ocr 0.1.0

A minimalist OCR library for Rust — from scratch, no external engine
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

pub const FONT_WIDTH: usize = 5;
pub const FONT_HEIGHT: usize = 7;

pub type GlyphData = [u8; FONT_HEIGHT];

pub fn glyph(c: char) -> Option<GlyphData> {
    Some(match c {
        ' ' => [0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00],
        '!' => [0x04, 0x04, 0x04, 0x04, 0x04, 0x00, 0x06],
        '"' => [0x0A, 0x0A, 0x00, 0x00, 0x00, 0x00, 0x00],
        '#' => [0x0A, 0x0A, 0x1F, 0x0A, 0x1F, 0x0A, 0x0A],
        '$' => [0x04, 0x0F, 0x14, 0x0E, 0x05, 0x1E, 0x04],
        '%' => [0x18, 0x19, 0x02, 0x04, 0x08, 0x13, 0x03],
        '&' => [0x08, 0x14, 0x14, 0x08, 0x15, 0x12, 0x0D],
        '\'' => [0x04, 0x04, 0x00, 0x00, 0x00, 0x00, 0x00],
        '(' => [0x02, 0x04, 0x08, 0x08, 0x08, 0x04, 0x02],
        ')' => [0x08, 0x04, 0x02, 0x02, 0x02, 0x04, 0x08],
        '*' => [0x00, 0x04, 0x15, 0x0E, 0x15, 0x04, 0x00],
        '+' => [0x00, 0x04, 0x04, 0x1F, 0x04, 0x04, 0x00],
        ',' => [0x00, 0x00, 0x00, 0x00, 0x00, 0x0C, 0x08],
        '-' => [0x00, 0x00, 0x00, 0x1F, 0x00, 0x00, 0x00],
        '.' => [0x00, 0x00, 0x00, 0x00, 0x06, 0x06, 0x06],
        '/' => [0x01, 0x02, 0x04, 0x08, 0x10, 0x00, 0x00],
        '0' => [0x0E, 0x11, 0x13, 0x15, 0x19, 0x11, 0x0E],
        '1' => [0x04, 0x0C, 0x04, 0x04, 0x04, 0x04, 0x0E],
        '2' => [0x0E, 0x11, 0x01, 0x02, 0x04, 0x08, 0x1F],
        '3' => [0x0E, 0x11, 0x01, 0x06, 0x01, 0x11, 0x0E],
        '4' => [0x02, 0x06, 0x0A, 0x12, 0x1F, 0x02, 0x02],
        '5' => [0x1F, 0x10, 0x1E, 0x01, 0x01, 0x11, 0x0E],
        '6' => [0x06, 0x08, 0x10, 0x1E, 0x11, 0x11, 0x0E],
        '7' => [0x1F, 0x01, 0x02, 0x04, 0x08, 0x08, 0x08],
        '8' => [0x0E, 0x11, 0x11, 0x0E, 0x11, 0x11, 0x0E],
        '9' => [0x0E, 0x11, 0x11, 0x0F, 0x01, 0x02, 0x0C],
        ':' => [0x00, 0x00, 0x04, 0x00, 0x04, 0x00, 0x00],
        ';' => [0x00, 0x00, 0x04, 0x00, 0x04, 0x08, 0x00],
        '<' => [0x02, 0x04, 0x08, 0x10, 0x08, 0x04, 0x02],
        '=' => [0x00, 0x00, 0x1F, 0x00, 0x1F, 0x00, 0x00],
        '>' => [0x08, 0x04, 0x02, 0x01, 0x02, 0x04, 0x08],
        '?' => [0x0E, 0x11, 0x01, 0x02, 0x04, 0x00, 0x04],
        '@' => [0x0E, 0x11, 0x17, 0x15, 0x17, 0x10, 0x0E],
        'A' => [0x0E, 0x11, 0x11, 0x1F, 0x11, 0x11, 0x11],
        'B' => [0x1E, 0x11, 0x11, 0x1E, 0x11, 0x11, 0x1E],
        'C' => [0x0E, 0x11, 0x10, 0x10, 0x10, 0x11, 0x0E],
        'D' => [0x1C, 0x12, 0x11, 0x11, 0x11, 0x12, 0x1C],
        'E' => [0x1F, 0x10, 0x10, 0x1E, 0x10, 0x10, 0x1F],
        'F' => [0x1F, 0x10, 0x10, 0x1E, 0x10, 0x10, 0x10],
        'G' => [0x0E, 0x11, 0x10, 0x17, 0x11, 0x11, 0x0F],
        'H' => [0x11, 0x11, 0x11, 0x1F, 0x11, 0x11, 0x11],
        'I' => [0x0E, 0x04, 0x04, 0x04, 0x04, 0x04, 0x0E],
        'J' => [0x07, 0x02, 0x02, 0x02, 0x02, 0x12, 0x0C],
        'K' => [0x11, 0x12, 0x14, 0x18, 0x14, 0x12, 0x11],
        'L' => [0x10, 0x10, 0x10, 0x10, 0x10, 0x10, 0x1F],
        'M' => [0x11, 0x1B, 0x15, 0x15, 0x11, 0x11, 0x11],
        'N' => [0x11, 0x19, 0x15, 0x13, 0x11, 0x11, 0x11],
        'O' => [0x0E, 0x11, 0x11, 0x11, 0x11, 0x11, 0x0E],
        'P' => [0x1E, 0x11, 0x11, 0x1E, 0x10, 0x10, 0x10],
        'Q' => [0x0E, 0x11, 0x11, 0x11, 0x15, 0x12, 0x0D],
        'R' => [0x1E, 0x11, 0x11, 0x1E, 0x14, 0x12, 0x11],
        'S' => [0x0E, 0x11, 0x10, 0x0E, 0x01, 0x11, 0x0E],
        'T' => [0x1F, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04],
        'U' => [0x11, 0x11, 0x11, 0x11, 0x11, 0x11, 0x0E],
        'V' => [0x11, 0x11, 0x11, 0x11, 0x0A, 0x0A, 0x04],
        'W' => [0x11, 0x11, 0x11, 0x15, 0x15, 0x1B, 0x11],
        'X' => [0x11, 0x11, 0x0A, 0x04, 0x0A, 0x11, 0x11],
        'Y' => [0x11, 0x11, 0x0A, 0x04, 0x04, 0x04, 0x04],
        'Z' => [0x1F, 0x01, 0x02, 0x04, 0x08, 0x10, 0x1F],
        '[' => [0x0E, 0x08, 0x08, 0x08, 0x08, 0x08, 0x0E],
        '\\' => [0x10, 0x08, 0x04, 0x02, 0x01, 0x00, 0x00],
        ']' => [0x0E, 0x02, 0x02, 0x02, 0x02, 0x02, 0x0E],
        '^' => [0x04, 0x0A, 0x11, 0x00, 0x00, 0x00, 0x00],
        '_' => [0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x1F],
        '`' => [0x08, 0x04, 0x00, 0x00, 0x00, 0x00, 0x00],
        'a' => [0x08, 0x04, 0x0E, 0x01, 0x0F, 0x11, 0x0F],
        'b' => [0x18, 0x10, 0x1E, 0x11, 0x11, 0x11, 0x1E],
        'c' => [0x00, 0x00, 0x0E, 0x11, 0x10, 0x11, 0x0E],
        'd' => [0x03, 0x01, 0x0F, 0x11, 0x11, 0x11, 0x0F],
        'e' => [0x00, 0x00, 0x0E, 0x11, 0x1F, 0x10, 0x0E],
        'f' => [0x03, 0x04, 0x08, 0x1E, 0x08, 0x08, 0x08],
        'g' => [0x00, 0x0F, 0x11, 0x11, 0x0F, 0x01, 0x0E],
        'h' => [0x18, 0x10, 0x1E, 0x11, 0x11, 0x11, 0x11],
        'i' => [0x00, 0x0C, 0x00, 0x0E, 0x04, 0x04, 0x0E],
        'j' => [0x00, 0x06, 0x00, 0x06, 0x02, 0x12, 0x0C],
        'k' => [0x10, 0x10, 0x12, 0x14, 0x18, 0x14, 0x12],
        'l' => [0x06, 0x0C, 0x04, 0x04, 0x04, 0x0C, 0x06],
        'm' => [0x00, 0x00, 0x1A, 0x15, 0x15, 0x15, 0x15],
        'n' => [0x00, 0x00, 0x1E, 0x11, 0x11, 0x11, 0x11],
        'o' => [0x00, 0x00, 0x0E, 0x11, 0x11, 0x11, 0x0E],
        'p' => [0x00, 0x00, 0x1E, 0x11, 0x11, 0x1E, 0x10],
        'q' => [0x00, 0x00, 0x0F, 0x11, 0x11, 0x0F, 0x01],
        'r' => [0x00, 0x00, 0x16, 0x19, 0x10, 0x10, 0x10],
        's' => [0x00, 0x00, 0x0E, 0x10, 0x0E, 0x01, 0x0E],
        't' => [0x08, 0x08, 0x1E, 0x08, 0x08, 0x08, 0x06],
        'u' => [0x00, 0x00, 0x11, 0x11, 0x11, 0x11, 0x0F],
        'v' => [0x00, 0x00, 0x11, 0x11, 0x11, 0x0A, 0x04],
        'w' => [0x00, 0x00, 0x11, 0x11, 0x15, 0x15, 0x0A],
        'x' => [0x00, 0x00, 0x11, 0x0A, 0x04, 0x0A, 0x11],
        'y' => [0x00, 0x00, 0x11, 0x11, 0x0F, 0x01, 0x0E],
        'z' => [0x00, 0x00, 0x1F, 0x02, 0x04, 0x08, 0x1F],
        '{' => [0x02, 0x04, 0x04, 0x08, 0x04, 0x04, 0x02],
        '|' => [0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04],
        '}' => [0x08, 0x04, 0x04, 0x02, 0x04, 0x04, 0x08],
        '~' => [0x00, 0x00, 0x08, 0x15, 0x02, 0x00, 0x00],
        _ => return None,
    })
}

pub fn glyph_to_pixels(data: &GlyphData) -> [[bool; FONT_WIDTH]; FONT_HEIGHT] {
    let mut pixels = [[false; FONT_WIDTH]; FONT_HEIGHT];
    for y in 0..FONT_HEIGHT {
        for x in 0..FONT_WIDTH {
            pixels[y][x] = (data[y] >> (FONT_WIDTH - 1 - x)) & 1 == 1;
        }
    }
    pixels
}

pub fn supported_chars() -> &'static [char] {
    &[
        ' ', '!', '"', '#', '$', '%', '&', '\'', '(', ')', '*', '+', ',', '-', '.', '/',
        '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
        ':', ';', '<', '=', '>', '?', '@',
        'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M',
        'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z',
        '[', '\\', ']', '^', '_', '`',
        'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm',
        'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',
        '{', '|', '}', '~',
    ]
}

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

    #[test]
    fn all_supported_chars_have_glyphs() {
        for &c in supported_chars() {
            assert!(glyph(c).is_some(), "missing glyph for '{}'", c);
        }
    }

    #[test]
    fn glyph_pixel_roundtrip() {
        let data = glyph('A').unwrap();
        let pixels = glyph_to_pixels(&data);
        // Row 0 of 'A' is 0x0E = 01110 → [false, true, true, true, false]
        assert_eq!(pixels[0], [false, true, true, true, false]);
        // Row 3 of 'A' is 0x1F = 11111 → all true
        assert_eq!(pixels[3], [true, true, true, true, true]);
    }

    #[test]
    fn space_is_all_zeros() {
        let data = glyph(' ').unwrap();
        assert!(data.iter().all(|&b| b == 0));
    }

    #[test]
    fn unsupported_char_returns_none() {
        assert!(glyph('á').is_none());
        assert!(glyph('中').is_none());
    }
}