nokhwa-iter helper crate

Cargo.toml

@@ -12,7 +12,7 @@ repository = "https://github.com/l1npengtul/nokhwa"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [workspace]
-members = ["nokhwa-bindings-macos", "nokhwa-bindings-windows", "nokhwa-bindings-linux", "nokhwa-core", "nokhwa-decoders"]
+members = ["nokhwa-bindings-macos", "nokhwa-bindings-windows", "nokhwa-bindings-linux", "nokhwa-core", "nokhwa-decoders", "nokhwa-iter-extensions"]
 
 [lib]
 crate-type = ["rlib"]

nokhwa-core/src/error.rs

@@ -13,7 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-use crate::frame_format::FrameFormat;
+use crate::frame_format::{CustomFrameFormat, FrameFormat};
 use std::fmt::Debug;
 use thiserror::Error;
 use crate::types::Backends;
@@ -66,6 +66,8 @@ pub enum NokhwaError {
     Decoder(String),
     #[error("Unsupported FrameFormat: {0}")]
     DecoderUnsupportedFrameFormat(FrameFormat),
+    #[error("The destination frame format from {0} to {1} is not supported.")]
+    DecoderUnsupportedCustomFrameFormatDestination(CustomFrameFormat, FrameFormat),
     #[error("Unsupported pixel configuration {0} with width {1}b.")]
     DecoderUnsupportedDestinationPixelFormat(&'static str, u32),
     #[error("Bad decoder configuration: {0}")]
@@ -79,7 +81,7 @@ pub enum NokhwaError {
     #[error("You need to pass in a destination hint, it is not optional for this decoder.")]
     DecoderDestinationHintRequired,
     #[error("Decoder already deinitialized. Unusable, please make a new decoder.")]
-    DecoderAlreadyDeinitialized
+    DecoderAlreadyDeinitialized,
 }
 //
 // pub enum InitializeError {}

nokhwa-core/src/frame_format.rs

@@ -205,13 +205,22 @@ define_frame_format_with_groups! {
     ]
 }
 
+impl FrameFormat {
+    pub fn is_custom(&self) -> bool {
+        if let FrameFormat::Custom(_) = self {
+            return true
+        }
+        false
+    }
+}
+
 impl Display for FrameFormat {
     fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
         write!(f, "{self:?}")
     }
 }
 
-#[derive(Copy, Clone, Debug, Hash, PartialOrd, PartialEq)]
+#[derive(Copy, Clone, Debug, Hash, Ord, PartialOrd, Eq, PartialEq)]
 #[cfg_attr(feature = "serialize", derive(serde::Serialize, serde::Deserialize))]
 pub enum CustomFrameFormat {
     UUID(u128),
@@ -222,6 +231,12 @@ pub enum CustomFrameFormat {
     F64(OrderedFloat<f64>),
 }
 
+impl Display for CustomFrameFormat {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        write!(f, "{self:?}")
+    }
+}
+
 #[macro_export]
 macro_rules! define_back_and_fourth_frame_format {
     ($fourcc_type:ty, { $( $frame_format:expr => $value:literal, )* }, $func_u8_8_to_fcc:expr, $func_fcc_to_u8_8:expr, $value_to_fcc_type:expr) => {

nokhwa-decoders/Cargo.toml

@@ -7,8 +7,9 @@ edition = "2024"
 ffmpeg = ["ffmpeg-the-third"]
 yuyv = ["dcv-color-primitives", "yuv"]
 mjpeg = ["zune-jpeg", "zune-core"]
+luma = ["itertools"]
 #static = ["ffmpeg-the-third/static"]
-async = []
+#async = []
 
 [dependencies]
 bytemuck = "1.23"
@@ -37,6 +38,10 @@ optional = true
 version = "0.5.0-rc2"
 optional = true
 
+[dependencies.itertools]
+version = "0.14.0"
+optional = true
+
 [dev-dependencies.image]
 workspace = true
 features = ["png", "jpeg", "avif"]

nokhwa-decoders/src/lib.rs

@@ -6,3 +6,5 @@ pub mod ffmpeg;
 pub mod mjpeg;
 #[cfg(feature = "yuyv")]
 pub mod yuv;
+#[cfg(feature = "luma")]
+pub mod luma;

nokhwa-decoders/src/luma.rs

@@ -0,0 +1,228 @@
+use std::collections::HashMap;
+use std::fmt::Debug;
+use std::mem::swap;
+use image::Pixel;
+use itertools::Itertools;
+use nokhwa_core::decoder::Decoder;
+use nokhwa_core::error::NokhwaError;
+use nokhwa_core::frame_buffer::FrameBuffer;
+use nokhwa_core::frame_format::{CustomFrameFormat, FrameFormat};
+use nokhwa_core::image::{DecodedImage, NonFloatScalarWidth};
+use nokhwa_core::types::{CameraFormat, Resolution};
+
+#[derive(Clone, Debug, PartialEq)]
+pub struct LumaDecoder {
+    luma_config: LumaConfig,
+}
+
+impl Decoder for LumaDecoder {
+    type Config = LumaConfig;
+    type OutputMeta = ();
+    type DestinationFormatHint = LumaDestination;
+
+    fn config(&self) -> &Self::Config {
+        &self.luma_config
+    }
+
+    fn set_config(&mut self, config: Self::Config) -> Result<(), NokhwaError> {
+        self.luma_config = config;
+        Ok(())
+    }
+
+    fn decode_to_buffer(&mut self, mut to_decode: FrameBuffer, mut buffer: impl AsMut<[u8]>, destination_format_hint: Option<Self::DestinationFormatHint>) -> Result<Self::OutputMeta, NokhwaError> {
+        let destination_hint = match destination_format_hint {
+            Some(h) => h,
+            None => return Err(NokhwaError::DecoderDestinationHintRequired)
+        };
+
+        let (width, max_value) = match self.config().format {
+            FrameFormat::Luma_8 => (1, u8::MAX as u32),
+            FrameFormat::Luma_10 => (2, 2_u32.pow(10)),
+            FrameFormat::Luma_12 => (2, 2_u32.pow(12)),
+            FrameFormat::Luma_14 => (2, 2_u32.pow(14)),
+            FrameFormat::Luma_16 | FrameFormat::Depth_16 => (2, u16::MAX as u32),
+            fmt => return Err(NokhwaError::DecoderUnsupportedFrameFormat(fmt))
+        };
+
+        let format = self.config().custom_frame_format_map.as_ref().map(|m| {
+            match self.config().format {
+                FrameFormat::Custom(cfmt) => {
+                    m.get(&cfmt).copied()
+                }
+                _ => None,
+            }
+        }).flatten().unwrap_or(self.config().format);
+
+        let r = filter_to_u8(self.config().channel_filters.red);
+        let g = filter_to_u8(self.config().channel_filters.green);
+        let b = filter_to_u8(self.config().channel_filters.blue);
+        let a = filter_to_u8(self.config().channel_filters.alpha);
+
+        let r_u16 = filter_to_u16(self.config().channel_filters.red);
+        let g_u16 = filter_to_u16(self.config().channel_filters.green);
+        let b_u16 = filter_to_u16(self.config().channel_filters.blue);
+        let a_u16 = filter_to_u16(self.config().channel_filters.alpha);
+
+        match format {
+            FrameFormat::Luma_8 => {
+                match destination_hint {
+                    LumaDestination::Luma8 => {
+                        swap(to_decode.as_mut(), buffer.as_mut())
+                    }
+                    LumaDestination::LumaA8 => {
+                        let default_alpha = u8::MAX * a;
+
+                        to_decode.buffer().into_iter().intersperse(default_alpha).co
+                    }
+                    LumaDestination::Rgb8 => {}
+                    LumaDestination::Rgba8 => {}
+                    LumaDestination::Rgb16 => {}
+                    LumaDestination::Rgba16 => {}
+                }
+            }
+            FrameFormat::Luma_10 => {}
+            FrameFormat::Luma_12 => {}
+            FrameFormat::Luma_14 => {}
+            FrameFormat::Luma_16 | FrameFormat::Depth_16 => {}
+            fmt => {
+                return Err(NokhwaError::DecoderUnsupportedFrameFormat(fmt))
+            }
+        }
+    }
+
+    fn decode_to_pixel_buffer<P: Pixel>(&mut self, to_decode: FrameBuffer, buffer: impl AsMut<[P::Subpixel]>) -> Result<Self::OutputMeta, NokhwaError>
+    where
+        <P as Pixel>::Subpixel: NonFloatScalarWidth
+    {
+        todo!()
+    }
+
+    fn decode<P: Pixel>(&mut self, to_decode: FrameBuffer) -> Result<DecodedImage<P, Self::OutputMeta>, NokhwaError>
+    where
+        <P as Pixel>::Subpixel: NonFloatScalarWidth
+    {
+        todo!()
+    }
+
+    fn output_decoder_min_size(&self, resolution: Resolution, destination_format: Self::DestinationFormatHint) -> usize {
+        todo!()
+    }
+
+    fn buffer_takes_destination_hint(&self) -> bool {
+        todo!()
+    }
+}
+
+fn filter_to_u8(filter: bool) -> u8 {
+    if filter {
+        1_u8
+    } else {
+        0_u8
+    }
+}
+
+
+fn filter_to_u16(filter: bool) -> u16 {
+    if filter {
+        1_u16
+    } else {
+        0_u16
+    }
+}
+
+
+
+#[derive(Clone, Debug, PartialEq)]
+pub struct LumaConfig {
+    pub mode: ConvertMode,
+    pub scaling_functions: ScalingFunctions,
+    pub channel_filters: ChannelFilters,
+    pub format: FrameFormat,
+    pub custom_frame_format_map: Option<HashMap<CustomFrameFormat, FrameFormat>>
+}
+
+impl TryFrom<FrameFormat> for LumaConfig {
+    type Error = NokhwaError;
+
+    fn try_from(value: FrameFormat) -> Result<Self, Self::Error> {
+        if !FrameFormat::BRIGHTNESS_LUMA.contains(&value) {
+            return Err(NokhwaError::DecoderUnsupportedFrameFormat(value))
+        }
+
+        Ok(LumaConfig {
+            mode: ConvertMode::default(),
+            scaling_functions: ScalingFunctions::default(),
+            channel_filters: ChannelFilters::default(),
+            format: value,
+            custom_frame_format_map: None,
+        })
+    }
+}
+
+#[derive(Clone, Debug, PartialEq)]
+pub enum ConvertMode {
+    Scaled,
+    Clipped
+}
+
+impl Default for ConvertMode {
+    fn default() -> Self {
+        ConvertMode::Scaled
+    }
+}
+
+#[derive(Clone, Debug, Default)]
+pub struct ScalingFunctions {
+    pub scale_up_u8_to_u16: Box<dyn FnMut(u8, u32) -> u16>,
+    pub scale_down_u8_to_u16: Box<dyn FnMut(u16, u32) -> u8>,
+}
+
+#[derive(Copy, Clone, Debug, Hash, Ord, PartialOrd, Eq, PartialEq)]
+pub struct ChannelFilters {
+    pub red: bool,
+    pub green: bool,
+    pub blue: bool,
+    pub alpha: bool,
+}
+
+impl Default for ChannelFilters {
+    fn default() -> Self {
+        ChannelFilters {
+            red: true,
+            green: true,
+            blue: true,
+            alpha: true,
+        }
+    }
+}
+
+#[derive(Copy, Clone, Debug, Hash, Ord, PartialOrd, Eq, PartialEq)]
+pub enum LumaDestination {
+    Luma8,
+    LumaA8,
+    Rgb8,
+    Rgba8,
+    Rgb16,
+    Rgba16,
+}
+
+struct ConstIter<T> where T: Copy + Clone + Debug + Default + Eq + Ord + PartialEq + PartialOrd {
+    pub val: T
+}
+
+impl<T> Iterator for ConstIter<T> where T: Copy + Clone + Debug + Default + Eq + Ord + PartialEq + PartialOrd {
+    type Item = T;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        Some(self.val)
+    }
+}
+
+impl<T> IntoIterator for ConstIter<T> where  T: Copy + Clone + Debug + Default + Eq + Ord + PartialEq + PartialOrd {
+    type Item = T;
+    type IntoIter = ConstIter<T>;
+
+    fn into_iter(self) -> Self::IntoIter {
+        self
+    }
+}

nokhwa-decoders/src/yuv.rs

@@ -1,9 +1,10 @@
+use std::collections::HashMap;
 use bytemuck::{cast_slice, cast_slice_mut, try_cast_slice_mut};
 
 use nokhwa_core::decoder::{Decoder, ImageBuffer, Pixel, Primitive};
 use nokhwa_core::error::NokhwaError;
 use nokhwa_core::frame_buffer::FrameBuffer;
-use nokhwa_core::frame_format::FrameFormat;
+use nokhwa_core::frame_format::{CustomFrameFormat, FrameFormat};
 use nokhwa_core::image::{DecodedImage, NonFloatScalarWidth};
 use nokhwa_core::types::{CameraFormat, Resolution};
 use yuv::{
@@ -45,6 +46,15 @@ impl Decoder for YUVDecoder {
         if !FrameFormat::YCBCR.contains(&config.yuv_type) {
             return Err(NokhwaError::DecoderUnsupportedFrameFormat(config.yuv_type));
         }
+
+        if let Some(custom_map) = &config.custom_frame_format_map {
+            if let Some((src, dest)) = custom_map.iter().find(|(_, value)| {
+                FrameFormat::YCBCR.contains(value)
+            }) {
+                return Err(NokhwaError::DecoderUnsupportedCustomFrameFormatDestination(*src, *dest))
+            }
+        }
+
         self.config = config;
         Ok(())
     }
@@ -60,13 +70,24 @@ impl Decoder for YUVDecoder {
             None => return Err(NokhwaError::DecoderDestinationHintRequired),
         };
 
+
+        let yuv_format = self.config().custom_frame_format_map.as_ref().map(|m| {
+            match self.config.yuv_type {
+                FrameFormat::Custom(cfmt) => {
+                    m.get(&cfmt).copied()
+                }
+                _ => None,
+            }
+        }).flatten().unwrap_or(self.config.yuv_type);
+
+
         let buffer = buffer.as_mut();
         if buffer.len() < self.output_decoder_min_size(self.config.resolution, destination_format) {
             return Err(NokhwaError::DecoderInvalidBuffer("Too small!".to_string()));
         }
 
-        let stride = figure_out_stride(self.config.yuv_type).ok_or(NokhwaError::DecoderUnsupportedFrameFormat(self.config.yuv_type))?;
+        let stride = figure_out_stride(yuv_format).ok_or(NokhwaError::DecoderUnsupportedFrameFormat(yuv_format))?;
-        let byte_width = figure_out_byte_width(self.config.yuv_type).ok_or(NokhwaError::DecoderUnsupportedFrameFormat(self.config.yuv_type))?;
+        let byte_width = figure_out_byte_width(yuv_format).ok_or(NokhwaError::DecoderUnsupportedFrameFormat(yuv_format))?;
 
 
         let stride_3px = 3 *
@@ -79,7 +100,7 @@ impl Decoder for YUVDecoder {
          let decode_status = match stride {
             Stride::Packed(stride) => {
                 let image = prepare_to_packed_image(&to_decode, self.config.resolution, byte_width, stride);
-                match self.config.yuv_type {
+                match yuv_format {
                     FrameFormat::Ayuv_32 => {
                         match destination_format {
                             YUVDestination::Rgb8 => Some(ayuv_to_rgb(&image, buffer, stride_3px, self.config.range, self.config.matrix, self.config.premultiply_alpha)),
@@ -129,16 +150,16 @@ impl Decoder for YUVDecoder {
                     }
                     _ => {
                         if FrameFormat::YCBCR_PACKED.contains(&self.config.yuv_type) {
-                            return Err(NokhwaError::NotImplementedError("etto blehhh!".to_string()))
+                            return Err(NokhwaError::NotImplementedError("etto blehhh! ()".to_string()))
                         }
                         // shouldnt happen
-                        return Err(NokhwaError::DecoderUnsupportedFrameFormat(self.config.yuv_type))
+                        return Err(NokhwaError::DecoderUnsupportedFrameFormat(yuv_format))
                     }
                 }
             }
             Stride::Semi(y_stride, uv_stride) => {
                 let image = prepare_to_semi_planar_image(&to_decode, self.config.resolution, byte_width, y_stride, uv_stride);
-                match self.config.yuv_type {
+                match yuv_format {
                     FrameFormat::NV24 => {
                         match destination_format {
                             YUVDestination::Rgb8 => Some(yuv_nv24_to_rgb(&image, buffer, stride_3px, self.config.range, self.config.matrix, self.config.mode)),
@@ -213,17 +234,17 @@ impl Decoder for YUVDecoder {
                         }
                     }
                     _ => {
-                        if FrameFormat::YCBCR_SEMI.contains(&self.config.yuv_type) {
+                        if FrameFormat::YCBCR_SEMI.contains(&yuv_format) {
                             return Err(NokhwaError::NotImplementedError("etto blehhh!".to_string()))
                         }
                         // shouldnt happen
-                        return Err(NokhwaError::DecoderUnsupportedFrameFormat(self.config.yuv_type))
+                        return Err(NokhwaError::DecoderUnsupportedFrameFormat(yuv_format))
                     }
                 }
             }
             Stride::Planar(y_stride, u_stride, v_stride, line_ratio) => {
                 let image = prepare_to_planar_image(&to_decode, self.config.resolution, byte_width, y_stride, u_stride, v_stride, line_ratio);
-                match self.config.yuv_type {
+                match yuv_format {
                     FrameFormat::Yuv_4_2_0 => {
                         match destination_format {
                             YUVDestination::Rgb8 => Some(yuv420_to_rgb(&image, buffer, stride_3px, self.config.range, self.config.matrix)),
@@ -234,11 +255,11 @@ impl Decoder for YUVDecoder {
                         }
                     }
                     _ => {
-                        if FrameFormat::YCBCR_PLANAR.contains(&self.config.yuv_type) {
+                        if FrameFormat::YCBCR_PLANAR.contains(&yuv_format) {
                             return Err(NokhwaError::NotImplementedError("etto blehhh!".to_string()))
                         }
                         // shouldnt happen
-                        return Err(NokhwaError::DecoderUnsupportedFrameFormat(self.config.yuv_type))
+                        return Err(NokhwaError::DecoderUnsupportedFrameFormat(yuv_format))
                     }
                 }
             }
@@ -247,7 +268,7 @@ impl Decoder for YUVDecoder {
             Some(Ok(_)) => Ok(()),
             Some(Err(why)) => Err(NokhwaError::Decoder(why.to_string())),
             None => Err(NokhwaError::DecoderUnsupportedFrameFormat(
-                self.config.yuv_type,
+                yuv_format,
             )),
         }
     }
@@ -362,7 +383,7 @@ impl YUVDestination {
     }
 }
 
-#[derive(Clone, Debug, PartialOrd, PartialEq)]
+#[derive(Clone, Debug, PartialEq)]
 pub struct YUVConfig {
     pub resolution: Resolution,
     pub yuv_type: FrameFormat,
@@ -370,6 +391,7 @@ pub struct YUVConfig {
     pub matrix: YuvStandardMatrix,
     pub mode: YuvConversionMode,
     pub premultiply_alpha: bool,
+    pub custom_frame_format_map: Option<HashMap<CustomFrameFormat, FrameFormat>>,
 }
 
 impl TryFrom<CameraFormat> for YUVConfig {
@@ -386,6 +408,7 @@ impl TryFrom<CameraFormat> for YUVConfig {
             matrix: YuvStandardMatrix::Bt601,
             mode: YuvConversionMode::Balanced,
             premultiply_alpha: false,
+            custom_frame_format_map: None,
         })
     }
 }
@@ -559,7 +582,7 @@ fn convert_bi_planar_image_to_u16(
 #[cfg(test)]
 mod test {
     use crate::yuv::{YUVConfig, YUVDecoder};
-    use image::{DynamicImage, EncodableLayout, ImageBuffer, ImageFormat, ImageReader, Pixel, PixelWithColorType, Rgb, Rgba};
+    use image::{DynamicImage, EncodableLayout, ImageBuffer, ImageFormat, Pixel, PixelWithColorType, Rgb, Rgba};
     use nokhwa_core::decoder::Decoder;
     use nokhwa_core::frame_buffer::FrameBuffer;
     use nokhwa_core::frame_format::FrameFormat;
@@ -567,7 +590,7 @@ mod test {
     use nokhwa_core::types::Resolution;
     use std::borrow::Cow;
     use std::fs::File;
-    use std::io::{BufReader, BufWriter, Read};
+    use std::io::{BufReader, Read};
     use yuv::{YuvConversionMode, YuvRange, YuvStandardMatrix};
 
     #[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
@@ -593,6 +616,7 @@ where
                 matrix: YuvStandardMatrix::Bt601,
                 mode: YuvConversionMode::Balanced,
                 premultiply_alpha: false,
+                custom_frame_format_map: None,
             }
         );
 

nokhwa-iter-extensions/Cargo.toml

@@ -0,0 +1,12 @@
+[package]
+name = "nokhwa-iter-extensions"
+version = "0.1.0"
+authors = ["l1npengtul <l1npengtul@protonmail.com>"]
+edition = "2024"
+description = "Core type definitions for nokhwa"
+keywords = ["iter", "iterator", "interweave", "duplicate"]
+categories = ["algorithms", "rust-patterns", "no-std", "no-std::no-alloc"]
+license = "MIT OR Apache-2.0"
+repository = "https://github.com/l1npengtul/nokhwa"
+
+[dependencies]

nokhwa-iter-extensions/src/duplicate.rs

@@ -0,0 +1,138 @@
+use core::iter::FusedIterator;
+
+#[derive(Copy, Clone, Debug, Default, Hash, Ord, PartialOrd, Eq, PartialEq)]
+enum DuplicateConstState {
+    #[default]
+    Started,
+    EmitDupe,
+    EmitReal,
+    Finished
+}
+
+/// Duplicates the items in the iterator `MULTIPLIER` times.
+///
+/// 0 acts as 1.
+///
+/// This iterator is _fused_.
+pub struct DuplicateConst<I, const MULTIPLIER: usize> where
+    I: Iterator,
+    <I as Iterator>::Item: Clone {
+    iter: I,
+    last_iter_item: Option<I::Item>,
+    running_count: usize,
+    state: DuplicateConstState,
+}
+
+impl<I, const MULTIPLIER: usize> DuplicateConst<I, MULTIPLIER> where I: Iterator,
+                                                                     <I as Iterator>::Item: Clone {
+    pub fn new(iter: I) -> DuplicateConst<I, MULTIPLIER> {
+        DuplicateConst {
+            iter,
+            last_iter_item: None,
+            running_count: MULTIPLIER.saturating_sub(1),
+            state: DuplicateConstState::default(),
+        }
+    }
+}
+
+impl<I, const MULTIPLIER: usize> Iterator for DuplicateConst<I, MULTIPLIER> where
+    I: Iterator,
+    <I as Iterator>::Item: Clone
+{
+    type Item = I::Item;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        match self.state {
+            DuplicateConstState::Started => {
+                match self.iter.next() {
+                    Some(i) => {
+                        if MULTIPLIER <= 1 {
+                            self.state = DuplicateConstState::EmitReal;
+                        } else {
+                            self.state = DuplicateConstState::EmitDupe;
+                        }
+                        self.last_iter_item = Some(i.clone());
+                        Some(i)
+                    }
+                    None => {
+                        self.state = DuplicateConstState::Finished;
+                        None
+                    }
+                }
+            }
+            DuplicateConstState::EmitDupe => {
+                self.running_count = self.running_count.saturating_sub(1);
+                if self.running_count <= 0 {
+                    self.state = DuplicateConstState::EmitReal;
+                }
+                self.last_iter_item.clone()
+            }
+            DuplicateConstState::EmitReal => {
+                match self.iter.next() {
+                    Some(i) => {
+                        self.last_iter_item = Some(i.clone());
+                        self.running_count = MULTIPLIER.saturating_sub(1);
+                        if MULTIPLIER <= 1 {
+                            self.state = DuplicateConstState::EmitReal;
+                        } else {
+                            self.state = DuplicateConstState::EmitDupe;
+                        }
+                        Some(i)
+                    }
+                    None => {
+                        self.state = DuplicateConstState::Finished;
+                        None
+                    }
+                }
+            }
+            DuplicateConstState::Finished => {
+                None
+            }
+        }
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        let (lower, upper) = self.iter.size_hint();
+        let multi = if MULTIPLIER == 0 { 1 } else { MULTIPLIER + 1 };
+        (lower * multi, upper.map(|u| u * multi))
+    }
+}
+
+impl<I, const MULTIPLIER: usize> FusedIterator for DuplicateConst<I, MULTIPLIER> where I: Iterator, <I as Iterator>::Item: Clone {}
+
+pub trait IterDuplicateConst: Iterator {
+    fn duplicate_const<const MULTIPLIER: usize>(self) -> DuplicateConst<Self, MULTIPLIER> where Self: Sized, Self::Item: Clone {
+        DuplicateConst::new(self)
+    }
+}
+
+impl<I: ?Sized> IterDuplicateConst for I where I: Iterator {}
+
+#[cfg(test)]
+mod test {
+    use crate::duplicate::IterDuplicateConst;
+
+    #[test]
+    pub fn zero_acts_as_one() {
+        let initial = vec![0, 0, 0, 0];
+        let test_condition = vec![0, 0, 0, 0];
+        let result = initial.into_iter().duplicate_const::<0>().collect::<Vec<i32>>();
+        assert_eq!(test_condition, result)
+    }
+
+    #[test]
+    pub fn one_is_one() {
+        let initial = vec![0, 0, 0, 0];
+        let test_condition = vec![0, 0, 0, 0];
+        let result = initial.into_iter().duplicate_const::<1>().collect::<Vec<i32>>();
+        assert_eq!(test_condition, result)
+    }
+
+    #[test]
+    pub fn multiples() {
+        let initial = vec![0, 0, 0, 0, 0];
+        let test_condition = vec![0; 25];
+        let result = initial.into_iter().duplicate_const::<5>().collect::<Vec<i32>>();
+        assert_eq!(test_condition, result)
+    }
+}

nokhwa-iter-extensions/src/interweave.rs

@@ -0,0 +1,155 @@
+use core::iter::FusedIterator;
+
+#[derive(Copy, Clone, Debug, Default, Hash, Ord, PartialOrd, Eq, PartialEq)]
+enum InterweaveState {
+    EmitFake,
+    #[default]
+    EmitReal,
+    Finished
+}
+
+/// Interweaves a value for every `PER` values of the original iterator.
+///
+/// `emit_last`: Allows you to set if a last item should be emitted even though it is not the "turn"
+/// of the "value" yet, e.g.
+///
+/// ```
+/// let initial = vec![1, 2, 1, 2, 1];
+//  let test_condition = vec![1, 2, 3, 1, 2, 3, 1, 3];
+//  let result = initial.iter().interweave::<2>(&3, true).cloned().collect::<Vec<i32>>();
+//  assert_eq!(test_condition, result);
+/// ```
+///
+/// This iterator is _fused_.
+pub struct Interweave<I, const PER: usize> where
+    I: Iterator,
+    <I as Iterator>::Item: Clone {
+    element: I::Item,
+    iter: I,
+    prev_state: InterweaveState,
+    state: InterweaveState,
+    count: usize,
+    emit_last: bool,
+}
+
+impl<I, const PER: usize> Interweave<I, PER> where I: Iterator, <I as Iterator>::Item: Clone {
+    pub fn new(item: I::Item, iterator: I, emit_last: bool) -> Interweave<I, PER> {
+        Interweave {
+            element: item,
+            iter: iterator,
+            prev_state: InterweaveState::default(),
+            state: InterweaveState::default(),
+            count: PER,
+            emit_last,
+        }
+    }
+}
+
+impl<I, const PER: usize> Iterator for Interweave<I, PER> where I: Iterator, <I as Iterator>::Item: Clone {
+    type Item = I::Item;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        match self.state {
+            InterweaveState::EmitFake => {
+                self.count = PER;
+                self.prev_state = InterweaveState::EmitFake;
+                self.state = InterweaveState::EmitReal;
+                Some(self.element.clone())
+            }
+            InterweaveState::EmitReal => {
+                self.count = self.count.saturating_sub(1);
+                match self.iter.next() {
+                    Some(i) => {
+                        if self.count <= 0 {
+                            self.state = InterweaveState::EmitFake;
+                        } else {
+                            self.state = InterweaveState::EmitReal;
+                        }
+                        self.prev_state = InterweaveState::EmitReal;
+                        Some(i)
+                    }
+                    None => {
+                        self.state = InterweaveState::Finished;
+                        if self.emit_last && self.prev_state != InterweaveState::EmitFake {
+                            Some(self.element.clone())
+                        } else {
+                            None
+                        }
+                    }
+                }
+            }
+            InterweaveState::Finished => {
+                None
+            }
+        }
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        let (lower, upper) = self.iter.size_hint();
+
+        if PER == 1 || PER == 0 {
+            return (lower * 2, upper.map(|u| u * 2))
+        }
+
+        let last = if self.emit_last { 1 } else { 0 };
+        let new_lower = lower + (lower / PER) + last;
+        let new_upper = upper.map(|u| { u + (u / PER) + last });
+        (new_lower, new_upper)
+    }
+}
+
+impl<I, const PER: usize> FusedIterator for Interweave<I, PER> where I: Iterator, <I as Iterator>::Item: Clone {}
+
+pub trait IterInterweave: Iterator {
+    fn interweave<const PER: usize>(self, item: Self::Item, emit_last: bool) -> Interweave<Self, PER> where Self: Sized, Self::Item: Clone {
+        Interweave::new(item, self, emit_last)
+    }
+}
+
+impl<I: ?Sized> IterInterweave for I where I: Iterator {}
+
+#[cfg(test)]
+mod test {
+    use crate::interweave::IterInterweave;
+
+    #[test]
+    pub fn zero_interweave() {
+        let initial = vec![0, 0, 0, 0, 0];
+        let test_condition = vec![0, 1, 0, 1, 0, 1, 0, 1, 0, 1];
+        let result = initial.iter().interweave::<1>(&1, false).cloned().collect::<Vec<i32>>();
+        assert_eq!(test_condition, result);
+    }
+
+    #[test]
+    pub fn empty_interweave_no_last() {
+        let initial: Vec<i32> = vec![];
+        let test_condition: Vec<i32> = vec![];
+        let result = initial.iter().interweave::<1>(&1, false).cloned().collect::<Vec<i32>>();
+        assert_eq!(test_condition, result);
+    }
+
+    #[test]
+    pub fn empty_interweave_with_last() {
+        let initial: Vec<i32> = vec![];
+        let test_condition: Vec<i32> = vec![1];
+        let result = initial.iter().interweave::<1>(&1, true).cloned().collect::<Vec<i32>>();
+        assert_eq!(test_condition, result);
+    }
+
+    #[test]
+    pub fn interweave_every_other() {
+        let initial = vec![1, 2, 1, 2, 1 ,2];
+        let test_condition = vec![1, 2, 3, 1, 2, 3, 1 , 2, 3];
+        let result = initial.iter().interweave::<2>(&3, true).cloned().collect::<Vec<i32>>();
+        assert_eq!(test_condition, result);
+    }
+
+    #[test]
+    pub fn interweave_every_other_not_fitting() {
+        let initial = vec![1, 2, 1, 2, 1];
+        let test_condition = vec![1, 2, 3, 1, 2, 3, 1, 3];
+        let result = initial.iter().interweave::<2>(&3, true).cloned().collect::<Vec<i32>>();
+        assert_eq!(test_condition, result);
+    }
+}
+

nokhwa-iter-extensions/src/lib.rs

@@ -0,0 +1,6 @@
+#![no_std]
+#[warn(clippy::pedantic)]
+
+pub mod interweave;
+pub mod duplicate;
+