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//! Lazy tiled image.
//!
//! This supports OSM-style "tiled" images, but not all of the tiles have to be present. If a tile
//! is not present, a default pixel is returned. The tile is allocated with the first call to a
//! mutating operation.
use std::{
fs::File,
io::{BufWriter, Write},
path::Path,
};
use color_eyre::eyre::Result;
use fnv::FnvHashMap;
use image::{
codecs::png::{CompressionType, FilterType, PngEncoder},
ColorType, ImageBuffer, ImageEncoder, Pixel, RgbaImage,
};
use num_traits::Zero;
use rayon::iter::{IntoParallelIterator, ParallelIterator};
pub const TILE_HEIGHT: u64 = 256;
pub const TILE_WIDTH: u64 = 256;
type TileIndex = (u64, u64);
/// Main "lazy image buffer" struct.
#[derive(Debug, Clone)]
pub struct TileLayer<P: Pixel> {
tiles: FnvHashMap<TileIndex, ImageBuffer<P, Vec<P::Subpixel>>>,
default_pixel: P,
}
impl<P: Pixel> TileLayer<P> {
pub fn from_pixel(pixel: P) -> Self {
TileLayer {
tiles: Default::default(),
default_pixel: pixel,
}
}
pub fn enumerate_tiles(
&self,
) -> impl Iterator<Item = (u64, u64, &ImageBuffer<P, Vec<P::Subpixel>>)> {
self.tiles.iter().map(|((x, y), t)| (*x, *y, t))
}
pub fn tile_mut(&mut self, tile_x: u64, tile_y: u64) -> &mut ImageBuffer<P, Vec<P::Subpixel>> {
self.tiles.entry((tile_x, tile_y)).or_insert_with(|| {
ImageBuffer::from_pixel(TILE_WIDTH as u32, TILE_HEIGHT as u32, self.default_pixel)
})
}
/// Enumerate all pixels that are explicitely set in this layer.
pub fn enumerate_pixels(&self) -> impl Iterator<Item = (u64, u64, &P)> {
self.tiles.iter().flat_map(|((tx, ty), tile)| {
tile.enumerate_pixels().map(move |(x, y, p)| {
(
u64::from(x) + tx * TILE_WIDTH,
u64::from(y) + ty * TILE_HEIGHT,
p,
)
})
})
}
pub fn pixels(&self) -> impl Iterator<Item = &P> {
self.enumerate_pixels().map(|x| x.2)
}
pub fn tile_count(&self) -> usize {
self.tiles.len()
}
/// Copies the non-zero pixels from `source` to `self`.
///
/// A zero-pixel is identified by comparing all its channels' values with `Zero::zero()`. If
/// any channel is non-zero, the pixel is considered non-zero and is copied.
///
/// The top-left pixel of `source` is copied to `(x, y)`.
///
/// This method is more efficient than repeatedly calling [`get_pixel_mut`], as it groups
/// pixels by tile and only does one tile lookup.
pub fn blit_nonzero(&mut self, x: u64, y: u64, source: &ImageBuffer<P, Vec<P::Subpixel>>) {
let zero = zero_pixel::<P>();
let source_width = u64::from(source.width());
let source_height = u64::from(source.height());
for tx in x / TILE_WIDTH..=(x + source_width) / TILE_WIDTH {
for ty in y / TILE_HEIGHT..=(y + source_height) / TILE_HEIGHT {
let tile = self.tile_mut(tx, ty);
let offset_x = (tx * TILE_WIDTH).saturating_sub(x);
let offset_y = (ty * TILE_HEIGHT).saturating_sub(y);
let local_min_x = x.saturating_sub(tx * TILE_WIDTH);
let local_min_y = y.saturating_sub(ty * TILE_HEIGHT);
let local_max_x = TILE_WIDTH.min(x + source_width - tx * TILE_WIDTH);
let local_max_y = TILE_HEIGHT.min(y + source_height - ty * TILE_HEIGHT);
// Keep x in the inner loop for better cache locality!
for (y, source_y) in (local_min_y..local_max_y).zip(offset_y..) {
for (x, source_x) in (local_min_x..local_max_x).zip(offset_x..) {
let pixel = source
.get_pixel(source_x.try_into().unwrap(), source_y.try_into().unwrap());
if pixel.channels() != zero.channels() {
*tile.get_pixel_mut(x.try_into().unwrap(), y.try_into().unwrap()) =
*pixel;
}
}
}
}
}
}
}
impl<P> TileLayer<P>
where
P: Pixel + Send,
P::Subpixel: Send,
{
pub fn into_parallel_tiles(
self,
) -> impl ParallelIterator<Item = (u64, u64, ImageBuffer<P, Vec<P::Subpixel>>)> {
IntoParallelIterator::into_par_iter(self.tiles).map(|((x, y), t)| (x, y, t))
}
}
pub fn compress_png<P: AsRef<Path>>(image: &RgbaImage, path: P) -> Result<()> {
let outstream = BufWriter::new(File::create(path)?);
compress_png_stream(image, outstream)
}
pub fn compress_png_stream<W: Write>(image: &RgbaImage, outstream: W) -> Result<()> {
let encoder =
PngEncoder::new_with_quality(outstream, CompressionType::Best, FilterType::Adaptive);
encoder.write_image(image, image.width(), image.height(), ColorType::Rgba8)?;
Ok(())
}
pub fn compress_png_as_bytes(image: &RgbaImage) -> Result<Vec<u8>> {
let mut buffer = Vec::new();
compress_png_stream(image, &mut buffer)?;
Ok(buffer)
}
fn zero_pixel<P: Pixel>() -> P {
let zeroes = vec![Zero::zero(); P::CHANNEL_COUNT as usize];
*P::from_slice(&zeroes)
}
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