Crate nopng 

nopng — a minimal, no_std PNG encoder/decoder.

See decode_image, encode_image, inspect_image, and ImageSpec for the main API.

Examples

Encode a 2x2 RGBA8 image:

let spec = nopng::ImageSpec::new(2, 2, nopng::PixelFormat::Rgba8);
let pixels = vec![255u8; spec.data_len()]; // white, fully opaque
let png_bytes = nopng::encode_image(&spec, &pixels)?;

Decode a PNG and convert to RGBA8:

let (spec, pixels) = nopng::decode_image(&png_bytes)?;
let rgba = nopng::reformat_pixels(&spec.pixel_format, &pixels, &nopng::PixelFormat::Rgba8)?;

Decode in the PNG’s native format and inspect it:

let (spec, pixels) = nopng::decode_image(&png_bytes)?;
match spec.pixel_format {
    nopng::PixelFormat::Rgba8 => { /* 4 bytes per pixel */ }
    nopng::PixelFormat::Gray8 => { /* 1 byte per pixel */ }
    _ => { /* ... */ }
}

Pre-inspect a PNG to learn its format before decoding:

let spec = nopng::inspect_image(&png_bytes)?;
println!("{}x{}", spec.width, spec.height);

Inspect, decode, and conditionally reformat:

let info = nopng::inspect_image(&png_bytes)?;
let (spec, pixels) = nopng::decode_image(&png_bytes)?;

// Only reformat when the native format isn't already RGBA8.
let rgba = if spec.pixel_format == nopng::PixelFormat::Rgba8 {
    pixels
} else {
    nopng::reformat_pixels(&spec.pixel_format, &pixels, &nopng::PixelFormat::Rgba8)?
};
assert_eq!(rgba.len(), info.width as usize * info.height as usize * 4);

Encode a 4-colour indexed (palette) image:

let palette = vec![
    255, 0, 0,   // index 0: red
    0, 255, 0,   // index 1: green
    0, 0, 255,   // index 2: blue
    255, 255, 0, // index 3: yellow
];
let spec = nopng::ImageSpec::new(
    2, 2,
    nopng::PixelFormat::Indexed8 { palette, trns: None },
);
let indices = vec![0, 1, 2, 3]; // one index per pixel
let png_bytes = nopng::encode_image(&spec, &indices)?;

Convert pixel data between formats without encoding/decoding:

// RGB8 pixels (3 bytes each)
let rgb = vec![255, 0, 0, 0, 255, 0]; // red, green
let rgba = nopng::reformat_pixels(
    &nopng::PixelFormat::Rgb8,
    &rgb,
    &nopng::PixelFormat::Rgba8,
)?;
assert_eq!(rgba, &[255, 0, 0, 255, 0, 255, 0, 255]);

Structs

ImageSpec

Image metadata describing dimensions, pixel format and interlacing.

Enums

Error

Errors returned by decoding and encoding operations.

PixelFormat

Describes the pixel layout of image data in a flat &[u8] buffer.

Functions

decode_image

Decodes PNG bytes into an ImageSpec and pixel data.

encode_image

Encodes an image described by spec into PNG bytes.

inspect_image

Reads PNG metadata from the PNG signature, IHDR, PLTE, and tRNS chunks, stopping at the first IDAT.

reformat_pixels

Converts pixel data from one PixelFormat to another.