OpenCV
Hacker ApprovedRanked 4 of 19 machine learning libraries by recommenders
Free, long-lived computer vision library that people find easy to start with and fast for image loading. Critics note uneven code and doubt the new engine.
Free, long-lived computer vision library that people find easy to start with and fast for image loading. Critics note uneven code and doubt the new engine.
62 people gave an opinion
- recommend it
- 46
- criticize it
- 16
- approval share
- 74%
Recommended in 11 of 13 months
- November 2025: recommended
- December 2025: recommended
- January 2026: recommended
- February 2026: not recommended
- March 2026: recommended
- April 2026: recommended
- May 2026: recommended
- June 2026: recommended
- July 2026: recommended
- August 2026: recommended
- September 2026: recommended
- October 2026: recommended
- November 2026: not recommended (month in progress)
Why it carries the badge
- 46 people recommend itNeeds 10 or more, met.
- 2.9 recommenders for every criticNeeds 2 to 1 or better, met.
- Recommended in 11 of 13 monthsNeeds 4 or more, met.
The same three rules apply to every product, and the badge can’t be bought. How the badge works
What people say about it
The reasons people give, with the number of comments that give each one. Open a reason to read what they said.
Why people recommend it
Each mark is one comment
Easy setup and Python bindings
“was the biggest boon for my online teaching experience because remotely dealing with install woes”
Comment from 10 Jun 2026 in “OpenCV 5 Is Here: The Biggest Leap in Years for Computer Vision” “was so easy and smooth to set up for doing tasks like generating thumbnails”
Comment from 9 Jun 2026 in “OpenCV 5 Is Here: The Biggest Leap in Years for Computer Vision” “python is easy and the bindings are not that hard”
Comment from 9 Jun 2026 in “OpenCV 5 Is Here: The Biggest Leap in Years for Computer Vision” - Comment from 16 Dec 2025 in “alpr.watch”
Good for learning computer vision
“it was OpenCV that made concepts like convolutions, softmax, minmax, and others finally click for me”
Comment from 9 Jun 2026 in “OpenCV 5 Is Here: The Biggest Leap in Years for Computer Vision” “I'm using it to do computer vision stuff (where I have no prior background!) with opencv.js”
Comment from 4 Dec 2025 in “Everyone in Seattle hates AI” “blown away by this announcement and super excited to get back into image processing”
Comment from 10 Jun 2026 in “OpenCV 5 Is Here: The Biggest Leap in Years for Computer Vision” Fast at loading images and video
“it remains hands down the best library for simply loading images and video”
Comment from 9 Jun 2026 in “OpenCV 5 Is Here: The Biggest Leap in Years for Computer Vision” “OpenCV is fast, but torchvision is faster.”
Comment from 11 Jun 2026 in “OpenCV 5 Is Here: The Biggest Leap in Years for Computer Vision” “always found opencv to work way way faster”
Comment from 5 Nov 2025 in “Grayskull: A tiny computer vision library in C for embedded systems, etc.” Long-lived and widely used underneath
“opencv has stood the test of time and I'm certain newer LLMs will likely not attempt to rewrite it from scratch”
Comment from 10 Jun 2026 in “OpenCV 5 Is Here: The Biggest Leap in Years for Computer Vision” “OpenCV is used behind the scenes for many of the fancy stuff those major AI provider pretend to do.”
Comment from 9 Jun 2026 in “OpenCV 5 Is Here: The Biggest Leap in Years for Computer Vision” “Despite its age, I think that OpenCV is still more than relevant today.”
Comment from 9 Jun 2026 in “OpenCV 5 Is Here: The Biggest Leap in Years for Computer Vision”
What people warn about
Each mark is one comment
New engine and ONNX questioned
“Quite a good release although not sure why they invest so much time into their ONNX engine.”
Comment from 9 Jun 2026 in “OpenCV 5 Is Here: The Biggest Leap in Years for Computer Vision” “No one uses ONNXRuntime (nor the new engine in OpenCV 5) in production.”
Comment from 9 Jun 2026 in “OpenCV 5 Is Here: The Biggest Leap in Years for Computer Vision” Uneven code, unstable direction
“its constituent parts are written by many different people who all kind of do things a little differently and it shows”
Comment from 9 Jun 2026 in “OpenCV 5 Is Here: The Biggest Leap in Years for Computer Vision” “Perpetual-Beta culture means the library will unlikely ever really fully stabilize.”
Comment from 9 Jun 2026 in “OpenCV 5 Is Here: The Biggest Leap in Years for Computer Vision” Input and gamma handling limits
“it will load images with the wrong gamma, it will give you floating point values that hide the limitation”
Comment from 9 Jun 2026 in “OpenCV 5 Is Here: The Biggest Leap in Years for Computer Vision” “The most annoying component is that OpenCV is limited to input shapes like (H, W, C)”
Comment from 11 Jun 2026 in “OpenCV 5 Is Here: The Biggest Leap in Years for Computer Vision” Slower than rewrites or newer methods
“performance is generally pretty low; I've been on projects where we rewrote OpenCV code into more-or-less obvious hand-rolled code and won 5x perf”
Comment from 9 Jun 2026 in “OpenCV 5 Is Here: The Biggest Leap in Years for Computer Vision” “never felt it was particularly complicated, but since the days of resnet there are much faster ways to the goal”
Comment from 17 Aug 2026 in “GPT 5.6 Sol is the best "vision" model OpenAI ever released”
Other machine learning libraries people recommend
The four most recommended other machine learning libraries, with the same counts for each, so you can compare like for like. The tick on each bar marks the 2 to 1 line the badge needs.
See all 19 machine learning libraries, rankedWhat people said
40 of the 66 comments that mention it, newest first. Each links to the original comment.
“they do provide functions like findChessboardCorners, CharucoDetector, stereoCalibrate”
“last time i played with opencv for this it didnt do a very good job at automatically calculating the k's”
“OpenCV has a number of tutorials on this using stuff like stereoBM”
“I often helped lab students who read a simple `make; make install` tutorial for OpenCV and permanently messed up their Python installs.”
“never felt it was particularly complicated, but since the days of resnet there are much faster ways to the goal”
“instructing the models to use deterministic tools (like OpenCV)”
“OpenCV is fast, but torchvision is faster.”
“The most annoying component is that OpenCV is limited to input shapes like (H, W, C)”
“was the biggest boon for my online teaching experience because remotely dealing with install woes”
“blown away by this announcement and super excited to get back into image processing”
“opencv has stood the test of time and I'm certain newer LLMs will likely not attempt to rewrite it from scratch”
“You can run OpenCV on a GPU-less Raspberry Pi or other IoT device just fine.”
“was so easy and smooth to set up for doing tasks like generating thumbnails”
“One can legally use/static-link OpenCV in most commercial projects, and there were only a few legal landmines people still try to document when possible.”
“python is easy and the bindings are not that hard”
“Despite its age, I think that OpenCV is still more than relevant today.”
“it will load images with the wrong gamma, it will give you floating point values that hide the limitation”
“One of the great things about OpenCV is how ubiquitous it is, there's a ton samples online and well represented in frontier model training data.”
“performance is generally pretty low; I've been on projects where we rewrote OpenCV code into more-or-less obvious hand-rolled code and won 5x perf”
“its constituent parts are written by many different people who all kind of do things a little differently and it shows”
“Perpetual-Beta culture means the library will unlikely ever really fully stabilize.”
“OpenCV is used behind the scenes for many of the fancy stuff those major AI provider pretend to do.”
“Quite a good release although not sure why they invest so much time into their ONNX engine.”
“it remains hands down the best library for simply loading images and video”
“it was OpenCV that made concepts like convolutions, softmax, minmax, and others finally click for me”
“this whole announcement feels more like OpenCV catching up to the modern world”
“No one uses ONNXRuntime (nor the new engine in OpenCV 5) in production.”
“Still great, needing fewer libraries is a good thing, but maybe a bit oversold”
“Until then, I would not call YOLO and OpenCV outdated, it's simply wrong.”
“the kind of performance an opencv function can get w/ just mask-matching”
“Not sure the engine fragmentation is the optimal solution.”
“Have you seen what you can do with just openCV? The world changed fast quite recently.”
“OpenCV is surprisingly effective and delightfully experimental and glitchy”
“Fast, but fragile: works on flat backgrounds, fails on textured images.”
“combines a cheap PTZ camera + OpenCV, Kalman filtering, PID control, and digital stabilization”
“OpenCV makes this all pretty darn easy”
“good old-fashioned OpenCV, because ML would be overkill for my case.”
“I'm using it to do computer vision stuff (where I have no prior background!) with opencv.js”
“which helped my side project get off the ground successfully”
“always found opencv to work way way faster”
Counts come from 1,795,640 Hacker News comments, November 2025 to November 2026. How we count. Report a mistake.