Enum Adam7Variant

#[non_exhaustive]
pub enum Adam7Variant {
    Sparse,
    Splat,
}

The algorithm to use when progressively filling pixel data from Adam7 interlaced passes.

Adam7 interlacing is a technique optionally used in PNG by which only a sub-sample of pixel data is encoded in the beginning of the image data chunks, followed by progressively larger subsets of the data in subsequent passes. Therefore a ‘rough image’ is available after ust a very tiny fraction of the data has been read which can be advantageous for loading an image from a slow IO medium while optimizing time-to-first-meaningful-paint and then replacing the presented data as it is streamed in.

There are trade-offs to make here. The strictly necessary requirement for an implementation is that the exact image is recovered after all passes are applied. However the intermediate states of the output are left to the implementation, as long as it follows the restriction of resulting in the intended image when all passes have been applied.

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.

Sparse

This is the adam7 de-interlace we do by default. Only pixels related to the pass are written. The output buffer should not be directly used for presentation until all passes are complete. At least the invalid pixels in the buffer should be masked. However, this performs the least amount of writes and is optimal when you’re only reading full frames.

This corresponds to crate::expand_interlaced_row.

Splat

A variant of the Adam7 de-interlace that ensures that all pixels are initialized after each pass, and are progressively refined towards the final image. Performs more writes than the other variant as some pixels are touched repeatedly, but ensures the buffer can be used as directly as possible for presentation.

This corresponds to crate::splat_interlaced_row.

Trait Implementations

impl Clone for Adam7Variant

fn clone(&self) -> Adam7Variant

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Adam7Variant

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

Formats the value using the given formatter.

impl Default for Adam7Variant

fn default() -> Adam7Variant

Returns the “default value” for a type.

impl PartialEq for Adam7Variant

fn eq(&self, other: &Adam7Variant) -> bool

Tests for self and other values to be equal, and is used by ==.

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

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Copy for Adam7Variant

impl Eq for Adam7Variant

impl StructuralPartialEq for Adam7Variant