gecko-dev/third_party/rust/image

Image

Maintainers: @nwin, @ccgn

How to contribute

An Image Processing Library

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

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

Usage

Add the following to the Cargo.toml in your project:

[dependencies]
image = "*"

and import using extern crate:

extern crate image;

// use image::

1. Documentation

https://docs.rs/image

2. Supported Image Formats

image provides implementations of common image format encoders and decoders.

2.1 Supported Image Formats

Format	Decoding	Encoding
PNG	All supported color types	Same as decoding
JPEG	Baseline and progressive	Baseline JPEG
GIF	Yes	Yes
BMP	Yes	RGB(8), RGBA(8), Gray(8), GrayA(8)
ICO	Yes	Yes
TIFF	Baseline(no fax support) + LZW + PackBits	No
Webp	Lossy(Luma channel only)	No
PNM	PBM, PGM, PPM, standard PAM	Yes

2.2 The ImageDecoder Trait

All image format decoders implement the ImageDecoder trait which provides the following methods:

• dimensions: Return a tuple containing the width and height of the image
• colortype: Return the color type of the image.
• row_len: Returns the length in bytes of one decoded row of the image
• read_scanline: Read one row from the image into buf Returns the row index
• read_image: Decode the entire image and return it as a Vector
• load_rect: Decode a specific region of the image

3 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.

4 Images

4.1 The GenericImage Trait

A trait that provides functions for manipulating images, parameterised over the image's pixel type.

pub trait GenericImage {
    /// The pixel type.
    type Pixel: Pixel;

    /// The width and height of this image.
    fn dimensions(&self) -> (u32, u32);

    /// The bounding rectangle of this image.
    fn bounds(&self) -> (u32, u32, u32, u32);

    /// Return the pixel located at (x, y)
    fn get_pixel(&self, x: u32, y: u32) -> Self::Pixel;

    /// Put a pixel at location (x, y)
    fn put_pixel(&mut self, x: u32, y: u32, pixel: Self::Pixel);

    /// Return an Iterator over the pixels of this image.
    /// The iterator yields the coordinates of each pixel
    /// along with their value
    fn pixels(&self) -> Pixels<Self>;
}

4.2 Representation of Images

image provides two main ways of representing image data:

4.2.1 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 GenericImage trait.

extern crate image;

use image::{GenericImage, ImageBuffer};

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

// Construct a new by repeated calls to the supplied closure.
let 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.
}

4.2.2 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's reimplement all image processing functions.

DynamicImage implement the GenericImage trait for RGBA pixels.

4.2.3 SubImage

A view into another image, delimited by the coordinates of a rectangle. This is used to perform image processing functions on a subregion of an image.

extern crate image;

use image::{GenericImage, ImageBuffer, imageops};

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

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

5 Image Processing Functions

These are the functions defined in the imageops module. All functions operate on types that implement the GenericImage trait.

• 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

6 Examples

6.1 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.

extern crate image;

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("test.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();
}

6.2 Generating Fractals

//! An example of generating julia fractals.
extern crate image;
extern crate num_complex;

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 data = (*pixel as image::Rgb<u8>).data;
            *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:

6.3 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.

extern crate image;

fn main() {

    let buffer: &[u8] = ...; // Generate the image data

    // Save the buffer as "image.png"
    image::save_buffer("image.png", buffer, 800, 600, image::RGB(8)).unwrap()
}