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//! Texture packing. use ImageSize; /// A texture packer using a skyline heuristic. /// /// For offline texture packing, see [texture_packer](https://github.com/pistondevelopers/texture_packer). /// /// Designed for adding textures one by one to current texture atlas. /// Packs tiles without backtracking or knowledge about future tiles. /// /// - Perfect at packing tiles of same size /// - Good at packing tiles of some unit size /// - Decent at packing tiles of similar sizes /// - Can be used with pre-sorted tile sizes for better packing /// /// Can also be used as storage for textures. /// /// ### Design /// /// A skyline is a list of non-hole atlas offsets, /// used to efficiently determine a good place to put the next tile. /// /// In this texture packer, /// only a single skyline is kept track of, /// since new texture atlases are created by need. /// /// This texture packer has runtime complexity `O(N^2)` for inserting a new tile, /// where `N` is the number of points in the skyline. /// Since `N` is usually a low number, the packing is pretty fast. /// /// The algorithm was designed by Sven Nilsen (2019) for Piston-Graphics. pub struct TexturePacker<T> { /// Stores current texture atlas and previously created ones. pub textures: Vec<T>, /// The index to the current texture atlas. pub atlas: usize, /// Texture atlas offsets from left to right. /// /// When a new tile is added with same offset, /// it updates the atlas offsets that it overlaps. /// This means that "holes" get filled in over time. pub skyline: Vec<[u32; 2]>, } impl<T: ImageSize> TexturePacker<T> { /// Returns a new `TexturePacker`. pub fn new() -> TexturePacker<T> { TexturePacker { textures: vec![], atlas: 0, skyline: vec![], } } /// Create a new texture atlas with an initial tile. /// /// The new texture atlas is made the current one. pub fn create(&mut self, size: [u32; 2], texture: T) -> usize { let id = self.textures.len(); if self.textures.len() > 0 { self.atlas += 1; } self.skyline = vec![ [0, size[1]], [size[0], 0], ]; self.textures.push(texture); id } /// Update current texture atlas. /// /// - ind: index of atlas offset in the skyline /// - size: size of new tile /// /// Returns the index of the current texture atlas and /// the atlas offset of the new tile. pub fn update(&mut self, ind: usize, size: [u32; 2]) -> (usize, [u32; 2]) { let texture = self.atlas; let offset = self.skyline[ind]; // Increase y-value of atlas offsets that are matched. let mut w = 0; for i in ind..self.skyline.len() { if self.skyline[i][1] <= offset[1] { self.skyline[i][1] = offset[1] + size[1]; } w = self.skyline[i][0] - offset[0]; if w >= size[1] { break; } } if w == 0 { // There is no end-point atlas offset. // Add new atlas offset point. self.skyline.push([offset[0] + size[0], offset[1]]); self.skyline.sort(); } (texture, offset) } /// Returns the index of atlas offset in skyline with room for a new tile. /// /// Returns `None` if no room was found in the current texture atlas. pub fn find_space( &self, size: [u32; 2] ) -> Option<usize> { if self.textures.len() == 0 {return None}; let texture = &self.textures[self.atlas]; let mut min: Option<(usize, u32)> = None; for i in 0..self.skyline.len() { let a = self.skyline[i]; let mut nxt = [texture.get_width(), texture.get_height()]; // Ignore next atlas offsets that have smaller y-value, // because they do not interfer. for j in i+1..self.skyline.len() { let b = self.skyline[j]; nxt[0] = b[0]; if b[1] > a[1] {break}; } if nxt[0] - a[0] >= size[0] && nxt[1] - a[1] >= size[1] { // There is room for the glyph. if min.is_none() || min.unwrap().1 > nxt[0] - a[0] || self.skyline[min.unwrap().0][1] > a[1] { // Pick the space with smallest y-value. min = Some((i, nxt[0] - a[0])); } } } min.map(|n| n.0) } }