cv-combinators-0.1.2: Functional Combinators for Computer Vision

Portabilitytested on GHC only
MaintainerNoam Lewis <>



ImageProcessors is a functional (Processor-based) interface to computer vision using OpenCV.

The Processor interface allows the primitives in this library to take care of all the allocation / deallocation of resources and other setup/teardown requirements, and to appropriately nest them when combining primitives.

Simple example:

 win = window 0        -- The number is essentially a label for the window
 cam = camera 0        -- Autodetect camera
 edge = canny 30 190 3 -- Edge detecting processor using canny operator

 test = cam >>> edge >>> win   

The last expression is a processor that captures frames from camera and displays edge-detected version in the window.



keyPressed :: Show a => a -> IO BoolSource

Some general utility functions for use with Processors and OpenCV

Predicate for pressed keys

runTill :: IOProcessor () b -> (b -> IO Bool) -> IO bSource

Runs the processor until a predicate is true, for predicates, and processors that take () as input (such as chains that start with a camera).

runTillKeyPressed :: Show a => IOProcessor () a -> IO ()Source

Name (and type) says it all.

camera :: Int -> ImageSourceSource

A capture device, using OpenCV's HighGui lib's cvCreateCameraCapture should work with most webcames. See OpenCV's docs for information. This processor outputs the latest image from the camera at each invocation.

window :: Int -> ImageSinkSource

A window that displays images. Note: windows with the same index will be the same this ok?

imageProcessor :: (Ptr IplImage -> Ptr IplImage -> IO (Ptr IplImage)) -> (Ptr IplImage -> IO (Ptr IplImage)) -> ImageProcessorSource

A convenience function for constructing a common type of processors that work exclusively on images

resize :: Int -> Int -> InterpolationMethod -> ImageProcessorSource

OpenCV's cvResize

dilate :: Int -> ImageProcessorSource

OpenCV's cvDilate



:: Int

Threshold 1

-> Int

Threshold 2

-> Int


-> ImageProcessor 

OpenCV's cvCanny



:: String

Cascade filename (OpenCV comes with several, including ones for face detection)

-> Double

scale factor

-> Int

min neighbors

-> HaarDetectFlag


-> CvSize

min size

-> IOProcessor (Ptr IplImage) [CvRect] 

Wrapper for OpenCV's cvHaarDetectObjects and the surrounding required things (mem storage, cascade loading, etc).

drawRects :: IOProcessor (Ptr IplImage, [CvRect]) (Ptr IplImage)Source

OpenCV's cvRectangle, currently without width, color or line type control