use-aspect-ratio 0.0.1

Primitive aspect-ratio helpers
Documentation 
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

#![forbid(unsafe_code)]
//! Primitive aspect-ratio helpers.
//!
//! These helpers validate dimensions, simplify ratios, and perform small
//! tolerance checks.
//!
//! # Examples
//!
//! ```rust
//! use use_aspect_ratio::{AspectRatio, aspect_label, fits_aspect_ratio};
//!
//! let ratio = AspectRatio::new(1920, 1080).unwrap();
//!
//! assert!((ratio.ratio() - (16.0 / 9.0)).abs() < 1.0e-12);
//! assert_eq!(ratio.simplified().label(), "16:9");
//! assert_eq!(aspect_label(1920, 1080).unwrap(), "16:9");
//! assert!(fits_aspect_ratio(1920, 1080, 1280, 720, 0.001).unwrap());
//! ```

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct AspectRatio {
    width: u32,
    height: u32,
}

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum AspectRatioError {
    InvalidWidth,
    InvalidHeight,
    InvalidTolerance,
}

fn gcd(mut left: u32, mut right: u32) -> u32 {
    while right != 0 {
        let remainder = left % right;
        left = right;
        right = remainder;
    }

    left
}

fn validate_dimensions(width: u32, height: u32) -> Result<(u32, u32), AspectRatioError> {
    if width == 0 {
        return Err(AspectRatioError::InvalidWidth);
    }

    if height == 0 {
        return Err(AspectRatioError::InvalidHeight);
    }

    Ok((width, height))
}

fn validate_tolerance(tolerance: f64) -> Result<f64, AspectRatioError> {
    if !tolerance.is_finite() || tolerance < 0.0 {
        Err(AspectRatioError::InvalidTolerance)
    } else {
        Ok(tolerance)
    }
}

impl AspectRatio {
    pub fn new(width: u32, height: u32) -> Result<Self, AspectRatioError> {
        let (width, height) = validate_dimensions(width, height)?;
        Ok(Self { width, height })
    }

    #[must_use]
    pub fn width(&self) -> u32 {
        self.width
    }

    #[must_use]
    pub fn height(&self) -> u32 {
        self.height
    }

    #[must_use]
    pub fn ratio(&self) -> f64 {
        f64::from(self.width) / f64::from(self.height)
    }

    #[must_use]
    pub fn simplified(&self) -> Self {
        let divisor = gcd(self.width, self.height);

        Self {
            width: self.width / divisor,
            height: self.height / divisor,
        }
    }

    #[must_use]
    pub fn label(&self) -> String {
        let simplified = self.simplified();
        format!("{}:{}", simplified.width, simplified.height)
    }
}

pub fn aspect_ratio(width: u32, height: u32) -> Result<f64, AspectRatioError> {
    Ok(AspectRatio::new(width, height)?.ratio())
}

pub fn simplify_ratio(width: u32, height: u32) -> Result<(u32, u32), AspectRatioError> {
    let simplified = AspectRatio::new(width, height)?.simplified();
    Ok((simplified.width, simplified.height))
}

pub fn aspect_label(width: u32, height: u32) -> Result<String, AspectRatioError> {
    Ok(AspectRatio::new(width, height)?.label())
}

pub fn fits_aspect_ratio(
    width: u32,
    height: u32,
    target_width: u32,
    target_height: u32,
    tolerance: f64,
) -> Result<bool, AspectRatioError> {
    let tolerance = validate_tolerance(tolerance)?;
    let source = aspect_ratio(width, height)?;
    let target = aspect_ratio(target_width, target_height)?;

    Ok((source - target).abs() <= tolerance)
}

#[cfg(test)]
mod tests {
    use super::{AspectRatio, AspectRatioError, aspect_label, fits_aspect_ratio, simplify_ratio};

    #[test]
    fn simplifies_common_aspect_ratios() {
        let aspect = AspectRatio::new(1920, 1080).unwrap();

        assert_eq!(aspect.width(), 1920);
        assert_eq!(aspect.height(), 1080);
        assert!((aspect.ratio() - (16.0 / 9.0)).abs() < 1.0e-12);
        assert_eq!(aspect.simplified(), AspectRatio::new(16, 9).unwrap());
        assert_eq!(simplify_ratio(1920, 1080).unwrap(), (16, 9));
        assert_eq!(aspect_label(1920, 1080).unwrap(), "16:9");
    }

    #[test]
    fn checks_ratio_tolerance_matches() {
        assert!(fits_aspect_ratio(1920, 1080, 1280, 720, 0.001).unwrap());
        assert!(!fits_aspect_ratio(1920, 1080, 1024, 768, 0.001).unwrap());
    }

    #[test]
    fn rejects_invalid_ratio_inputs() {
        assert_eq!(
            AspectRatio::new(0, 1080),
            Err(AspectRatioError::InvalidWidth)
        );
        assert_eq!(
            AspectRatio::new(1920, 0),
            Err(AspectRatioError::InvalidHeight)
        );
        assert_eq!(
            fits_aspect_ratio(1920, 1080, 1280, 720, f64::NAN),
            Err(AspectRatioError::InvalidTolerance)
        );
    }
}