imagesize/formats/
ico.rs

1use crate::util::*;
2use crate::{ImageError, ImageResult, ImageSize};
3
4use std::io::{BufRead, Seek, SeekFrom};
5
6pub fn size<R: BufRead + Seek>(reader: &mut R) -> ImageResult<ImageSize> {
7    reader.seek(SeekFrom::Start(4))?;
8    let img_count = read_u16(reader, &Endian::Little)?;
9    let mut sizes = Vec::with_capacity(img_count as usize);
10
11    for _ in 0..img_count {
12        if let Ok(size) = ico_image_size(reader) {
13            sizes.push(size)
14        } else {
15            // if we don't have all the bytes of the headers, just
16            // return the largest one found so far
17            break;
18        }
19        // each ICONDIRENTRY (image header) is 16 bytes, skip the last 14
20        reader.seek(SeekFrom::Current(14))?;
21    }
22    sizes.into_iter().max().ok_or(ImageError::CorruptedImage)
23}
24
25pub fn matches(header: &[u8]) -> bool {
26    header.starts_with(&[0, 0, 1, 0])
27}
28
29/// Reads two bytes to determine an individual image's size within an ICO
30fn ico_image_size<R: BufRead + Seek>(reader: &mut R) -> ImageResult<ImageSize> {
31    // ICO dimensions are 1-256 pixels, with a byte value of 0 representing 256
32    Ok(ImageSize {
33        width: read_u8(reader)?.wrapping_sub(1) as usize + 1,
34        height: read_u8(reader)?.wrapping_sub(1) as usize + 1,
35    })
36}
imagesize/formats/ico.rs

imagesize/formats/
ico.rs
