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Use enlargeable types in to_luma functions. #1651

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Jan 16, 2022
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Use enlargeable types in to_luma functions. #1651

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df69f88
Use enlargeable types in to_luma functions.
kaj May 11, 2020
75a0b71
Add conversion test
HeroicKatora Jan 12, 2022
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127 changes: 56 additions & 71 deletions src/color.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2,7 +2,7 @@ use std::ops::{Index, IndexMut};

use num_traits::{NumCast, ToPrimitive, Zero};

use crate::traits::{Pixel, Primitive};
use crate::traits::{Enlargeable, Pixel, Primitive};

/// An enumeration over supported color types and bit depths
#[derive(Copy, PartialEq, Eq, Debug, Clone, Hash)]
Expand Down Expand Up @@ -203,23 +203,20 @@ impl From<ColorType> for ExtendedColorType {

macro_rules! define_colors {
{$(
$ident:ident,
$channels: expr,
$alphas: expr,
$interpretation: literal,
$sample_color_type: ident,
#[$doc:meta];
$(#[$doc:meta])*
pub struct $ident:ident<T: $($bound:ident)*>([T; $channels:expr, $alphas:expr])
= $interpretation:literal;
)*} => {

$( // START Structure definitions

#[$doc]
$(#[$doc])*
#[derive(PartialEq, Eq, Clone, Debug, Copy, Hash)]
#[repr(C)]
#[allow(missing_docs)]
pub struct $ident<T: Primitive> (pub [T; $channels]);
pub struct $ident<T> (pub [T; $channels]);

impl<T: Primitive> Pixel for $ident<T> {
impl<T: $($bound+)*> Pixel for $ident<T> {
type Subpixel = T;

const CHANNEL_COUNT: u8 = $channels;
Expand Down Expand Up @@ -332,22 +329,22 @@ impl<T: Primitive> Pixel for $ident<T> {
}
}

impl<T: Primitive> Index<usize> for $ident<T> {
impl<T> Index<usize> for $ident<T> {
type Output = T;
#[inline(always)]
fn index(&self, _index: usize) -> &T {
&self.0[_index]
}
}

impl<T: Primitive> IndexMut<usize> for $ident<T> {
impl<T> IndexMut<usize> for $ident<T> {
#[inline(always)]
fn index_mut(&mut self, _index: usize) -> &mut T {
&mut self.0[_index]
}
}

impl<T: Primitive> From<[T; $channels]> for $ident<T> {
impl<T> From<[T; $channels]> for $ident<T> {
fn from(c: [T; $channels]) -> Self {
Self(c)
}
Expand All @@ -359,10 +356,17 @@ impl<T: Primitive> From<[T; $channels]> for $ident<T> {
}

define_colors! {
Rgb, 3, 0, "RGB", RGB_COLOR_TYPE, #[doc = "RGB colors"];
Luma, 1, 0, "Y", L_COLOR_TYPE, #[doc = "Grayscale colors"];
Rgba, 4, 1, "RGBA", RGBA_COLOR_TYPE, #[doc = "RGB colors + alpha channel"];
LumaA, 2, 1, "YA", LA_COLOR_TYPE, #[doc = "Grayscale colors + alpha channel"];
/// RGB colors.
///
/// For the purpose of color conversion, as well as blending, the implementation of `Pixel`
/// assumes an `sRGB` color space of its data.
pub struct Rgb<T: Primitive Enlargeable>([T; 3, 0]) = "RGB";
/// Grayscale colors.
pub struct Luma<T: Primitive>([T; 1, 0]) = "Y";
/// RGB colors + alpha channel
pub struct Rgba<T: Primitive Enlargeable>([T; 4, 1]) = "RGBA";
/// Grayscale colors + alpha channel
pub struct LumaA<T: Primitive>([T; 2, 1]) = "YA";
}

/// Convert from one pixel component type to another. For example, convert from `u8` to `f32` pixel values.
Expand Down Expand Up @@ -462,18 +466,18 @@ where
}

/// Coefficients to transform from sRGB to a CIE Y (luminance) value.
const SRGB_LUMA: [f32; 3] = [0.2126, 0.7152, 0.0722];
const SRGB_LUMA: [u32; 3] = [2126, 7152, 722];
const SRGB_LUMA_DIV: u32 = 10000;

#[inline]
fn rgb_to_luma<T: Primitive>(rgb: &[T]) -> T {
let l = SRGB_LUMA[0] * rgb[0].to_f32().unwrap()
+ SRGB_LUMA[1] * rgb[1].to_f32().unwrap()
+ SRGB_LUMA[2] * rgb[2].to_f32().unwrap();
NumCast::from(l).unwrap()
fn rgb_to_luma<T: Primitive + Enlargeable>(rgb: &[T]) -> T {
let l = <T::Larger as NumCast>::from(SRGB_LUMA[0]).unwrap() * rgb[0].to_larger()
+ <T::Larger as NumCast>::from(SRGB_LUMA[1]).unwrap() * rgb[1].to_larger()
+ <T::Larger as NumCast>::from(SRGB_LUMA[2]).unwrap() * rgb[2].to_larger();
T::clamp_from(l / <T::Larger as NumCast>::from(SRGB_LUMA_DIV).unwrap())
}

// `FromColor` for Luma

impl<S: Primitive, T: Primitive> FromColor<Luma<S>> for Luma<T>
where
T: FromPrimitive<S>,
Expand All @@ -494,7 +498,7 @@ where
}
}

impl<S: Primitive, T: Primitive> FromColor<Rgb<S>> for Luma<T>
impl<S: Primitive + Enlargeable, T: Primitive> FromColor<Rgb<S>> for Luma<T>
where
T: FromPrimitive<S>,
{
Expand All @@ -505,7 +509,7 @@ where
}
}

impl<S: Primitive, T: Primitive> FromColor<Rgba<S>> for Luma<T>
impl<S: Primitive + Enlargeable, T: Primitive> FromColor<Rgba<S>> for Luma<T>
where
T: FromPrimitive<S>,
{
Expand All @@ -531,7 +535,7 @@ where
}
}

impl<S: Primitive, T: Primitive> FromColor<Rgb<S>> for LumaA<T>
impl<S: Primitive + Enlargeable, T: Primitive> FromColor<Rgb<S>> for LumaA<T>
where
T: FromPrimitive<S>,
{
Expand All @@ -543,7 +547,7 @@ where
}
}

impl<S: Primitive, T: Primitive> FromColor<Rgba<S>> for LumaA<T>
impl<S: Primitive + Enlargeable, T: Primitive> FromColor<Rgba<S>> for LumaA<T>
where
T: FromPrimitive<S>,
{
Expand Down Expand Up @@ -573,8 +577,8 @@ where
T: FromPrimitive<S>,
{
fn from_color(&mut self, other: &Rgba<S>) {
let own = self.channels_mut();
let other = other.channels();
let own = &mut self.0;
let other = &other.0;
own[0] = T::from_primitive(other[0]);
own[1] = T::from_primitive(other[1]);
own[2] = T::from_primitive(other[2]);
Expand All @@ -587,8 +591,8 @@ where
T: FromPrimitive<S>,
{
fn from_color(&mut self, other: &Rgb<S>) {
let rgba = self.channels_mut();
let rgb = other.channels();
let rgba = &mut self.0;
let rgb = &other.0;
rgba[0] = T::from_primitive(rgb[0]);
rgba[1] = T::from_primitive(rgb[1]);
rgba[2] = T::from_primitive(rgb[2]);
Expand All @@ -601,8 +605,8 @@ where
T: FromPrimitive<S>,
{
fn from_color(&mut self, gray: &LumaA<S>) {
let rgba = self.channels_mut();
let gray = gray.channels();
let rgba = &mut self.0;
let gray = &gray.0;
rgba[0] = T::from_primitive(gray[0]);
rgba[1] = T::from_primitive(gray[0]);
rgba[2] = T::from_primitive(gray[0]);
Expand All @@ -615,8 +619,8 @@ where
T: FromPrimitive<S>,
{
fn from_color(&mut self, gray: &Luma<S>) {
let rgba = self.channels_mut();
let gray = gray.channels()[0];
let rgba = &mut self.0;
let gray = gray.0[0];
rgba[0] = T::from_primitive(gray);
rgba[1] = T::from_primitive(gray);
rgba[2] = T::from_primitive(gray);
Expand All @@ -631,8 +635,8 @@ where
T: FromPrimitive<S>,
{
fn from_color(&mut self, other: &Rgb<S>) {
let own = self.channels_mut();
let other = other.channels();
let own = &mut self.0;
let other = &other.0;
own[0] = T::from_primitive(other[0]);
own[1] = T::from_primitive(other[1]);
own[2] = T::from_primitive(other[2]);
Expand All @@ -644,8 +648,8 @@ where
T: FromPrimitive<S>,
{
fn from_color(&mut self, other: &Rgba<S>) {
let rgb = self.channels_mut();
let rgba = other.channels();
let rgb = &mut self.0;
let rgba = &other.0;
rgb[0] = T::from_primitive(rgba[0]);
rgb[1] = T::from_primitive(rgba[1]);
rgb[2] = T::from_primitive(rgba[2]);
Expand All @@ -657,8 +661,8 @@ where
T: FromPrimitive<S>,
{
fn from_color(&mut self, other: &LumaA<S>) {
let rgb = self.channels_mut();
let gray = other.channels()[0];
let rgb = &mut self.0;
let gray = other.0[0];
rgb[0] = T::from_primitive(gray);
rgb[1] = T::from_primitive(gray);
rgb[2] = T::from_primitive(gray);
Expand All @@ -670,41 +674,14 @@ where
T: FromPrimitive<S>,
{
fn from_color(&mut self, other: &Luma<S>) {
let rgb = self.channels_mut();
let gray = other.channels()[0];
let rgb = &mut self.0;
let gray = other.0[0];
rgb[0] = T::from_primitive(gray);
rgb[1] = T::from_primitive(gray);
rgb[2] = T::from_primitive(gray);
}
}

/*macro_rules! downcast_bit_depth_early {
($src:ident, $intermediate:ident, $dst:ident) => {
impl FromColor<$src<u16>> for $dst<u8> {
fn from_color(&mut self, other: &$src<u16>) {
let mut intermediate: $intermediate<u8> = $intermediate([Zero::zero(); <$intermediate<u8> as Pixel>::CHANNEL_COUNT as usize]);
intermediate.from_color(other);
self.from_color(&intermediate);
}
}
};
}


// Downcasts
// LumaA
downcast_bit_depth_early!(Luma, Luma, LumaA);
downcast_bit_depth_early!(Rgb, Rgb, LumaA);
downcast_bit_depth_early!(Rgba, Rgba, LumaA);
// Rgb
downcast_bit_depth_early!(Luma, Luma, Rgb);
downcast_bit_depth_early!(LumaA, LumaA, Rgb);
downcast_bit_depth_early!(Rgba, Rgba, Rgb);
// Rgba
downcast_bit_depth_early!(Luma, Luma, Rgba);
downcast_bit_depth_early!(LumaA, LumaA, Rgba);
downcast_bit_depth_early!(Rgb, Rgb, Rgba);*/

/// Blends a color inter another one
pub(crate) trait Blend {
/// Blends a color in-place.
Expand Down Expand Up @@ -989,4 +966,12 @@ mod tests {
test_lossless_conversion!(Rgb<u8>, Rgb<u16>, Rgb<u8>);
test_lossless_conversion!(Rgba<u8>, Rgba<u16>, Rgba<u8>);
}

#[test]
fn accuracy_conversion() {
use super::{Luma, Pixel, Rgb};
let pixel = Rgb::from([13, 13, 13]);
let Luma([luma]) = pixel.to_luma();
assert_eq!(luma, 13);
}
}
37 changes: 34 additions & 3 deletions src/traits.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -70,16 +70,21 @@ declare_primitive!(f64: (0.0)..1.0);
/// An Enlargable::Larger value should be enough to calculate
/// the sum (average) of a few hundred or thousand Enlargeable values.
pub trait Enlargeable: Sized + Bounded + NumCast {
type Larger: Primitive + AddAssign;
type Larger: Copy + NumCast + Num + PartialOrd<Self::Larger> + Clone + Bounded + AddAssign;

fn clamp_from(n: Self::Larger) -> Self {
// Note: Only unsigned value types supported.
if n > NumCast::from(Self::max_value()).unwrap() {
if n > Self::max_value().to_larger() {
Self::max_value()
} else if n < Self::min_value().to_larger() {
Self::min_value()
} else {
NumCast::from(n).unwrap()
}
}

fn to_larger(self) -> Self::Larger {
NumCast::from(self).unwrap()
}
}

impl Enlargeable for u8 {
Expand All @@ -91,9 +96,35 @@ impl Enlargeable for u16 {
impl Enlargeable for u32 {
type Larger = u64;
}
impl Enlargeable for u64 {
type Larger = u128;
}
impl Enlargeable for usize {
// Note: On 32-bit architectures, u64 should be enough here.
type Larger = u128;
}
impl Enlargeable for i8 {
type Larger = i32;
}
impl Enlargeable for i16 {
type Larger = i32;
}
impl Enlargeable for i32 {
type Larger = i64;
}
impl Enlargeable for i64 {
type Larger = i128;
}
impl Enlargeable for isize {
// Note: On 32-bit architectures, i64 should be enough here.
type Larger = i128;
}
impl Enlargeable for f32 {
type Larger = f64;
}
impl Enlargeable for f64 {
type Larger = f64;
}

/// Linear interpolation without involving floating numbers.
pub trait Lerp: Bounded + NumCast {
Expand Down