Raw-rs: add post-processing steps (#1923)

* add convert_to_rgb step

* add code to generate gamma correction curve

* add gamma correction step

* fix clippy warnings and cargo fmt

* remove unnecessary dependencies

* Code review 1

* Code review 2

* fix the order of operations

* Code review 3

---------

Co-authored-by: Keavon Chambers <keavon@keavon.com>

Author: elbertronnie

Cargo.lock

@@ -13,7 +13,7 @@ repository = "https://github.com/GraphiteEditor/Graphite/tree/master/libraries/r
 documentation = "https://docs.rs/raw-rs"
 
 [features]
-raw-rs-tests = ["dep:image", "dep:libraw-rs", "dep:palette", "dep:reqwest"]
+raw-rs-tests = ["dep:image", "dep:libraw-rs", "dep:reqwest"]
 
 [dependencies]
 # Local dependencies
@@ -33,4 +33,3 @@ reqwest = { workspace = true, optional = true }
 
 # Optional dependencies (should be dev dependencies, but Cargo currently doesn't allow optional dev dependencies)
 libraw-rs = { version = "0.0.4", optional = true }
-palette = { version = "0.7.6", optional = true }

libraries/raw-rs/Cargo.toml

@@ -26,7 +26,10 @@ pub fn decode_a100<R: Read + Seek>(ifd: Ifd, file: &mut TiffRead<R>) -> RawImage
 		#[allow(unreachable_code)]
 		maximum: (1 << 12) - 1,
 		black: SubtractBlack::None,
-		camera_to_xyz: None,
+		camera_model: None,
+		white_balance_multiplier: None,
+		camera_to_rgb: None,
+		rgb_to_camera: None,
 	}
 }
 

libraries/raw-rs/src/decoder/arw1.rs

@@ -49,7 +49,10 @@ pub fn decode<R: Read + Seek>(ifd: Ifd, file: &mut TiffRead<R>) -> RawImage {
 		cfa_pattern: ifd.cfa_pattern.try_into().unwrap(),
 		maximum: (1 << 14) - 1,
 		black: SubtractBlack::CfaGrid([512, 512, 512, 512]), // TODO: Find the correct way to do this
-		camera_to_xyz: None,
+		camera_model: None,
+		white_balance_multiplier: None,
+		camera_to_rgb: None,
+		rgb_to_camera: None,
 	}
 }
 

libraries/raw-rs/src/decoder/arw2.rs

@@ -57,6 +57,9 @@ pub fn decode<R: Read + Seek>(ifd: Ifd, file: &mut TiffRead<R>) -> RawImage {
 		cfa_pattern: ifd.cfa_pattern.try_into().unwrap(),
 		maximum: if bits_per_sample == 16 { u16::MAX } else { (1 << bits_per_sample) - 1 },
 		black: SubtractBlack::CfaGrid(ifd.black_level),
-		camera_to_xyz: None,
+		camera_model: None,
+		white_balance_multiplier: None,
+		camera_to_rgb: None,
+		rgb_to_camera: None,
 	}
 }

libraries/raw-rs/src/decoder/uncompressed.rs

@@ -73,5 +73,7 @@ fn linear_demosaic_rggb(mut raw_image: RawImage) -> Image<u16> {
 		data: raw_image.data,
 		width: raw_image.width,
 		height: raw_image.height,
+		rgb_to_camera: raw_image.rgb_to_camera,
+		histogram: None,
 	}
 }

libraries/raw-rs/src/demosaicing/linear_demosaicing.rs

@@ -1,10 +1,11 @@
 pub mod decoder;
 pub mod demosaicing;
 pub mod metadata;
+pub mod postprocessing;
 pub mod preprocessing;
 pub mod tiff;
 
-use crate::preprocessing::camera_data::camera_to_xyz;
+use crate::metadata::identify::CameraModel;
 
 use tag_derive::Tag;
 use tiff::file::TiffRead;
@@ -27,14 +28,21 @@ pub struct RawImage {
 	pub cfa_pattern: [u8; 4],
 	pub maximum: u16,
 	pub black: SubtractBlack,
-	pub camera_to_xyz: Option<[f64; 9]>,
+	pub camera_model: Option<CameraModel>,
+	pub white_balance_multiplier: Option<[f64; 3]>,
+	pub camera_to_rgb: Option<[[f64; 3]; 3]>,
+	pub rgb_to_camera: Option<[[f64; 3]; 3]>,
 }
 
 pub struct Image<T> {
 	pub data: Vec<T>,
 	pub width: usize,
 	pub height: usize,
+	/// We can assume this will be 3 for all non-obscure, modern cameras.
+	/// See <https://github.com/GraphiteEditor/Graphite/pull/1923#discussion_r1725070342> for more information.
 	pub channels: u8,
+	pub rgb_to_camera: Option<[[f64; 3]; 3]>,
+	pub histogram: Option<[[usize; 0x2000]; 3]>,
 }
 
 #[allow(dead_code)]
@@ -68,27 +76,32 @@ pub fn decode<R: Read + Seek>(reader: &mut R) -> Result<RawImage, DecoderError>
 		}
 	};
 
-	raw_image.camera_to_xyz = camera_to_xyz(&camera_model);
+	raw_image.camera_model = Some(camera_model);
 
 	Ok(raw_image)
 }
 
 pub fn process_8bit(raw_image: RawImage) -> Image<u8> {
-	let raw_image = crate::preprocessing::subtract_black::subtract_black(raw_image);
-	let raw_image = crate::preprocessing::raw_to_image::raw_to_image(raw_image);
-	let raw_image = crate::preprocessing::scale_colors::scale_colors(raw_image);
-	let image = crate::demosaicing::linear_demosaicing::linear_demosaic(raw_image);
+	let image = process_16bit(raw_image);
 
 	Image {
 		channels: image.channels,
 		data: image.data.iter().map(|x| (x >> 8) as u8).collect(),
 		width: image.width,
 		height: image.height,
+		rgb_to_camera: image.rgb_to_camera,
+		histogram: image.histogram,
 	}
 }
 
-pub fn process_16bit(_image: RawImage) -> Image<u16> {
-	todo!()
+pub fn process_16bit(raw_image: RawImage) -> Image<u16> {
+	let raw_image = crate::preprocessing::camera_data::calculate_conversion_matrices(raw_image);
+	let raw_image = crate::preprocessing::subtract_black::subtract_black(raw_image);
+	let raw_image = crate::preprocessing::raw_to_image::raw_to_image(raw_image);
+	let raw_image = crate::preprocessing::scale_colors::scale_colors(raw_image);
+	let image = crate::demosaicing::linear_demosaicing::linear_demosaic(raw_image);
+	let image = crate::postprocessing::convert_to_rgb::convert_to_rgb(image);
+	crate::postprocessing::gamma_correction::gamma_correction(image)
 }
 
 #[derive(Error, Debug)]

libraries/raw-rs/src/lib.rs

@@ -0,0 +1,40 @@
+use crate::Image;
+
+const CHANNELS_IN_RGB: usize = 3;
+
+pub fn convert_to_rgb(mut image: Image<u16>) -> Image<u16> {
+	let Some(rgb_to_camera) = image.rgb_to_camera else { return image };
+
+	// Rarely this might be 4 instead of 3 if an obscure Bayer filter is used, such as RGBE or CYGM, instead of the typical RGGB.
+	// See: <https://github.com/GraphiteEditor/Graphite/pull/1923#discussion_r1725070342>.
+	let channels = image.channels as usize;
+	let mut data = Vec::with_capacity(CHANNELS_IN_RGB * image.width * image.height);
+	let mut histogram = [[0; 0x2000]; CHANNELS_IN_RGB];
+
+	for i in 0..(image.height * image.width) {
+		let start = i * channels;
+		let end = start + channels;
+		let input_pixel = &mut image.data[start..end];
+
+		let mut output_pixel = [0.; CHANNELS_IN_RGB];
+		for (channel, &value) in input_pixel.iter().enumerate() {
+			output_pixel[0] += rgb_to_camera[0][channel] * value as f64;
+			output_pixel[1] += rgb_to_camera[1][channel] * value as f64;
+			output_pixel[2] += rgb_to_camera[2][channel] * value as f64;
+		}
+
+		for (output_pixel_channel, histogram_channel) in output_pixel.iter().zip(histogram.iter_mut()) {
+			let final_sum = (*output_pixel_channel as u16).clamp(0, u16::MAX);
+
+			histogram_channel[final_sum as usize >> CHANNELS_IN_RGB] += 1;
+
+			data.push(final_sum);
+		}
+	}
+
+	image.data = data;
+	image.histogram = Some(histogram);
+	image.channels = CHANNELS_IN_RGB as u8;
+
+	image
+}

libraries/raw-rs/src/postprocessing/convert_to_rgb.rs

@@ -0,0 +1,89 @@
+use crate::Image;
+use std::f64::consts::E;
+
+pub fn gamma_correction(mut image: Image<u16>) -> Image<u16> {
+	let Some(histogram) = image.histogram else { return image };
+
+	let percentage = image.width * image.height;
+
+	let mut white = 0;
+	for channel_histogram in histogram {
+		let mut total = 0;
+		for i in (0x20..0x2000).rev() {
+			total += channel_histogram[i] as u64;
+
+			if total * 100 > percentage as u64 {
+				white = white.max(i);
+				break;
+			}
+		}
+	}
+
+	let curve = generate_gamma_curve(0.45, 4.5, (white << 3) as f64);
+
+	for value in image.data.iter_mut() {
+		*value = curve[*value as usize];
+	}
+	image.histogram = None;
+
+	image
+}
+
+/// `max_intensity` must be non-zero.
+fn generate_gamma_curve(power: f64, threshold: f64, max_intensity: f64) -> Vec<u16> {
+	debug_assert!(max_intensity != 0.);
+
+	let (mut bound_start, mut bound_end) = if threshold >= 1. { (0., 1.) } else { (1., 0.) };
+
+	let mut transition_point = 0.;
+	let mut transition_ratio = 0.;
+	let mut curve_adjustment = 0.;
+
+	if threshold != 0. && (threshold - 1.) * (power - 1.) <= 0. {
+		for _ in 0..48 {
+			transition_point = (bound_start + bound_end) / 2.;
+
+			if power != 0. {
+				let temp_transition_ratio = transition_point / threshold;
+				let exponential_power = temp_transition_ratio.powf(-power);
+				let normalized_exponential_power = (exponential_power - 1.) / power;
+				let comparison_result = normalized_exponential_power - (1. / transition_point);
+
+				let bound_to_update = if comparison_result > -1. { &mut bound_end } else { &mut bound_start };
+				*bound_to_update = transition_point;
+			} else {
+				let adjusted_transition_point = E.powf(1. - 1. / transition_point);
+				let transition_point_ratio = transition_point / adjusted_transition_point;
+
+				let bound_to_update = if transition_point_ratio < threshold { &mut bound_end } else { &mut bound_start };
+				*bound_to_update = transition_point;
+			}
+		}
+
+		transition_ratio = transition_point / threshold;
+
+		if power != 0. {
+			curve_adjustment = transition_point * ((1. / power) - 1.);
+		}
+	}
+
+	let mut curve = vec![0xffff; 0x1_0000];
+	let length = curve.len() as f64;
+
+	for (i, entry) in curve.iter_mut().enumerate() {
+		let ratio = (i as f64) / max_intensity;
+		if ratio < 1. {
+			let altered_ratio = if ratio < transition_ratio {
+				ratio * threshold
+			} else if power != 0. {
+				ratio.powf(power) * (1. + curve_adjustment) - curve_adjustment
+			} else {
+				ratio.ln() * transition_point + 1.
+			};
+
+			*entry = (length * altered_ratio) as u16;
+		}
+	}
+
+	curve
+}

libraries/raw-rs/src/postprocessing/gamma_correction.rs

@@ -0,0 +1,2 @@
+pub mod convert_to_rgb;
+pub mod gamma_correction;