DCV Color Primitives - dcp

DCV Color Primitives is a library to perform image color model conversion.

Design guidelines

Aware of the underlying hardware and supplemental cpu extension sets (up to avx2)
Support data coming from a single buffer or coming from multiple image planes
Support non-tightly packed data
Support images greater than 4GB (64 bit)
Support ARM (aarch64)[*]
Support WebAssembly[*]

Image format conversion

The library is currenty able to convert the following pixel formats:

| Source pixel format | Destination pixel formats | | -------------------- | -------------------------- | | ARGB | I420, I444, NV12 | | BGR | I420, I444, NV12 | | BGRA | I420, I444, NV12, RGB | | I420 | BGRA | | I444 | BGRA | | NV12 | BGRA | | RGB | BGRA |

Color models

The supported color models are:

YCbCr, ITU-R Recommendation BT.601 (standard video system)
YCbCr, ITU-R Recommendation BT.709 (CSC systems)

Requirements

Rust stable (at least 1.39)
Python3 and Fractions module (needed only if you want to execute the benchmark)

Windows

Install rustup: https://www.rust-lang.org/tools/install
If you want to execute the benchmark:
- Install Python 3: https://www.python.org/downloads/
- Install fraction module: pip install Fraction

Linux

Install rustup (see https://forge.rust-lang.org/infra/other-installation-methods.html) curl https://sh.rustup.rs -sSf | sh
If you want to execute the benchmark:
- Install Python 3 (example for Ubuntu): apt install python3
- Install fraction module: pip install Fraction

You may require administrative privileges.

Building

Open a terminal inside the library root directory.

To build for debug experience: cargo build

To build an optimized library: cargo build --release

Run unit tests: cargo test

Run benchmark: python benches/geninput.py cargo bench

WebAssembly

Install the needed dependencies: rustup target add wasm32-unknown-unknown

To build for debug experience: cargo build --target wasm32-unknown-unknown

To test, ensure you have installed wasm-pack. Then: wasm-pack test --node

Usage

Initialize the library

This function has to be called before any other library function call:

```rust use dcvcolorprimitives as dcp;

fn main() { dcp::initialize(); } ```

Image conversion

Convert an image from bgra to nv12 (single plane) format containing yuv in BT601:

```rust use dcvcolorprimitives as dcp; use dcp::{convert_image, ColorSpace, ImageFormat, PixelFormat};

fn main() { dcp::initialize();

const WIDTH: u32 = 640;
const HEIGHT: u32 = 480;

let src_buffers: &[&[u8]] = &[&[0u8; 4 * (WIDTH as usize) * (HEIGHT as usize)]];
let dst_buffers: &mut [&mut [u8]] =
    &mut [&mut [0u8; 3 * (WIDTH as usize) * (HEIGHT as usize) / 2]];

let src_format = ImageFormat {
    pixel_format: PixelFormat::Bgra,
    color_space: ColorSpace::Lrgb,
    num_planes: 1,
};

let dst_format = ImageFormat {
    pixel_format: PixelFormat::Nv12,
    color_space: ColorSpace::Bt601,
    num_planes: 1,
};

convert_image(
    WIDTH,
    HEIGHT,
    &src_format,
    None,
    src_buffers,
    &dst_format,
    None,
    dst_buffers,
);

} ```

Error Handling

The library functions return a Result describing the operation outcome:

| Result | Description | | ---------------------------------- | --------------------------------------------------------------------- | | Ok(()) | The operation succeeded | | Err(ErrorKind::NotInitialized) | The library is not initialized | | Err(ErrorKind::InvalidValue) | One or more parameters have invalid values for the called function | | Err(ErrorKind::InvalidOperation) | The combination of parameters is unsupported for the called function | | Err(ErrorKind::NotEnoughData) | One or more buffers are not correctly sized |

In the following example, result will match Err(ErrorKind::InvalidValue), because ColorSpace::Bt709 color space is not compatible with PixelFormat::Bgra:

```rust use dcvcolorprimitives as dcp; use dcp::{convert_image, ColorSpace, ErrorKind, ImageFormat, PixelFormat};

fn main() { dcp::initialize();

const WIDTH: u32 = 640;
const HEIGHT: u32 = 480;

let src_buffers: &[&[u8]] = &[&[0u8; 4 * (WIDTH as usize) * (HEIGHT as usize)]];
let dst_buffers: &mut [&mut [u8]] =
    &mut [&mut [0u8; 3 * (WIDTH as usize) * (HEIGHT as usize) / 2]];

let src_format = ImageFormat {
    pixel_format: PixelFormat::Bgra,
    color_space: ColorSpace::Bt709,
    num_planes: 1,
};

let dst_format = ImageFormat {
    pixel_format: PixelFormat::Nv12,
    color_space: ColorSpace::Bt601,
    num_planes: 1,
};

let status = convert_image(
    WIDTH,
    HEIGHT,
    &src_format,
    None,
    src_buffers,
    &dst_format,
    None,
    dst_buffers,
);

match status {
    Err(ErrorKind::InvalidValue) => (),
    _ => panic!("Expected ErrorKind::InvalidValue"),
}

} ```

Even better, you might want to propagate errors to the caller function or mix with some other error types: ```rust use dcvcolorprimitives as dcp; use dcp::{convert_image, ColorSpace, ImageFormat, PixelFormat}; use std::error;

fn main() -> Result<(), Box> { dcp::initialize();

const WIDTH: u32 = 640;
const HEIGHT: u32 = 480;

let src_buffers: &[&[u8]] = &[&[0u8; 4 * (WIDTH as usize) * (HEIGHT as usize)]];
let dst_buffers: &mut [&mut [u8]] =
    &mut [&mut [0u8; 3 * (WIDTH as usize) * (HEIGHT as usize) / 2]];

let src_format = ImageFormat {
    pixel_format: PixelFormat::Bgra,
    color_space: ColorSpace::Bt709,
    num_planes: 1,
};

let dst_format = ImageFormat {
    pixel_format: PixelFormat::Nv12,
    color_space: ColorSpace::Bt601,
    num_planes: 1,
};

convert_image(
    WIDTH,
    HEIGHT,
    &src_format,
    None,
    src_buffers,
    &dst_format,
    None,
    dst_buffers,
)?;

Ok(())

} ```

Buffer size computation

So far, buffers were sized taking into account the image pixel format and dimensions; However, you can use a function to compute how many bytes are needed to store an image of a given format and size:

```rust use dcvcolorprimitives as dcp; use dcp::{getbufferssize, ColorSpace, ImageFormat, PixelFormat}; use std::error;

fn main() -> Result<(), Box> { dcp::initialize();

const WIDTH: u32 = 640;
const HEIGHT: u32 = 480;
const NUM_PLANES: u32 = 1;

let format = ImageFormat {
    pixel_format: PixelFormat::Bgra,
    color_space: ColorSpace::Lrgb,
    num_planes: NUM_PLANES,
};

let sizes: &mut [usize] = &mut [0usize; NUM_PLANES as usize];
get_buffers_size(WIDTH, HEIGHT, &format, None, sizes)?;

let buffer: Vec<_> = vec![0u8; sizes[0]];

// Do something with buffer
// --snip--

Ok(())

} ```

Image planes

If your data is scattered in multiple buffers that are not necessarily contiguous, you can provide image planes:

```rust use dcvcolorprimitives as dcp; use dcp::{convertimage, getbuffers_size, ColorSpace, ImageFormat, PixelFormat}; use std::error;

fn main() -> Result<(), Box> { dcp::initialize();

const WIDTH: u32 = 640;
const HEIGHT: u32 = 480;
const NUM_SRC_PLANES: u32 = 2;
const NUM_DST_PLANES: u32 = 1;

let src_format = ImageFormat {
    pixel_format: PixelFormat::Nv12,
    color_space: ColorSpace::Bt709,
    num_planes: NUM_SRC_PLANES,
};

let src_sizes: &mut [usize] = &mut [0usize; NUM_SRC_PLANES as usize];
get_buffers_size(WIDTH, HEIGHT, &src_format, None, src_sizes)?;

let src_y: Vec<_> = vec![0u8; src_sizes[0]];
let src_uv: Vec<_> = vec![0u8; src_sizes[1]];
let src_buffers: &[&[u8]] = &[&src_y[..], &src_uv[..]];

let dst_format = ImageFormat {
    pixel_format: PixelFormat::Bgra,
    color_space: ColorSpace::Lrgb,
    num_planes: NUM_DST_PLANES,
};

let dst_sizes: &mut [usize] = &mut [0usize; NUM_DST_PLANES as usize];
get_buffers_size(WIDTH, HEIGHT, &dst_format, None, dst_sizes)?;

let mut dst_rgba: Vec<_> = vec![0u8; dst_sizes[0]];
let dst_buffers: &mut [&mut [u8]] = &mut [&mut dst_rgba[..]];

convert_image(
    WIDTH,
    HEIGHT,
    &src_format,
    None,
    src_buffers,
    &dst_format,
    None,
    dst_buffers,
)?;

Ok(())

} ```

Stride support

To take into account data which is not tightly packed, you can provide image strides:

```rust use dcvcolorprimitives as dcp; use dcp::{convertimage, getbuffers_size, ColorSpace, ImageFormat, PixelFormat}; use std::error;

fn main() -> Result<(), Box> { dcp::initialize();

const WIDTH: u32 = 640;
const HEIGHT: u32 = 480;
const NUM_SRC_PLANES: u32 = 1;
const NUM_DST_PLANES: u32 = 2;
const RGB_STRIDE: usize = 4 * (((3 * (WIDTH as usize)) + 3) / 4);

let src_format = ImageFormat {
    pixel_format: PixelFormat::Bgr,
    color_space: ColorSpace::Lrgb,
    num_planes: NUM_SRC_PLANES,
};

let src_strides: &[usize] = &[RGB_STRIDE];

let src_sizes: &mut [usize] = &mut [0usize; NUM_SRC_PLANES as usize];
get_buffers_size(WIDTH, HEIGHT, &src_format, Some(src_strides), src_sizes)?;

let src_rgba: Vec<_> = vec![0u8; src_sizes[0]];
let src_buffers: &[&[u8]] = &[&src_rgba[..]];

let dst_format = ImageFormat {
    pixel_format: PixelFormat::Nv12,
    color_space: ColorSpace::Bt709,
    num_planes: NUM_DST_PLANES,
};

let dst_sizes: &mut [usize] = &mut [0usize; NUM_DST_PLANES as usize];
get_buffers_size(WIDTH, HEIGHT, &dst_format, None, dst_sizes)?;

let mut dst_y: Vec<_> = vec![0u8; dst_sizes[0]];
let mut dst_uv: Vec<_> = vec![0u8; dst_sizes[1]];
let dst_buffers: &mut [&mut [u8]] = &mut [&mut dst_y[..], &mut dst_uv[..]];

convert_image(
    WIDTH,
    HEIGHT,
    &src_format,
    Some(src_strides),
    src_buffers,
    &dst_format,
    None,
    dst_buffers,
)?;

Ok(())

} ```

See documentation for further information.

C bindings

DCV Color Primitives provides C bindings. A static library will be automatically generated for the default build.

In order to include DCV Color Primitives inside your application library, you need to: * Statically link to dcvcolorprimitives * Link to ws2_32.lib and userenv.lib, for Windows * Link to dl, for Linux

The API is slightly different than the rust one. Check dcvcolorprimitives.h for examples and further information.

A meson build system is provided in order to build the static library and install it together with include file and a pkgconfig file. There are also some unit tests written in C, to add some coverage also for the bindings. Minimal instructions are provided below, refer to meson's help for further instructions:

Windows Visual Studio is required. At least the following packages are required:
- MSBuild
- MSVC - C++ build tools
- Windows 10 SDK
Install meson, you can choose one of the following methods:
1. Using meson msi installer
2. Download from https://github.com/mesonbuild/meson/releases
3. Install both Meson and Ninja
4. Install meson through pip
5. Download and install python3: https://www.python.org/downloads/
6. Install meson and ninja: pip install meson ninja
All build commands have to be issued from Native Tools Command Prompt for VS (x86 or x64 depending on what platform you want to build)
Linux The following example is for Ubuntu:

```

install python3

apt install python3

install meson. See https://mesonbuild.com/Getting-meson.html for details or if you want to install through pip.

apt install meson

install ninja

apt install ninja-build ```

You may require administrative privileges.
Build Move inside the library root directory: cd `dcv_color_primitives_root_dir`

Then: meson --buildtype release builddir ninja -C builddir
Run the tests cd builddir meson test -t 10

A timeout scale factor of 10 is required because some tests take longer than default 30 seconds to complete.
Install ninja -C builddir install

License

This library is licensed under the MIT-0 License. See the LICENSE file.

DCV Color Primitives - dcp

Design guidelines

Image format conversion

Color models

Requirements

Windows

Linux

Building

WebAssembly

Usage

Initialize the library

Image conversion

Error Handling

Buffer size computation

Image planes

Stride support

C bindings

install python3

install meson. See https://mesonbuild.com/Getting-meson.html for details or if you want to install through pip.

install ninja

License