webp_screenshot_rust/encoder/

gpu.rs

//! GPU-accelerated WebP encoding using compute shaders
//!
//! Supports:
//! - DirectCompute on Windows
//! - Metal on macOS
//! - Vulkan/OpenCL on Linux

use crate::{
    error::{EncodingError, EncodingResult},
    types::{RawImage, WebPConfig},
};

use std::sync::Arc;

/// GPU backend type
#[derive(Debug, Clone, Copy)]
pub enum GpuBackend {
    DirectCompute,
    Metal,
    Vulkan,
    OpenCL,
    None,
}

/// GPU-accelerated WebP encoder
pub struct GpuWebPEncoder {
    backend: GpuBackend,
    device: Option<Arc<dyn GpuDevice>>,
}

/// Trait for GPU device abstraction
trait GpuDevice: Send + Sync {
    /// Encode image to WebP using GPU
    fn encode(&self, image: &RawImage, config: &WebPConfig) -> EncodingResult<Vec<u8>>;

    /// Get device name
    fn name(&self) -> String;

    /// Get available memory
    #[allow(dead_code)]
    fn available_memory(&self) -> usize;
}

impl GpuWebPEncoder {
    /// Create a new GPU-accelerated encoder
    pub fn new() -> Self {
        let (backend, device) = Self::detect_and_initialize();

        Self { backend, device }
    }

    /// Detect available GPU backend and initialize
    fn detect_and_initialize() -> (GpuBackend, Option<Arc<dyn GpuDevice>>) {
        #[cfg(target_os = "windows")]
        {
            if let Some(device) = DirectComputeDevice::new() {
                return (GpuBackend::DirectCompute, Some(Arc::new(device)));
            }
        }

        #[cfg(target_os = "macos")]
        {
            if let Some(device) = MetalDevice::new() {
                return (GpuBackend::Metal, Some(Arc::new(device)));
            }
        }

        #[cfg(target_os = "linux")]
        {
            if let Some(device) = VulkanDevice::new() {
                return (GpuBackend::Vulkan, Some(Arc::new(device)));
            }
        }

        (GpuBackend::None, None)
    }

    /// Check if GPU acceleration is available
    pub fn is_available(&self) -> bool {
        self.device.is_some()
    }

    /// Encode image using GPU
    pub fn encode(&self, image: &RawImage, config: &WebPConfig) -> EncodingResult<Vec<u8>> {
        match &self.device {
            Some(device) => device.encode(image, config),
            None => Err(EncodingError::UnsupportedFeature(
                "GPU encoding not available".to_string(),
            )),
        }
    }

    /// Get GPU backend name
    pub fn backend_name(&self) -> String {
        match self.backend {
            GpuBackend::DirectCompute => "DirectCompute".to_string(),
            GpuBackend::Metal => "Metal".to_string(),
            GpuBackend::Vulkan => "Vulkan".to_string(),
            GpuBackend::OpenCL => "OpenCL".to_string(),
            GpuBackend::None => "None".to_string(),
        }
    }

    /// Get device information
    pub fn device_info(&self) -> Option<String> {
        self.device.as_ref().map(|d| d.name())
    }
}

// Windows DirectCompute implementation
#[cfg(target_os = "windows")]
struct DirectComputeDevice {
    // Would contain:
    // - ID3D11Device
    // - ID3D11DeviceContext
    // - Compute shaders
}

#[cfg(target_os = "windows")]
impl DirectComputeDevice {
    fn new() -> Option<Self> {
        // Initialize DirectCompute
        // This would:
        // 1. Create D3D11 device
        // 2. Load compute shaders
        // 3. Create buffers

        // For now, return None as this requires complex Windows API integration
        None
    }
}

#[cfg(target_os = "windows")]
impl GpuDevice for DirectComputeDevice {
    fn encode(&self, _image: &RawImage, _config: &WebPConfig) -> EncodingResult<Vec<u8>> {
        // DirectCompute WebP encoding:
        // 1. Upload image to GPU texture
        // 2. Run DCT compute shader
        // 3. Run quantization shader
        // 4. Run entropy coding shader
        // 5. Download compressed data

        Err(EncodingError::UnsupportedFeature(
            "DirectCompute encoding not yet implemented".to_string(),
        ))
    }

    fn name(&self) -> String {
        "DirectCompute Device".to_string()
    }

    fn available_memory(&self) -> usize {
        0
    }
}

// macOS Metal implementation
#[cfg(target_os = "macos")]
struct MetalDevice {
    // Would contain:
    // - Metal device
    // - Command queue
    // - Compute pipeline states
}

#[cfg(target_os = "macos")]
impl MetalDevice {
    fn new() -> Option<Self> {
        #[cfg(feature = "gpu")]
        {
            use metal::*;

            // Get default Metal device
            if let Some(_device) = Device::system_default() {
                // Initialize Metal compute pipeline
                // This would:
                // 1. Load Metal shaders
                // 2. Create pipeline states
                // 3. Setup buffers

                // For now, return None as full implementation requires shader compilation
                return None;
            }
        }

        None
    }
}

#[cfg(target_os = "macos")]
impl GpuDevice for MetalDevice {
    fn encode(&self, _image: &RawImage, _config: &WebPConfig) -> EncodingResult<Vec<u8>> {
        // Metal WebP encoding:
        // 1. Create Metal texture from image
        // 2. Dispatch compute kernels for:
        //    - Color space conversion
        //    - DCT transform
        //    - Quantization
        //    - Entropy coding
        // 3. Copy result back to CPU

        Err(EncodingError::UnsupportedFeature(
            "Metal encoding not yet implemented".to_string(),
        ))
    }

    fn name(&self) -> String {
        "Metal GPU Device".to_string()
    }

    fn available_memory(&self) -> usize {
        0
    }
}

// Linux Vulkan implementation
#[cfg(target_os = "linux")]
struct VulkanDevice {
    // Would contain:
    // - Vulkan instance
    // - Physical device
    // - Logical device
    // - Command buffers
    // - Compute pipelines
}

#[cfg(target_os = "linux")]
impl VulkanDevice {
    fn new() -> Option<Self> {
        // Initialize Vulkan
        // This would:
        // 1. Create Vulkan instance
        // 2. Select physical device
        // 3. Create logical device
        // 4. Load SPIR-V shaders
        // 5. Create compute pipelines

        None
    }
}

#[cfg(target_os = "linux")]
impl GpuDevice for VulkanDevice {
    fn encode(&self, _image: &RawImage, _config: &WebPConfig) -> EncodingResult<Vec<u8>> {
        Err(EncodingError::UnsupportedFeature(
            "Vulkan encoding not yet implemented".to_string(),
        ))
    }

    fn name(&self) -> String {
        "Vulkan GPU Device".to_string()
    }

    fn available_memory(&self) -> usize {
        0
    }
}

// Stub implementations for other platforms
#[cfg(not(any(target_os = "windows", target_os = "macos", target_os = "linux")))]
struct DirectComputeDevice;
#[cfg(not(any(target_os = "windows", target_os = "macos", target_os = "linux")))]
struct MetalDevice;
#[cfg(not(any(target_os = "windows", target_os = "macos", target_os = "linux")))]
struct VulkanDevice;

/// GPU compute shader for WebP DCT transform
#[allow(dead_code)]
const DCT_COMPUTE_SHADER: &str = r#"
// Simplified DCT compute shader (HLSL/Metal/GLSL)
// This would contain the actual DCT transform implementation

[[kernel]]
void dct_transform(
    texture2d<float, access::read> input [[texture(0)]],
    texture2d<float, access::write> output [[texture(1)]],
    uint2 gid [[thread_position_in_grid]]
) {
    // 8x8 DCT transform
    float block[8][8];

    // Read 8x8 block
    for (int y = 0; y < 8; y++) {
        for (int x = 0; x < 8; x++) {
            block[y][x] = input.read(gid * 8 + uint2(x, y)).r;
        }
    }

    // Apply DCT
    // ... DCT implementation ...

    // Write result
    for (int y = 0; y < 8; y++) {
        for (int x = 0; x < 8; x++) {
            output.write(float4(block[y][x]), gid * 8 + uint2(x, y));
        }
    }
}
"#;

/// GPU compute shader for WebP quantization
#[allow(dead_code)]
const QUANTIZATION_COMPUTE_SHADER: &str = r#"
// Quantization compute shader
[[kernel]]
void quantize(
    texture2d<float, access::read> dct_coeffs [[texture(0)]],
    texture2d<int, access::write> quantized [[texture(1)]],
    constant float& quality [[buffer(0)]],
    uint2 gid [[thread_position_in_grid]]
) {
    float coeff = dct_coeffs.read(gid).r;
    float quant_table = get_quant_value(gid, quality);
    int quantized_value = round(coeff / quant_table);
    quantized.write(int4(quantized_value), gid);
}
"#;

/// Helper functions for GPU encoding
impl GpuWebPEncoder {
    /// Estimate encoding time based on image size and GPU
    pub fn estimate_encoding_time(&self, width: u32, height: u32) -> std::time::Duration {
        if self.device.is_none() {
            return std::time::Duration::from_secs(0);
        }

        // Rough estimation based on GPU performance
        let pixels = (width * height) as u64;
        let base_time_us = match self.backend {
            GpuBackend::DirectCompute => pixels / 10000, // ~10M pixels/sec
            GpuBackend::Metal => pixels / 12000,         // ~12M pixels/sec
            GpuBackend::Vulkan => pixels / 8000,         // ~8M pixels/sec
            _ => pixels / 5000,
        };

        std::time::Duration::from_micros(base_time_us)
    }

    /// Check if image size is suitable for GPU encoding
    pub fn is_size_suitable(&self, width: u32, height: u32) -> bool {
        // GPU encoding is beneficial for larger images
        let pixels = width * height;
        pixels >= 1920 * 1080 // At least Full HD
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_gpu_detection() {
        let encoder = GpuWebPEncoder::new();
        println!("GPU Backend: {}", encoder.backend_name());
        println!("GPU Available: {}", encoder.is_available());

        if let Some(info) = encoder.device_info() {
            println!("GPU Device: {}", info);
        }
    }

    #[test]
    fn test_size_suitability() {
        let encoder = GpuWebPEncoder::new();

        assert!(encoder.is_size_suitable(1920, 1080)); // Full HD
        assert!(encoder.is_size_suitable(3840, 2160)); // 4K
        assert!(!encoder.is_size_suitable(640, 480));  // Too small
    }
}