Crate denise_image 

Image decoding for Denise: bytes in, premultiplied pixels out.

let bytes = std::fs::read("logo.png")?;
let picture = denise_image::decode(&bytes)?;
let (pixels, size) = picture.into_parts();
// denise_ui::widgets::Image::new(pixels, size)

decode recognises the format from the bytes; the per-format functions exist for callers that already know. Every decoder produces the same thing: tightly packed rows of premultiplied 0xAARRGGBB, which is exactly what Canvas::blit and the Image widget in denise-ui consume. The multiply by alpha happens here, once, so drawing never pays it.

Formats, and what each costs

Format	Decoder	Feature
PNG (including APNG’s first frame)	the png crate	png, default
JPEG	the zune-jpeg crate	jpeg, default
GIF (first frame)	the gif crate	gif, default
BMP, uncompressed 24/32-bit	this crate, ~100 lines	always

Each decoder is a cargo feature so a panel pays binary size only for the formats it ships — the same arrangement as truetype/shaping in denise-text. The measured costs are in the README. BMP is not gated because the hand-rolled decoder is smaller than the gate would be.

Animated GIFs decode to their first frame — deliberately. Playback is a frame cache times the animation clock, and belongs to a later issue; the gif crate underneath streams frames, so nothing here forecloses it.

What this crate refuses to do

No file I/O — the application reads bytes and passes them, because a decoder that opens paths is unusable over the FFI and wrong in an embedded toolkit. No scaling — that is the rasteriser’s job, at draw time. And nothing decodes to more than MAX_PIXELS pixels: a panel toolkit has no business allocating a third of a small board’s RAM because a file’s header asked it to.

Structs

Picture

Decoded pixels: tightly packed premultiplied 0xAARRGGBB rows.

Enums

DecodeError

Why a decode failed.

Constants

MAX_PIXELS

The most pixels a decode is willing to produce: 32 megapixels, which is 128 MiB of u32 — past every real panel asset and comfortably inside what a header lying about its dimensions could otherwise make decode allocate.

Functions

decode

Decodes an image, recognising the format from the bytes themselves.

decode_bmp

Decodes an uncompressed 24- or 32-bit BMP — which is virtually every BMP actually in circulation. Bottom-up and top-down rows both handled.

decode_gifgif

Decodes a GIF to its first frame, composed at the file’s full logical size — a frame smaller than the screen lands at its offset on transparent pixels, exactly as a viewer would show it.

decode_jpegjpeg

Decodes a JPEG. Greyscale and CMYK files come out as the colour they show.

decode_pngpng

Decodes a PNG. Palette, greyscale and 16-bit files are expanded to 8-bit colour by the decoder; an APNG decodes to its first frame.