chuot/assets/loader/
png.rs

1//! PNG asset loading.
2
3use std::io::Cursor;
4
5use png::{BitDepth, ColorType, Decoder, Transformations};
6use rgb::RGBA8;
7
8use super::Loader;
9use crate::assets::Id;
10
11/// PNG asset loader.
12///
13/// Loader type returned is `(width, height, pixels)`, where `pixels` is an array of RGBA pixels.
14#[non_exhaustive]
15pub struct PngLoader;
16
17impl Loader<(u32, u32, Vec<RGBA8>)> for PngLoader {
18    const EXTENSION: &'static str = "png";
19
20    #[inline]
21    fn load(bytes: &[u8], id: &Id) -> (u32, u32, Vec<RGBA8>) {
22        // Copy the bytes into a cursor
23        let cursor = Cursor::new(bytes.to_vec());
24
25        // Decode the PNG
26        let mut decoder = Decoder::new(cursor);
27
28        // Discard text chunks
29        decoder.set_ignore_text_chunk(true);
30        // Make it faster by not checking if it's correct
31        decoder.ignore_checksums(true);
32
33        // Convert indexed images to RGBA
34        decoder
35            .set_transformations(Transformations::normalize_to_color8() | Transformations::ALPHA);
36
37        // Start parsing the PNG
38        let mut reader = decoder.read_info().unwrap();
39
40        // Ensure we can use the PNG colors
41        let (color_type, bits) = reader.output_color_type();
42
43        // Must be 8 bit RGBA or indexed
44        assert!(
45            color_type == ColorType::Rgba && bits == BitDepth::Eight,
46            "PNG of asset with ID '{id}' is not 8 bit RGB with an alpha channel"
47        );
48
49        // Read the PNG
50        let mut pixels = vec![RGBA8::default(); reader.output_buffer_size()];
51        let info = reader
52            .next_frame(bytemuck::cast_slice_mut(&mut pixels))
53            .expect("Error reading image");
54
55        (info.width, info.height, pixels)
56    }
57}
chuot/assets/loader/png.rs

chuot/assets/loader/
png.rs
