pdf-interpret 0.5.1

A crate for interpreting PDF files.
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

use crate::function::{Clamper, Values};
use pdf_syntax::object::Dict;
use pdf_syntax::object::Number;
use pdf_syntax::object::dict::keys::{C0, C1, N};
use smallvec::{SmallVec, smallvec};

/// A type 2 function (exponential function).
#[derive(Debug)]
pub(crate) struct Type2 {
    c0: Values,
    c1: Values,
    clamper: Clamper,
    n: f32,
}

impl Type2 {
    /// Create a new type 2 function.
    pub(crate) fn new(dict: &Dict<'_>) -> Option<Self> {
        let c0 = dict.get::<Values>(C0).unwrap_or(smallvec![0.0]);
        let c1 = dict.get::<Values>(C1).unwrap_or(smallvec![1.0]);
        let clamper = Clamper::new(dict)?;
        let n = dict.get::<Number>(N)?.as_f64() as f32;

        Some(Self { c0, c1, clamper, n })
    }

    /// Evaluate the function with the given input.
    pub(crate) fn eval(&self, input: f32) -> Values {
        let mut input = [input];
        self.clamper.clamp_input(&mut input);

        let mut out = self
            .c0
            .iter()
            .zip(self.c1.iter())
            .map(|(c0, c1)| *c0 + input[0].powf(self.n) * (*c1 - *c0))
            .collect::<SmallVec<_>>();

        self.clamper.clamp_output(&mut out);

        out
    }
}

#[cfg(test)]
mod tests {
    use crate::function::Function;

    use pdf_syntax::object::Object;
    use pdf_syntax::object::{Dict, FromBytes};
    use smallvec::smallvec;

    #[test]
    fn simple() {
        let func = Function::new(&Object::Dict(
            Dict::from_bytes(
                b"<<
              /FunctionType 2
              /Domain [ 0  1 ]
              /C0 [ 0 20  ]
              /C1 [ 30 -50 ]
              /N 1
            >>",
            )
            .unwrap(),
        ))
        .unwrap();

        assert_eq!(func.eval(smallvec![0.0]).unwrap().as_ref(), &[0.0, 20.0]);
        assert_eq!(func.eval(smallvec![0.5]).unwrap().as_ref(), &[15.0, -15.0]);
        assert_eq!(func.eval(smallvec![1.0]).unwrap().as_ref(), &[30.0, -50.0]);
    }

    #[test]
    fn with_exponent() {
        let func = Function::new(&Object::Dict(
            Dict::from_bytes(
                b"<<
              /FunctionType 2
              /Domain [ 0  1 ]
              /C0 [ 0  ]
              /C1 [ 30 ]
              /N 2
            >>",
            )
            .unwrap(),
        ))
        .unwrap();

        assert_eq!(func.eval(smallvec![0.5]), Some(smallvec![7.5]));
    }

    #[test]
    fn clamp_domain() {
        let func = Function::new(&Object::Dict(
            Dict::from_bytes(
                b"<<
              /FunctionType 2
              /Domain [ 0.2  0.8 ]
              /C0 [ 0  ]
              /C1 [ 30 ]
              /N 2
            >>",
            )
            .unwrap(),
        ))
        .unwrap();

        assert_eq!(
            func.eval(smallvec![0.0]).as_ref(),
            func.eval(smallvec![0.2]).as_ref(),
        );
        assert_eq!(
            func.eval(smallvec![-10.]).as_ref(),
            func.eval(smallvec![0.2]).as_ref(),
        );
        assert_eq!(
            func.eval(smallvec![0.8]).as_ref(),
            func.eval(smallvec![0.8]).as_ref(),
        );
        assert_eq!(
            func.eval(smallvec![1.2]).as_ref(),
            func.eval(smallvec![1.0]).as_ref(),
        );
    }

    #[test]
    fn clamp_range() {
        let func = Function::new(&Object::Dict(
            Dict::from_bytes(
                b"<<
              /FunctionType 2
              /Domain [ 0.0  1.0 ]
              /Range [10.0 20.0]
              /C0 [ 0  ]
              /C1 [ 30 ]
              /N 1
            >>",
            )
            .unwrap(),
        ))
        .unwrap();

        assert_eq!(func.eval(smallvec![0.0]), Some(smallvec![10.0]));
        assert_eq!(func.eval(smallvec![0.5]), Some(smallvec![15.0]));
        assert_eq!(func.eval(smallvec![1.0]), Some(smallvec![20.0]));
    }
}