ovtile/open/
grid_layer.rs

1use alloc::{string::String, vec::Vec};
2
3use crate::{delta_decode_array, delta_encode_array, open::Extent};
4
5use libm::round;
6use pbf::{ProtoRead, ProtoWrite, Protobuf};
7
8// TODO: This could be faster if we don't read in the grid data on parsing but only if the user needs it
9
10/// Gridded data object to read from
11#[derive(Default, Debug, PartialEq)]
12pub struct GridData {
13    /// The name of the gridded data
14    pub name: String,
15    /// The grid data
16    pub data: Vec<f64>,
17    /// The extent for remapping the data with a value between 0 and extent
18    pub extent: Extent,
19    /// The size of the tile (width and height)
20    pub size: f64,
21    /// The minimum grid value
22    pub min: f64,
23    /// The maximum grid value
24    pub max: f64,
25}
26impl GridData {
27    /// create a new GridData object
28    pub fn new(
29        name: String,
30        extent: Extent,
31        size: f64,
32        min: f64,
33        max: f64,
34        data: Vec<f64>,
35    ) -> Self {
36        GridData { name, data, extent, size, min, max }
37    }
38}
39impl ProtoRead for GridData {
40    fn read(&mut self, tag: u64, pb: &mut Protobuf) {
41        match tag {
42            0 => self.extent = pb.read_varint(),
43            1 => self.size = pb.read_varint(),
44            2 => self.min = pb.read_varint(),
45            3 => self.max = pb.read_varint(),
46            4 => {
47                self.data = delta_decode_array(&pb.read_packed())
48                    .into_iter()
49                    .map(|v| unmap_value(v as f64, self.min, self.max, self.extent.into()))
50                    .collect()
51            }
52            5 => self.name = pb.read_string(),
53            #[tarpaulin::skip]
54            _ => panic!("unknown tag: {}", tag),
55        }
56    }
57}
58impl ProtoWrite for GridData {
59    fn write(&self, pb: &mut Protobuf) {
60        let max = self.data.iter().fold(f64::MIN, |a, b| f64::max(a, *b));
61        let min = self.data.iter().fold(f64::MAX, |a, b| f64::min(a, *b));
62        let re_mapped: Vec<u32> =
63            self.data.iter().map(|v| remap_value(*v, min, max, self.extent.into())).collect();
64        let d_coded = delta_encode_array(&re_mapped);
65
66        pb.write_varint_field(0, self.extent);
67        pb.write_varint_field(1, self.size);
68        pb.write_varint_field(2, min);
69        pb.write_varint_field(3, max);
70        pb.write_packed_varint(4, &d_coded);
71        pb.write_string_field(5, &self.name);
72    }
73}
74
75/// map the value to the range 0->extent
76fn remap_value(value: f64, min: f64, max: f64, extent: f64) -> u32 {
77    round(((value - min) * extent) / (max - min)) as u32
78}
79
80/// map the value back to floats
81fn unmap_value(value: f64, min: f64, max: f64, extent: f64) -> f64 {
82    (value * (max - min)) / extent + min
83}
84
85/// convert rgb to elevation using terrarium formula
86pub fn convert_terrarium_elevation_data(r: u8, g: u8, b: u8) -> f64 {
87    r as f64 * 256. + g as f64 + b as f64 / 256. - 32768.
88}
89
90/// convert rgb to elevation using mapbox formula
91pub fn convert_mapbox_elevation_data(r: u8, g: u8, b: u8) -> f64 {
92    -10000. + (r as f64 * 256. * 256. + g as f64 * 256. + b as f64) * 0.1
93}
ovtile/open/grid_layer.rs

ovtile/open/
grid_layer.rs
