add write api to capture directly gated by a feature

Cargo.toml

@@ -15,7 +15,7 @@ repository = "https://github.com/l1npengtul/nokhwa"
 default = []
 input-uvc = ["uvc", "uvc/vendor", "ouroboros"]
 input-v4l = ["v4l"]
-input-opencv = ["opencv"]
+input-opencv = ["opencv", "opencv/clang-runtime"]
 output-wgpu = ["wgpu"]
 docs-only = ["input-uvc", "input-v4l", "input-opencv", "output-wgpu"]
 

README.md

@@ -32,7 +32,7 @@ The default feature includes nothing. Anything starting with `input-*` is a feat
 Conversely, anything that starts with `output-*` controls a feature that controls the output of something (usually a frame from the camera)
 
 `output-*` features:
- - `output-wgpu`: Copies a frame directly into a wgpu texture.
+ - `output-wgpu`: Enables the API to copy a frame directly into a `wgpu` texture.
 
 You many want to pick and choose to reduce bloat.
 

src/backends/capture/uvc_backend.rs

@@ -465,9 +465,3 @@ impl<'a> CaptureBackendTrait for UVCCaptureDevice<'a> {
         Ok(())
     }
 }
-
-// use default
-#[cfg(feature = "output-wgpu")]
-use crate::GpuCopyBackendTrait;
-#[cfg(feature = "output-wgpu")]
-impl<'a> GpuCopyBackendTrait for UVCCaptureDevice<'a> {}

src/backends/capture/v4l2.rs

@@ -414,9 +414,3 @@ impl<'a> CaptureBackendTrait for V4LCaptureDevice<'a> {
         Ok(())
     }
 }
-
-// use default
-#[cfg(feature = "output-wgpu")]
-use crate::GpuCopyBackendTrait;
-#[cfg(feature = "output-wgpu")]
-impl<'a> GpuCopyBackendTrait for V4LCaptureDevice<'a> {}

src/camera_traits.rs

@@ -5,6 +5,12 @@ use crate::{
 use image::{buffer::ConvertBuffer, ImageBuffer, Rgb, RgbaImage};
 use std::{collections::HashMap, convert::TryFrom, num::NonZeroU32};
 
+#[cfg(feature = "output-wgpu")]
+use wgpu::{
+    Device as WgpuDevice, Extent3d, ImageCopyTexture, ImageDataLayout, Queue as WgpuQueue,
+    Texture as WgpuTexture, TextureDescriptor, TextureDimension, TextureFormat, TextureUsage,
+};
+
 /// This trait is for any backend that allows you to grab and take frames from a camera.
 /// Many of the backends are **blocking**, if the camera is occupied the library will block while it waits for it to become availible.
 ///
@@ -69,21 +75,21 @@ pub trait CaptureBackendTrait {
     /// # Errors
     /// If the backend fails to get the frame (e.g. already taken, busy, doesn't exist anymore), or [`open_stream()`](CaptureBackendTrait::open_stream()) has not been called yet, this will error.
     fn get_frame_raw(&mut self) -> Result<Vec<u8>, NokhwaError>;
+    /// The minimum buffer size needed to write the current frame. If `rgba` is true, it will instead return the minimum size of the RGBA buffer needed.
+    fn min_buffer_size(&self, rgba: bool) -> usize;
+    /// Directly writes the current frame(RGB24) into said `buffer`. If `convert_rgba` is true, the buffer written will be written as an RGBA frame instead of a RGB frame. Returns the amount of bytes written on successful capture.
+    /// # Errors
+    /// If the backend fails to get the frame (e.g. already taken, busy, doesn't exist anymore), or [`open_stream()`](CaptureBackendTrait::open_stream()) has not been called yet, this will error.
+    fn get_frame_buffer(
+        &mut self,
+        buffer: &mut [u8],
+        convert_rgba: bool,
+    ) -> Result<usize, NokhwaError>;
     /// Will drop the stream.
     /// # Errors
     /// Please check the `Quirks` section of each backend.
     fn stop_stream(&mut self) -> Result<(), NokhwaError>;
-}
-
-#[cfg(feature = "output-wgpu")]
-use wgpu::{
-    Device as WgpuDevice, Extent3d, ImageCopyTexture, ImageDataLayout, Queue as WgpuQueue,
-    Texture as WgpuTexture, TextureDescriptor, TextureDimension, TextureFormat, TextureUsage,
-};
-
-/// Trait that allows the user to copy directly into a Wgpu Texture
-#[cfg(feature = "output-wgpu")]
-pub trait GpuCopyBackendTrait: CaptureBackendTrait {
+    #[cfg(feature = "output-wgpu")]
     /// Directly copies a frame to a Wgpu texture.
     /// # Errors
     /// If the frame cannot be captured or the resolution is 0 on any axis, this will error.