在Matlab R2013a 和R2014a中已经实现MSER特征的提取。
- 一、函数detectMSERFeatures
输入的是M*N的灰度图片。可以指定阈值刻度，区域范围，感兴趣区域等参数。
输出的是MSERRegions
class，即框住区域的椭圆由椭圆中心的坐标，椭圆的长短轴，椭圆的方向（有长轴与x方向形成的角），即区域内所有像素的坐标。
Detect MSER features and return MSERRegions object
Syntax
· regions = detectMSERFeatures(I) example
· regions = detectMSERFeatures(I,Name,Value)
Description
regions
= detectMSERFeatures(I)
returns an MSERRegions
object, regions, containing information about MSER features detected in the 2-D
grayscale input image, I. This object uses Maximally Stable Extremal Regions
(MSER) algorithm to find regions.
regions
= detectMSERFeatures(I,Name,Value)
sets additional options specified by one or moreName,Value pair arguments.
Code Generation Support:
Supports MATLAB Function block: No
For code generation, the function outputs regions.PixelList as an array. The
region sizes are defined in regions.Lengths. Generated code for this function
uses a precompiled platform-specific
shared library.
Code
Generation Support, Usage Notes, and Limitations
Examples
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Find MSER Regions in an Image
Read image and detect MSER regions.
I = imread(‘cameraman.tif‘);
regions = detectMSERFeatures(I);
Visualize MSER regions which are described by pixel lists stored inside
the returned ‘regions‘ object.
figure; imshow(I); hold ;
plot(regions, ‘showPixelList‘, true, ‘showEllipses‘, false);
Display ellipses and centroids fit into the regions.
figure; imshow(I); hold ;
plot(regions); % by default, plot displays ellipses and centroids
Input Arguments
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I — Input
imageM-by-N 2-D grayscale
image
Input image, specified in grayscale. It must be real and nonsparse.
Data Types: uint8 | int16 | uint16 | single | double
Name-Value Pair Arguments
Specify optional comma-separated pairs of Name,Value arguments. Name is the
argument name andValue is the corresponding value. Name must appear inside
single quotes (‘ ‘). You can specify several name and value pair arguments in
any order as Name1,Value1,...,NameN,ValueN.
Example: ‘RegionAreaRange‘,[30 14000], specifies the size of the
region in pixels.
‘ThresholdDelta‘ — Step size between intensity threshold
levels2 (default) | percent numeric value
Step size between intensity threshold levels, specified as the
comma-separated pair consisting of ‘ThresholdDelta‘ and a numeric value in the
range (0,100]. This value is expressed as a percentage of the input data type
range used in selecting extremal regions while testing for their stability.
Decrease this value to return more regions. Typical values range from 0.8 to
4.
‘RegionAreaRange‘ — Size of the region[30
14000] (default) | two-element vector
Size of the region in pixels, specified as the comma-separated pair
consisting of ‘RegionAreaRange‘ and a two-element vector. The vector,
[minArea maxArea], allows the selection of regions containing
pixels to be between minArea and maxArea, inclusive.
‘MaxAreaVariation‘ — Maximum area variation between extremal
regions0.25 (default) | positive scalar
Maximum area variation between extremal regions at varying intensity
thresholds, specified as the comma-separated pair consisting of
‘MaxAreaVariation‘ and a positive scalar value. Increasing this value returns a
greater number of regions, but they may be less stable. Stable regions are very
similar in size over varying intensity thresholds. Typical values range from 0.1
to 1.0.
‘ROI‘ — Rectangular region of interest[1 1 size(I,2)
size(I,1)]
(default) | vector
Rectangular region of interest, specified as a vector. The vector must be in
the format [x y widthheight]. When you specify an ROI, the
function detects corners within the area located at [x y] of size
specified by [width height] . The [x y] elements
specify the upper left corner of the region.
Output Arguments
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regions — MSER regions objectMSERRegions
object (default)
MSER regions object, returned as a MSERRegions
object. The object contains information about MSER features detected in the
grayscale input image.
More About
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Algorithms
Intensity Threshold Levels
The MSER detector incrementally steps through the intensity range of the
input image to detect stable regions. The ThresholdDelta
parameter determines the number of increments the detector tests for stability.
You can think of the threshold delta value as the size of a cup to fill a bucket
with water. The smaller the cup, the more number of increments it takes to fill
up the bucket. The bucket can be thought of as the intensity profile of the
region.
The MSER object checks the variation of the region area size between
different intensity thresholds. The variation must be less than the value of the
MaxAreaVariation
parameter to be considered stable.
At a high level, MSER can be explained, by thinking of the intensity profile
of an image representing a series of buckets. Imagine the tops of the buckets
flush with the ground, and a hose turned on at one of the buckets. As the water
fills into the bucket, it overflows and the next bucket starts filling up.
Smaller regions of water join and become bigger bodies of water, and finally the
whole area gets filled. As water is filling up into a bucket, it is checked
against the MSER stability criterion. Regions appear, grow and merge at
different intensity thresholds。
- 二 MSERRegions class
Object for storing MSER regions
Description
This object describes MSER regions and corresponding ellipses that have the
same second moments as the regions. It passes data between the detectMSERFeatures
and extractFeaturesfunctions.
The object can also be used to manipulate and plot the data returned by these
functions.
Although MSERRegions may hold many regions, it is a scalar object.
Therefore,NUMEL(MSERRegions)
always returns 1. This value may differ from LENGTH(MSERRegions),
which returns the true number of regions held by the object.
Construction
regions = MSERRegions(pixellist) constructs an MSER regions object,
regions, from an M-by-1 cell array of
regions,pixellist. Each cell contains a P-by-2 array of [x y]
coordinates for the detected MSER regions, where P varies based on the
number of pixels in a region.
CODE GENERATION SUPPORT
Compile-time constant inputs: No restrictions.
Supports MATLAB Function block: Yes
For code generation, you must specify both the pixellist
cell array and the length of each array, as the second input. The
object outputs, regions.PixelList as an array. The region sizes are
defined inregions.Lengths.
Generated code for this function uses a precompiled platform-specific
shared library.
Code
Generation Support, Usage Notes, and Limitations
Input Arguments
pixellist
M-by-2 cell array of [x y] coordinates of the detected MSER
regions.
Properties
The following properties are read-only and are calculated once the input
pixel list is specified.
Count
Number of stored regions
Default: 0
Location
An M-by-2 array of [x y] centroid coordinates of ellipses that have
the same second moments as the MSER regions.
Axes
A two-element vector, [majorAxis minorAxis]. This vector specifies the major
and minor axis of the ellipse that have the same second moments as the MSER
regions.
Orientation
A value in the range from -pi/2 to +pi/2 radians. This value represents the
orientation of the ellipse as measured from the X-axis to the major axis
of the ellipse. You can use this property for visualization purposes.
Methods
isempty
Returns
true for empty object
length
Number
of stored points
plot
Plot
MSER regions
size
Size
of the MSERRegions object
Matlab mser(最大极值稳定区域)