Skip to content
Algorithm Atlas
Back to categories

Image Processing

Algorithms that transform or analyze images.

Image processing algorithms work directly with pixels to detect edges, smooth noise, segment regions, or fill connected areas.

Image ProcessingO(w h)

Sobel Edge Detection

Finds edges by measuring horizontal and vertical brightness changes.

BeginnerCoreFormula3 links
Image ProcessingEdge DetectionFiltering
Image ProcessingO(w h k)

Gaussian Blur

Smooths an image by convolving it with a Gaussian kernel.

BeginnerCoreFormula17 links
Image ProcessingSmoothingFiltering
Image ProcessingO(w h)

Thresholding

Separates pixels into groups based on whether they cross a chosen value.

BeginnerFoundationFormula3 links
Image ProcessingSegmentationClassic
Image ProcessingO(a)

Flood Fill

Fills a connected region starting from one seed point.

BeginnerFoundationNo formula2 links
Image ProcessingSegmentationGraphTraversal
Image ProcessingO(w h k)

Bilateral Filter

Smooths images while preserving edges by considering distance and color similarity.

IntermediateExtendedFormula1 links
Image ProcessingFilteringSmoothing
Image ProcessingO(w h)

Canny Edge Detection

Finds thin edges by smoothing, measuring gradients, suppressing nonmaxima, and linking thresholds.

IntermediateCoreFormula7 links
Image ProcessingEdge DetectionFiltering
Image ProcessingO(w h + k)

Histogram Equalization

Improves contrast by spreading image intensities across the available range.

BeginnerCoreFormula1 links
Image ProcessingSegmentationClassic
Image ProcessingO(p a)

Hough Transform

Detects shapes by voting in a parameter space.

IntermediateExtendedFormula1 links
Image ProcessingEdge DetectionGeometry
Image ProcessingO(w h)

Laplacian Edge Detection

Finds edges by measuring second-order brightness changes.

BeginnerExtendedFormula2 links
Image ProcessingEdge DetectionFiltering
Image ProcessingO(w h k)

Morphological Erosion

Shrinks bright or foreground regions using a local structuring element.

BeginnerExtendedFormula2 links
Image ProcessingMorphologySegmentation
Image ProcessingO(pixels * kernel_size)

Difference of Gaussians

Highlights image structures by subtracting two Gaussian-blurred versions at different scales.

IntermediateExtendedFormula1 links
Image ProcessingFilteringEdge DetectionSmoothing
Image ProcessingO(pixels)

Connected Component Labeling

Assigns labels to contiguous foreground regions in a binary or segmented image.

IntermediateCoreNo formula3 links
Image ProcessingSegmentationGraph Connectivity
Image ProcessingO(pixels * kernel)

Unsharp Masking

Sharpens an image by adding back high-frequency detail separated by blur.

BeginnerCoreFormula1 links
Image ProcessingFilteringSmoothingEdge Enhancement
Image ProcessingO(pixels * template)

Template Matching

Finds image regions that resemble a smaller template patch.

IntermediateCoreFormula3 links
Image ProcessingPattern MatchingCorrelationSearch
Image ProcessingO(iterations * graph_cut)

GrabCut

Segments foreground from background using graph cuts and color models.

AdvancedExtendedFormula1 links
Image ProcessingSegmentationGraphOptimization
Image ProcessingO(pixels * window)

Lucas-Kanade Optical Flow

Estimates local image motion by solving small least-squares systems over patches.

AdvancedCoreFormula3 links
Image ProcessingMotion EstimationLinear AlgebraEstimation
Image ProcessingO(iterations * pixels)

Horn-Schunck Optical Flow

Estimates dense optical flow by combining brightness constancy with smoothness.

AdvancedExtendedFormula1 links
Image ProcessingMotion EstimationOptimizationSmoothing
Image ProcessingO(pixels)

Image Pyramid

Stores progressively downsampled versions of an image for multi-scale processing.

IntermediateCoreFormula4 links
Image ProcessingSmoothingResamplingMulti Scale
Image ProcessingO(1)

Integral Image

Precomputes cumulative pixel sums so rectangular sums are answered in constant time.

IntermediateCoreFormula1 links
Image ProcessingPrefix SumRange QueryFiltering
Image ProcessingO(pixels * kernel)

Morphological Dilation

Expands bright or foreground regions according to a structuring element.

BeginnerCoreFormula4 links
Image ProcessingMorphologySegmentationFiltering
Image ProcessingO(pixels log pixels)

Watershed Segmentation

Segments regions by treating image intensity as a terrain flooded from markers.

AdvancedExtendedNo formula2 links
Image ProcessingSegmentationMorphologyGraph
Image ProcessingO(p k)

FAST Corner Detection

FAST Corner Detection detects repeatable local image features.

IntermediateCoreNo formula3 links
Image Processing
Image ProcessingO(p k)

Harris Corner Detection

Harris Corner Detection detects repeatable local image features.

IntermediateCoreFormula3 links
Image Processing
Image ProcessingO(p k)

Shi-Tomasi Corner Detection

Shi-Tomasi Corner Detection detects repeatable local image features.

IntermediateCoreFormula2 links
Image Processing
Image ProcessingO(p k)

SIFT Feature Detection

SIFT Feature Detection detects repeatable local image features.

IntermediateCoreNo formula3 links
Image Processing
Image ProcessingO(p k)

SURF Feature Detection

SURF Feature Detection detects repeatable local image features.

IntermediateExtendedNo formula3 links
Image Processing
Image ProcessingO(p k)

ORB Feature Detection

ORB Feature Detection detects repeatable local image features.

IntermediateCoreNo formula3 links
Image Processing
Image ProcessingO(p k)

RANSAC Image Homography

RANSAC Image Homography transforms image pixels into features, masks, or restored output.

IntermediateCoreNo formula1 links
Image Processing
Image ProcessingO(p k)

Otsu Thresholding

Otsu Thresholding separates pixels by intensity or local contrast.

IntermediateCoreFormula1 links
Image Processing
Image ProcessingO(p k)

Adaptive Thresholding

Adaptive Thresholding separates pixels by intensity or local contrast.

IntermediateCoreFormula1 links
Image Processing
Image ProcessingO(p k)

K-Means Image Segmentation

K-Means Image Segmentation partitions an image into meaningful regions.

IntermediateCoreNo formula1 links
Image Processing
Image ProcessingO(p k)

Mean Shift Segmentation

Mean Shift Segmentation partitions an image into meaningful regions.

IntermediateExtendedNo formula1 links
Image Processing
Image ProcessingO(p k)

Region Growing

Region Growing transforms image pixels into features, masks, or restored output.

IntermediateExtendedNo formula1 links
Image Processing
Image ProcessingO(p k)

Active Contour Model

Active Contour Model partitions an image into meaningful regions.

IntermediateExtendedNo formula1 links
Image Processing
Image ProcessingO(p k)

Anisotropic Diffusion

Anisotropic Diffusion transforms image pixels into features, masks, or restored output.

IntermediateExtendedFormula1 links
Image Processing
Image ProcessingO(p k)

Richardson-Lucy Deconvolution

Richardson-Lucy Deconvolution transforms image pixels into features, masks, or restored output.

IntermediateSpecializedFormula1 links
Image Processing
Image ProcessingO(p k)

Retinex Algorithm

Retinex Algorithm transforms image pixels into features, masks, or restored output.

IntermediateSpecializedFormula1 links
Image Processing
Image ProcessingO(n log n)

HOG Feature Descriptor

Describes local image shape by accumulating gradient-orientation histograms over cells.

IntermediateCoreNo formula5 links
Image Processing
Image ProcessingO(n log n)

SIFT

Detects and describes scale-invariant image keypoints from local gradient structure.

IntermediateCoreNo formula7 links
Image Processing
Image ProcessingO(n log n)

SURF

SURF addresses fast feature detection by approximating Hessian responses with integral-image box filters.

IntermediateExtendedNo formula3 links
Image ProcessingApproximation
Image ProcessingO(n log n)

ORB

Detects oriented FAST keypoints and describes them with rotated binary BRIEF-style tests.

IntermediateCoreNo formula7 links
Image Processing
Image ProcessingO((V + E) log V)

RANSAC Homography Estimation

Estimates a planar homography while rejecting mismatched feature correspondences.

IntermediateCoreNo formula5 links
Image ProcessingRandomnessGraph