];
if alpha == 255 {
rgb.extend_from_slice(&[px[0], px[1], px[2]]);
out[0] = px[0];
out[1] = px[1];
out[2] = px[2];
} else if alpha == 0 {
rgb.extend_from_slice(&[255, 255, 255]);
out[0] = 255;
out[1] = 255;
out[2] = 255;
} else {
let a = u32::from(alpha);
let inv = 255 - a;
rgb.extend_from_slice(&[
((u32::from(px[0]) * a + 255 * inv + 127) / 255) as u8,
((u32::from(px[1]) * a + 255 * inv + 127) / 255) as u8,
((u32::from(px[2]) * a + 255 * inv + 127) / 255) as u8,
]);
out[0] = ((u32::from(px[0]) * a + 255 * inv + 127) / 255) as u8;
out[1] = ((u32::from(px[1]) * a + 255 * inv + 127) / 255) as u8;
out[2] = ((u32::from(px[2]) * a + 255 * inv + 127) / 255) as u8;
}
i += 3;
}
rgb
dst
}

pub fn encode_png_rgba(rgba: &[u8], width: u32, height: u32) -> image::ImageResult<Vec<u8>> {
Expand Down Expand Up @@ -246,6 +251,67 @@ mod tests {
);
}

fn extend_flatten_rgba_to_rgb_over_white(rgba: &[u8]) -> Vec<u8> {
let mut rgb = Vec::with_capacity(rgba.len() / 4 * 3);
for px in rgba.chunks_exact(4) {
let alpha = px[3];
if alpha == 255 {
rgb.extend_from_slice(&[px[0], px[1], px[2]]);
} else if alpha == 0 {
rgb.extend_from_slice(&[255, 255, 255]);
} else {
let a = u32::from(alpha);
let inv = 255 - a;
rgb.extend_from_slice(&[
((u32::from(px[0]) * a + 255 * inv + 127) / 255) as u8,
((u32::from(px[1]) * a + 255 * inv + 127) / 255) as u8,
((u32::from(px[2]) * a + 255 * inv + 127) / 255) as u8,
]);
}
}
rgb
}

fn rgba_with_alpha(pixels: usize, alpha_of: impl Fn(usize) -> u8) -> Vec<u8> {
let mut rgba = Vec::with_capacity(pixels * 4);
for i in 0..pixels {
rgba.extend_from_slice(&[
(i & 0xff) as u8,
((i >> 4) & 0xff) as u8,
i.wrapping_mul(17) as u8,
alpha_of(i),
]);
}
rgba
}

#[test]
fn flatten_rgba_to_rgb_over_white_matches_extend_formula() {
assert_eq!(flatten_rgba_to_rgb_over_white(&[1, 2, 3, 255]), [1, 2, 3]);
assert_eq!(
flatten_rgba_to_rgb_over_white(&[1, 2, 3, 0]),
[255, 255, 255]
);
assert_eq!(
flatten_rgba_to_rgb_over_white(&[10, 0, 255, 128]),
[132, 127, 255]
);

let opaque = rgba_with_alpha(256, |_| 255);
let transparent = rgba_with_alpha(256, |_| 0);
let mixed = rgba_with_alpha(256, |i| match i % 3 {
0 => 0,
1 => 255,
_ => (i * 17) as u8,
});
for rgba in [&opaque[..], &transparent[..], &mixed[..]] {
assert_eq!(
flatten_rgba_to_rgb_over_white(rgba),
extend_flatten_rgba_to_rgb_over_white(rgba)
);
}
}

#[test]
fn png_round_trips_rgba() {
let rgba = [10, 20, 30, 40, 50, 60, 70, 255];
Expand Down