Move image/svg handling into iced_graphics

The `TextureStore` trait is implemented by the atlas, and can also be
implemented in the glow renderer or in a software renderer.

The API here may be improved in the future, but API stability is
presumably not a huge issue since these types will only be used by
renderer backends.

graphics/src/image/raster.rs

@@ -0,0 +1,236 @@
+//! Raster image loading and caching
+
+use iced_native::image;
+use std::collections::{HashMap, HashSet};
+
+use bitflags::bitflags;
+
+use super::{TextureStore, TextureStoreEntry};
+
+/// Entry in cache corresponding to an image handle
+#[derive(Debug)]
+pub enum Memory<T: TextureStore> {
+    /// Image data on host
+    Host(::image_rs::ImageBuffer<::image_rs::Rgba<u8>, Vec<u8>>),
+    /// Texture store entry
+    Device(T::Entry),
+    /// Image not found
+    NotFound,
+    /// Invalid image data
+    Invalid,
+}
+
+impl<T: TextureStore> Memory<T> {
+    /// Width and height of image
+    pub fn dimensions(&self) -> (u32, u32) {
+        match self {
+            Memory::Host(image) => image.dimensions(),
+            Memory::Device(entry) => entry.size(),
+            Memory::NotFound => (1, 1),
+            Memory::Invalid => (1, 1),
+        }
+    }
+}
+
+/// Caches image raster data
+#[derive(Debug)]
+pub struct Cache<T: TextureStore> {
+    map: HashMap<u64, Memory<T>>,
+    hits: HashSet<u64>,
+}
+
+impl<T: TextureStore> Cache<T> {
+    /// Load image
+    pub fn load(&mut self, handle: &image::Handle) -> &mut Memory<T> {
+        if self.contains(handle) {
+            return self.get(handle).unwrap();
+        }
+
+        let memory = match handle.data() {
+            image::Data::Path(path) => {
+                if let Ok(image) = image_rs::open(path) {
+                    let operation = std::fs::File::open(path)
+                        .ok()
+                        .map(std::io::BufReader::new)
+                        .and_then(|mut reader| {
+                            Operation::from_exif(&mut reader).ok()
+                        })
+                        .unwrap_or_else(Operation::empty);
+
+                    Memory::Host(operation.perform(image.to_rgba8()))
+                } else {
+                    Memory::NotFound
+                }
+            }
+            image::Data::Bytes(bytes) => {
+                if let Ok(image) = image_rs::load_from_memory(bytes) {
+                    let operation =
+                        Operation::from_exif(&mut std::io::Cursor::new(bytes))
+                            .ok()
+                            .unwrap_or_else(Operation::empty);
+
+                    Memory::Host(operation.perform(image.to_rgba8()))
+                } else {
+                    Memory::Invalid
+                }
+            }
+            image::Data::Pixels {
+                width,
+                height,
+                pixels,
+            } => {
+                if let Some(image) = image_rs::ImageBuffer::from_vec(
+                    *width,
+                    *height,
+                    pixels.to_vec(),
+                ) {
+                    Memory::Host(image)
+                } else {
+                    Memory::Invalid
+                }
+            }
+        };
+
+        self.insert(handle, memory);
+        self.get(handle).unwrap()
+    }
+
+    /// Load image and upload raster data
+    pub fn upload(
+        &mut self,
+        handle: &image::Handle,
+        state: &mut T::State<'_>,
+        store: &mut T,
+    ) -> Option<&T::Entry> {
+        let memory = self.load(handle);
+
+        if let Memory::Host(image) = memory {
+            let (width, height) = image.dimensions();
+
+            let entry = store.upload(width, height, image, state)?;
+
+            *memory = Memory::Device(entry);
+        }
+
+        if let Memory::Device(allocation) = memory {
+            Some(allocation)
+        } else {
+            None
+        }
+    }
+
+    /// Trim cache misses from cache
+    pub fn trim(&mut self, store: &mut T, state: &mut T::State<'_>) {
+        let hits = &self.hits;
+
+        self.map.retain(|k, memory| {
+            let retain = hits.contains(k);
+
+            if !retain {
+                if let Memory::Device(entry) = memory {
+                    store.remove(entry, state);
+                }
+            }
+
+            retain
+        });
+
+        self.hits.clear();
+    }
+
+    fn get(&mut self, handle: &image::Handle) -> Option<&mut Memory<T>> {
+        let _ = self.hits.insert(handle.id());
+
+        self.map.get_mut(&handle.id())
+    }
+
+    fn insert(&mut self, handle: &image::Handle, memory: Memory<T>) {
+        let _ = self.map.insert(handle.id(), memory);
+    }
+
+    fn contains(&self, handle: &image::Handle) -> bool {
+        self.map.contains_key(&handle.id())
+    }
+}
+
+impl<T: TextureStore> Default for Cache<T> {
+    fn default() -> Self {
+        Self {
+            map: HashMap::new(),
+            hits: HashSet::new(),
+        }
+    }
+}
+
+bitflags! {
+    struct Operation: u8 {
+        const FLIP_HORIZONTALLY = 0b001;
+        const ROTATE_180 = 0b010;
+        const FLIP_DIAGONALLY = 0b100;
+    }
+}
+
+impl Operation {
+    // Meaning of the returned value is described e.g. at:
+    // https://magnushoff.com/articles/jpeg-orientation/
+    fn from_exif<R>(reader: &mut R) -> Result<Self, exif::Error>
+    where
+        R: std::io::BufRead + std::io::Seek,
+    {
+        let exif = exif::Reader::new().read_from_container(reader)?;
+
+        Ok(exif
+            .get_field(exif::Tag::Orientation, exif::In::PRIMARY)
+            .and_then(|field| field.value.get_uint(0))
+            .and_then(|value| u8::try_from(value).ok())
+            .and_then(|value| Self::from_bits(value.saturating_sub(1)))
+            .unwrap_or_else(Self::empty))
+    }
+
+    fn perform<P>(
+        self,
+        image: image_rs::ImageBuffer<P, Vec<P::Subpixel>>,
+    ) -> image_rs::ImageBuffer<P, Vec<P::Subpixel>>
+    where
+        P: image_rs::Pixel + 'static,
+    {
+        use image_rs::imageops;
+
+        let mut image = if self.contains(Self::FLIP_DIAGONALLY) {
+            flip_diagonally(image)
+        } else {
+            image
+        };
+
+        if self.contains(Self::ROTATE_180) {
+            imageops::rotate180_in_place(&mut image);
+        }
+
+        if self.contains(Self::FLIP_HORIZONTALLY) {
+            imageops::flip_horizontal_in_place(&mut image);
+        }
+
+        image
+    }
+}
+
+fn flip_diagonally<I>(
+    image: I,
+) -> image_rs::ImageBuffer<I::Pixel, Vec<<I::Pixel as image_rs::Pixel>::Subpixel>>
+where
+    I: image_rs::GenericImage,
+    I::Pixel: 'static,
+{
+    let (width, height) = image.dimensions();
+    let mut out = image_rs::ImageBuffer::new(height, width);
+
+    for x in 0..width {
+        for y in 0..height {
+            let p = image.get_pixel(x, y);
+
+            out.put_pixel(y, x, p);
+        }
+    }
+
+    out
+}