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(&self, from: &ImageStore<'_, u8, 3>, into: &mut ImageStoreMut<'_, f32, 3>) {
49        let lab_stride = into.width as u32 * 3u32 * size_of::<f32>() as u32;
50
51        rgb_to_lch(
52            from.buffer.as_ref(),
53            from.width as u32 * 3u32,
54            into.buffer.borrow_mut(),
55            lab_stride,
56            into.width as u32,
57            into.height as u32,
58            &SRGB_TO_XYZ_D65,
59            TransferFunction::Srgb,
60        );
61    }
62
63    fn merge(&self, from: &ImageStore<'_, f32, 3>, into: &mut ImageStoreMut<'_, u8, 3>) {
64        let new_lab_stride = into.width as u32 * 3 * size_of::<f32>() as u32;
65        lch_to_rgb(
66            from.buffer.as_ref(),
67            new_lab_stride,
68            into.buffer.borrow_mut(),
69            into.width as u32 * 3,
70            into.width as u32,
71            into.height as u32,
72            &XYZ_TO_SRGB_D65,
73            TransferFunction::Srgb,
74        );
75    }
76
77    fn bit_depth(&self) -> usize {
78        8
79    }
80}
81
82struct LchRgbaSplitter {}
83
84impl Splitter<u8, f32, 4> for LchRgbaSplitter {
85    fn split(&self, from: &ImageStore<'_, u8, 4>, into: &mut ImageStoreMut<'_, f32, 4>) {
86        let lab_stride = into.width as u32 * 4u32 * size_of::<f32>() as u32;
87
88        rgba_to_lch_with_alpha(
89            from.buffer.as_ref(),
90            from.width as u32 * 4u32,
91            into.buffer.borrow_mut(),
92            lab_stride,
93            into.width as u32,
94            into.height as u32,
95            &SRGB_TO_XYZ_D65,
96            TransferFunction::Srgb,
97        );
98    }
99
100    fn merge(&self, from: &ImageStore<'_, f32, 4>, into: &mut ImageStoreMut<'_, u8, 4>) {
101        let new_lab_stride = into.width as u32 * 4 * size_of::<f32>() as u32;
102        lch_with_alpha_to_rgba(
103            from.buffer.as_ref(),
104            new_lab_stride,
105            into.buffer.borrow_mut(),
106            into.width as u32 * 4,
107            into.width as u32,
108            into.height as u32,
109            &XYZ_TO_SRGB_D65,
110            TransferFunction::Srgb,
111        );
112    }
113
114    fn bit_depth(&self) -> usize {
115        8
116    }
117}
118
119impl LChScaler {
120    pub fn new(filter: ResamplingFunction) -> Self {
121        LChScaler {
122            scaler: Scaler::new(filter),
123        }
124    }
125}
126
127impl LChScaler {
128    pub fn set_threading_policy(&mut self, threading_policy: ThreadingPolicy) -> Self {
129        self.scaler.set_threading_policy(threading_policy);
130        *self
131    }
132
133    pub fn plan_rgb_resampling(
134        &self,
135        source_size: ImageSize,
136        target_size: ImageSize,
137    ) -> Result<Arc<Resampling<u8, 3>>, PicScaleError> {
138        let intercept = self
139            .scaler
140            .plan_rgb_resampling_f32(source_size, target_size)?;
141        let scratch_size = intercept.scratch_size();
142        Ok(Arc::new(SplitPlanInterceptor {
143            intercept,
144            splitter: Arc::new(LchRgbSplitter {}),
145            inner_scratch: scratch_size,
146        }))
147    }
148
149    pub fn plan_rgba_resampling(
150        &self,
151        source_size: ImageSize,
152        target_size: ImageSize,
153        premultiply_alpha: bool,
154    ) -> Result<Arc<Resampling<u8, 4>>, PicScaleError> {
155        let intercept =
156            self.scaler
157                .plan_rgba_resampling_f32(source_size, target_size, premultiply_alpha)?;
158        let scratch_size = intercept.scratch_size();
159        Ok(Arc::new(SplitPlanInterceptor {
160            intercept,
161            splitter: Arc::new(LchRgbaSplitter {}),
162            inner_scratch: scratch_size,
163        }))
164    }
165}
pic_scale/colors/lch_scaler.rs

pic_scale/colors/
lch_scaler.rs
