# Image [](https://travis-ci.org/PistonDevelopers/image)
Maintainers: @nwin, @ccgn
[How to contribute](https://github.com/PistonDevelopers/piston/blob/master/CONTRIBUTING.md)
## 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 ```ImageBuf```.
### Usage
Add the following to the Cargo.toml in your project:
```
[dependencies.image]
git = "https://github.com/PistonDevelopers/image"
```
and import using ```extern crate```:
```rust
extern crate image;
//Use image::
```
## 1. Documentation
http://www.rust-ci.org/PistonDevelopers/piston/doc/image/index.html
## 2. Supported Image Formats
```image``` provides implementations of common image format encoders and decoders.
### 2.1 Supported Image Formats
| JPEG | Baseline JPEG | Baseline JPEG |
| PNG | All supported color types | Same as decoding|
| GIF | Yes | No |
| Webp | Lossy(Luma channel only) | No |
| PPM | No | 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.
```rust
pub trait GenericImage<P> {
///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) -> P;
///Put a pixel at location (x, y)
fn put_pixel(&mut self, x: u32, y: u32, pixel: P);
///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 ```ImageBuf```
An image parametarised 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.
```rust
extern crate image;
use image::{
GenericImage
ImageBuf,
};
//Construct a new ImageBuf with the specified width and height.
let img = ImageBuf::new(512, 512);
//Construct a new by repeated calls to the supplied closure.
let img = ImageBuf::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 using 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 ```ImageBuf<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.
```rust
extern crate image;
use image::{
GenericImage
ImageBuf,
imageops
};
let mut img = ImageBuf::new(512, 512);
let subimg = imageops::crop(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
+ **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.
```rust
extern crate image;
use std::io::File;
use image::GenericImage;
fn main() {
//Use the open function to load an image from a PAth.
//```open``` returns a dynamic image.
let img = image::open(&Path::new("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());
let fout = File::create(&Path::new("test.png")).unwrap();
//Write the contents of this image to the Writer in PNG format.
let _ = img.save(fout, image::PNG);
}
```
### 6.2 Generating Fractals
```rust
//!An example of generating julia fractals.
extern crate num;
extern crate image;
use std::io::File;
use num::complex::Complex;
// The GenericImage trait provides the method put_pixel.
use image::GenericImage;
fn main() {
let max_iterations = 256u16;
let imgx = 800;
let imgy = 800;
let scalex = 4.0 / imgx as f32;
let scaley = 4.0 / imgy as f32;
//Create a new ImgBuf with width: imgx and height: imgy
let mut imbuf = image::ImageBuf::new(imgx, imgy);
for y in range(0, imgy) {
let cy = y as f32 * scaley - 2.0;
for x in range(0, imgx) {
let cx = x as f32 * scalex - 2.0;
let mut z = Complex::new(cx, cy);
let c = Complex::new(-0.4, 0.6);
let mut i = 0;
for t in range(0, max_iterations) {
if z.norm() > 2.0 {
break
}
z = z * z + c;
i = t;
}
// Create an 8bit pixel of type Luma and value i
let pixel = image::Luma(i as u8);
// Put a pixel in the image at coordinates x and y
imbuf.put_pixel(x, y, pixel);
}
}
// Save the image as "fractal.png"
let fout = File::create(&Path::new("fractal.png")).unwrap();
//We must indicate the image's color type and what format to save as.
let _ = image::ImageLuma8(imbuf).save(fout, image::PNG);
}
```
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.
```rust
extern crate image;
fn main() {
let buffer: &[u8] = ...; // Generate the image data
// Save the buffer as "image.png"
image::save_buffer(&Path::new("image.png"), buffer, 800, 600, image::RGB(8))
}
```