vtk-pure-rs 0.2.0

Pure Rust visualization toolkit — data structures, filters, I/O, rendering
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

use crate::data::ImageData;

/// Compute Peak Signal-to-Noise Ratio between two images.
///
/// PSNR = 10*log10(MAX²/MSE) where MAX is the peak signal value.
/// Higher = more similar. Returns (psnr_db, mse).
pub fn image_psnr(a: &ImageData, b: &ImageData, scalars: &str, max_value: f64) -> (f64, f64) {
    let aa=match a.point_data().get_array(scalars){Some(x)=>x,None=>return(0.0,0.0)};
    let ba=match b.point_data().get_array(scalars){Some(x)=>x,None=>return(0.0,0.0)};
    let n=aa.num_tuples().min(ba.num_tuples());
    if n==0{return(0.0,0.0);}

    let mut buf_a=[0.0f64]; let mut buf_b=[0.0f64];
    let mut mse=0.0;
    for i in 0..n{
        aa.tuple_as_f64(i,&mut buf_a); ba.tuple_as_f64(i,&mut buf_b);
        mse+=(buf_a[0]-buf_b[0]).powi(2);
    }
    mse/=n as f64;

    let psnr=if mse>1e-15{10.0*(max_value*max_value/mse).log10()}else{f64::INFINITY};
    (psnr, mse)
}

/// Compute Mean Absolute Error between two images.
pub fn image_mae(a: &ImageData, b: &ImageData, scalars: &str) -> f64 {
    let aa=match a.point_data().get_array(scalars){Some(x)=>x,None=>return 0.0};
    let ba=match b.point_data().get_array(scalars){Some(x)=>x,None=>return 0.0};
    let n=aa.num_tuples().min(ba.num_tuples());
    if n==0{return 0.0;}
    let mut buf_a=[0.0f64]; let mut buf_b=[0.0f64];
    let mut mae=0.0;
    for i in 0..n{aa.tuple_as_f64(i,&mut buf_a);ba.tuple_as_f64(i,&mut buf_b);mae+=(buf_a[0]-buf_b[0]).abs();}
    mae/n as f64
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::data::{AnyDataArray, DataArray};

    #[test]
    fn identical_infinite_psnr() {
        let mut img=ImageData::with_dimensions(4,1,1);
        img.point_data_mut().add_array(AnyDataArray::F64(DataArray::from_vec("v",vec![50.0;4],1)));
        let (psnr,mse)=image_psnr(&img,&img,"v",255.0);
        assert!(psnr==f64::INFINITY);
        assert_eq!(mse,0.0);
    }

    #[test]
    fn known_mse() {
        let mut a=ImageData::with_dimensions(4,1,1);
        a.point_data_mut().add_array(AnyDataArray::F64(DataArray::from_vec("v",vec![0.0;4],1)));
        let mut b=ImageData::with_dimensions(4,1,1);
        b.point_data_mut().add_array(AnyDataArray::F64(DataArray::from_vec("v",vec![10.0;4],1)));

        let (_,mse)=image_psnr(&a,&b,"v",255.0);
        assert!((mse-100.0).abs()<1e-10);
    }

    #[test]
    fn mae_basic() {
        let mut a=ImageData::with_dimensions(4,1,1);
        a.point_data_mut().add_array(AnyDataArray::F64(DataArray::from_vec("v",vec![0.0;4],1)));
        let mut b=ImageData::with_dimensions(4,1,1);
        b.point_data_mut().add_array(AnyDataArray::F64(DataArray::from_vec("v",vec![5.0;4],1)));

        assert!((image_mae(&a,&b,"v")-5.0).abs()<1e-10);
    }

    #[test]
    fn missing_array() {
        let img=ImageData::with_dimensions(3,1,1);
        let (psnr,_)=image_psnr(&img,&img,"nope",255.0);
        assert_eq!(psnr,0.0);
    }
}