png_pong 0.9.3

A pure Rust PNG/APNG encoder & decoder
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

use std::io::{Read, Write};

use parsenic::{be::Read as _, Read as _, Reader};

use super::{Chunk, DecoderError, EncoderError};
use crate::{consts, decoder::Parser, encoder::Enc};

/// Suggested background color chunk (bKGD)
#[derive(Copy, Clone, Debug)]
pub enum Background {
    /// 8-bit palette background index
    Palette(u8),
    /// 1-16 bit gray background value
    Gray(u16),
    /// 1-16 bits for each of Red, Green and Blue
    Rgb(u16, u16, u16),
}

impl Background {
    pub(crate) fn parse<R: Read>(
        parse: &mut Parser<R>,
    ) -> Result<Chunk, DecoderError> {
        match parse.len() {
            1 => {
                let buffer: [u8; 1] = parse.bytes()?;
                let mut reader = Reader::new(&buffer);
                let index = reader.u8()?;

                reader.end().unwrap();
                Ok(Chunk::Background(Background::Palette(index)))
            }
            2 => {
                let buffer: [u8; 2] = parse.bytes()?;
                let mut reader = Reader::new(&buffer);
                let value = reader.u16()?;

                reader.end().unwrap();
                Ok(Chunk::Background(Background::Gray(value)))
            }
            6 => {
                let buffer: [u8; 6] = parse.bytes()?;
                let mut reader = Reader::new(&buffer);
                let [r, g, b] = [reader.u16()?, reader.u16()?, reader.u16()?];

                reader.end().unwrap();
                Ok(Chunk::Background(Background::Rgb(r, g, b)))
            }
            _ => Err(DecoderError::ChunkLength(consts::BACKGROUND)),
        }
    }

    pub(crate) fn write<W: Write>(
        &self,
        enc: &mut Enc<W>,
    ) -> Result<(), EncoderError> {
        use Background::*;
        match *self {
            Palette(v) => {
                enc.prepare(1, consts::BACKGROUND)?;
                enc.u8(v)?;
            }
            Gray(v) => {
                enc.prepare(2, consts::BACKGROUND)?;
                enc.u16(v)?
            }
            Rgb(r, g, b) => {
                enc.prepare(6, consts::BACKGROUND)?;
                enc.u16(r)?;
                enc.u16(g)?;
                enc.u16(b)?;
            }
        }
        enc.write_crc()
    }
}