251 lines
9.6 KiB
Markdown
251 lines
9.6 KiB
Markdown
# Image
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[](https://crates.io/crates/image)
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[](https://docs.rs/image)
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[](https://github.com/image-rs/image/actions)
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[](https://gitter.im/image-rs/image?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge)
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Maintainers: [@HeroicKatora](https://github.com/HeroicKatora), [@fintelia](https://github.com/fintelia)
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[How to contribute](https://github.com/image-rs/organization/blob/master/CONTRIBUTING.md)
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## An Image Processing Library
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This crate provides basic image processing functions and methods for converting to and from various image formats.
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All image processing functions provided operate on types that implement the `GenericImageView` and `GenericImage` traits and return an `ImageBuffer`.
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## Supported Image Formats
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`image` provides implementations of common image format encoders and decoders.
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<!--- NOTE: Make sure to keep this table in sync with the one in src/lib.rs -->
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| Format | Decoding | Encoding |
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| ------ | -------- | -------- |
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| AVIF | Only 8-bit \*\* | Lossy |
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| BMP | Yes | Rgb8, Rgba8, Gray8, GrayA8 |
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| DDS | DXT1, DXT3, DXT5 | No |
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| Farbfeld | Yes | Yes |
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| GIF | Yes | Yes |
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| ICO | Yes | Yes |
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| JPEG | Baseline and progressive | Baseline JPEG |
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| OpenEXR | Rgb32F, Rgba32F (no dwa compression) | Rgb32F, Rgba32F (no dwa compression) |
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| PNG | All supported color types | Same as decoding |
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| PNM | PBM, PGM, PPM, standard PAM | Yes |
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| QOI | Yes | Yes |
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| TGA | Yes | Rgb8, Rgba8, Bgr8, Bgra8, Gray8, GrayA8 |
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| TIFF | Baseline(no fax support) + LZW + PackBits | Rgb8, Rgba8, Gray8 |
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| WebP | Yes | Rgb8, Rgba8 \* |
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- \* Requires the `webp-encoder` feature, uses the libwebp C library.
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- \*\* Requires the `avif-decoder` feature, uses the libdav1d C library.
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### The [`ImageDecoder`](https://docs.rs/image/*/image/trait.ImageDecoder.html) and [`ImageDecoderRect`](https://docs.rs/image/*/image/trait.ImageDecoderRect.html) Traits
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All image format decoders implement the `ImageDecoder` trait which provide
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basic methods for getting image metadata and decoding images. Some formats
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additionally provide `ImageDecoderRect` implementations which allow for
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decoding only part of an image at once.
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The most important methods for decoders are...
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+ **dimensions**: Return a tuple containing the width and height of the image.
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+ **color_type**: Return the color type of the image data produced by this decoder.
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+ **read_image**: Decode the entire image into a slice of bytes.
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## Pixels
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`image` provides the following pixel types:
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+ **Rgb**: RGB pixel
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+ **Rgba**: RGB with alpha (RGBA pixel)
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+ **Luma**: Grayscale pixel
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+ **LumaA**: Grayscale with alpha
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All pixels are parameterised by their component type.
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## Images
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Individual pixels within images are indexed with (0,0) at the top left corner.
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### The [`GenericImageView`](https://docs.rs/image/*/image/trait.GenericImageView.html) and [`GenericImage`](https://docs.rs/image/*/image/trait.GenericImage.html) Traits
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Traits that provide methods for inspecting (`GenericImageView`) and manipulating (`GenericImage`) images, parameterised over the image's pixel type.
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Some of these methods for `GenericImageView` are...
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+ **dimensions**: Return a tuple containing the width and height of the image.
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+ **get_pixel**: Returns the pixel located at (x, y).
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+ **pixels**: Returns an Iterator over the pixels of this image.
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While some of the methods for `GenericImage` are...
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+ **put_pixel**: Put a pixel at location (x, y).
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+ **copy_from**: Copies all of the pixels from another image into this image.
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### Representation of Images
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`image` provides two main ways of representing image data:
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#### [`ImageBuffer`](https://docs.rs/image/*/image/struct.ImageBuffer.html)
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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.
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```rust
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use image::{GenericImage, GenericImageView, ImageBuffer, RgbImage};
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// Construct a new RGB ImageBuffer with the specified width and height.
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let img: RgbImage = ImageBuffer::new(512, 512);
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// Construct a new by repeated calls to the supplied closure.
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let mut img = ImageBuffer::from_fn(512, 512, |x, y| {
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if x % 2 == 0 {
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image::Luma([0u8])
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} else {
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image::Luma([255u8])
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}
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});
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// Obtain the image's width and height.
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let (width, height) = img.dimensions();
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// Access the pixel at coordinate (100, 100).
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let pixel = img[(100, 100)];
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// Or use the `get_pixel` method from the `GenericImage` trait.
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let pixel = *img.get_pixel(100, 100);
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// Put a pixel at coordinate (100, 100).
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img.put_pixel(100, 100, pixel);
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// Iterate over all pixels in the image.
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for pixel in img.pixels() {
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// Do something with pixel.
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}
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```
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#### [`DynamicImage`](https://docs.rs/image/*/image/enum.DynamicImage.html)
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A `DynamicImage` is an enumeration over all supported `ImageBuffer<P>` types.
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Its exact image type is determined at runtime. It is the type returned when opening an image.
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For convenience `DynamicImage` reimplements all image processing functions.
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`DynamicImage` implement the `GenericImageView` and `GenericImage` traits for RGBA pixels.
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#### [`SubImage`](https://docs.rs/image/*/image/struct.SubImage.html)
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A view into another image, delimited by the coordinates of a rectangle.
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The coordinates given set the position of the top left corner of the rectangle.
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This is used to perform image processing functions on a subregion of an image.
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```rust
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use image::{GenericImageView, ImageBuffer, RgbImage, imageops};
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let mut img: RgbImage = ImageBuffer::new(512, 512);
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let subimg = imageops::crop(&mut img, 0, 0, 100, 100);
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assert!(subimg.dimensions() == (100, 100));
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```
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## Image Processing Functions
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These are the functions defined in the `imageops` module. All functions operate on types that implement the `GenericImage` trait.
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Note that some of the functions are very slow in debug mode. Make sure to use release mode if you experience any performance issues.
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+ **blur**: Performs a Gaussian blur on the supplied image.
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+ **brighten**: Brighten the supplied image.
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+ **huerotate**: Hue rotate the supplied image by degrees.
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+ **contrast**: Adjust the contrast of the supplied image.
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+ **crop**: Return a mutable view into an image.
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+ **filter3x3**: Perform a 3x3 box filter on the supplied image.
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+ **flip_horizontal**: Flip an image horizontally.
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+ **flip_vertical**: Flip an image vertically.
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+ **grayscale**: Convert the supplied image to grayscale.
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+ **invert**: Invert each pixel within the supplied image This function operates in place.
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+ **resize**: Resize the supplied image to the specified dimensions.
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+ **rotate180**: Rotate an image 180 degrees clockwise.
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+ **rotate270**: Rotate an image 270 degrees clockwise.
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+ **rotate90**: Rotate an image 90 degrees clockwise.
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+ **unsharpen**: Performs an unsharpen mask on the supplied image.
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For more options, see the [`imageproc`](https://crates.io/crates/imageproc) crate.
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## Examples
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### Opening and Saving Images
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`image` provides the `open` function for opening images from a path. The image
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format is determined from the path's file extension. An `io` module provides a
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reader which offer some more control.
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```rust,no_run
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use image::GenericImageView;
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fn main() {
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// Use the open function to load an image from a Path.
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// `open` returns a `DynamicImage` on success.
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let img = image::open("tests/images/jpg/progressive/cat.jpg").unwrap();
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// The dimensions method returns the images width and height.
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println!("dimensions {:?}", img.dimensions());
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// The color method returns the image's `ColorType`.
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println!("{:?}", img.color());
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// Write the contents of this image to the Writer in PNG format.
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img.save("test.png").unwrap();
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}
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```
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### Generating Fractals
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```rust,no_run
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//! An example of generating julia fractals.
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fn main() {
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let imgx = 800;
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let imgy = 800;
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let scalex = 3.0 / imgx as f32;
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let scaley = 3.0 / imgy as f32;
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// Create a new ImgBuf with width: imgx and height: imgy
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let mut imgbuf = image::ImageBuffer::new(imgx, imgy);
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// Iterate over the coordinates and pixels of the image
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for (x, y, pixel) in imgbuf.enumerate_pixels_mut() {
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let r = (0.3 * x as f32) as u8;
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let b = (0.3 * y as f32) as u8;
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*pixel = image::Rgb([r, 0, b]);
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}
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// A redundant loop to demonstrate reading image data
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for x in 0..imgx {
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for y in 0..imgy {
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let cx = y as f32 * scalex - 1.5;
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let cy = x as f32 * scaley - 1.5;
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let c = num_complex::Complex::new(-0.4, 0.6);
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let mut z = num_complex::Complex::new(cx, cy);
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let mut i = 0;
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while i < 255 && z.norm() <= 2.0 {
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z = z * z + c;
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i += 1;
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}
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let pixel = imgbuf.get_pixel_mut(x, y);
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let image::Rgb(data) = *pixel;
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*pixel = image::Rgb([data[0], i as u8, data[2]]);
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}
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}
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// Save the image as “fractal.png”, the format is deduced from the path
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imgbuf.save("fractal.png").unwrap();
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}
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```
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Example output:
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<img src="examples/fractal.png" alt="A Julia Fractal, c: -0.4 + 0.6i" width="500" />
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### Writing raw buffers
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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.
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```rust,no_run
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fn main() {
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let buffer: &[u8] = unimplemented!(); // Generate the image data
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// Save the buffer as "image.png"
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image::save_buffer("image.png", buffer, 800, 600, image::ColorType::Rgb8).unwrap()
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}
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```
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