Enum DecodeCapability 

#[non_exhaustive]
pub enum DecodeCapability {
    Sequential,
    Regions,
}

What a decoder can produce without a full decode.

The scheduler uses this to decide whether it may request arbitrary regions from a source or must pull rows in order (ARCHITECTURE §Layer 2).

Variants (Non-exhaustive)

Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.

Sequential

Emits rows in top-to-bottom order as bytes arrive.

Out-of-order region requests are not supported; the engine reads forward. This covers non-interlaced PNG, baseline JPEG, GIF frames, strip TIFF and raw.

Regions

Can produce an arbitrary region without decoding the whole image.

This covers tiled TIFF, and is what makes the giant-image thumbnail path constant-memory.

A JPEG decoding at a reduced M/8 scale is not this, though an earlier version of this comment said it was: scaled decode lowers the resolution but still emits rows in order, and every coefficient is still entropy-decoded. It is a decoder configuration, not a capability, and claiming otherwise would be a lie the scheduler acts on.

Trait Implementations

impl Clone for DecodeCapability

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 DecodeCapability

impl Debug for DecodeCapability

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

Formats the value using the given formatter.

impl Eq for DecodeCapability

impl Hash for DecodeCapability

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl PartialEq for DecodeCapability

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

Equality operator ==.

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

Inequality operator !=.

impl StructuralPartialEq for DecodeCapability