Struct DecodeSize 

pub struct DecodeSize {
    pub width: Option<u32>,
    pub height: Option<u32>,
}

The image stores, for an application that loads its own pictures or sizes the cache. The size an image is decoded at, in physical pixels: the full size of the file, or a smaller one that the place it is shown at needs.

A twelve-megapixel photograph shown as an 80×80 thumbnail does not need 48 MB of pixels, and on a phone a gallery of them is what gets an application killed for memory. Decoding at the size shown keeps the cost to what is on the screen.

• Neither side given: the file’s own size (DecodeSize::FULL).
• One side: that side, and the other from the image’s own ratio.
• Both: the smallest size, at the image’s own ratio, that covers both. The ratio is never changed, so a picture cropped to a square box keeps its shape, and one letterboxed into it is not short of pixels either.

An image is never decoded larger than the file: asking for more gives the file’s own size.

Fields

width: Option<u32>

The width wanted, in physical pixels.

height: Option<u32>

The height wanted, in physical pixels.

Implementations

impl DecodeSize

pub const FULL: DecodeSize

The file’s own size.

pub fn new(width: Option<u32>, height: Option<u32>) -> DecodeSize

A size with either side, both, or neither.

pub fn is_full(self) -> bool

Whether this is the file’s own size.

pub fn target(self, full_width: u32, full_height: u32) -> (u32, u32)

The size a full_width × full_height image is decoded at, by the rules above.

use frus_core::DecodeSize;
let photo = (4000, 3000);
// A square thumbnail covered by the photo, at the photo's own ratio.
assert_eq!(DecodeSize::new(Some(200), Some(200)).target(photo.0, photo.1), (267, 200));
// One side: the other follows.
assert_eq!(DecodeSize::new(Some(400), None).target(photo.0, photo.1), (400, 300));
// Never larger than the file.
assert_eq!(DecodeSize::new(Some(8000), None).target(photo.0, photo.1), photo);

Trait Implementations

impl Clone for DecodeSize

fn clone(&self) -> DecodeSize

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for DecodeSize

impl Debug for DecodeSize

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

Formats the value using the given formatter.

impl Default for DecodeSize

fn default() -> DecodeSize

Returns the “default value” for a type.

impl Eq for DecodeSize

impl Hash for DecodeSize

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

where __H: Hasher,

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 DecodeSize

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

Equality operator ==.

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

Inequality operator !=.

impl StructuralPartialEq for DecodeSize