pic_scale/colors/
lch_scaler.rs

1/*
2 * Copyright (c) Radzivon Bartoshyk 3/2026. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without modification,
5 * are permitted provided that the following conditions are met:
6 *
7 * 1.  Redistributions of source code must retain the above copyright notice, this
8 * list of conditions and the following disclaimer.
9 *
10 * 2.  Redistributions in binary form must reproduce the above copyright notice,
11 * this list of conditions and the following disclaimer in the documentation
12 * and/or other materials provided with the distribution.
13 *
14 * 3.  Neither the name of the copyright holder nor the names of its
15 * contributors may be used to endorse or promote products derived from
16 * this software without specific prior written permission.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
19 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
20 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
21 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
22 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
23 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
24 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
25 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
26 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
27 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
28 */
29use crate::colors::common_splitter::{SplitPlanInterceptor, Splitter};
30use crate::plan::Resampling;
31use crate::validation::PicScaleError;
32use crate::{ImageSize, ImageStore, ImageStoreMut, ResamplingFunction, Scaler, ThreadingPolicy};
33use colorutils_rs::{
34    SRGB_TO_XYZ_D65, TransferFunction, XYZ_TO_SRGB_D65, lch_to_rgb, lch_with_alpha_to_rgba,
35    rgb_to_lch, rgba_to_lch_with_alpha,
36};
37use std::sync::Arc;
38
39#[derive(Debug, Copy, Clone)]
40/// Converts image to *CIE LCH(uv)* components scales it and convert back
41pub struct LChScaler {
42    pub(crate) scaler: Scaler,
43}
44
45struct LchRgbSplitter {}
46
47impl Splitter<u8, f32, 3> for LchRgbSplitter {
48    fn split(
49        &self,
50        from: &ImageStore<'_, u8, 3>,
51        into: &mut ImageStoreMut<'_, f32, 3>,
52    ) -> Result<(), PicScaleError> {
53        let mut dst_buffer = into.to_colorutils_buffer_mut();
54        rgb_to_lch(
55            &from.to_colorutils_buffer(),
56            &mut dst_buffer,
57            &SRGB_TO_XYZ_D65,
58            TransferFunction::Srgb,
59        )
60        .map_err(|x| PicScaleError::Generic(x.to_string()))
61    }
62
63    fn merge(
64        &self,
65        from: &ImageStore<'_, f32, 3>,
66        into: &mut ImageStoreMut<'_, u8, 3>,
67    ) -> Result<(), PicScaleError> {
68        let mut dst_buffer = into.to_colorutils_buffer_mut();
69        lch_to_rgb(
70            &from.to_colorutils_buffer(),
71            &mut dst_buffer,
72            &XYZ_TO_SRGB_D65,
73            TransferFunction::Srgb,
74        )
75        .map_err(|x| PicScaleError::Generic(x.to_string()))
76    }
77
78    fn bit_depth(&self) -> usize {
79        8
80    }
81}
82
83struct LchRgbaSplitter {}
84
85impl Splitter<u8, f32, 4> for LchRgbaSplitter {
86    fn split(
87        &self,
88        from: &ImageStore<'_, u8, 4>,
89        into: &mut ImageStoreMut<'_, f32, 4>,
90    ) -> Result<(), PicScaleError> {
91        let mut dst_buffer = into.to_colorutils_buffer_mut();
92        rgba_to_lch_with_alpha(
93            &from.to_colorutils_buffer(),
94            &mut dst_buffer,
95            &SRGB_TO_XYZ_D65,
96            TransferFunction::Srgb,
97        )
98        .map_err(|x| PicScaleError::Generic(x.to_string()))
99    }
100
101    fn merge(
102        &self,
103        from: &ImageStore<'_, f32, 4>,
104        into: &mut ImageStoreMut<'_, u8, 4>,
105    ) -> Result<(), PicScaleError> {
106        let mut dst_buffer = into.to_colorutils_buffer_mut();
107        lch_with_alpha_to_rgba(
108            &from.to_colorutils_buffer(),
109            &mut dst_buffer,
110            &XYZ_TO_SRGB_D65,
111            TransferFunction::Srgb,
112        )
113        .map_err(|x| PicScaleError::Generic(x.to_string()))
114    }
115
116    fn bit_depth(&self) -> usize {
117        8
118    }
119}
120
121impl LChScaler {
122    pub fn new(filter: ResamplingFunction) -> Self {
123        LChScaler {
124            scaler: Scaler::new(filter),
125        }
126    }
127}
128
129impl LChScaler {
130    pub fn set_threading_policy(&mut self, threading_policy: ThreadingPolicy) -> Self {
131        self.scaler.set_threading_policy(threading_policy);
132        *self
133    }
134
135    pub fn plan_rgb_resampling(
136        &self,
137        source_size: ImageSize,
138        target_size: ImageSize,
139    ) -> Result<Arc<Resampling<u8, 3>>, PicScaleError> {
140        let intercept = self
141            .scaler
142            .plan_rgb_resampling_f32(source_size, target_size)?;
143        let scratch_size = intercept.scratch_size();
144        Ok(Arc::new(SplitPlanInterceptor {
145            intercept,
146            splitter: Arc::new(LchRgbSplitter {}),
147            inner_scratch: scratch_size,
148        }))
149    }
150
151    pub fn plan_rgba_resampling(
152        &self,
153        source_size: ImageSize,
154        target_size: ImageSize,
155        premultiply_alpha: bool,
156    ) -> Result<Arc<Resampling<u8, 4>>, PicScaleError> {
157        let intercept =
158            self.scaler
159                .plan_rgba_resampling_f32(source_size, target_size, premultiply_alpha)?;
160        let scratch_size = intercept.scratch_size();
161        Ok(Arc::new(SplitPlanInterceptor {
162            intercept,
163            splitter: Arc::new(LchRgbaSplitter {}),
164            inner_scratch: scratch_size,
165        }))
166    }
167}
pic_scale/colors/lch_scaler.rs

pic_scale/colors/
lch_scaler.rs
