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New node: 'Photo Filter' to warm or cool an image by multiplying it with a filter color in XYZ #4539

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Merged
Keavon merged 1 commit into from
Sep 16, 2026
Merged

New node: 'Photo Filter' to warm or cool an image by multiplying it with a filter color in XYZ #4539

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122 changes: 115 additions & 7 deletions node-graph/nodes/raster/src/adjustments.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -23,13 +23,7 @@ use raster_types::{CPU, Raster};
#[cfg(feature = "std")]
use vector_types::Gradient;

// TODO: Implement the following:
// Photo Filter
// Aims for interoperable compatibility with:
// https://www.adobe.com/devnet-apps/photoshop/fileformatashtml/#:~:text=%27phfl%27%20%3D%20Photo%20Filter
// https://www.adobe.com/devnet-apps/photoshop/fileformatashtml/#:~:text=of%20the%20file.-,Photo%20Filter,-Key%20is%20%27phfl
//
// Color Lookup
// TODO: Implement 'Color Lookup':
// Aims for interoperable compatibility with:
// https://www.adobe.com/devnet-apps/photoshop/fileformatashtml/#:~:text=%27clrL%27%20%3D%20Color%20Lookup
// https://www.adobe.com/devnet-apps/photoshop/fileformatashtml/#:~:text=Color%20Lookup%20(Photoshop%20CS6
Expand Down Expand Up @@ -1390,6 +1384,8 @@ pub enum DomainWarpType {
// Aims for interoperable compatibility with:
// https://www.adobe.com/devnet-apps/photoshop/fileformatashtml/#:~:text=%27mixr%27%20%3D%20Channel%20Mixer
// https://www.adobe.com/devnet-apps/photoshop/fileformatashtml/#:~:text=Lab%20color%20only-,Channel%20Mixer,-Key%20is%20%27mixr
//
// TODO: CMYK source channels once Graphite supports the CMYK color space.
#[node_macro::node(category("Raster: Adjustment"), properties("channel_mixer_properties"), shader_node(PerPixelAdjust))]
fn channel_mixer<T: Adjust<Color>>(
_: impl Ctx,
Expand Down Expand Up @@ -1906,6 +1902,93 @@ fn color_balance<T: Adjust<Color>>(
image
}

// Aims for interoperable compatibility with:
// https://www.adobe.com/devnet-apps/photoshop/fileformatashtml/#:~:text=%27phfl%27%20%3D%20Photo%20Filter
// https://www.adobe.com/devnet-apps/photoshop/fileformatashtml/#:~:text=of%20the%20file.-,Photo%20Filter,-Key%20is%20%27phfl
#[node_macro::node(category("Raster: Adjustment"), shader_node(PerPixelAdjust))]
fn photo_filter<T: Adjust<Color>>(
_: impl Ctx,
#[implementations(Raster<CPU>, Color, Gradient)]
#[gpu_image]
image: Item<T>,
#[default("ec8a00")] color: Item<Color>,
#[default(25.)] density: Item<PercentageF32>,
#[default(true)] preserve_luminosity: Item<bool>,
) -> Item<T> {
let mut image = image;
let color = color.into_element();
let density = (density.into_element() / 100.).clamp(0., 1.);
let preserve_luminosity = preserve_luminosity.into_element();

// The image is multiplied in XYZ by the filter color normalized to the white point, with density easing that multiplier toward 1
let filter_xyz = multiply_matrix(&SRGB_TO_XYZ_D50, [color.r(), color.g(), color.b()]);
let factor = [
1. + density * (filter_xyz[0] / WHITE_XYZ_D50[0] - 1.),
1. + density * (filter_xyz[1] / WHITE_XYZ_D50[1] - 1.),
1. + density * (filter_xyz[2] / WHITE_XYZ_D50[2] - 1.),
];

image.element_mut().adjust(|pixel| {
let [r_in, g_in, b_in, alpha] = pixel.to_gamma_srgb_channels();
let xyz = multiply_matrix(&SRGB_TO_XYZ_D50, [srgb_to_linear(r_in), srgb_to_linear(g_in), srgb_to_linear(b_in)]);
let filtered = multiply_matrix(&XYZ_D50_TO_SRGB, [xyz[0] * factor[0], xyz[1] * factor[1], xyz[2] * factor[2]]);
let mut r = linear_to_srgb(filtered[0].clamp(0., 1.));
let mut g = linear_to_srgb(filtered[1].clamp(0., 1.));
let mut b = linear_to_srgb(filtered[2].clamp(0., 1.));

if preserve_luminosity {
[r, g, b] = set_luminosity(r, g, b, luma_rec_601_fixed(r, g, b), luma_rec_601_fixed(r_in, g_in, b_in));
}

Color::from_gamma_srgb_channels(r, g, b, alpha)
});
image
}

// sRGB colorants adapted to D50 as in the sRGB IEC61966-2.1 ICC profile, row major, and their inverse
const SRGB_TO_XYZ_D50: [[f32; 3]; 3] = [[0.43607, 0.38515, 0.14307], [0.22249, 0.71687, 0.06061], [0.01392, 0.09708, 0.71410]];
const XYZ_D50_TO_SRGB: [[f32; 3]; 3] = [[3.134096, -1.6174, -0.490638], [-0.978793, 1.916295, 0.033454], [0.071971, -0.228987, 1.40538]];
const WHITE_XYZ_D50: [f32; 3] = [0.96420, 1., 0.82491];

fn multiply_matrix(matrix: &[[f32; 3]; 3], vector: [f32; 3]) -> [f32; 3] {
[
matrix[0][0] * vector[0] + matrix[0][1] * vector[1] + matrix[0][2] * vector[2],
matrix[1][0] * vector[0] + matrix[1][1] * vector[1] + matrix[1][2] * vector[2],
matrix[2][0] * vector[0] + matrix[2][1] * vector[1] + matrix[2][2] * vector[2],
]
}

/// The Rec. 601 luma in the 14-bit fixed point that PSD interop depends on.
fn luma_rec_601_fixed(r: f32, g: f32, b: f32) -> f32 {
(4915. * r + 9667. * g + 1802. * b) / 16384.
}

fn pull_toward_luminosity(channels: [f32; 3], luminosity: f32, scale: f32) -> [f32; 3] {
[
luminosity + (channels[0] - luminosity) * scale,
luminosity + (channels[1] - luminosity) * scale,
luminosity + (channels[2] - luminosity) * scale,
]
}

/// The Luminosity blend mode's construction: shifts gamma-encoded channels from `luma` to `luminosity`,
/// then pulls them toward it just enough to bring every channel back into 0..1.
fn set_luminosity(r: f32, g: f32, b: f32, luma: f32, luminosity: f32) -> [f32; 3] {
let shift = luminosity - luma;
let mut channels = [r + shift, g + shift, b + shift];

let low = channels[0].min(channels[1]).min(channels[2]);
if low < 0. {
channels = pull_toward_luminosity(channels, luminosity, luminosity / (luminosity - low));
}
let high = channels[0].max(channels[1]).max(channels[2]);
if high > 1. {
channels = pull_toward_luminosity(channels, luminosity, (1. - luminosity) / (high - luminosity));
}

[channels[0].clamp(0., 1.), channels[1].clamp(0., 1.), channels[2].clamp(0., 1.)]
}

#[cfg(feature = "std")]
mod _graphene_hash_impls {
use super::{
Expand Down Expand Up @@ -2475,4 +2558,29 @@ mod tests {
let result = run_color_balance([128., 128., 128.], [-39., 6., 42.], [21., 0., -25.], [20., -35., 45.], false);
assert_close(result, [124., 120., 164.]);
}

/// Runs Photo Filter on one gamma-space RGB value (0..255) and returns the gamma-space result on the same scale.
fn run_photo_filter(input: [f32; 3], filter: [f32; 3], density: f32, preserve_luminosity: bool) -> [f32; 3] {
let pixel = Color::from_gamma_srgb_channels(input[0] / 255., input[1] / 255., input[2] / 255., 1.);
let filter = Color::from_gamma_srgb_channels(filter[0] / 255., filter[1] / 255., filter[2] / 255., 1.);
let result = photo_filter((), Item::new_from_element(pixel), filter.into(), density.into(), preserve_luminosity.into());
let [r, g, b, _] = result.into_element().to_gamma_srgb_channels();
[r * 255., g * 255., b * 255.]
}

#[test]
fn photo_filter_multiplies_in_xyz() {
assert_close(run_photo_filter([0., 255., 0.], [255., 0., 0.], 100., false), [146., 103., 0.]);
assert_close(run_photo_filter([0., 0., 255.], [255., 0., 0.], 100., false), [116., 0., 37.]);
assert_close(run_photo_filter([100., 100., 100.], [128., 128., 128.], 100., false), [46., 46., 46.]);
assert_close(run_photo_filter([100., 100., 100.], [236., 138., 0.], 25., false), [98., 91., 87.]);
assert_close(run_photo_filter([200., 200., 200.], [255., 255., 255.], 100., false), [200., 200., 200.]);
}

#[test]
fn photo_filter_preserve_luminosity_shifts_then_clips_toward_luminosity() {
assert_close(run_photo_filter([20., 20., 20.], [255., 0., 0.], 100., true), [34., 14., 14.]);
assert_close(run_photo_filter([160., 160., 160.], [255., 0., 0.], 100., true), [255., 120., 120.]);
assert_close(run_photo_filter([90., 90., 90.], [236., 138., 0.], 25., true), [95., 88., 85.]);
}
}
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