--- title: "EdgeDetect" language: "en" type: "Symbol" summary: "EdgeDetect[image] finds edges in image and returns the result as a binary image. EdgeDetect[image, r] finds edges at the scale of the specified pixel range r. EdgeDetect[image, r, t] uses a threshold t for selecting image edges." keywords: - image edges - image boundary - line detection - edge detection - Canny - Sobel - Shen - Castan - Prewitt - hysteresis threshold - contour - Hough - Radon - edge canonical_url: "https://reference.wolfram.com/language/ref/EdgeDetect.html" source: "Wolfram Language Documentation" related_guides: - title: "Feature Detection" link: "https://reference.wolfram.com/language/guide/FeatureDetection.en.md" - title: "Image Processing & Analysis" link: "https://reference.wolfram.com/language/guide/ImageProcessing.en.md" - title: "3D Images" link: "https://reference.wolfram.com/language/guide/3DImages.en.md" - title: "Scientific Data Analysis" link: "https://reference.wolfram.com/language/guide/ScientificDataAnalysis.en.md" - title: "Computational Photography" link: "https://reference.wolfram.com/language/guide/ComputationalPhotography.en.md" - title: "Signal Visualization & Analysis" link: "https://reference.wolfram.com/language/guide/SignalAnalysis.en.md" related_functions: - title: "ImageLines" link: "https://reference.wolfram.com/language/ref/ImageLines.en.md" - title: "GradientFilter" link: "https://reference.wolfram.com/language/ref/GradientFilter.en.md" - title: "FindImageShapes" link: "https://reference.wolfram.com/language/ref/FindImageShapes.en.md" - title: "MorphologicalPerimeter" link: "https://reference.wolfram.com/language/ref/MorphologicalPerimeter.en.md" - title: "MorphologicalBinarize" link: "https://reference.wolfram.com/language/ref/MorphologicalBinarize.en.md" - title: "CrossingDetect" link: "https://reference.wolfram.com/language/ref/CrossingDetect.en.md" - title: "CornerFilter" link: "https://reference.wolfram.com/language/ref/CornerFilter.en.md" - title: "GaussianMatrix" link: "https://reference.wolfram.com/language/ref/GaussianMatrix.en.md" - title: "ShenCastanMatrix" link: "https://reference.wolfram.com/language/ref/ShenCastanMatrix.en.md" --- # EdgeDetect EdgeDetect[image] finds edges in image and returns the result as a binary image. EdgeDetect[image, r] finds edges at the scale of the specified pixel range r. EdgeDetect[image, r, t] uses a threshold t for selecting image edges. ## Details and Options * Edges of an image are a set of points between image regions and are typically computed by linking high-gradient pixels. In practice, an edge can have an arbitrary shape. * ``EdgeDetect`` uses gradient methods to find edges and works with arbitrary 2D and 3D images. * ``EdgeDetect[image]`` is equivalent to ``EdgeDetect[image, 2]``. * The following range specifications ``r`` can be used: | | | | -------------------- | --------------------------------------------------------------- | | r | radius r in every dimension (default r = 2) | | {rrow, rcol} | in 2D, range rrow in height, rcol in width | | {rslice, rrow, rcol} | in 3D, range rslice in height, rrow in depth, and rcol in width | * ``EdgeDetect[image, r, t]`` uses hysteresis thresholding with a global threshold ``t``. For additional forms of the threshold parameter, see the reference page for ``MorphologicalBinarize``. * The following options can be specified: | | | | | ------- | --------- | --------------------- | | Method | Automatic | edge detection method | | Padding | "Fixed" | padding method | * Possible settings for ``Method`` include: | | | | ------------ | ------------------------------------------------------ | | "Canny" | first-order directional Gaussian derivatives (default) | | "ShenCastan" | first-order derivatives of exponentials | | "Sobel" | binomial generalization of Sobel masks | * By default, all straight and curved edges are returned. Selection of edges based on their straightness can be done by setting ``Method -> {"method", "StraightEdges" -> s}``. The default behavior is equivalent to ``"StraightEdges" -> 0``. A setting ``"StraightEdges" -> 1`` selects only the longest and strongest lines. * ``"StraightEdges"`` is ignored when used with ``Image3D`` objects. ## Examples (8) ### Basic Examples (1) Detecting edges in a color image: ```wl In[1]:= EdgeDetect[[image]] Out[1]= [image] ``` ### Scope (4) Find edges in a color image: ```wl In[1]:= EdgeDetect[[image]] Out[1]= [image] ``` --- Specify the scale of edges to detect: ```wl In[1]:= EdgeDetect[[image], 1] Out[1]= [image] ``` Specify larger scale to detect coarse features: ```wl In[2]:= EdgeDetect[[image], 10] Out[2]= [image] ``` --- Edge selection using an explicit global threshold: ```wl In[1]:= EdgeDetect[[image], 6, 0.1] Out[1]= [image] ``` --- Edges of a 3D image: ```wl In[1]:= i = [image]; In[2]:= Image3D[#, ClipRange -> {{15, 30}, All, {15, 30}}]& /@ {i, EdgeDetect[i]} Out[2]= {[image], [image]} ``` ### Options (2) #### Method (2) Shen–Castan edge detection: ```wl In[1]:= EdgeDetect[[image], 3, Method -> "ShenCastan"] Out[1]= [image] ``` --- By default, all edges are returned, regardless of their straightness: ```wl In[1]:= i = [image]; EdgeDetect[i, 1, .2] Out[1]= [image] ``` Filter detected edges with their straightness: ```wl In[2]:= EdgeDetect[i, 1, 0.2, Method -> {"Canny", "StraightEdges" -> 0.4}] Out[2]= [image] ``` ### Properties & Relations (1) ``EdgeDetect`` might return edges that are thicker than one pixel: ```wl In[1]:= e = EdgeDetect[[image]] Out[1]= [image] ``` Use ``Thinning`` to get single-pixel-wide edges: ```wl In[2]:= Thinning[e] Out[2]= [image] ``` ## See Also * [`ImageLines`](https://reference.wolfram.com/language/ref/ImageLines.en.md) * [`GradientFilter`](https://reference.wolfram.com/language/ref/GradientFilter.en.md) * [`FindImageShapes`](https://reference.wolfram.com/language/ref/FindImageShapes.en.md) * [`MorphologicalPerimeter`](https://reference.wolfram.com/language/ref/MorphologicalPerimeter.en.md) * [`MorphologicalBinarize`](https://reference.wolfram.com/language/ref/MorphologicalBinarize.en.md) * [`CrossingDetect`](https://reference.wolfram.com/language/ref/CrossingDetect.en.md) * [`CornerFilter`](https://reference.wolfram.com/language/ref/CornerFilter.en.md) * [`GaussianMatrix`](https://reference.wolfram.com/language/ref/GaussianMatrix.en.md) * [`ShenCastanMatrix`](https://reference.wolfram.com/language/ref/ShenCastanMatrix.en.md) ## Related Guides * [Feature Detection](https://reference.wolfram.com/language/guide/FeatureDetection.en.md) * [Image Processing & Analysis](https://reference.wolfram.com/language/guide/ImageProcessing.en.md) * [3D Images](https://reference.wolfram.com/language/guide/3DImages.en.md) * [Scientific Data Analysis](https://reference.wolfram.com/language/guide/ScientificDataAnalysis.en.md) * [Computational Photography](https://reference.wolfram.com/language/guide/ComputationalPhotography.en.md) * [Signal Visualization & Analysis](https://reference.wolfram.com/language/guide/SignalAnalysis.en.md) ## Related Links * [An Elementary Introduction to the Wolfram Language: Images](https://www.wolfram.com/language/elementary-introduction/10-images.html) * [An Elementary Introduction to the Wolfram Language: Strings and Text](https://www.wolfram.com/language/elementary-introduction/11-strings-and-text.html) * [An Elementary Introduction to the Wolfram Language: Ways to Apply Functions](https://www.wolfram.com/language/elementary-introduction/25-ways-to-apply-functions.html) * [An Elementary Introduction to the Wolfram Language: Applying Functions Repeatedly](https://www.wolfram.com/language/elementary-introduction/27-applying-functions-repeatedly.html) * [An Elementary Introduction to the Wolfram Language: Creating Websites and Apps](https://www.wolfram.com/language/elementary-introduction/36-creating-websites-and-apps.html) ## History * [Introduced in 2010 (8.0)](https://reference.wolfram.com/language/guide/SummaryOfNewFeaturesIn80.en.md) \| [Updated in 2014 (10.0)](https://reference.wolfram.com/language/guide/SummaryOfNewFeaturesIn100.en.md)