Struct Header 

#[non_exhaustive]
pub struct Header {
    pub width: u32,
    pub height: u32,
    pub bit_depth: u8,
    pub color_type: ColorType,
    pub interlaced: bool,
}

A parsed IHDR chunk (§11.2.2).

Fields (Non-exhaustive)

Non-exhaustive structs could have additional fields added in future. Therefore, non-exhaustive structs cannot be constructed in external crates using the traditional Struct { .. } syntax; cannot be matched against without a wildcard ..; and struct update syntax will not work.

width: u32

Image width in pixels.

height: u32

Image height in pixels.

bit_depth: u8

Bits per channel: 1, 2, 4, 8 or 16.

color_type: ColorType

How samples are interpreted.

interlaced: bool

Whether the image is Adam7 interlaced.

Implementations

impl Header

pub fn parse(payload: &[u8], limits: &Limits) -> Result<Self>

Parse a 13-byte IHDR payload, validating it against limits.

Dimension limits are enforced here, before any pixel buffer exists (SPEC §Safety), so a header claiming 4 billion pixels costs nothing.

Errors

Returns PixelsError::Malformed for an invalid header, or PixelsError::LimitExceeded if the dimensions exceed limits.

pub const fn bits_per_pixel(&self) -> usize

Bits per pixel in the encoded stream.

pub const fn row_bytes(&self, width: u32) -> usize

Bytes in one filtered scanline of width pixels, excluding the filter byte. Sub-byte depths round up.

pub const fn filter_stride(&self) -> usize

Bytes per pixel, rounded up — the filter offset (§9.2).

For depths below 8 this is 1, which is what the filters require.

pub const fn output_format(&self, has_transparency: bool) -> PixelFormat

The pixel format this header decodes into.

The mapping is constrained by SPEC §Pixel formats, which has no 16-bit grey-with-alpha type. Rather than silently truncating those to 8 bits, they widen to Rgba16: more memory, but no data thrown away by a decoder the caller did not ask to be lossy.

Sub-byte greyscale expands to Gray8 and palettes expand to RGB or RGBA, because the engine’s formats are byte-aligned and unpalettised.

pub fn descriptor( &self, has_transparency: bool, limits: &Limits, ) -> Result<ImageDescriptor>

The engine descriptor for this header.

Errors

Propagates ImageDescriptor::with_limits.

pub fn filtered_size(&self) -> usize

Total filtered bytes the whole image decompresses to.

This is the exact output limit handed to inflate, which is what turns a decompression bomb into a malformed-input error (SPEC §Safety).

Trait Implementations

impl Clone for Header

fn clone(&self) -> Self

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for Header

impl Debug for Header

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Eq for Header

impl PartialEq for Header

fn eq(&self, other: &Self) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for Header