1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310

#[cfg(feature = "serialize")]
use serde::{Deserialize, Serialize};

#[cfg(feature = "rand")]
pub mod sample;

#[derive(Debug, Clone, Copy)]
#[cfg_attr(feature = "serialize", derive(Serialize, Deserialize))]
pub struct WeightsU16 {
    r: u16,
    g: u16,
    b: u16,
    sum: u32,
}

impl WeightsU16 {
    pub const fn new(r: u16, g: u16, b: u16) -> Self {
        Self {
            r,
            g,
            b,
            sum: r as u32 + g as u32 + b as u32,
        }
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
#[cfg_attr(feature = "serialize", derive(Serialize, Deserialize))]
pub struct Rgb24 {
    pub r: u8,
    pub g: u8,
    pub b: u8,
}

impl Rgb24 {
    pub const fn new(r: u8, g: u8, b: u8) -> Self {
        Self { r, g, b }
    }
    pub const fn new_grey(c: u8) -> Self {
        Self::new(c, c, c)
    }
    pub fn floor(self, min: u8) -> Self {
        Self {
            r: self.r.max(min),
            g: self.g.max(min),
            b: self.b.max(min),
        }
    }
    pub fn ceil(self, max: u8) -> Self {
        Self {
            r: self.r.min(max),
            g: self.g.min(max),
            b: self.b.min(max),
        }
    }
    pub fn to_f32_rgb(self) -> [f32; 3] {
        [
            self.r as f32 / 255.,
            self.g as f32 / 255.,
            self.b as f32 / 255.,
        ]
    }
    pub fn to_f32_rgba(self, alpha: f32) -> [f32; 4] {
        [
            self.r as f32 / 255.,
            self.g as f32 / 255.,
            self.b as f32 / 255.,
            alpha,
        ]
    }
    pub fn saturating_add(self, other: Self) -> Self {
        Self {
            r: self.r.saturating_add(other.r),
            g: self.g.saturating_add(other.g),
            b: self.b.saturating_add(other.b),
        }
    }
    pub fn saturating_sub(self, other: Self) -> Self {
        Self {
            r: self.r.saturating_sub(other.r),
            g: self.g.saturating_sub(other.g),
            b: self.b.saturating_sub(other.b),
        }
    }
    pub fn saturating_scalar_mul(self, scalar: u32) -> Self {
        fn single_channel(channel: u8, scalar: u32) -> u8 {
            let as_u32 = channel as u32 * scalar;
            as_u32.min(::std::u8::MAX as u32) as u8
        }
        Self {
            r: single_channel(self.r, scalar),
            g: single_channel(self.g, scalar),
            b: single_channel(self.b, scalar),
        }
    }
    pub fn scalar_div(self, scalar: u32) -> Self {
        fn single_channel(channel: u8, scalar: u32) -> u8 {
            let as_u32 = channel as u32 / scalar;
            as_u32.min(::std::u8::MAX as u32) as u8
        }
        Self {
            r: single_channel(self.r, scalar),
            g: single_channel(self.g, scalar),
            b: single_channel(self.b, scalar),
        }
    }
    pub fn saturating_scalar_mul_div(self, numerator: u32, denominator: u32) -> Self {
        fn single_channel(channel: u8, numerator: u32, denominator: u32) -> u8 {
            let as_u32 = ((channel as u32) * (numerator)) / denominator;
            as_u32.min(::std::u8::MAX as u32) as u8
        }
        Self {
            r: single_channel(self.r, numerator, denominator),
            g: single_channel(self.g, numerator, denominator),
            b: single_channel(self.b, numerator, denominator),
        }
    }
    pub const fn normalised_mul(self, other: Self) -> Self {
        const fn single_channel(a: u8, b: u8) -> u8 {
            ((a as u32 * b as u32) / 255) as u8
        }
        Self {
            r: single_channel(self.r, other.r),
            g: single_channel(self.g, other.g),
            b: single_channel(self.b, other.b),
        }
    }
    pub const fn normalised_scalar_mul(self, scalar: u8) -> Self {
        const fn single_channel(c: u8, scalar: u8) -> u8 {
            ((c as u32 * scalar as u32) / 255) as u8
        }
        Self {
            r: single_channel(self.r, scalar),
            g: single_channel(self.g, scalar),
            b: single_channel(self.b, scalar),
        }
    }
    pub const fn linear_interpolate(self, to: Rgb24, by: u8) -> Self {
        const fn interpolate_channel(from: u8, to: u8, by: u8) -> u8 {
            let total_delta = to as i32 - from as i32;
            let current_delta = (total_delta * by as i32) / 255;
            (from as i32 + current_delta) as u8
        }
        Self {
            r: interpolate_channel(self.r, to.r, by),
            g: interpolate_channel(self.g, to.g, by),
            b: interpolate_channel(self.b, to.b, by),
        }
    }
    pub fn min_channel(self) -> u8 {
        self.r.min(self.g).min(self.b)
    }
    pub fn max_channel(self) -> u8 {
        self.r.max(self.g).max(self.b)
    }
    pub fn saturating_channel_total(self) -> u8 {
        self.r.saturating_add(self.g).saturating_add(self.b)
    }
    pub const fn complement(self) -> Self {
        Self {
            r: 255 - self.r,
            g: 255 - self.g,
            b: 255 - self.b,
        }
    }
    pub const fn weighted_mean_u16(self, weights: WeightsU16) -> u8 {
        let weighted_sum = self.r as u32 * weights.r as u32
            + self.g as u32 * weights.g as u32
            + self.b as u32 * weights.b as u32;
        (weighted_sum / weights.sum) as u8
    }
}

#[cfg(test)]
mod test {
    use super::*;

    #[test]
    fn add() {
        let a = Rgb24::new(255, 0, 200);
        let b = Rgb24::new(0, 255, 200);
        let c = a.saturating_add(b);
        assert_eq!(c, Rgb24::new(255, 255, 255));
    }

    #[test]
    fn sub() {
        let a = Rgb24::new(255, 0, 200);
        let b = Rgb24::new(0, 255, 200);
        let c = a.saturating_sub(b);
        assert_eq!(c, Rgb24::new(255, 0, 0));
    }

    #[test]
    fn mul_div() {
        assert_eq!(
            Rgb24::new(1, 2, 3).saturating_scalar_mul_div(1500, 1000),
            Rgb24::new(1, 3, 4)
        );
        assert_eq!(
            Rgb24::new(1, 2, 3).saturating_scalar_mul_div(1500, 1),
            Rgb24::new(255, 255, 255)
        );
    }

    #[test]
    fn mul() {
        assert_eq!(
            Rgb24::new(20, 40, 60).saturating_scalar_mul(2),
            Rgb24::new(40, 80, 120),
        );
        assert_eq!(
            Rgb24::new(20, 40, 60).saturating_scalar_mul(10000),
            Rgb24::new(255, 255, 255),
        );
    }

    #[test]
    fn div() {
        assert_eq!(Rgb24::new(20, 40, 60).scalar_div(2), Rgb24::new(10, 20, 30));
        assert_eq!(
            Rgb24::new(255, 255, 255).scalar_div(256),
            Rgb24::new(0, 0, 0)
        );
    }

    #[test]
    #[should_panic]
    fn div_by_zero() {
        Rgb24::new(0, 0, 0).scalar_div(0);
    }

    #[test]
    fn normalised_mul() {
        assert_eq!(
            Rgb24::new(255, 255, 255).normalised_mul(Rgb24::new(1, 2, 3)),
            Rgb24::new(1, 2, 3)
        );
        assert_eq!(
            Rgb24::new(255, 127, 0).normalised_mul(Rgb24::new(10, 20, 30)),
            Rgb24::new(10, 9, 0)
        );
    }

    #[test]
    fn grey() {
        assert_eq!(Rgb24::new_grey(37), Rgb24::new(37, 37, 37));
    }

    #[test]
    fn floor() {
        assert_eq!(Rgb24::new(100, 5, 0).floor(10), Rgb24::new(100, 10, 10));
    }

    #[test]
    fn ceil() {
        assert_eq!(Rgb24::new(255, 250, 20).ceil(200), Rgb24::new(200, 200, 20));
    }

    #[test]
    fn normalised_scalar_mul() {
        assert_eq!(
            Rgb24::new(255, 128, 0).normalised_scalar_mul(128),
            Rgb24::new(128, 64, 0)
        );
    }

    #[test]
    fn interpolate() {
        let from = Rgb24::new(0, 255, 100);
        let to = Rgb24::new(255, 0, 120);
        assert_eq!(from.linear_interpolate(to, 0), from);
        assert_eq!(from.linear_interpolate(to, 255), to);
        assert_eq!(from.linear_interpolate(to, 63), Rgb24::new(63, 192, 104));
    }

    #[test]
    fn weighted_mean() {
        assert_eq!(
            Rgb24::new(14, 120, 201).weighted_mean_u16(WeightsU16::new(0, 0, 1)),
            201
        );
        assert_eq!(
            Rgb24::new(14, 120, 201).weighted_mean_u16(WeightsU16::new(299, 587, 114)),
            97
        );
        assert_eq!(
            Rgb24::new(0, 0, 0).weighted_mean_u16(WeightsU16::new(299, 587, 114)),
            0
        );
        assert_eq!(
            Rgb24::new(255, 255, 255).weighted_mean_u16(WeightsU16::new(299, 587, 114)),
            255
        );
        assert_eq!(
            Rgb24::new(255, 255, 255).weighted_mean_u16(WeightsU16::new(
                std::u16::MAX,
                std::u16::MAX,
                std::u16::MAX
            )),
            255
        );
    }

    #[test]
    #[should_panic]
    fn weighted_mean_zero() {
        Rgb24::new(1, 2, 3).weighted_mean_u16(WeightsU16::new(0, 0, 0));
    }
}