# Image
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Maintainers: [@HeroicKatora](https://github.com/HeroicKatora), [@fintelia](https://github.com/fintelia)

[How to contribute](https://github.com/image-rs/organization/blob/master/CONTRIBUTING.md)

## 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.

<!--- NOTE: Make sure to keep this table in sync with the one in src/lib.rs -->

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

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

### The [`ImageDecoder`](https://docs.rs/image/*/image/trait.ImageDecoder.html) and [`ImageDecoderRect`](https://docs.rs/image/*/image/trait.ImageDecoderRect.html) 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**: RGB with alpha (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`](https://docs.rs/image/*/image/trait.GenericImageView.html) and [`GenericImage`](https://docs.rs/image/*/image/trait.GenericImage.html) 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`](https://docs.rs/image/*/image/struct.ImageBuffer.html)
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.

```rust
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`](https://docs.rs/image/*/image/enum.DynamicImage.html)
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`](https://docs.rs/image/*/image/struct.SubImage.html)
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.

```rust
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`](https://crates.io/crates/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.

```rust,no_run
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

```rust,no_run
//! 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:

<img src="examples/fractal.png" alt="A Julia Fractal, c: -0.4 + 0.6i" width="500" />

### 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.

```rust,no_run
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()
}
```
