libcruft-util/colour.cpp

/*
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 *
 * Copyright 2010-2017 Danny Robson <danny@nerdcruft.net>
 */

#include "colour.hpp"

#include "ascii.hpp"
#include "parse/value.hpp"


///////////////////////////////////////////////////////////////////////////////
static cruft::srgba4f
parse_hex (cruft::view<const char*> &str)
{
    if (str.size () != strlen ("#012345"))
        throw std::invalid_argument ("expected length of 7");

    if (str[0] != '#')
        throw std::invalid_argument ("expected leading '#'");

    if (!cruft::ascii::is_hex (str[1]) ||
        !cruft::ascii::is_hex (str[2]) ||
        !cruft::ascii::is_hex (str[3]) ||
        !cruft::ascii::is_hex (str[4]) ||
        !cruft::ascii::is_hex (str[5]) ||
        !cruft::ascii::is_hex (str[6]))
    {
        throw std::invalid_argument ("expected hex digits");
    }

    uint8_t r = cruft::ascii::from_hex (str[1]) << 4u | cruft::ascii::from_hex (str[2]);
    uint8_t g = cruft::ascii::from_hex (str[3]) << 4u | cruft::ascii::from_hex (str[4]);
    uint8_t b = cruft::ascii::from_hex (str[5]) << 4u | cruft::ascii::from_hex (str[6]);

    str = str.consume (7u);
    return cruft::srgba<4,uint8_t> { r, g, b, 255 }.template cast<float> ();
}



///////////////////////////////////////////////////////////////////////////////
template <>
cruft::srgba4f
cruft::parse::value<cruft::srgba4f> (cruft::view<const char*> &str)
{
    return parse_hex (str);
}