pixelbench 0.2.0

Speedtest for your CPU vs GPU — find out if GPU acceleration is actually worth it on your machine.

pixelbench

Speedtest for your CPU vs GPU — find out if GPU acceleration is actually worth it on your machine.

Live: pixelbench.netlify.app

pixelbench runs identical image-processing workloads (blur, threshold, edge detection, and more) on your CPU and your GPU, then shows you exactly where the GPU wins and where it embarrassingly loses. No CUDA required — it uses OpenCV's OpenCL backend, so it works on integrated Intel/AMD graphics, NVIDIA, and Apple machines alike.

Reality check. "GPUs are faster at image processing" is a half-truth. On the laptop this tool was born on (i5-12450H + Intel UHD graphics), the GPU is 4.6x faster at bilateral filtering — and 26% slower at a 4K Gaussian blur. Whether the GPU wins depends on the task, the image size, and your hardware. That's the whole point of measuring.

This project grew out of my bachelor's thesis at Kharkiv National University of Radio Electronics: "Computer Vision and the Effect of Hardware on the Performance of Image Processing Tasks."

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Try it in your browser

pixelbench.netlify.app — the web/ folder contains pixelbench-web, the same comparison with no install: the CPU pass runs single-threaded TypeScript over typed arrays, the GPU pass runs WebGPU compute shaders (WGSL), and every GPU result is verified against the CPU output before it is reported.

• Built with React + TypeScript + Vite; React Router for pages (benchmark + full methodology writeup)
• Dark instrument-style UI: CPU/GPU comparison bars per operation, JetBrains Mono numerals, summary stat panel, JSON export
• Deploys to Netlify as a static site (netlify.toml handles base, build, and the SPA redirect)

cd web
npm install
npm run dev

Note the two tools answer different questions: the CLI measures native performance (OpenCV + OpenCL), the web version measures the browser stack (JS vs WebGPU). Same machine, different stories — on the laptop this was built on, the GPU wins 10/10 in the browser but only 18/24 natively, because single-threaded JavaScript is a much softer baseline than OpenCV's hand-optimized C++.

Sample output

CPU: 12th Gen Intel(R) Core(TM) i5-12450H (12 threads)   GPU: Intel(R) UHD Graphics
Windows 11 · Python 3.12 · OpenCV 5.0 · median of 20 runs, 5 warmup

1080p
┌──────────────────────┬──────────┬──────────┬─────────────┐
│ Task                 │ CPU (ms) │ GPU (ms) │ GPU speedup │
├──────────────────────┼──────────┼──────────┼─────────────┤
│ Grayscale conversion │     0.97 │     0.58 │       1.67x │
│ Gaussian blur 15x15  │     4.92 │     5.14 │       0.96x │
│ Median blur 5x5      │     9.04 │     4.23 │       2.14x │
│ Bilateral filter d=9 │    44.49 │     9.62 │       4.63x │
│ Binary threshold     │     0.98 │     0.16 │       5.95x │
│ Sobel edges          │     1.53 │     0.64 │       2.38x │
│ Canny edges          │     5.06 │     1.87 │       2.71x │
│ Resize to 50%        │     0.61 │     0.52 │       1.16x │
└──────────────────────┴──────────┴──────────┴─────────────┘

Verdict: GPU won 18/24 tasks on this machine. Faster hardware isn't
always faster — it depends on the task and image size.

Install & run

Run it without cloning anything (uv required):

uvx --from git+https://github.com/OkeahDavid/pixelbench pixelbench

Or clone and run:

git clone https://github.com/OkeahDavid/pixelbench
cd pixelbench
uv run pixelbench

To install pixelbench as a permanent command: uv tool install .

No uv? pip works too: pip install -e . then pixelbench, or pip install opencv-python numpy rich and python -m pixelbench.

Options

pixelbench --sizes 720p,1080p,1440p,4k   # image sizes to test
           --tasks gaussian_blur,canny   # subset of tasks (default: all 8)
           --iterations 50               # timed runs per op (default: 20)
           --no-gpu                      # CPU-only pass
           --json results/mine.json      # save machine-readable results
           --leaderboard                 # print a row for the table below

Leaderboard

Run pixelbench --leaderboard and open a PR (or an issue) with your row — laptops, desktops, potatoes, and workstations all welcome. Median speedup is across all tasks and sizes.

CPU	GPU	OS	Median GPU speedup	Best win
12th Gen Intel(R) Core(TM) i5-12450H	Intel(R) UHD Graphics	Windows	1.90x	5.95x (Binary threshold, 1080p)

Methodology (the fine print that makes numbers honest)

• Same code path, two backends. Every task calls the same OpenCV function; the CPU pass gets a numpy array, the GPU pass gets a cv2.UMat, which routes through OpenCV's transparent OpenCL API.
• Transfer excluded. The test image is uploaded to the GPU before timing starts. Numbers measure compute, not PCIe/RAM copies. (A transfer-inclusive mode is on the roadmap — for one-shot processing it changes the story.)
• Warmup runs precede every measurement, because OpenCL compiles kernels on first use and that spike shouldn't pollute your numbers.
• Median, not mean. Each iteration is timed individually and the median is reported, so a background Windows update can't skew your results.
• cv2.ocl.finish() after every GPU op, so asynchronous work can't leak outside the timing window.
• Deterministic test image. A synthetic photo-like image (gradients + shapes + noise, fixed seed) is generated per size — every machine benchmarks the exact same pixels.

Roadmap

• CUDA backend — detected automatically on CUDA-enabled OpenCV builds with an NVIDIA GPU; adds a third comparison column (CPU vs OpenCL vs CUDA). The standard opencv-python wheel does not include CUDA.
• Transfer-inclusive timing mode (--include-transfer)
• Speedup charts (--chart, matplotlib)
• Hosted leaderboard with auto-submit

License

MIT © Okeah David Chidugam