1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300
//! Various utilities for working with Cairo image surfaces.
use std::alloc;
use std::slice;
pub mod iterators;
pub mod shared_surface;
pub mod srgb;
// These two are for Cairo's platform-endian 0xaarrggbb pixels
#[cfg(target_endian = "little")]
use rgb::alt::BGRA8;
#[cfg(target_endian = "little")]
#[allow(clippy::upper_case_acronyms)]
pub type CairoARGB = BGRA8;
#[cfg(target_endian = "big")]
use rgb::alt::ARGB8;
#[cfg(target_endian = "big")]
#[allow(clippy::upper_case_acronyms)]
pub type CairoARGB = ARGB8;
/// Analogous to `rgb::FromSlice`, to convert from `[T]` to `[CairoARGB]`
#[allow(clippy::upper_case_acronyms)]
pub trait AsCairoARGB {
/// Reinterpret slice as `CairoARGB` pixels.
fn as_cairo_argb(&self) -> &[CairoARGB];
/// Reinterpret mutable slice as `CairoARGB` pixels.
fn as_cairo_argb_mut(&mut self) -> &mut [CairoARGB];
}
// SAFETY: transmuting from u32 to CairoRGB is based on the following assumptions:
// * there are no invalid bit representations for ARGB
// * u32 and ARGB are the same size
// * u32 is sufficiently aligned
impl AsCairoARGB for [u32] {
fn as_cairo_argb(&self) -> &[CairoARGB] {
const LAYOUT_U32: alloc::Layout = alloc::Layout::new::<u32>();
const LAYOUT_ARGB: alloc::Layout = alloc::Layout::new::<CairoARGB>();
let _: [(); LAYOUT_U32.size()] = [(); LAYOUT_ARGB.size()];
let _: [(); 0] = [(); LAYOUT_U32.align() % LAYOUT_ARGB.align()];
unsafe { slice::from_raw_parts(self.as_ptr() as *const _, self.len()) }
}
fn as_cairo_argb_mut(&mut self) -> &mut [CairoARGB] {
unsafe { slice::from_raw_parts_mut(self.as_mut_ptr() as *mut _, self.len()) }
}
}
/// Modes which specify how the values of out of bounds pixels are computed.
///
/// <https://www.w3.org/TR/filter-effects/#element-attrdef-fegaussianblur-edgemode>
#[derive(Debug, Clone, Copy, Eq, PartialEq)]
pub enum EdgeMode {
/// The nearest inbounds pixel value is returned.
Duplicate,
/// The image is extended by taking the color values from the opposite of the image.
///
/// Imagine the image being tiled infinitely, with the original image at the origin.
Wrap,
/// Zero RGBA values are returned.
None,
}
/// Trait to convert pixels in various formats to our own Pixel layout.
pub trait ToPixel {
fn to_pixel(&self) -> Pixel;
}
/// Trait to convert pixels in various formats to Cairo's endian-dependent 0xaarrggbb.
pub trait ToCairoARGB {
fn to_cairo_argb(&self) -> CairoARGB;
}
impl ToPixel for CairoARGB {
#[inline]
fn to_pixel(&self) -> Pixel {
Pixel {
r: self.r,
g: self.g,
b: self.b,
a: self.a,
}
}
}
impl ToPixel for image::Rgba<u8> {
#[inline]
fn to_pixel(&self) -> Pixel {
Pixel {
r: self.0[0],
g: self.0[1],
b: self.0[2],
a: self.0[3],
}
}
}
impl ToCairoARGB for Pixel {
#[inline]
fn to_cairo_argb(&self) -> CairoARGB {
CairoARGB {
r: self.r,
g: self.g,
b: self.b,
a: self.a,
}
}
}
/// Extension methods for `cairo::ImageSurfaceData`.
pub trait ImageSurfaceDataExt {
/// Sets the pixel at the given coordinates. Assumes the `ARgb32` format.
fn set_pixel(&mut self, stride: usize, pixel: Pixel, x: u32, y: u32);
}
/// A pixel consisting of R, G, B and A values.
pub type Pixel = rgb::RGBA8;
pub trait PixelOps {
fn premultiply(self) -> Self;
fn unpremultiply(self) -> Self;
fn diff(&self, other: &Self) -> Self;
fn to_luminance_mask(&self) -> Self;
fn to_u32(&self) -> u32;
fn from_u32(x: u32) -> Self;
}
impl PixelOps for Pixel {
/// Returns an unpremultiplied value of this pixel.
///
/// For a fully transparent pixel, a transparent black pixel will be returned.
#[inline]
fn unpremultiply(self) -> Self {
if self.a == 0 {
Self {
r: 0,
g: 0,
b: 0,
a: 0,
}
} else {
let alpha = f32::from(self.a) / 255.0;
self.map_rgb(|x| ((f32::from(x) / alpha) + 0.5) as u8)
}
}
/// Returns a premultiplied value of this pixel.
#[inline]
fn premultiply(self) -> Self {
let a = self.a as u32;
self.map_rgb(|x| (((x as u32) * a + 127) / 255) as u8)
}
#[inline]
fn diff(&self, other: &Pixel) -> Pixel {
self.iter()
.zip(other.iter())
.map(|(l, r)| (l as i32 - r as i32).unsigned_abs() as u8)
.collect()
}
/// Returns a 'mask' pixel with only the alpha channel
///
/// Assuming, the pixel is linear RGB (not sRGB)
/// y = luminance
/// Y = 0.2126 R + 0.7152 G + 0.0722 B
/// 1.0 opacity = 255
///
/// When Y = 1.0, pixel for mask should be 0xFFFFFFFF
/// (you get 1.0 luminance from 255 from R, G and B)
///
/// r_mult = 0xFFFFFFFF / (255.0 * 255.0) * .2126 = 14042.45 ~= 14042
/// g_mult = 0xFFFFFFFF / (255.0 * 255.0) * .7152 = 47239.69 ~= 47240
/// b_mult = 0xFFFFFFFF / (255.0 * 255.0) * .0722 = 4768.88 ~= 4769
///
/// This allows for the following expected behaviour:
/// (we only care about the most significant byte)
/// if pixel = 0x00FFFFFF, pixel' = 0xFF......
/// if pixel = 0x00020202, pixel' = 0x02......
/// if pixel = 0x00000000, pixel' = 0x00......
#[inline]
fn to_luminance_mask(&self) -> Self {
let r = u32::from(self.r);
let g = u32::from(self.g);
let b = u32::from(self.b);
Self {
r: 0,
g: 0,
b: 0,
a: (((r * 14042 + g * 47240 + b * 4769) * 255) >> 24) as u8,
}
}
/// Returns the pixel value as a `u32`, in the same format as `cairo::Format::ARgb32`.
#[inline]
fn to_u32(&self) -> u32 {
(u32::from(self.a) << 24)
| (u32::from(self.r) << 16)
| (u32::from(self.g) << 8)
| u32::from(self.b)
}
/// Converts a `u32` in the same format as `cairo::Format::ARgb32` into a `Pixel`.
#[inline]
fn from_u32(x: u32) -> Self {
Self {
r: ((x >> 16) & 0xFF) as u8,
g: ((x >> 8) & 0xFF) as u8,
b: (x & 0xFF) as u8,
a: ((x >> 24) & 0xFF) as u8,
}
}
}
impl<'a> ImageSurfaceDataExt for cairo::ImageSurfaceData<'a> {
#[inline]
fn set_pixel(&mut self, stride: usize, pixel: Pixel, x: u32, y: u32) {
let this: &mut [u8] = &mut *self;
// SAFETY: this code assumes that cairo image surface data is correctly
// aligned for u32. This assumption is justified by the Cairo docs,
// which say this:
//
// https://cairographics.org/manual/cairo-Image-Surfaces.html#cairo-image-surface-create-for-data
//
// > This pointer must be suitably aligned for any kind of variable,
// > (for example, a pointer returned by malloc).
#[allow(clippy::cast_ptr_alignment)]
let this: &mut [u32] =
unsafe { slice::from_raw_parts_mut(this.as_mut_ptr() as *mut u32, this.len() / 4) };
this.set_pixel(stride, pixel, x, y);
}
}
impl ImageSurfaceDataExt for [u8] {
#[inline]
fn set_pixel(&mut self, stride: usize, pixel: Pixel, x: u32, y: u32) {
let this = &mut self[y as usize * stride + x as usize * 4..];
this[..4].copy_from_slice(&pixel.to_u32().to_ne_bytes());
}
}
impl ImageSurfaceDataExt for [u32] {
#[inline]
fn set_pixel(&mut self, stride: usize, pixel: Pixel, x: u32, y: u32) {
self[(y as usize * stride + x as usize * 4) / 4] = pixel.to_u32();
}
}
#[cfg(test)]
mod tests {
use super::*;
use proptest::prelude::*;
#[test]
fn pixel_diff() {
let a = Pixel::new(0x10, 0x20, 0xf0, 0x40);
assert_eq!(a, a.diff(&Pixel::default()));
let b = Pixel::new(0x50, 0xff, 0x20, 0x10);
assert_eq!(a.diff(&b), Pixel::new(0x40, 0xdf, 0xd0, 0x30));
}
// Floating-point reference implementation
fn premultiply_float(pixel: Pixel) -> Pixel {
let alpha = f64::from(pixel.a) / 255.0;
pixel.map_rgb(|x| ((f64::from(x) * alpha) + 0.5) as u8)
}
prop_compose! {
fn arbitrary_pixel()(a: u8, r: u8, g: u8, b: u8) -> Pixel {
Pixel { r, g, b, a }
}
}
proptest! {
#[test]
fn pixel_premultiply(pixel in arbitrary_pixel()) {
prop_assert_eq!(pixel.premultiply(), premultiply_float(pixel));
}
#[test]
fn pixel_unpremultiply(pixel in arbitrary_pixel()) {
let roundtrip = pixel.premultiply().unpremultiply();
if pixel.a == 0 {
prop_assert_eq!(roundtrip, Pixel::default());
} else {
// roundtrip can't be perfect, the accepted error depends on alpha
let tolerance = 0xff / pixel.a;
let diff = roundtrip.diff(&pixel);
prop_assert!(diff.r <= tolerance, "red component value differs by more than {}: {:?}", tolerance, roundtrip);
prop_assert!(diff.g <= tolerance, "green component value differs by more than {}: {:?}", tolerance, roundtrip);
prop_assert!(diff.b <= tolerance, "blue component value differs by more than {}: {:?}", tolerance, roundtrip);
prop_assert_eq!(pixel.a, roundtrip.a);
}
}
}
}