/src/image/src/images/sub_image.rs

Source
use crate::{flat::ViewOfPixel, math::Rect, GenericImage, GenericImageView, ImageBuffer, Pixel};
use std::ops::{Deref, DerefMut};

/// A View into another image
///
/// Instances of this struct can be created using:
///   - [`GenericImage::sub_image`] to create a mutable view,
///   - [`GenericImageView::view`] to create an immutable view,
///   - [`SubImage::new`] to instantiate the struct directly.
///
/// Note that this does _not_ implement `GenericImage`, but it dereferences to one which allows you
/// to use it as if it did. See [Design Considerations](#Design-Considerations) below for details.
///
/// # Design Considerations
///
/// For reasons relating to coherence, this is not itself a `GenericImage` or a `GenericImageView`.
/// In short, we want to reserve the ability of adding traits implemented for _all_ generic images
/// but in a different manner for `SubImage`. This may be required to ensure that stacking
/// sub-images comes at no double indirect cost.
///
/// If, ultimately, this is not needed then a directly implementation of `GenericImage` can and
/// will get added. This inconvenience may alternatively get resolved if Rust allows some forms of
/// specialization, which might make this trick unnecessary and thus also allows for a direct
/// implementation.
#[derive(Copy, Clone)]
pub struct SubImage<I> {
    inner: SubImageInner<I>,
}

/// The inner type of `SubImage` that implements `GenericImage{,View}`.
///
/// This type is _nominally_ `pub` but it is not exported from the crate. It should be regarded as
/// an existential type in any case.
#[derive(Copy, Clone)]
pub struct SubImageInner<I> {
    image: I,
    xoffset: u32,
    yoffset: u32,
    xstride: u32,
    ystride: u32,
}

/// Alias to access Pixel behind a reference
type DerefPixel<I> = <<I as Deref>::Target as GenericImageView>::Pixel;

/// Alias to access Subpixel behind a reference
type DerefSubpixel<I> = <DerefPixel<I> as Pixel>::Subpixel;

impl<I> SubImage<I> {
    /// Construct a new subimage
    /// The coordinates set the position of the top left corner of the `SubImage`.
    pub fn new(image: I, rect: Rect) -> SubImage<I> {
        SubImage {
            inner: SubImageInner {
                image,
                xoffset: rect.x,
                yoffset: rect.y,
                xstride: rect.width,
                ystride: rect.height,
            },
        }
    }

    /// Change the coordinates of this subimage.
    pub fn change_bounds(&mut self, x: u32, y: u32, width: u32, height: u32) {
        self.inner.xoffset = x;
        self.inner.yoffset = y;
        self.inner.xstride = width;
        self.inner.ystride = height;
    }

    /// The offsets of this subimage relative to the underlying image.
    pub fn offsets(&self) -> (u32, u32) {
        (self.inner.xoffset, self.inner.yoffset)
    }

    /// Convert this subimage to an `ImageBuffer`
    pub fn to_image(&self) -> ImageBuffer<DerefPixel<I>, Vec<DerefSubpixel<I>>>
    where
        I: Deref,
        I::Target: GenericImageView + 'static,
    {
        let borrowed = &*self.inner.image;
        let mut out = borrowed.buffer_with_dimensions(self.inner.xstride, self.inner.ystride);

        for y in 0..self.inner.ystride {
            for x in 0..self.inner.xstride {
                let p = borrowed.get_pixel(x + self.inner.xoffset, y + self.inner.yoffset);
                out.put_pixel(x, y, p);
            }
        }

        out
    }
}

/// Methods for readable images.
impl<I> SubImage<I>
where
    I: Deref,
    I::Target: GenericImageView,
{
    /// Create a sub-view of the image.
    ///
    /// The coordinates given are relative to the current view on the underlying image.
    ///
    /// Note that this method is preferred to the one from `GenericImageView`. This is accessible
    /// with the explicit method call syntax but it should rarely be needed due to causing an
    /// extra level of indirection.
    ///
    /// ```
    /// use image::{GenericImageView, RgbImage, SubImage};
    /// use image::math::Rect;
    /// let buffer = RgbImage::new(10, 10);
    ///
    /// let selection = Rect::from_xy_ranges(0..10, 0..10);
    /// let subimage: SubImage<&RgbImage> = buffer.view(selection);
    /// let subview: SubImage<&RgbImage> = subimage.view(selection);
    ///
    /// // Less efficient and NOT &RgbImage
    /// let _: SubImage<&_> = GenericImageView::view(&*subimage, selection);
    /// ```
    pub fn view(&self, mut rect: Rect) -> SubImage<&I::Target> {
        rect.assert_in_bounds_of(&self.inner);
        rect.x = self.inner.xoffset.saturating_add(rect.x);
        rect.y = self.inner.yoffset.saturating_add(rect.y);
        SubImage::new(&*self.inner.image, rect)
    }

    /// Get a reference to the underlying image.
    pub fn inner(&self) -> &I::Target {
        &self.inner.image
    }
}

impl<I> SubImage<I>
where
    I: DerefMut,
    I::Target: GenericImage,
{
    /// Create a mutable sub-view of the image.
    ///
    /// The coordinates given are relative to the current view on the underlying image.
    pub fn sub_image(&mut self, mut rect: Rect) -> SubImage<&mut I::Target> {
        rect.assert_in_bounds_of(&self.inner);
        rect.x = self.inner.xoffset.saturating_add(rect.x);
        rect.y = self.inner.yoffset.saturating_add(rect.y);
        SubImage::new(&mut *self.inner.image, rect)
    }

    /// Get a mutable reference to the underlying image.
    pub fn inner_mut(&mut self) -> &mut I::Target {
        &mut self.inner.image
    }
}

impl<I> Deref for SubImage<I>
where
    I: Deref,
{
    type Target = SubImageInner<I>;

    fn deref(&self) -> &Self::Target {
        &self.inner
    }
}

impl<I> DerefMut for SubImage<I>
where
    I: DerefMut,
{
    fn deref_mut(&mut self) -> &mut Self::Target {
        &mut self.inner
    }
}

#[allow(deprecated)]
impl<I> GenericImageView for SubImageInner<I>
where
    I: Deref,
    I::Target: GenericImageView,
{
    type Pixel = DerefPixel<I>;

    fn dimensions(&self) -> (u32, u32) {
        (self.xstride, self.ystride)
    }

    fn get_pixel(&self, x: u32, y: u32) -> Self::Pixel {
        self.image.get_pixel(x + self.xoffset, y + self.yoffset)
    }

    /// Create a buffer with the (color) metadata of the underlying image.
    fn buffer_with_dimensions(
        &self,
        width: u32,
        height: u32,
    ) -> ImageBuffer<
        <I::Target as GenericImageView>::Pixel,
        Vec<<<I::Target as GenericImageView>::Pixel as Pixel>::Subpixel>,
    > {
        self.image.buffer_with_dimensions(width, height)
    }

    fn to_pixel_view(&self) -> Option<ViewOfPixel<'_, Self::Pixel>> {
        let inner = self.image.to_pixel_view()?;

        // Now pivot the inner descriptor.
        let mut descriptor = inner.into_inner();

        let offset = descriptor.index(0, self.xoffset, self.yoffset)?;
        descriptor.samples = descriptor.samples.get(offset..)?;
        descriptor.layout.width = self.xstride;
        descriptor.layout.height = self.ystride;

        descriptor.into_view().ok()
    }
}

#[allow(deprecated)]
impl<I> GenericImage for SubImageInner<I>
where
    I: DerefMut,
    I::Target: GenericImage + Sized,
{
    fn get_pixel_mut(&mut self, x: u32, y: u32) -> &mut Self::Pixel {
        self.image.get_pixel_mut(x + self.xoffset, y + self.yoffset)
    }

    fn put_pixel(&mut self, x: u32, y: u32, pixel: Self::Pixel) {
        self.image
            .put_pixel(x + self.xoffset, y + self.yoffset, pixel);
    }

    /// DEPRECATED: This method will be removed. Blend the pixel directly instead.
    fn blend_pixel(&mut self, x: u32, y: u32, pixel: Self::Pixel) {
        self.image
            .blend_pixel(x + self.xoffset, y + self.yoffset, pixel);
    }

    fn copy_from<O>(&mut self, other: &O, x: u32, y: u32) -> Result<(), crate::ImageError>
    where
        O: GenericImageView<Pixel = Self::Pixel>,
    {
        Rect::from_image_at(other, x, y).test_in_bounds(self)?;
        // Dispatch the inner images `copy_from` method with adjusted offsets. this ensures its
        // potentially optimized implementation gets used.
        self.image
            .copy_from(other, x + self.xoffset, y + self.yoffset)
    }
}

#[cfg(test)]
mod tests {
    use crate::{math::Rect, metadata::Cicp, GenericImageView, RgbaImage};

    #[test]
    fn preserves_color_space() {
        let mut buffer = RgbaImage::new(16, 16);
        buffer[(0, 0)] = crate::Rgba([0xff, 0, 0, 255]);
        buffer.set_rgb_primaries(Cicp::DISPLAY_P3.primaries);

        let view = buffer.view(Rect::from_xy_ranges(0..16, 0..16));
        let result = view.buffer_like();

        assert_eq!(buffer.color_space(), result.color_space());
    }

    #[test]
    fn deep_preserves_color_space() {
        let mut buffer = RgbaImage::new(16, 16);
        buffer[(0, 0)] = crate::Rgba([0xff, 0, 0, 255]);
        buffer.set_rgb_primaries(Cicp::DISPLAY_P3.primaries);

        let view = buffer.view(Rect::from_xy_ranges(0..16, 0..16));
        let view = view.view(Rect::from_xy_ranges(0..16, 0..16));
        let result = view.buffer_like();

        assert_eq!(buffer.color_space(), result.color_space());
    }
}

Coverage Report

Created: 2026-03-07 07:19

Line	Count	Source
1		use crate::{flat::ViewOfPixel, math::Rect, GenericImage, GenericImageView, ImageBuffer, Pixel};
2		use std::ops::{Deref, DerefMut};
3
4		/// A View into another image
5		///
6		/// Instances of this struct can be created using:
7		/// - [`GenericImage::sub_image`] to create a mutable view,
8		/// - [`GenericImageView::view`] to create an immutable view,
9		/// - [`SubImage::new`] to instantiate the struct directly.
10		///
11		/// Note that this does _not_ implement `GenericImage`, but it dereferences to one which allows you
12		/// to use it as if it did. See [Design Considerations](#Design-Considerations) below for details.
13		///
14		/// # Design Considerations
15		///
16		/// For reasons relating to coherence, this is not itself a `GenericImage` or a `GenericImageView`.
17		/// In short, we want to reserve the ability of adding traits implemented for _all_ generic images
18		/// but in a different manner for `SubImage`. This may be required to ensure that stacking
19		/// sub-images comes at no double indirect cost.
20		///
21		/// If, ultimately, this is not needed then a directly implementation of `GenericImage` can and
22		/// will get added. This inconvenience may alternatively get resolved if Rust allows some forms of
23		/// specialization, which might make this trick unnecessary and thus also allows for a direct
24		/// implementation.
25		#[derive(Copy, Clone)]
26		pub struct SubImage<I> {
27		inner: SubImageInner<I>,
28		}
29
30		/// The inner type of `SubImage` that implements `GenericImage{,View}`.
31		///
32		/// This type is _nominally_ `pub` but it is not exported from the crate. It should be regarded as
33		/// an existential type in any case.
34		#[derive(Copy, Clone)]
35		pub struct SubImageInner<I> {
36		image: I,
37		xoffset: u32,
38		yoffset: u32,
39		xstride: u32,
40		ystride: u32,
41		}
42
43		/// Alias to access Pixel behind a reference
44		type DerefPixel<I> = <<I as Deref>::Target as GenericImageView>::Pixel;
45
46		/// Alias to access Subpixel behind a reference
47		type DerefSubpixel<I> = <DerefPixel<I> as Pixel>::Subpixel;
48
49		impl<I> SubImage<I> {
50		/// Construct a new subimage
51		/// The coordinates set the position of the top left corner of the `SubImage`.
52	0	pub fn new(image: I, rect: Rect) -> SubImage<I> {
53	0	SubImage {
54	0	inner: SubImageInner {
55	0	image,
56	0	xoffset: rect.x,
57	0	yoffset: rect.y,
58	0	xstride: rect.width,
59	0	ystride: rect.height,
60	0	},
61	0	}
62	0	} Unexecuted instantiation: <image::images::sub_image::SubImage<&image::images::buffer::ImageBuffer<image::color::Rgb<f32>, alloc::vec::Vec<f32>>>>::new Unexecuted instantiation: <image::images::sub_image::SubImage<&image::images::buffer::ImageBuffer<image::color::Rgb<u8>, alloc::vec::Vec<u8>>>>::new Unexecuted instantiation: <image::images::sub_image::SubImage<&image::images::buffer::ImageBuffer<image::color::Rgb<u16>, alloc::vec::Vec<u16>>>>::new Unexecuted instantiation: <image::images::sub_image::SubImage<&image::images::buffer::ImageBuffer<image::color::Luma<u8>, alloc::vec::Vec<u8>>>>::new Unexecuted instantiation: <image::images::sub_image::SubImage<&image::images::buffer::ImageBuffer<image::color::Luma<u16>, alloc::vec::Vec<u16>>>>::new Unexecuted instantiation: <image::images::sub_image::SubImage<&image::images::buffer::ImageBuffer<image::color::Rgba<f32>, alloc::vec::Vec<f32>>>>::new Unexecuted instantiation: <image::images::sub_image::SubImage<&image::images::buffer::ImageBuffer<image::color::Rgba<u8>, alloc::vec::Vec<u8>>>>::new Unexecuted instantiation: <image::images::sub_image::SubImage<&image::images::buffer::ImageBuffer<image::color::Rgba<u16>, alloc::vec::Vec<u16>>>>::new Unexecuted instantiation: <image::images::sub_image::SubImage<&image::images::buffer::ImageBuffer<image::color::LumaA<u8>, alloc::vec::Vec<u8>>>>::new Unexecuted instantiation: <image::images::sub_image::SubImage<&image::images::buffer::ImageBuffer<image::color::LumaA<u16>, alloc::vec::Vec<u16>>>>::new
63
64		/// Change the coordinates of this subimage.
65	0	pub fn change_bounds(&mut self, x: u32, y: u32, width: u32, height: u32) {
66	0	self.inner.xoffset = x;
67	0	self.inner.yoffset = y;
68	0	self.inner.xstride = width;
69	0	self.inner.ystride = height;
70	0	}
71
72		/// The offsets of this subimage relative to the underlying image.
73	0	pub fn offsets(&self) -> (u32, u32) {
74	0	(self.inner.xoffset, self.inner.yoffset)
75	0	}
76
77		/// Convert this subimage to an `ImageBuffer`
78	0	pub fn to_image(&self) -> ImageBuffer<DerefPixel<I>, Vec<DerefSubpixel<I>>>
79	0	where
80	0	I: Deref,
81	0	I::Target: GenericImageView + 'static,
82		{
83	0	let borrowed = &*self.inner.image;
84	0	let mut out = borrowed.buffer_with_dimensions(self.inner.xstride, self.inner.ystride);
85
86	0	for y in 0..self.inner.ystride {
87	0	for x in 0..self.inner.xstride {
88	0	let p = borrowed.get_pixel(x + self.inner.xoffset, y + self.inner.yoffset);
89	0	out.put_pixel(x, y, p);
90	0	}
91		}
92
93	0	out
94	0	} Unexecuted instantiation: <image::images::sub_image::SubImage<&image::images::buffer::ImageBuffer<image::color::Rgb<f32>, alloc::vec::Vec<f32>>>>::to_image Unexecuted instantiation: <image::images::sub_image::SubImage<&image::images::buffer::ImageBuffer<image::color::Rgb<u8>, alloc::vec::Vec<u8>>>>::to_image Unexecuted instantiation: <image::images::sub_image::SubImage<&image::images::buffer::ImageBuffer<image::color::Rgb<u16>, alloc::vec::Vec<u16>>>>::to_image Unexecuted instantiation: <image::images::sub_image::SubImage<&image::images::buffer::ImageBuffer<image::color::Luma<u8>, alloc::vec::Vec<u8>>>>::to_image Unexecuted instantiation: <image::images::sub_image::SubImage<&image::images::buffer::ImageBuffer<image::color::Luma<u16>, alloc::vec::Vec<u16>>>>::to_image Unexecuted instantiation: <image::images::sub_image::SubImage<&image::images::buffer::ImageBuffer<image::color::Rgba<f32>, alloc::vec::Vec<f32>>>>::to_image Unexecuted instantiation: <image::images::sub_image::SubImage<&image::images::buffer::ImageBuffer<image::color::Rgba<u8>, alloc::vec::Vec<u8>>>>::to_image Unexecuted instantiation: <image::images::sub_image::SubImage<&image::images::buffer::ImageBuffer<image::color::Rgba<u16>, alloc::vec::Vec<u16>>>>::to_image Unexecuted instantiation: <image::images::sub_image::SubImage<&image::images::buffer::ImageBuffer<image::color::LumaA<u8>, alloc::vec::Vec<u8>>>>::to_image Unexecuted instantiation: <image::images::sub_image::SubImage<&image::images::buffer::ImageBuffer<image::color::LumaA<u16>, alloc::vec::Vec<u16>>>>::to_image
95		}
96
97		/// Methods for readable images.
98		impl<I> SubImage<I>
99		where
100		I: Deref,
101		I::Target: GenericImageView,
102		{
103		/// Create a sub-view of the image.
104		///
105		/// The coordinates given are relative to the current view on the underlying image.
106		///
107		/// Note that this method is preferred to the one from `GenericImageView`. This is accessible
108		/// with the explicit method call syntax but it should rarely be needed due to causing an
109		/// extra level of indirection.
110		///
111		/// ```
112		/// use image::{GenericImageView, RgbImage, SubImage};
113		/// use image::math::Rect;
114		/// let buffer = RgbImage::new(10, 10);
115		///
116		/// let selection = Rect::from_xy_ranges(0..10, 0..10);
117		/// let subimage: SubImage<&RgbImage> = buffer.view(selection);
118		/// let subview: SubImage<&RgbImage> = subimage.view(selection);
119		///
120		/// // Less efficient and NOT &RgbImage
121		/// let _: SubImage<&_> = GenericImageView::view(&*subimage, selection);
122		/// ```
123	0	pub fn view(&self, mut rect: Rect) -> SubImage<&I::Target> {
124	0	rect.assert_in_bounds_of(&self.inner);
125	0	rect.x = self.inner.xoffset.saturating_add(rect.x);
126	0	rect.y = self.inner.yoffset.saturating_add(rect.y);
127	0	SubImage::new(&*self.inner.image, rect)
128	0	}
129
130		/// Get a reference to the underlying image.
131	0	pub fn inner(&self) -> &I::Target {
132	0	&self.inner.image
133	0	}
134		}
135
136		impl<I> SubImage<I>
137		where
138		I: DerefMut,
139		I::Target: GenericImage,
140		{
141		/// Create a mutable sub-view of the image.
142		///
143		/// The coordinates given are relative to the current view on the underlying image.
144	0	pub fn sub_image(&mut self, mut rect: Rect) -> SubImage<&mut I::Target> {
145	0	rect.assert_in_bounds_of(&self.inner);
146	0	rect.x = self.inner.xoffset.saturating_add(rect.x);
147	0	rect.y = self.inner.yoffset.saturating_add(rect.y);
148	0	SubImage::new(&mut *self.inner.image, rect)
149	0	}
150
151		/// Get a mutable reference to the underlying image.
152	0	pub fn inner_mut(&mut self) -> &mut I::Target {
153	0	&mut self.inner.image
154	0	}
155		}
156
157		impl<I> Deref for SubImage<I>
158		where
159		I: Deref,
160		{
161		type Target = SubImageInner<I>;
162
163	0	fn deref(&self) -> &Self::Target {
164	0	&self.inner
165	0	}
166		}
167
168		impl<I> DerefMut for SubImage<I>
169		where
170		I: DerefMut,
171		{
172	0	fn deref_mut(&mut self) -> &mut Self::Target {
173	0	&mut self.inner
174	0	}
175		}
176
177		#[allow(deprecated)]
178		impl<I> GenericImageView for SubImageInner<I>
179		where
180		I: Deref,
181		I::Target: GenericImageView,
182		{
183		type Pixel = DerefPixel<I>;
184
185	0	fn dimensions(&self) -> (u32, u32) {
186	0	(self.xstride, self.ystride)
187	0	}
188
189	0	fn get_pixel(&self, x: u32, y: u32) -> Self::Pixel {
190	0	self.image.get_pixel(x + self.xoffset, y + self.yoffset)
191	0	}
192
193		/// Create a buffer with the (color) metadata of the underlying image.
194	0	fn buffer_with_dimensions(
195	0	&self,
196	0	width: u32,
197	0	height: u32,
198	0	) -> ImageBuffer<
199	0	<I::Target as GenericImageView>::Pixel,
200	0	Vec<<<I::Target as GenericImageView>::Pixel as Pixel>::Subpixel>,
201	0	> {
202	0	self.image.buffer_with_dimensions(width, height)
203	0	}
204
205	0	fn to_pixel_view(&self) -> Option<ViewOfPixel<'_, Self::Pixel>> {
206	0	let inner = self.image.to_pixel_view()?;
207
208		// Now pivot the inner descriptor.
209	0	let mut descriptor = inner.into_inner();
210
211	0	let offset = descriptor.index(0, self.xoffset, self.yoffset)?;
212	0	descriptor.samples = descriptor.samples.get(offset..)?;
213	0	descriptor.layout.width = self.xstride;
214	0	descriptor.layout.height = self.ystride;
215
216	0	descriptor.into_view().ok()
217	0	}
218		}
219
220		#[allow(deprecated)]
221		impl<I> GenericImage for SubImageInner<I>
222		where
223		I: DerefMut,
224		I::Target: GenericImage + Sized,
225		{
226	0	fn get_pixel_mut(&mut self, x: u32, y: u32) -> &mut Self::Pixel {
227	0	self.image.get_pixel_mut(x + self.xoffset, y + self.yoffset)
228	0	}
229
230	0	fn put_pixel(&mut self, x: u32, y: u32, pixel: Self::Pixel) {
231	0	self.image
232	0	.put_pixel(x + self.xoffset, y + self.yoffset, pixel);
233	0	}
234
235		/// DEPRECATED: This method will be removed. Blend the pixel directly instead.
236	0	fn blend_pixel(&mut self, x: u32, y: u32, pixel: Self::Pixel) {
237	0	self.image
238	0	.blend_pixel(x + self.xoffset, y + self.yoffset, pixel);
239	0	}
240
241	0	fn copy_from<O>(&mut self, other: &O, x: u32, y: u32) -> Result<(), crate::ImageError>
242	0	where
243	0	O: GenericImageView<Pixel = Self::Pixel>,
244		{
245	0	Rect::from_image_at(other, x, y).test_in_bounds(self)?;
246		// Dispatch the inner images `copy_from` method with adjusted offsets. this ensures its
247		// potentially optimized implementation gets used.
248	0	self.image
249	0	.copy_from(other, x + self.xoffset, y + self.yoffset)
250	0	}
251		}
252
253		#[cfg(test)]
254		mod tests {
255		use crate::{math::Rect, metadata::Cicp, GenericImageView, RgbaImage};
256
257		#[test]
258		fn preserves_color_space() {
259		let mut buffer = RgbaImage::new(16, 16);
260		buffer[(0, 0)] = crate::Rgba([0xff, 0, 0, 255]);
261		buffer.set_rgb_primaries(Cicp::DISPLAY_P3.primaries);
262
263		let view = buffer.view(Rect::from_xy_ranges(0..16, 0..16));
264		let result = view.buffer_like();
265
266		assert_eq!(buffer.color_space(), result.color_space());
267		}
268
269		#[test]
270		fn deep_preserves_color_space() {
271		let mut buffer = RgbaImage::new(16, 16);
272		buffer[(0, 0)] = crate::Rgba([0xff, 0, 0, 255]);
273		buffer.set_rgb_primaries(Cicp::DISPLAY_P3.primaries);
274
275		let view = buffer.view(Rect::from_xy_ranges(0..16, 0..16));
276		let view = view.view(Rect::from_xy_ranges(0..16, 0..16));
277		let result = view.buffer_like();
278
279		assert_eq!(buffer.color_space(), result.color_space());
280		}
281		}