mirx 0.32.3

MIRX binary image format — flat & chunk-based container for ahead-of-time UI assets
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

/// On-disk discriminants are byte-stable once shipped. Naming and byte-order
/// match `mirui::ColorFormat` so reader output is zero-copy on the mirui side.
/// Discriminants are partitioned by family: `byte >> 4` identifies the family
/// (1 = indexed, 2 = alpha-only, 3 = luma, 4 = RGB565, 5 = RGB888, 6 = 32-bit),
/// leaving the rest of each 16-byte run open for same-family extensions.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
#[repr(u8)]
#[allow(non_camel_case_types)]
pub enum ColorFormat {
    I1 = 0x10,
    I2 = 0x11,
    I4 = 0x12,
    I8 = 0x13,

    A1 = 0x20,
    A2 = 0x21,
    A4 = 0x22,
    A8 = 0x23,

    L8 = 0x30,

    RGB565 = 0x40,
    RGB565Swapped = 0x41,
    RGB565A8 = 0x42,

    RGB888 = 0x50,

    XRGB8888 = 0x60,
    RGBA8888 = 0x61,
    BGRA8888 = 0x62,
}

/// Sentinel byte stored in the CHUNK header `primary_color_format` slot when
/// the chunk has no fixed pixel format (e.g. a VECTOR chunk).
pub const PRIMARY_FORMAT_NONE: u8 = 0xFF;

impl ColorFormat {
    pub const fn from_u8(b: u8) -> Option<Self> {
        Some(match b {
            0x10 => Self::I1,
            0x11 => Self::I2,
            0x12 => Self::I4,
            0x13 => Self::I8,
            0x20 => Self::A1,
            0x21 => Self::A2,
            0x22 => Self::A4,
            0x23 => Self::A8,
            0x30 => Self::L8,
            0x40 => Self::RGB565,
            0x41 => Self::RGB565Swapped,
            0x42 => Self::RGB565A8,
            0x50 => Self::RGB888,
            0x60 => Self::XRGB8888,
            0x61 => Self::RGBA8888,
            0x62 => Self::BGRA8888,
            _ => return None,
        })
    }

    pub const fn to_u8(self) -> u8 {
        self as u8
    }

    pub const fn palette_entries(self) -> Option<u32> {
        match self {
            Self::I1 => Some(2),
            Self::I2 => Some(4),
            Self::I4 => Some(16),
            Self::I8 => Some(256),
            _ => None,
        }
    }

    /// FLAT extra bytes; RGB565A8 intentionally uses the v1 no-padding alpha
    /// plane, so `stride` is ignored.
    pub const fn extra_size(self, width: u32, height: u32, _stride: u32) -> Option<u32> {
        match self {
            Self::I1 | Self::I2 | Self::I4 | Self::I8 => {
                let entries = match self {
                    Self::I1 => 2,
                    Self::I2 => 4,
                    Self::I4 => 16,
                    Self::I8 => 256,
                    _ => 0,
                };
                Some(entries * 4)
            }
            Self::RGB565A8 => match width.checked_mul(height) {
                Some(n) => Some(n),
                None => None,
            },
            _ => Some(0),
        }
    }
}

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

    #[test]
    fn round_trip_byte_values() {
        for byte in 0u8..=255 {
            if let Some(fmt) = ColorFormat::from_u8(byte) {
                assert_eq!(fmt.to_u8(), byte, "from_u8({byte:#x}) round-trips");
            }
        }
    }

    #[test]
    fn unknown_byte_is_none() {
        assert!(ColorFormat::from_u8(0x00).is_none());
        assert!(ColorFormat::from_u8(0x14).is_none());
        assert!(ColorFormat::from_u8(0x24).is_none());
        assert!(ColorFormat::from_u8(0x63).is_none());
        assert!(ColorFormat::from_u8(0xFF).is_none());
    }

    #[test]
    fn palette_entries_match_bpp() {
        assert_eq!(ColorFormat::I1.palette_entries(), Some(2));
        assert_eq!(ColorFormat::I2.palette_entries(), Some(4));
        assert_eq!(ColorFormat::I4.palette_entries(), Some(16));
        assert_eq!(ColorFormat::I8.palette_entries(), Some(256));
        assert_eq!(ColorFormat::RGB565.palette_entries(), None);
    }

    #[test]
    fn extra_size_for_indexed_formats() {
        assert_eq!(ColorFormat::I1.extra_size(64, 64, 8), Some(8));
        assert_eq!(ColorFormat::I2.extra_size(64, 64, 16), Some(16));
        assert_eq!(ColorFormat::I4.extra_size(64, 64, 32), Some(64));
        assert_eq!(ColorFormat::I8.extra_size(64, 64, 64), Some(1024));
    }

    #[test]
    fn extra_size_for_rgb565a8_is_alpha_plane() {
        assert_eq!(ColorFormat::RGB565A8.extra_size(16, 16, 32), Some(256));
    }

    #[test]
    fn extra_size_for_simple_formats_is_zero() {
        assert_eq!(ColorFormat::RGB565.extra_size(100, 50, 200), Some(0));
        assert_eq!(ColorFormat::RGBA8888.extra_size(1, 1, 4), Some(0));
        assert_eq!(ColorFormat::BGRA8888.extra_size(2, 2, 8), Some(0));
        assert_eq!(ColorFormat::A8.extra_size(8, 8, 8), Some(0));
    }
}