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color: Support CSS Color Level 4 rgb & hsl syntax (#113) #121

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Merged
merged 1 commit into from
Apr 11, 2017
Merged

color: Support CSS Color Level 4 rgb & hsl syntax (#113) #121

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193 changes: 135 additions & 58 deletions src/color.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@

use std::cmp;
use std::fmt;
use std::f32::consts::PI;

use super::{Token, Parser, ToCss};
use tokenizer::NumericValue;
Expand Down Expand Up @@ -398,75 +399,151 @@ fn clamp_f32(val: f32) -> u8 {

#[inline]
fn parse_color_function(name: &str, arguments: &mut Parser) -> Result<Color, ()> {
let (is_rgb, has_alpha) = match_ignore_ascii_case! { name,
"rgba" => (true, true),
"rgb" => (true, false),
"hsl" => (false, false),
"hsla" => (false, true),
let is_rgb = match_ignore_ascii_case! { name,
"rgb" | "rgba" => true,
"hsl" | "hsla" => false,
_ => return Err(())
};

let (red, green, blue, uses_commas) = if is_rgb {
parse_rgb_components_rgb(arguments)?
} else {
parse_rgb_components_hsl(arguments)?
};

let alpha = if !arguments.is_exhausted() {
if uses_commas {
try!(arguments.expect_comma());
} else {
match try!(arguments.next()) {
Token::Delim('/') => {},
_ => return Err(())
};
};
let token = try!(arguments.next());
match token {
Token::Number(NumericValue { value: v, .. }) => {
clamp_f32(v)
}
Token::Percentage(ref v) => {
clamp_f32(v.unit_value)
}
_ => {
return Err(())
}
}
} else {
255
};

try!(arguments.expect_exhausted());
rgba(red, green, blue, alpha)
}


#[inline]
fn parse_rgb_components_rgb(arguments: &mut Parser) -> Result<(u8, u8, u8, bool), ()> {
let red: u8;
let green: u8;
let blue: u8;
if is_rgb {
// Either integers or percentages, but all the same type.
// https://drafts.csswg.org/css-color/#rgb-functions
match try!(arguments.next()) {
Token::Number(NumericValue { int_value: Some(v), .. }) => {
red = clamp_i32(v);
let mut uses_commas = false;

// Either integers or percentages, but all the same type.
// https://drafts.csswg.org/css-color/#rgb-functions
match try!(arguments.next()) {
Token::Number(NumericValue { value: v, .. }) => {
red = clamp_i32(v as i32);
green = clamp_i32(match try!(arguments.next()) {
Token::Number(NumericValue { value: v, .. }) => v,
Token::Comma => {
uses_commas = true;
try!(arguments.expect_number())
}
_ => return Err(())
} as i32);
if uses_commas {
try!(arguments.expect_comma());
green = clamp_i32(try!(arguments.expect_integer()));
try!(arguments.expect_comma());
blue = clamp_i32(try!(arguments.expect_integer()));
}
Token::Percentage(ref v) => {
red = clamp_f32(v.unit_value);
try!(arguments.expect_comma());
green = clamp_f32(try!(arguments.expect_percentage()));
blue = clamp_i32(try!(arguments.expect_number()) as i32);
}
Token::Percentage(ref v) => {
red = clamp_f32(v.unit_value);
green = clamp_f32(match try!(arguments.next()) {
Token::Percentage(ref v) => v.unit_value,
Token::Comma => {
uses_commas = true;
try!(arguments.expect_percentage())
}
_ => return Err(())
});
if uses_commas {
try!(arguments.expect_comma());
blue = clamp_f32(try!(arguments.expect_percentage()));
}
_ => return Err(())
};
} else {
let hue_degrees = try!(arguments.expect_number());
// Subtract an integer before rounding, to avoid some rounding errors:
let hue_normalized_degrees = hue_degrees - 360. * (hue_degrees / 360.).floor();
let hue = hue_normalized_degrees / 360.;
// Saturation and lightness are clamped to 0% ... 100%
// https://drafts.csswg.org/css-color/#the-hsl-notation
try!(arguments.expect_comma());
let saturation = try!(arguments.expect_percentage()).max(0.).min(1.);
try!(arguments.expect_comma());
let lightness = try!(arguments.expect_percentage()).max(0.).min(1.);

// https://drafts.csswg.org/css-color/#hsl-color
// except with h pre-multiplied by 3, to avoid some rounding errors.
fn hue_to_rgb(m1: f32, m2: f32, mut h3: f32) -> f32 {
if h3 < 0. { h3 += 3. }
if h3 > 3. { h3 -= 3. }

if h3 * 2. < 1. { m1 + (m2 - m1) * h3 * 2. }
else if h3 * 2. < 3. { m2 }
else if h3 < 2. { m1 + (m2 - m1) * (2. - h3) * 2. }
else { m1 }
blue = clamp_f32(try!(arguments.expect_percentage()));
}
let m2 = if lightness <= 0.5 { lightness * (saturation + 1.) }
else { lightness + saturation - lightness * saturation };
let m1 = lightness * 2. - m2;
let hue_times_3 = hue * 3.;
red = clamp_f32(hue_to_rgb(m1, m2, hue_times_3 + 1.));
green = clamp_f32(hue_to_rgb(m1, m2, hue_times_3));
blue = clamp_f32(hue_to_rgb(m1, m2, hue_times_3 - 1.));
}
_ => return Err(())
};
return Ok((red, green, blue, uses_commas));
}

let alpha = if has_alpha {
try!(arguments.expect_comma());
clamp_f32(try!(arguments.expect_number()))
} else {
255
#[inline]
fn parse_rgb_components_hsl(arguments: &mut Parser) -> Result<(u8, u8, u8, bool), ()> {
let mut uses_commas = false;
// Hue given as an angle
// https://drafts.csswg.org/css-values/#angles
let hue_degrees = match try!(arguments.next()) {
Token::Number(NumericValue { value: v, .. }) => v,
Token::Dimension(NumericValue { value: v, .. }, unit) => {
match_ignore_ascii_case! { &*unit,
"deg" => v,
"grad" => v * 360. / 400.,
"rad" => v * 360. / (2. * PI),
"turn" => v * 360.,
_ => return Err(())
}
}
_ => return Err(())
};
try!(arguments.expect_exhausted());
rgba(red, green, blue, alpha)
// Subtract an integer before rounding, to avoid some rounding errors:
let hue_normalized_degrees = hue_degrees - 360. * (hue_degrees / 360.).floor();
let hue = hue_normalized_degrees / 360.;

// Saturation and lightness are clamped to 0% ... 100%
// https://drafts.csswg.org/css-color/#the-hsl-notation
let saturation = match try!(arguments.next()) {
Token::Percentage(ref v) => v.unit_value,
Token::Comma => {
uses_commas = true;
try!(arguments.expect_percentage())
}
_ => return Err(())
};
let saturation = saturation.max(0.).min(1.);

if uses_commas {
try!(arguments.expect_comma());
}

let lightness = try!(arguments.expect_percentage());
let lightness = lightness.max(0.).min(1.);

// https://drafts.csswg.org/css-color/#hsl-color
// except with h pre-multiplied by 3, to avoid some rounding errors.
fn hue_to_rgb(m1: f32, m2: f32, mut h3: f32) -> f32 {
if h3 < 0. { h3 += 3. }
if h3 > 3. { h3 -= 3. }

if h3 * 2. < 1. { m1 + (m2 - m1) * h3 * 2. }
else if h3 * 2. < 3. { m2 }
else if h3 < 2. { m1 + (m2 - m1) * (2. - h3) * 2. }
else { m1 }
}
let m2 = if lightness <= 0.5 { lightness * (saturation + 1.) }
else { lightness + saturation - lightness * saturation };
let m1 = lightness * 2. - m2;
let hue_times_3 = hue * 3.;
let red = clamp_f32(hue_to_rgb(m1, m2, hue_times_3 + 1.));
let green = clamp_f32(hue_to_rgb(m1, m2, hue_times_3));
let blue = clamp_f32(hue_to_rgb(m1, m2, hue_times_3 - 1.));
return Ok((red, green, blue, uses_commas));
}
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