RGB to YCbCr

rgb2ycbcr.py

def rgb_to_ycbcr(r, g, b):
    assert(255>=r)
    assert(255>=g)
    assert(255>=b)
    y  = 0.299*r + 0.587*g    + 0.114*b
    cb = 128     - 0.168736*r - 0.331364*g + 0.5*b
    cr = 128     + 0.5*r      - 0.418688*g - 0.081312*b
    return int(y), int(cb), int(cr)

rgb2ycbcr.rs

fn rgb_to_ycbcr(r: u8, g: u8, b: u8) -> (f64, f64, f64) {
    let r = r as f64;
    let g = g as f64;
    let b = b as f64;

    let y : f64 = 0.299*r + 0.587*g    + 0.114*b;
    let cb: f64 = 128.0   - 0.168736*r - 0.331364*g + 0.5*b;
    let cr: f64 = 128.0   + 0.5*r      - 0.418688*g - 0.081312*b;
    (y, cb, cr)
}

ycbcr2rgb.py

def ycbcr_to_rgb(y, cb, cr):
    r = y + 1.402   * (cr-128)
    g = y - 0.34414 * (cb-128) -  0.71414 * (cr-128)
    b = y + 1.772   * (cb-128)
    if b < 255: b += 1
    return int(r), int(g), int(b)

ycbcr2rgb.rs

fn ycbcr_to_rgb(y: f64, cb: f64, cr: f64) -> (u8, u8, u8) {
    let r: f64 = y + 1.402   * (cr-128.0);
    let g: f64 = y - 0.34414 * (cb-128.0) -  0.71414 * (cr-128.0);
    let mut b: f64 = y + 1.772   * (cb-128.0);
    if b < 255.0f64 {
        b += 1.0;
    }
    (r as u8, g as u8, b as u8)
}