basic no_std support

.github/workflows/rust.yml

@@ -2,9 +2,10 @@ name: Rust CI
 
 on:
   push:
-    branches: [ master, next ]
-  pull_request:
-    branches: [ master, next ]
+  # TODO(interstellar) revert
+  #   branches: [ master, next ]
+  # pull_request:
+  #   branches: [ master, next ]
 
 jobs:
   build:
@@ -13,7 +14,7 @@ jobs:
     strategy:
       matrix:
         rust: ["1.61.0", stable, beta, nightly]
-        features: [gif, jpeg, png, tiff, ico, pnm, tga, webp, bmp, hdr, dxt, dds, farbfeld, openexr, jpeg_rayon, webp-encoder, '']
+        features: [gif, jpeg, png, tiff, ico, pnm, tga, webp, bmp, hdr, dxt, dds, farbfeld, openexr, jpeg_rayon, webp-encoder, std]
     steps:
     - uses: actions/checkout@v2
     - uses: actions-rs/toolchain@v1
@@ -45,7 +46,7 @@ jobs:
     runs-on: ubuntu-20.04
     strategy:
       matrix:
-        features: [gif, jpeg, png, tiff, ico, pnm, tga, webp, bmp, hdr, dxt, dds, farbfeld, openexr, jpeg_rayon, webp-encoder, '']
+        features: [gif, jpeg, png, tiff, ico, pnm, tga, webp, bmp, hdr, dxt, dds, farbfeld, openexr, jpeg_rayon, webp-encoder, std]
 
     # we are using the cross project for cross compilation to mips:
     # https://github.com/cross-rs/cross
@@ -120,6 +121,19 @@ jobs:
       env:
         SYSTEM_DEPS_DAV1D_BUILD_INTERNAL: always
 
+  no_std_check:
+    runs-on: ubuntu-20.04
+    steps:
+    - uses: actions/checkout@v2
+    - uses: actions-rs/toolchain@v1
+      with:
+        toolchain: nightly
+        override: true
+    - name: build
+      run: |
+        cargo install cargo-no-std-check
+        cargo no-std-check --no-default-features --features=alloc
+
   clippy:
     runs-on: ubuntu-20.04
     steps:

Cargo.toml

@@ -31,10 +31,10 @@ path = "./src/lib.rs"
 
 [dependencies]
 bytemuck = { version = "1.7.0", features = ["extern_crate_alloc"] } # includes cast_vec
-byteorder = "1.3.2"
+byteorder = { version = "1.3.2", default-features = false }
 num-rational = { version = "0.4", default-features = false }
-num-traits = "0.2.0"
-gif = { version = "0.12", optional = true }
+num-traits = { version = "0.2", default-features = false }
+gif = { version = "0.12", optional = true, default-features = false }
 jpeg = { package = "jpeg-decoder", version = "0.3.0", default-features = false, optional = true }
 png = { version = "0.17.6", optional = true }
 scoped_threadpool = { version = "0.1", optional = true }
@@ -44,7 +44,9 @@ rgb = { version = "0.8.25", optional = true }
 mp4parse = { version = "0.12.0", optional = true }
 dav1d = { version = "0.6.0", optional = true }
 dcv-color-primitives = { version = "0.4.0", optional = true }
-color_quant = "1.1"
+# TODO(interstellar) no_std not supported on crate.io; need a fork/patch
+# NOTE: also an optional dependency of "gif"
+color_quant = { version = "1.1", git = "https://github.com/Interstellar-Network/color_quant.git", branch = "sgx-nostd-compat", default-features = false, optional = true }
 exr = { version = "1.5.0", optional = true }
 qoi = { version = "0.4", optional = true }
 libwebp = { package = "webp", version = "0.2.2", default-features = false, optional = true }
@@ -61,38 +63,47 @@ jpeg = { package = "jpeg-decoder", version = "0.3.0", default-features = false,
 
 [features]
 # TODO: Add "avif" to this list while preparing for 0.24.0
-default = ["gif", "jpeg", "ico", "png", "pnm", "tga", "tiff", "webp", "bmp", "hdr", "dxt", "dds", "farbfeld", "jpeg_rayon", "openexr", "qoi"]
-
-ico = ["bmp", "png"]
-pnm = []
-tga = []
-bmp = []
-hdr = ["scoped_threadpool"]
-dxt = []
+default = ["std", "gif", "jpeg", "ico", "png", "pnm", "tga", "tiff", "webp", "bmp", "hdr", "dxt", "dds", "farbfeld", "jpeg_rayon", "openexr", "qoi"]
+
+# MUST always compile with either "std" or "alloc"
+# TODO(interstellar) add compile error in case of neither?
+std = ["num-traits/std", "byteorder/std", "color_quant/std"]
+alloc = ["num-traits/libm", "color_quant/num-traits"]
+
+gif = ["std", "gif/default"]
+jpeg = ["std", "dep:jpeg"]
+png = ["std", "dep:png"]
+tiff = ["std", "dep:tiff"]
+ico = ["std", "bmp", "png"]
+pnm = ["std"]
+tga = ["std"]
+bmp = ["std"]
+hdr = ["std", "scoped_threadpool"]
+dxt = ["std"]
 dds = ["dxt"]
-farbfeld = []
-openexr = ["exr"]
-qoi = ["dep:qoi"]
+farbfeld = ["std"]
+openexr = ["std", "exr"]
+qoi = ["std", "dep:qoi"]
 
 # Enables WebP decoder support.
-webp = []
+webp = ["std"]
 # Non-default, not included in `webp`. Requires native dependency libwebp.
-webp-encoder = ["libwebp"]
+webp-encoder = ["std", "libwebp"]
 
 # Enables multi-threading.
 # Requires latest stable Rust.
-jpeg_rayon = ["jpeg/rayon"]
+jpeg_rayon = ["std", "jpeg/rayon"]
 # Non-default, enables avif support.
 # Requires latest stable Rust.
-avif = ["avif-encoder"]
+avif = ["std", "avif-encoder"]
 # Requires latest stable Rust and recent nasm (>= 2.14).
-avif-encoder = ["ravif", "rgb"]
+avif-encoder = ["std", "ravif", "rgb"]
 # Non-default, even in `avif`. Requires stable Rust and native dependency libdav1d.
-avif-decoder = ["mp4parse", "dcv-color-primitives", "dav1d"]
+avif-decoder = ["std", "mp4parse", "dcv-color-primitives", "dav1d"]
 
 # Build some inline benchmarks. Useful only during development.
 # Requires rustc nightly for feature test.
-benchmarks = []
+benchmarks = ["std"]
 
 [[bench]]
 path = "benches/decode.rs"
@@ -107,3 +118,39 @@ harness = false
 [[bench]]
 name = "copy_from"
 harness = false
+
+[[example]]
+name = "tile"
+required-features = ["std"]
+
+[[example]]
+name = "fractal"
+required-features = ["std"]
+
+[[example]]
+name = "scaleup"
+required-features = ["std"]
+
+[[example]]
+name = "concat"
+required-features = ["std"]
+
+[[example]]
+name = "gradient"
+required-features = ["std"]
+
+[[example]]
+name = "opening"
+required-features = ["std"]
+
+[[example]]
+name = "decode"
+required-features = ["std"]
+
+[[example]]
+name = "scaledown"
+required-features = ["std"]
+
+[[example]]
+name = "convert"
+required-features = ["std"]

README.md

@@ -18,21 +18,21 @@ All image processing functions provided operate on types that implement the `Gen
 
 `image` provides implementations of common image format encoders and decoders.
 
-| Format | Decoding | Encoding |
-| ------ | -------- | -------- |
-| PNG    | All supported color types | Same as decoding |
-| JPEG   | Baseline and progressive | Baseline JPEG |
-| GIF    | Yes | Yes |
-| BMP    | Yes | Rgb8, Rgba8, Gray8, GrayA8 |
-| ICO    | Yes | Yes |
-| TIFF   | Baseline(no fax support) + LZW + PackBits | Rgb8, Rgba8, Gray8 |
-| WebP   | Yes | Rgb8, Rgba8 \* |
-| AVIF   | Only 8-bit \*\* | Lossy |
-| PNM    | PBM, PGM, PPM, standard PAM | Yes |
-| DDS    | DXT1, DXT3, DXT5 | No |
-| TGA    | Yes | Rgb8, Rgba8, Bgr8, Bgra8, Gray8, GrayA8 |
-| OpenEXR  | Rgb32F, Rgba32F (no dwa compression) | Rgb32F, Rgba32F (no dwa compression) |
-| farbfeld | Yes | Yes |
+| Format   | Decoding                                  | Encoding                                |
+| -------- | ----------------------------------------- | --------------------------------------- |
+| PNG      | All supported color types                 | Same as decoding                        |
+| JPEG     | Baseline and progressive                  | Baseline JPEG                           |
+| GIF      | Yes                                       | Yes                                     |
+| BMP      | Yes                                       | Rgb8, Rgba8, Gray8, GrayA8              |
+| ICO      | Yes                                       | Yes                                     |
+| TIFF     | Baseline(no fax support) + LZW + PackBits | Rgb8, Rgba8, Gray8                      |
+| WebP     | Yes                                       | Rgb8, Rgba8 \*                          |
+| AVIF     | Only 8-bit \*\*                           | Lossy                                   |
+| PNM      | PBM, PGM, PPM, standard PAM               | Yes                                     |
+| DDS      | DXT1, DXT3, DXT5                          | No                                      |
+| TGA      | Yes                                       | Rgb8, Rgba8, Bgr8, Bgra8, Gray8, GrayA8 |
+| OpenEXR  | Rgb32F, Rgba32F (no dwa compression)      | Rgb32F, Rgba32F (no dwa compression)    |
+| farbfeld | Yes                                       | Yes                                     |
 
 - \* Requires the `webp-encoder` feature, uses the libwebp C library.
 - \*\* Requires the `avif-decoder` feature, uses the libdav1d C library.
@@ -60,7 +60,7 @@ The most important methods for decoders are...
 All pixels are parameterised by their component type.
 
 ## Images
-Individual pixels within images are indexed with (0,0) at the top left corner. 
+Individual pixels within images are indexed with (0,0) at the top left corner.
 ### The [`GenericImageView`](https://docs.rs/image/*/image/trait.GenericImageView.html) and [`GenericImage`](https://docs.rs/image/*/image/trait.GenericImage.html) Traits
 
 Traits that provide methods for inspecting (`GenericImageView`) and manipulating (`GenericImage`) images, parameterised over the image's pixel type.
@@ -166,6 +166,7 @@ reader which offer some more control.
 ```rust,no_run
 use image::GenericImageView;
 
+#[cfg(feature = "std")]
 fn main() {
     // Use the open function to load an image from a Path.
     // `open` returns a `DynamicImage` on success.
@@ -180,6 +181,8 @@ fn main() {
     // Write the contents of this image to the Writer in PNG format.
     img.save("test.png").unwrap();
 }
+#[cfg(not(feature = "std"))]
+fn main() {}
 ```
 
 ### Generating Fractals
@@ -225,6 +228,7 @@ fn main() {
     }
 
     // Save the image as “fractal.png”, the format is deduced from the path
+    #[cfg(feature = "std")]
     imgbuf.save("fractal.png").unwrap();
 }
 ```
@@ -242,6 +246,7 @@ fn main() {
     let buffer: &[u8] = unimplemented!(); // Generate the image data
 
     // Save the buffer as "image.png"
+    #[cfg(feature = "std")]
     image::save_buffer("image.png", buffer, 800, 600, image::ColorType::Rgb8).unwrap()
 }
 ```

src/animation.rs

@@ -1,5 +1,9 @@
-use std::iter::Iterator;
-use std::time::Duration;
+use alloc::boxed::Box;
+use alloc::vec::Vec;
+use core::cmp::Ordering::Equal;
+use core::cmp::Ordering::Less;
+use core::iter::Iterator;
+use core::time::Duration;
 
 use num_rational::Ratio;
 
@@ -179,7 +183,7 @@ impl Delay {
     /// Note that `denom_bound` bounds nominator and denominator of all intermediate
     /// approximations and the end result.
     fn closest_bounded_fraction(denom_bound: u32, nom: u32, denom: u32) -> (u32, u32) {
-        use std::cmp::Ordering::{self, *};
+        use core::cmp::Ordering::{self, *};
         assert!(0 < denom);
         assert!(0 < denom_bound);
         assert!(nom < denom);

src/buffer.rs

@@ -1,12 +1,13 @@
 //! Contains the generic `ImageBuffer` struct.
+use alloc::vec::Vec;
+use core::fmt;
+use core::marker::PhantomData;
+use core::ops::{Deref, DerefMut, Index, IndexMut, Range};
+use core::slice::{ChunksExact, ChunksExactMut};
 use num_traits::Zero;
-use std::fmt;
-use std::marker::PhantomData;
-use std::ops::{Deref, DerefMut, Index, IndexMut, Range};
-use std::path::Path;
-use std::slice::{ChunksExact, ChunksExactMut};
 
 use crate::color::{FromColor, Luma, LumaA, Rgb, Rgba};
+#[cfg(feature = "std")]
 use crate::dynimage::{save_buffer, save_buffer_with_format, write_buffer_with_format};
 use crate::error::ImageResult;
 use crate::flat::{FlatSamples, SampleLayout};
@@ -629,6 +630,7 @@ where
 /// Overlays an image on top of a larger background raster.
 ///
 /// ```no_run
+/// # #[cfg(feature = "std")] {
 /// use image::{GenericImage, GenericImageView, ImageBuffer, open};
 ///
 /// let on_top = open("path/to/some.png").unwrap().into_rgb8();
@@ -641,15 +643,18 @@ where
 /// });
 ///
 /// image::imageops::overlay(&mut img, &on_top, 128, 128);
+/// }
 /// ```
 ///
 /// Convert an RgbaImage to a GrayImage.
 ///
 /// ```no_run
+/// # #[cfg(feature = "std")] {
 /// use image::{open, DynamicImage};
 ///
 /// let rgba = open("path/to/some.png").unwrap().into_rgba8();
 /// let gray = DynamicImage::ImageRgba8(rgba).into_luma8();
+/// }
 /// ```
 #[derive(Debug, Hash, PartialEq, Eq)]
 pub struct ImageBuffer<P: Pixel, Container> {
@@ -979,6 +984,7 @@ where
     }
 }
 
+#[cfg(feature = "std")]
 impl<P, Container> ImageBuffer<P, Container>
 where
     P: Pixel,
@@ -990,7 +996,7 @@ where
     /// The image format is derived from the file extension.
     pub fn save<Q>(&self, path: Q) -> ImageResult<()>
     where
-        Q: AsRef<Path>,
+        Q: AsRef<std::path::Path>,
         P: PixelWithColorType,
     {
         save_buffer(
@@ -1003,6 +1009,7 @@ where
     }
 }
 
+#[cfg(feature = "std")]
 impl<P, Container> ImageBuffer<P, Container>
 where
     P: Pixel,
@@ -1016,7 +1023,7 @@ where
     /// supported types.
     pub fn save_with_format<Q>(&self, path: Q, format: ImageFormat) -> ImageResult<()>
     where
-        Q: AsRef<Path>,
+        Q: AsRef<std::path::Path>,
         P: PixelWithColorType,
     {
         // This is valid as the subpixel is u8.
@@ -1031,6 +1038,7 @@ where
     }
 }
 
+#[cfg(feature = "std")]
 impl<P, Container> ImageBuffer<P, Container>
 where
     P: Pixel,
@@ -1360,11 +1368,13 @@ where
     /// use image::GrayImage;
     ///
     /// let image_path = "examples/fractal.png";
+    /// # #[cfg(feature = "std")] {
     /// let image = image::open(&image_path)
     ///     .expect("Open file failed")
     ///     .to_rgba8();
     ///
     /// let gray_image: GrayImage = image.convert();
+    /// }
     /// ```
     fn convert(&self) -> ImageBuffer<ToType, Vec<ToType::Subpixel>> {
         let mut buffer: ImageBuffer<ToType, Vec<ToType::Subpixel>> =
@@ -1407,6 +1417,7 @@ mod test {
     use crate::math::Rect;
     use crate::GenericImage as _;
     use crate::{color, Rgb};
+    use alloc::vec::Vec;
 
     #[test]
     /// Tests if image buffers from slices work