Module image 

The image table: every PNG in a Bundle the game names, by bundle path, with its size. Screens name a picture by an ImageId from this table; the platform layer decodes and draws it. Only each file’s header is read here, never its pixels.

A one-bit screen’s bundle may hold a one-bit picture file (crate::bitmap) at a PNG’s path in place of the PNG: the table then gives the size of the PNG it was made from (its source size), so the image’s id and size are the same as with the PNG.

As formats (ADR-0007): an image’s size is the ImageInfo kind, read by PngInfo and OneBitInfo, and ImageTable::load_with builds the table with every image format a game registers. Its pixels are the Image kind, which Png reads with the png feature. A game that draws through shuyi-app needs none: the platform decodes a PNG’s pixels when it uploads the picture.

Structs

Image

An image’s pixels: four bytes each (red, green, blue, alpha), row by row from the top.

ImageId

Names one image of an ImageTable: its interned bundle path. Cheap to copy and compare. Only ImageTable::id makes one, so an id always names an image some table holds.

ImageInfo

An image’s size in pixels. Build it with ImageInfo::new or ImageInfo::checked (ADR-0039).

ImageRect

A rectangle of an image, in image pixels.

ImageTable

Every image the game can draw, by bundle path (/-separated). Build it with ImageTable::new, Default or ImageTable::load (ADR-0039).

Picture

A picture: a rectangle of an image.

Png

PNG read for its pixels (png, .png), with the png feature. Its size is checked first, as PngInfo does, so a picture too big is refused before its pixels are decoded.

PngInfo

PNG read for its size (png, .png): only its header, never its pixels. The size must be one ImageInfo::checked allows.

Constants

MAX_PNG_BYTES

The most bytes a PNG may have: 64 MiB, what a MAX_SIDE square of 8-bit RGBA pixels takes without compression.

MAX_SIDE

The longest side an image may have, in pixels: what every graphics card the engine runs on (WebGL included) takes as one texture.

PNG_SIGNATURE

The first eight bytes of every PNG file.

Functions

png_size

Width and height from a PNG’s header, or None if bytes isn’t a PNG.