Crate edgefirst_codec 

Image codec for decoding JPEG/PNG into pre-allocated EdgeFirst tensors.

This crate provides the ImageDecoder struct and ImageLoad extension trait for decoding image files directly into existing tensor buffers — including DMA-BUF tensors with GPU-aligned pitch padding. The core design goal is allocate once, decode many: users create a tensor at the maximum expected image size during program initialisation, then call ImageLoad::load_image in the hot loop with zero per-frame allocations.

Quick Start

use edgefirst_codec::{ImageDecoder, ImageLoad};
use edgefirst_tensor::{CpuAccess, Tensor, TensorTrait, TensorMemory, PixelFormat};

// Allocate once (at init), sized for the largest expected image. The
// decoder CPU-writes the pixels: declare `CpuAccess::Write`.
let mut tensor = Tensor::<u8>::image(1920, 1080, PixelFormat::Nv12, Some(TensorMemory::Mem),
                                      CpuAccess::Write)
    .expect("allocation");
let mut decoder = ImageDecoder::new();

// Decode many (in hot loop). The decoder sets the tensor's dimensions and
// native format (JPEG → Nv12/Grey); call `convert()` for RGB.
let jpeg_bytes = std::fs::read("frame.jpg").unwrap();
let info = tensor.load_image(&mut decoder, &jpeg_bytes).expect("decode");
assert!(info.width <= 1920);
assert!(info.height <= 1080);

Performance

For best performance, allocate tensors via ImageProcessor::create_image() which selects the optimal memory backend (DMA → PBO → Mem) with GPU-aligned pitch. Free-standing tensors work but cannot use PBO and may not have aligned pitch.

Strided Buffers

The decoder respects effective_row_stride() on the destination tensor. When a DMA tensor has GPU-aligned pitch padding, decoded pixel rows are written at the correct stride offsets — no intermediate contiguous buffer is exposed to the caller.

Structs

ImageDecoder

Reusable image decoder with internal scratch buffers.

ImageInfo

Metadata returned after a successful image decode.

Enums

CodecError

Errors that can occur during image decoding.

UnsupportedFeature

A specific image-format feature that the codec does not implement.

Traits

ImageLoad

Extension trait for loading images into pre-allocated tensors.

ImagePixel

Marker trait for pixel element types supported by image decoding.

Functions

nvjpeg_available

Returns true when the nvJPEG GPU JPEG decoder is available at runtime — Linux with CUDA + libnvjpeg loaded and opted in via EDGEFIRST_ENABLE_NVJPEG (off by default, so it never silently contends with CUDA inference). When true the codec prefers it over the V4L2/CPU backends for CUDA-backed destinations. Always false on other platforms or when the nvjpeg feature is disabled. Useful for benchmarks and consumers that branch on backend availability.

peek_info

Parse image headers and return the native dimensions, format, and EXIF orientation without decoding pixels.

Type Aliases

Result

Result type for codec operations.