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decoder.rs
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decoder.rs
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use byteorder::{LittleEndian, ReadBytesExt};
use std::convert::TryFrom;
use std::io::{self, Cursor, Read, Seek, SeekFrom};
use std::marker::PhantomData;
use std::{error, fmt, mem};
use crate::color::ColorType;
use crate::error::{
DecodingError, ImageError, ImageResult, UnsupportedError, UnsupportedErrorKind,
};
use crate::image::{self, ImageDecoder, ImageFormat};
use self::InnerDecoder::*;
use crate::codecs::bmp::BmpDecoder;
use crate::codecs::png::{PngDecoder, PNG_SIGNATURE};
/// Errors that can occur during decoding and parsing an ICO image or one of its enclosed images.
#[derive(Debug, Copy, Clone, Hash, PartialEq, Eq, PartialOrd, Ord)]
enum DecoderError {
/// The ICO directory is empty
NoEntries,
/// The number of color planes (0 or 1), or the horizontal coordinate of the hotspot for CUR files too big.
IcoEntryTooManyPlanesOrHotspot,
/// The bit depth (may be 0 meaning unspecified), or the vertical coordinate of the hotspot for CUR files too big.
IcoEntryTooManyBitsPerPixelOrHotspot,
/// The entry is in PNG format and specified a length that is shorter than PNG header.
PngShorterThanHeader,
/// The enclosed PNG is not in RGBA, which is invalid: https://blogs.msdn.microsoft.com/oldnewthing/20101022-00/?p=12473/.
PngNotRgba,
/// The entry is in BMP format and specified a data size that is not correct for the image and optional mask data.
InvalidDataSize,
/// The dimensions specified by the entry does not match the dimensions in the header of the enclosed image.
ImageEntryDimensionMismatch {
/// The mismatched subimage's type
format: IcoEntryImageFormat,
/// The dimensions specified by the entry
entry: (u16, u16),
/// The dimensions of the image itself
image: (u32, u32),
},
}
impl fmt::Display for DecoderError {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
match self {
DecoderError::NoEntries => f.write_str("ICO directory contains no image"),
DecoderError::IcoEntryTooManyPlanesOrHotspot => {
f.write_str("ICO image entry has too many color planes or too large hotspot value")
}
DecoderError::IcoEntryTooManyBitsPerPixelOrHotspot => f.write_str(
"ICO image entry has too many bits per pixel or too large hotspot value",
),
DecoderError::PngShorterThanHeader => {
f.write_str("Entry specified a length that is shorter than PNG header!")
}
DecoderError::PngNotRgba => f.write_str("The PNG is not in RGBA format!"),
DecoderError::InvalidDataSize => {
f.write_str("ICO image data size did not match expected size")
}
DecoderError::ImageEntryDimensionMismatch {
format,
entry,
image,
} => f.write_fmt(format_args!(
"Entry{:?} and {}{:?} dimensions do not match!",
entry, format, image
)),
}
}
}
impl From<DecoderError> for ImageError {
fn from(e: DecoderError) -> ImageError {
ImageError::Decoding(DecodingError::new(ImageFormat::Ico.into(), e))
}
}
impl error::Error for DecoderError {}
/// The image formats an ICO may contain
#[derive(Debug, Copy, Clone, Hash, PartialEq, Eq, PartialOrd, Ord)]
enum IcoEntryImageFormat {
/// PNG in ARGB
Png,
/// BMP with optional alpha mask
Bmp,
}
impl fmt::Display for IcoEntryImageFormat {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.write_str(match self {
IcoEntryImageFormat::Png => "PNG",
IcoEntryImageFormat::Bmp => "BMP",
})
}
}
impl Into<ImageFormat> for IcoEntryImageFormat {
fn into(self) -> ImageFormat {
match self {
IcoEntryImageFormat::Png => ImageFormat::Png,
IcoEntryImageFormat::Bmp => ImageFormat::Bmp,
}
}
}
/// An ico decoder
pub struct IcoDecoder<R: Read> {
selected_entry: DirEntry,
inner_decoder: InnerDecoder<R>,
}
enum InnerDecoder<R: Read> {
Bmp(BmpDecoder<R>),
Png(PngDecoder<R>),
}
#[derive(Clone, Copy, Default)]
struct DirEntry {
width: u8,
height: u8,
// We ignore some header fields as they will be replicated in the PNG, BMP and they are not
// necessary for determining the best_entry.
#[allow(unused)]
color_count: u8,
// Wikipedia has this to say:
// Although Microsoft's technical documentation states that this value must be zero, the icon
// encoder built into .NET (System.Drawing.Icon.Save) sets this value to 255. It appears that
// the operating system ignores this value altogether.
#[allow(unused)]
reserved: u8,
// We ignore some header fields as they will be replicated in the PNG, BMP and they are not
// necessary for determining the best_entry.
#[allow(unused)]
num_color_planes: u16,
bits_per_pixel: u16,
image_length: u32,
image_offset: u32,
}
impl<R: Read + Seek> IcoDecoder<R> {
/// Create a new decoder that decodes from the stream ```r```
pub fn new(mut r: R) -> ImageResult<IcoDecoder<R>> {
let entries = read_entries(&mut r)?;
let entry = best_entry(entries)?;
let decoder = entry.decoder(r)?;
Ok(IcoDecoder {
selected_entry: entry,
inner_decoder: decoder,
})
}
}
fn read_entries<R: Read>(r: &mut R) -> ImageResult<Vec<DirEntry>> {
let _reserved = r.read_u16::<LittleEndian>()?;
let _type = r.read_u16::<LittleEndian>()?;
let count = r.read_u16::<LittleEndian>()?;
(0..count).map(|_| read_entry(r)).collect()
}
fn read_entry<R: Read>(r: &mut R) -> ImageResult<DirEntry> {
Ok(DirEntry {
width: r.read_u8()?,
height: r.read_u8()?,
color_count: r.read_u8()?,
reserved: r.read_u8()?,
num_color_planes: {
// This may be either the number of color planes (0 or 1), or the horizontal coordinate
// of the hotspot for CUR files.
let num = r.read_u16::<LittleEndian>()?;
if num > 256 {
return Err(DecoderError::IcoEntryTooManyPlanesOrHotspot.into());
}
num
},
bits_per_pixel: {
// This may be either the bit depth (may be 0 meaning unspecified),
// or the vertical coordinate of the hotspot for CUR files.
let num = r.read_u16::<LittleEndian>()?;
if num > 256 {
return Err(DecoderError::IcoEntryTooManyBitsPerPixelOrHotspot.into());
}
num
},
image_length: r.read_u32::<LittleEndian>()?,
image_offset: r.read_u32::<LittleEndian>()?,
})
}
/// Find the entry with the highest (color depth, size).
fn best_entry(mut entries: Vec<DirEntry>) -> ImageResult<DirEntry> {
let mut best = entries.pop().ok_or(DecoderError::NoEntries)?;
let mut best_score = (
best.bits_per_pixel,
u32::from(best.real_width()) * u32::from(best.real_height()),
);
for entry in entries {
let score = (
entry.bits_per_pixel,
u32::from(entry.real_width()) * u32::from(entry.real_height()),
);
if score > best_score {
best = entry;
best_score = score;
}
}
Ok(best)
}
impl DirEntry {
fn real_width(&self) -> u16 {
match self.width {
0 => 256,
w => u16::from(w),
}
}
fn real_height(&self) -> u16 {
match self.height {
0 => 256,
h => u16::from(h),
}
}
fn matches_dimensions(&self, width: u32, height: u32) -> bool {
u32::from(self.real_width()) == width && u32::from(self.real_height()) == height
}
fn seek_to_start<R: Read + Seek>(&self, r: &mut R) -> ImageResult<()> {
r.seek(SeekFrom::Start(u64::from(self.image_offset)))?;
Ok(())
}
fn is_png<R: Read + Seek>(&self, r: &mut R) -> ImageResult<bool> {
self.seek_to_start(r)?;
// Read the first 8 bytes to sniff the image.
let mut signature = [0u8; 8];
r.read_exact(&mut signature)?;
Ok(signature == PNG_SIGNATURE)
}
fn decoder<R: Read + Seek>(&self, mut r: R) -> ImageResult<InnerDecoder<R>> {
let is_png = self.is_png(&mut r)?;
self.seek_to_start(&mut r)?;
if is_png {
Ok(Png(PngDecoder::new(r)?))
} else {
Ok(Bmp(BmpDecoder::new_with_ico_format(r)?))
}
}
}
/// Wrapper struct around a `Cursor<Vec<u8>>`
pub struct IcoReader<R>(Cursor<Vec<u8>>, PhantomData<R>);
impl<R> Read for IcoReader<R> {
fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
self.0.read(buf)
}
fn read_to_end(&mut self, buf: &mut Vec<u8>) -> io::Result<usize> {
if self.0.position() == 0 && buf.is_empty() {
mem::swap(buf, self.0.get_mut());
Ok(buf.len())
} else {
self.0.read_to_end(buf)
}
}
}
impl<'a, R: 'a + Read + Seek> ImageDecoder<'a> for IcoDecoder<R> {
type Reader = IcoReader<R>;
fn dimensions(&self) -> (u32, u32) {
match self.inner_decoder {
Bmp(ref decoder) => decoder.dimensions(),
Png(ref decoder) => decoder.dimensions(),
}
}
fn color_type(&self) -> ColorType {
match self.inner_decoder {
Bmp(ref decoder) => decoder.color_type(),
Png(ref decoder) => decoder.color_type(),
}
}
fn into_reader(self) -> ImageResult<Self::Reader> {
Ok(IcoReader(
Cursor::new(image::decoder_to_vec(self).map_err(|(_, e)| e)?),
PhantomData,
))
}
fn read_image(self, buf: &mut [u8]) -> ImageResult<()> {
assert_eq!(u64::try_from(buf.len()), Ok(self.total_bytes()));
match self.inner_decoder {
Png(decoder) => {
if self.selected_entry.image_length < PNG_SIGNATURE.len() as u32 {
return Err(DecoderError::PngShorterThanHeader.into());
}
// Check if the image dimensions match the ones in the image data.
let (width, height) = decoder.dimensions();
if !self.selected_entry.matches_dimensions(width, height) {
return Err(DecoderError::ImageEntryDimensionMismatch {
format: IcoEntryImageFormat::Png,
entry: (
self.selected_entry.real_width(),
self.selected_entry.real_height(),
),
image: (width, height),
}
.into());
}
// Embedded PNG images can only be of the 32BPP RGBA format.
// https://blogs.msdn.microsoft.com/oldnewthing/20101022-00/?p=12473/
if decoder.color_type() != ColorType::Rgba8 {
return Err(DecoderError::PngNotRgba.into());
}
decoder.read_image(buf)
}
Bmp(mut decoder) => {
let (width, height) = decoder.dimensions();
if !self.selected_entry.matches_dimensions(width, height) {
return Err(DecoderError::ImageEntryDimensionMismatch {
format: IcoEntryImageFormat::Bmp,
entry: (
self.selected_entry.real_width(),
self.selected_entry.real_height(),
),
image: (width, height),
}
.into());
}
// The ICO decoder needs an alpha channel to apply the AND mask.
if decoder.color_type() != ColorType::Rgba8 {
return Err(ImageError::Unsupported(
UnsupportedError::from_format_and_kind(
ImageFormat::Bmp.into(),
UnsupportedErrorKind::Color(decoder.color_type().into()),
),
));
}
decoder.read_image_data(buf)?;
let r = decoder.reader();
let image_end = r.seek(SeekFrom::Current(0))?;
let data_end =
u64::from(self.selected_entry.image_offset + self.selected_entry.image_length);
let mask_row_bytes = ((width + 31) / 32) * 4;
let mask_length = u64::from(mask_row_bytes) * u64::from(height);
// data_end should be image_end + the mask length (mask_row_bytes * height).
// According to
// https://devblogs.microsoft.com/oldnewthing/20101021-00/?p=12483
// the mask is required, but according to Wikipedia
// https://en.wikipedia.org/wiki/ICO_(file_format)
// the mask is not required. Unfortunately, Wikipedia does not have a citation
// for that claim, so we can't be sure which is correct.
if data_end >= image_end + mask_length {
// If there's an AND mask following the image, read and apply it.
for y in 0..height {
let mut x = 0;
for _ in 0..mask_row_bytes {
// Apply the bits of each byte until we reach the end of the row.
let mask_byte = r.read_u8()?;
for bit in (0..8).rev() {
if x >= width {
break;
}
if mask_byte & (1 << bit) != 0 {
// Set alpha channel to transparent.
buf[((height - y - 1) * width + x) as usize * 4 + 3] = 0;
}
x += 1;
}
}
}
Ok(())
} else if data_end == image_end {
// accept images with no mask data
Ok(())
} else {
Err(DecoderError::InvalidDataSize.into())
}
}
}
}
}
#[cfg(test)]
mod test {
use super::*;
// Test if BMP images without alpha channel inside ICOs don't panic.
// Because the test data is invalid decoding should produce an error.
#[test]
fn bmp_16_with_missing_alpha_channel() {
let data = vec![
0x00, 0x00, 0x01, 0x00, 0x01, 0x00, 0x0e, 0x04, 0xc3, 0x7e, 0x00, 0x00, 0x00, 0x00,
0x7c, 0x00, 0x00, 0x00, 0x0e, 0x00, 0x00, 0x00, 0xf8, 0xff, 0xff, 0xff, 0x01, 0x00,
0x10, 0x00, 0x00, 0x00, 0x00, 0x00, 0x12, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x8f, 0xf6, 0xff, 0xff, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x20, 0x66, 0x74, 0x83, 0x70, 0x61, 0x76, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02,
0x00, 0x00, 0x00, 0x00, 0xff, 0xff, 0xff, 0xeb, 0x00, 0x9b, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x4e, 0x47, 0x0d,
0x0a, 0x1a, 0x0a, 0x00, 0x00, 0x00, 0x62, 0x49, 0x48, 0x44, 0x52, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0x0c,
0x00, 0x00, 0x00, 0xc3, 0x3f, 0x94, 0x61, 0xaa, 0x17, 0x4d, 0x8d, 0x79, 0x1d, 0x8b,
0x10, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x14, 0x2e, 0x28, 0x40, 0xe5, 0x9f,
0x4b, 0x4d, 0xe9, 0x87, 0xd3, 0xda, 0xd6, 0x89, 0x81, 0xc5, 0xa4, 0xa1, 0x60, 0x98,
0x31, 0xc7, 0x1d, 0xb6, 0x8f, 0x20, 0xc8, 0x3e, 0xee, 0xd8, 0xe4, 0x8f, 0xee, 0x7b,
0x48, 0x9b, 0x88, 0x25, 0x13, 0xda, 0xa4, 0x13, 0xa4, 0x00, 0x00, 0x00, 0x00, 0x40,
0x16, 0x01, 0xff, 0xff, 0xff, 0xff, 0xe9, 0x0c, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0xa3, 0x66, 0x64, 0x41, 0x54, 0xa3, 0xa3, 0x00, 0x00, 0x00, 0xb8, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xa3, 0x66, 0x64, 0x41, 0x54, 0xa3, 0xa3,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x8f, 0xf6, 0xff, 0xff,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x20, 0x66, 0x74, 0x83, 0x70, 0x61, 0x76,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0x00, 0x00, 0x00, 0x00, 0xff, 0xff, 0xff,
0xeb, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x08, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a, 0x00, 0x00, 0x00, 0x62, 0x49,
0x48, 0x44, 0x52, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x08, 0x00, 0x00,
0x00, 0x00, 0x00, 0xff, 0xff, 0x94, 0xc8, 0x00, 0x02, 0x0c, 0x00, 0xff, 0xff, 0xc6,
0x84, 0x00, 0x2a, 0x75, 0x03, 0xa3, 0x05, 0xfb, 0xe1, 0x6e, 0xe8, 0x27, 0xd6, 0xd3,
0x96, 0xc1, 0xe4, 0x30, 0x0c, 0x05, 0xb9, 0xa3, 0x8b, 0x29, 0xda, 0xa4, 0xf1, 0x4d,
0xf3, 0xb2, 0x98, 0x2b, 0xe6, 0x93, 0x07, 0xf9, 0xca, 0x2b, 0xc2, 0x39, 0x20, 0xba,
0x7c, 0xa0, 0xb1, 0x43, 0xe6, 0xf9, 0xdc, 0xd1, 0xc2, 0x52, 0xdc, 0x41, 0xc1, 0x2f,
0x29, 0xf7, 0x46, 0x32, 0xda, 0x1b, 0x72, 0x8c, 0xe6, 0x2b, 0x01, 0xe5, 0x49, 0x21,
0x89, 0x89, 0xe4, 0x3d, 0xa1, 0xdb, 0x3b, 0x4a, 0x0b, 0x52, 0x86, 0x52, 0x33, 0x9d,
0xb2, 0xcf, 0x4a, 0x86, 0x53, 0xd7, 0xa9, 0x4b, 0xaf, 0x62, 0x06, 0x49, 0x53, 0x00,
0xc3, 0x3f, 0x94, 0x61, 0xaa, 0x17, 0x4d, 0x8d, 0x79, 0x1d, 0x8b, 0x10, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x14, 0x2e, 0x28, 0x40, 0xe5, 0x9f, 0x4b, 0x4d, 0xe9,
0x87, 0xd3, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xe7, 0xc5, 0x00,
0x02, 0x00, 0x00, 0x00, 0x06, 0x00, 0x0b, 0x00, 0x50, 0x31, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x06, 0x76, 0x76, 0x01, 0x00, 0x00, 0x00, 0x76, 0x00,
0x00, 0x23, 0x3f, 0x52, 0x41, 0x44, 0x49, 0x41, 0x4e, 0x43, 0x45, 0x61, 0x50, 0x35,
0x00, 0x00, 0x00, 0x00, 0x00, 0x03, 0x4d, 0x47, 0x49, 0x46, 0x38, 0x37, 0x61, 0x05,
0x50, 0x37, 0x00, 0x00, 0x00, 0x00, 0x00, 0xc7, 0x37, 0x61,
];
let decoder = IcoDecoder::new(Cursor::new(&data)).unwrap();
let mut buf = vec![0; usize::try_from(decoder.total_bytes()).unwrap()];
assert!(decoder.read_image(&mut buf).is_err());
}
}