Image

An Image Processing Library

This crate provides basic image processing functions and methods for converting to and from various image formats.

All image processing functions provided operate on types that implement the GenericImageView and GenericImage traits and return an ImageBuffer.

Supported Image Formats

image provides implementations of common image format encoders and decoders.

Format	Decoding	Encoding
PNG	All supported color types	Same as decoding
JPEG	Baseline and progressive	Baseline JPEG
GIF	Yes	Yes
BMP	Yes	Rgb8, Rgba8, Gray8, GrayA8
ICO	Yes	Yes
TIFF	Baseline(no fax support) + LZW + PackBits	Rgb8, Rgba8, Gray8
WebP	Yes	Rgb8, Rgba8 *
AVIF	Only 8-bit **	Lossy
PNM	PBM, PGM, PPM, standard PAM	Yes
DDS	DXT1, DXT3, DXT5	No
TGA	Yes	Rgb8, Rgba8, Bgr8, Bgra8, Gray8, GrayA8
OpenEXR	Rgb32F, Rgba32F (no dwa compression)	Rgb32F, Rgba32F (no dwa compression)
farbfeld	Yes	Yes

* Requires the webp-encoder feature, uses the libwebp C library.
** Requires the avif-decoder feature, uses the libdav1d C library.

The `ImageDecoder` and `ImageDecoderRect` Traits

All image format decoders implement the ImageDecoder trait which provide basic methods for getting image metadata and decoding images. Some formats additionally provide ImageDecoderRect implementations which allow for decoding only part of an image at once.

The most important methods for decoders are...

dimensions: Return a tuple containing the width and height of the image.
color_type: Return the color type of the image data produced by this decoder.
read_image: Decode the entire image into a slice of bytes.

Pixels

image provides the following pixel types:

Rgb: RGB pixel
Rgba: RGBA pixel
Luma: Grayscale pixel
LumaA: Grayscale with alpha

All pixels are parameterised by their component type.

Images

Individual pixels within images are indexed with (0,0) at the top left corner.

The `GenericImageView` and `GenericImage` Traits

Traits that provide methods for inspecting (GenericImageView) and manipulating (GenericImage) images, parameterised over the image's pixel type.

Some of these methods for GenericImageView are...

dimensions: Return a tuple containing the width and height of the image.
get_pixel: Returns the pixel located at (x, y).
pixels: Returns an Iterator over the pixels of this image.

While some of the methods for GenericImage are...

put_pixel: Put a pixel at location (x, y).
copy_from: Copies all of the pixels from another image into this image.

Representation of Images

image provides two main ways of representing image data:

`ImageBuffer`

An image parameterised by its Pixel types, represented by a width and height and a vector of pixels. It provides direct access to its pixels and implements the GenericImageView and GenericImage traits.

use image::{GenericImage, GenericImageView, ImageBuffer, RgbImage};

// Construct a new RGB ImageBuffer with the specified width and height.
let img: RgbImage = ImageBuffer::new(512, 512);

// Construct a new by repeated calls to the supplied closure.
let mut img = ImageBuffer::from_fn(512, 512, |x, y| {
    if x % 2 == 0 {
        image::Luma([0u8])
    } else {
        image::Luma([255u8])
    }
});

// Obtain the image's width and height.
let (width, height) = img.dimensions();

// Access the pixel at coordinate (100, 100).
let pixel = img[(100, 100)];

// Or use the `get_pixel` method from the `GenericImage` trait.
let pixel = *img.get_pixel(100, 100);

// Put a pixel at coordinate (100, 100).
img.put_pixel(100, 100, pixel);

// Iterate over all pixels in the image.
for pixel in img.pixels() {
    // Do something with pixel.
}

`DynamicImage`

A DynamicImage is an enumeration over all supported ImageBuffer<P> types. Its exact image type is determined at runtime. It is the type returned when opening an image. For convenience DynamicImage reimplements all image processing functions.

DynamicImage implement the GenericImageView and GenericImage traits for RGBA pixels.

`SubImage`

A view into another image, delimited by the coordinates of a rectangle. The coordinates given set the position of the top left corner of the rectangle. This is used to perform image processing functions on a subregion of an image.

use image::{GenericImageView, ImageBuffer, RgbImage, imageops};

let mut img: RgbImage = ImageBuffer::new(512, 512);
let subimg = imageops::crop(&mut img, 0, 0, 100, 100);

assert!(subimg.dimensions() == (100, 100));

Image Processing Functions

These are the functions defined in the imageops module. All functions operate on types that implement the GenericImage trait. Note that some of the functions are very slow in debug mode. Make sure to use release mode if you experience any performance issues.

blur: Performs a Gaussian blur on the supplied image.
brighten: Brighten the supplied image.
huerotate: Hue rotate the supplied image by degrees.
contrast: Adjust the contrast of the supplied image.
crop: Return a mutable view into an image.
filter3x3: Perform a 3x3 box filter on the supplied image.
flip_horizontal: Flip an image horizontally.
flip_vertical: Flip an image vertically.
grayscale: Convert the supplied image to grayscale.
invert: Invert each pixel within the supplied image This function operates in place.
resize: Resize the supplied image to the specified dimensions.
rotate180: Rotate an image 180 degrees clockwise.
rotate270: Rotate an image 270 degrees clockwise.
rotate90: Rotate an image 90 degrees clockwise.
unsharpen: Performs an unsharpen mask on the supplied image.

For more options, see the imageproc crate.

Examples

Opening and Saving Images

image provides the open function for opening images from a path. The image format is determined from the path's file extension. An io module provides a reader which offer some more control.

use image::GenericImageView;

fn main() {
    // Use the open function to load an image from a Path.
    // `open` returns a `DynamicImage` on success.
    let img = image::open("tests/images/jpg/progressive/cat.jpg").unwrap();

    // The dimensions method returns the images width and height.
    println!("dimensions {:?}", img.dimensions());

    // The color method returns the image's `ColorType`.
    println!("{:?}", img.color());

    // Write the contents of this image to the Writer in PNG format.
    img.save("test.png").unwrap();
}

Generating Fractals

//! An example of generating julia fractals.
fn main() {
    let imgx = 800;
    let imgy = 800;

    let scalex = 3.0 / imgx as f32;
    let scaley = 3.0 / imgy as f32;

    // Create a new ImgBuf with width: imgx and height: imgy
    let mut imgbuf = image::ImageBuffer::new(imgx, imgy);

    // Iterate over the coordinates and pixels of the image
    for (x, y, pixel) in imgbuf.enumerate_pixels_mut() {
        let r = (0.3 * x as f32) as u8;
        let b = (0.3 * y as f32) as u8;
        *pixel = image::Rgb([r, 0, b]);
    }

    // A redundant loop to demonstrate reading image data
    for x in 0..imgx {
        for y in 0..imgy {
            let cx = y as f32 * scalex - 1.5;
            let cy = x as f32 * scaley - 1.5;

            let c = num_complex::Complex::new(-0.4, 0.6);
            let mut z = num_complex::Complex::new(cx, cy);

            let mut i = 0;
            while i < 255 && z.norm() <= 2.0 {
                z = z * z + c;
                i += 1;
            }

            let pixel = imgbuf.get_pixel_mut(x, y);
            let image::Rgb(data) = *pixel;
            *pixel = image::Rgb([data[0], i as u8, data[2]]);
        }
    }

    // Save the image as “fractal.png”, the format is deduced from the path
    imgbuf.save("fractal.png").unwrap();
}

Example output:

Writing raw buffers

If the high level interface is not needed because the image was obtained by other means, image provides the function save_buffer to save a buffer to a file.

fn main() {

    let buffer: &[u8] = unimplemented!(); // Generate the image data

    // Save the buffer as "image.png"
    image::save_buffer("image.png", buffer, 800, 600, image::ColorType::Rgb8).unwrap()
}

cycraig/image