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DarkRoom/core/dr-gpu/src/grain.rs
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dtourolle 8ea3c3181a Upload the learned demosaic's result, and blend grain back into it
DemosaicedImage::from_rgb_f32 takes the network's linear camera RGB and
stands it beside the classical source of the same photograph: the matrix,
profile tables and as-shot balance are that source's, the id is new, so
nothing downstream can tell which demosaic ran and every cache keyed on the
source sees a new one.

GrainBlend is the denoise's live control. It returns only the brightness of
the noise the network removed, taken after the as-shot balance and handed
back divided by it, so the grain is neutral in the finished picture; colour
speckle and demosaic false colour stay out. It writes a new source rather
than adding a term to the adjust shader: the blend depends on two images and
one number, a 20 MP pass is milliseconds, and a fresh source id is all the
adjust pass's caches need. The test reads it back: at 0 the network's
result, at 1 the same white-balanced step in every channel.
2026-10-03 11:20:48 -04:00

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//! TRACES: FR-DEV-3g
//! Grain back into a denoised photograph, as brightness only.
//!
//! The learned denoise's one live control. The network's result and the
//! classical demosaic of the same mosaic differ by the noise the network
//! removed — plus the classical path's colour speckle and demosaic false
//! colour, which nobody wants back. So only the brightness of the difference
//! is returned, in proportion to `grain`:
//!
//! `out = denoised + grain · ΔY / wb`, with `ΔY = Y(wb · (classical − denoised))`
//!
//! `Y` is taken after the as-shot balance and handed back divided by it, so
//! the grain is neutral in the finished picture rather than tinted the
//! colour of the sensor's raw response. At 0 the result is the network's
//! exactly; at 1 the brightness noise is all back, the colour noise none.
//!
//! A pass of its own producing a new source rather than a term in the
//! adjust shader: the blend depends only on the two images and one number,
//! a 20 MP pass is a few milliseconds, and a new source id is all the
//! adjust pass's caches need to know it changed.
use std::sync::Arc;
use crate::demosaic::DemosaicedImage;
use crate::{GpuContext, GpuError};
const SHADER: &str = r#"
struct Params {
grain: f32,
_pad0: f32,
_pad1: f32,
_pad2: f32,
wb: vec4<f32>,
}
@group(0) @binding(0) var denoised: texture_2d<f32>;
@group(0) @binding(1) var classical: texture_2d<f32>;
@group(0) @binding(2) var<uniform> p: Params;
@group(0) @binding(3) var out: texture_storage_2d<rgba16float, write>;
@compute @workgroup_size(8, 8)
fn main(@builtin(global_invocation_id) gid: vec3<u32>) {
let dims = textureDimensions(denoised);
if (gid.x >= dims.x || gid.y >= dims.y) {
return;
}
let xy = vec2<i32>(gid.xy);
let d = textureLoad(denoised, xy, 0).rgb;
let c = textureLoad(classical, xy, 0).rgb;
let wb = p.wb.rgb;
let dy = p.grain * dot(vec3<f32>(0.2126, 0.7152, 0.0722), wb * (c - d));
textureStore(out, xy, vec4<f32>(d + dy / wb, 1.0));
}
"#;
#[repr(C)]
#[derive(Copy, Clone, bytemuck::Pod, bytemuck::Zeroable)]
struct Params {
grain: f32,
_pad: [f32; 3],
wb: [f32; 4],
}
pub struct GrainBlend {
ctx: GpuContext,
pipeline: wgpu::ComputePipeline,
layout: wgpu::BindGroupLayout,
}
impl GrainBlend {
pub fn new(ctx: &GpuContext) -> Self {
let device = &ctx.device;
let module = device.create_shader_module(wgpu::ShaderModuleDescriptor {
label: Some("grain-blend"),
source: wgpu::ShaderSource::Wgsl(SHADER.into()),
});
let texture = |binding| wgpu::BindGroupLayoutEntry {
binding,
visibility: wgpu::ShaderStages::COMPUTE,
ty: wgpu::BindingType::Texture {
sample_type: wgpu::TextureSampleType::Float { filterable: false },
view_dimension: wgpu::TextureViewDimension::D2,
multisampled: false,
},
count: None,
};
let layout = device.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
label: Some("grain-blend-layout"),
entries: &[
texture(0),
texture(1),
wgpu::BindGroupLayoutEntry {
binding: 2,
visibility: wgpu::ShaderStages::COMPUTE,
ty: wgpu::BindingType::Buffer {
ty: wgpu::BufferBindingType::Uniform,
has_dynamic_offset: false,
min_binding_size: None,
},
count: None,
},
wgpu::BindGroupLayoutEntry {
binding: 3,
visibility: wgpu::ShaderStages::COMPUTE,
ty: wgpu::BindingType::StorageTexture {
access: wgpu::StorageTextureAccess::WriteOnly,
format: DemosaicedImage::FORMAT,
view_dimension: wgpu::TextureViewDimension::D2,
},
count: None,
},
],
});
let pipeline_layout = device.create_pipeline_layout(&wgpu::PipelineLayoutDescriptor {
label: Some("grain-blend-pipeline-layout"),
bind_group_layouts: &[Some(&layout)],
immediate_size: 0,
});
let pipeline = device.create_compute_pipeline(&wgpu::ComputePipelineDescriptor {
label: Some("grain-blend"),
layout: Some(&pipeline_layout),
module: &module,
entry_point: Some("main"),
compilation_options: Default::default(),
cache: None,
});
Self {
ctx: ctx.clone(),
pipeline,
layout,
}
}
/// `denoised` with `grain` (0–1) of `classical`'s brightness noise back.
/// Both must be the same photograph at the same size.
pub fn blend(
&self,
denoised: &DemosaicedImage,
classical: &DemosaicedImage,
grain: f32,
) -> Result<Arc<DemosaicedImage>, GpuError> {
let (w, h) = (denoised.texture().width(), denoised.texture().height());
if (classical.texture().width(), classical.texture().height()) != (w, h) {
return Err(GpuError::TooLarge(format!(
"grain from a {}×{} source into a {w}×{h} one",
classical.texture().width(),
classical.texture().height()
)));
}
let device = &self.ctx.device;
let texture = device.create_texture(&wgpu::TextureDescriptor {
label: Some("grain-blended-source"),
size: wgpu::Extent3d {
width: w,
height: h,
depth_or_array_layers: 1,
},
mip_level_count: 1,
sample_count: 1,
dimension: wgpu::TextureDimension::D2,
format: DemosaicedImage::FORMAT,
usage: wgpu::TextureUsages::STORAGE_BINDING
| wgpu::TextureUsages::TEXTURE_BINDING
| wgpu::TextureUsages::COPY_SRC,
view_formats: &[],
});
let out_view = texture.create_view(&Default::default());
let wb = denoised.as_shot_wb();
let g = wb[1].max(1e-6);
let params = Params {
grain: grain.clamp(0.0, 1.0),
_pad: [0.0; 3],
// Green-normalised, and never zero: the shader divides by it.
wb: [(wb[0] / g).max(1e-3), 1.0, (wb[2] / g).max(1e-3), 1.0],
};
use wgpu::util::DeviceExt;
let buffer = device.create_buffer_init(&wgpu::util::BufferInitDescriptor {
label: Some("grain-blend-params"),
contents: bytemuck::bytes_of(&params),
usage: wgpu::BufferUsages::UNIFORM,
});
let bind = device.create_bind_group(&wgpu::BindGroupDescriptor {
label: Some("grain-blend-bg"),
layout: &self.layout,
entries: &[
wgpu::BindGroupEntry {
binding: 0,
resource: wgpu::BindingResource::TextureView(denoised.view()),
},
wgpu::BindGroupEntry {
binding: 1,
resource: wgpu::BindingResource::TextureView(classical.view()),
},
wgpu::BindGroupEntry {
binding: 2,
resource: buffer.as_entire_binding(),
},
wgpu::BindGroupEntry {
binding: 3,
resource: wgpu::BindingResource::TextureView(&out_view),
},
],
});
let mut enc = device.create_command_encoder(&wgpu::CommandEncoderDescriptor {
label: Some("grain-blend"),
});
{
let mut pass = enc.begin_compute_pass(&wgpu::ComputePassDescriptor {
label: Some("grain-blend"),
timestamp_writes: None,
});
pass.set_pipeline(&self.pipeline);
pass.set_bind_group(0, &bind, &[]);
pass.dispatch_workgroups(w.div_ceil(8), h.div_ceil(8), 1);
}
self.ctx.queue.submit(Some(enc.finish()));
Ok(Arc::new(denoised.sibling(texture, w, h)))
}
}