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

// gray.rs      Grayscale pixel format.
//
// Copyright (c) 2018-2019  Douglas P Lau
//
use crate::{
    Alpha, Channel, Ch8, Ch16, Ch32, Format, Opaque, PixModes, Translucent,
};

/// Gray pixel [Format](trait.Format.html), with optional
/// [Alpha](trait.Alpha.html) channel.
///
/// For types, see: [Gray8](type.Gray8.html), [Gray16](type.Gray16.html),
/// [Gray32](type.Gray32.html), [GrayAlpha8](type.GrayAlpha8.html),
/// [GrayAlpha16](type.GrayAlpha16.html), [GrayAlpha32](type.GrayAlpha32.html)
#[derive(Clone, Copy, Debug, Default, PartialEq)]
#[repr(C)]
pub struct Gray<C: Channel, A: Alpha> {
    value: C,
    alpha: A,
}

impl<C: Channel, A: Alpha> PixModes for Gray<C, A> { }

impl<C: Channel, A: Alpha> Iterator for Gray<C, A> {
    type Item = Self;

    fn next(&mut self) -> Option<Self::Item> {
        Some(*self)
    }
}

impl<C, A> From<u8> for Gray<C, A>
    where C: Channel, C: From<Ch8>, A: Alpha, A: From<Opaque<C>>
{
    /// Convert from a `u8` value.
    fn from(c: u8) -> Self {
        Gray::new(Ch8::new(c))
    }
}

impl<C: Channel, A: Alpha> Gray<C, A> {
    /// Create an [Opaque](struct.Opaque.html) gray value.
    pub fn new<H>(value: H) -> Self
        where C: From<H>, A: From<Opaque<C>>
    {
        let value = C::from(value);
        let alpha = A::from(Opaque::default());
        Gray { value, alpha }
    }
    /// Create a [Translucent](struct.Translucent.html) gray value.
    pub fn with_alpha<H>(value: H, alpha: H) -> Self
        where C: From<H>, A: From<C>
    {
        let value = C::from(value);
        let alpha = A::from(C::from(alpha));
        Gray { value, alpha }
    }
    /// Get the gray value.
    pub fn value(self) -> C {
        self.value
    }
    /// Get the alpha value.
    pub fn alpha(self) -> A {
        self.alpha
    }
}

impl<C, A> Format for Gray<C, A>
    where C: Channel, A: Alpha<Chan=C> + From<C>
{
    type Chan = C;

    /// Get *red*, *green*, *blue* and *alpha* `Channel`s
    fn rgba(self) -> [Self::Chan; 4] {
        [self.value, self.value, self.value, self.alpha.value()]
    }

    /// Make a pixel with given RGBA `Channel`s
    fn with_rgba(rgba: [Self::Chan; 4]) -> Self {
        let value = rgba[0].max(rgba[1]).max(rgba[2]); // FIXME
        let alpha = rgba[3];
        Gray::with_alpha(value, alpha)
    }

    /// Get channel-wise difference
    fn difference(self, rhs: Self) -> Self {
        let v = if self.value > rhs.value { self.value - rhs.value }
                else { rhs.value - self.value };
        let a = if self.alpha.value() > rhs.alpha.value() {
            self.alpha.value() - rhs.alpha.value()
        } else {
            rhs.alpha.value() - self.alpha.value()
        };
        Gray::with_alpha(v, a)
    }

    /// Check if all `Channel`s are within threshold
    fn within_threshold(self, rhs: Self) -> bool {
        self.value <= rhs.value &&
        self.alpha.value() <= rhs.alpha.value()
    }
}

/// [Opaque](struct.Opaque.html) 8-bit [Gray](struct.Gray.html) pixel
/// [Format](trait.Format.html).
pub type Gray8 = Gray<Ch8, Opaque<Ch8>>;

/// [Opaque](struct.Opaque.html) 16-bit [Gray](struct.Gray.html) pixel
/// [Format](trait.Format.html).
pub type Gray16 = Gray<Ch16, Opaque<Ch16>>;

/// [Opaque](struct.Opaque.html) 32-bit [Gray](struct.Gray.html) pixel
/// [Format](trait.Format.html).
pub type Gray32 = Gray<Ch32, Opaque<Ch32>>;

/// [Translucent](struct.Translucent.html) 8-bit [Gray](struct.Gray.html) pixel
/// [Format](trait.Format.html).
pub type GrayAlpha8 = Gray<Ch8, Translucent<Ch8>>;

/// [Translucent](struct.Translucent.html) 16-bit [Gray](struct.Gray.html) pixel
/// [Format](trait.Format.html).
pub type GrayAlpha16 = Gray<Ch16, Translucent<Ch16>>;

/// [Translucent](struct.Translucent.html) 32-bit [Gray](struct.Gray.html) pixel
/// [Format](trait.Format.html).
pub type GrayAlpha32 = Gray<Ch32, Translucent<Ch32>>;

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

    #[test]
    fn check_sizes() {
        assert_eq!(std::mem::size_of::<Gray8>(), 1);
        assert_eq!(std::mem::size_of::<Gray16>(), 2);
        assert_eq!(std::mem::size_of::<Gray32>(), 4);
        assert_eq!(std::mem::size_of::<GrayAlpha8>(), 2);
        assert_eq!(std::mem::size_of::<GrayAlpha16>(), 4);
        assert_eq!(std::mem::size_of::<GrayAlpha32>(), 8);
    }
}