Basic Structures

CvPoint

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CvPoint

2D point with integer coordinates (usually zero-based).

typedef struct CvPoint
{
    int x;
    int y;
}
CvPoint;

x

x-coordinate

y

y-coordinate

/* Constructor */
inline CvPoint cvPoint( int x, int y );

/* Conversion from CvPoint2D32f */
inline CvPoint cvPointFrom32f( CvPoint2D32f point );

CvPoint2D32f

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CvPoint2D32f

2D point with floating-point coordinates

typedef struct CvPoint2D32f
{
    float x;
    float y;
}
CvPoint2D32f;

x

x-coordinate

y

y-coordinate

/* Constructor */
inline CvPoint2D32f cvPoint2D32f( double x, double y );

/* Conversion from CvPoint */
inline CvPoint2D32f cvPointTo32f( CvPoint point );

CvPoint3D32f

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CvPoint3D32f

3D point with floating-point coordinates

typedef struct CvPoint3D32f
{
    float x;
    float y;
    float z;
}
CvPoint3D32f;

x

x-coordinate

y

y-coordinate

z

z-coordinate

/* Constructor */
inline CvPoint3D32f cvPoint3D32f( double x, double y, double z );

CvPoint2D64f

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CvPoint2D64f

2D point with double precision floating-point coordinates

typedef struct CvPoint2D64f
{
    double x;
    double y;
}
CvPoint2D64f;

x

x-coordinate

y

y-coordinate

/* Constructor */
inline CvPoint2D64f cvPoint2D64f( double x, double y );

/* Conversion from CvPoint */
inline CvPoint2D64f cvPointTo64f( CvPoint point );

CvPoint3D64f

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CvPoint3D64f

3D point with double precision floating-point coordinates

typedef struct CvPoint3D64f
{
    double x;
    double y;
    double z;
}
CvPoint3D64f;

x

x-coordinate

y

y-coordinate

z

z-coordinate

/* Constructor */
inline CvPoint3D64f cvPoint3D64f( double x, double y, double z );

CvSize

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CvSize

Pixel-accurate size of a rectangle.

typedef struct CvSize
{
    int width;
    int height;
}
CvSize;

width

Width of the rectangle

height

Height of the rectangle

/* Constructor */
inline CvSize cvSize( int width, int height );

CvSize2D32f

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CvSize2D32f

Sub-pixel accurate size of a rectangle.

typedef struct CvSize2D32f
{
    float width;
    float height;
}
CvSize2D32f;

width

Width of the rectangle

height

Height of the rectangle

/* Constructor */
inline CvSize2D32f cvSize2D32f( double width, double height );

CvRect

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CvRect

Offset (usually the top-left corner) and size of a rectangle.

typedef struct CvRect
{
    int x;
    int y;
    int width;
    int height;
}
CvRect;

x

x-coordinate of the top-left corner

y

y-coordinate of the top-left corner (bottom-left for Windows bitmaps)

width

Width of the rectangle

height

Height of the rectangle

/* Constructor */
inline CvRect cvRect( int x, int y, int width, int height );

CvScalar

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CvScalar

A container for 1-,2-,3- or 4-tuples of doubles.

typedef struct CvScalar
{
    double val[4];
}
CvScalar;

/* Constructor:
initializes val[0] with val0, val[1] with val1, etc.
*/
inline CvScalar cvScalar( double val0, double val1=0,
                          double val2=0, double val3=0 );
/* Constructor:
initializes all of val[0]...val[3] with val0123
*/
inline CvScalar cvScalarAll( double val0123 );

/* Constructor:
initializes val[0] with val0, and all of val[1]...val[3] with zeros
*/
inline CvScalar cvRealScalar( double val0 );

CvTermCriteria

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CvTermCriteria

Termination criteria for iterative algorithms.

#define CV_TERMCRIT_ITER    1
#define CV_TERMCRIT_NUMBER  CV_TERMCRIT_ITER
#define CV_TERMCRIT_EPS     2

typedef struct CvTermCriteria
{
    int    type;
    int    max_iter;
    double epsilon;
}
CvTermCriteria;

type

A combination of CV _ TERMCRIT _ ITER and CV _ TERMCRIT _ EPS

max_iter

Maximum number of iterations

epsilon

Required accuracy

/* Constructor */
inline CvTermCriteria cvTermCriteria( int type, int max_iter, double epsilon );

/* Check and transform a CvTermCriteria so that
   type=CV_TERMCRIT_ITER+CV_TERMCRIT_EPS
   and both max_iter and epsilon are valid */
CvTermCriteria cvCheckTermCriteria( CvTermCriteria criteria,
                                    double default_eps,
                                    int default_max_iters );

CvMat

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CvMat

A multi-channel matrix.

typedef struct CvMat
{
    int type;
    int step;

    int* refcount;

    union
    {
        uchar* ptr;
        short* s;
        int* i;
        float* fl;
        double* db;
    } data;

#ifdef __cplusplus
    union
    {
        int rows;
        int height;
    };

    union
    {
        int cols;
        int width;
    };
#else
    int rows;
    int cols;
#endif

} CvMat;

type

A CvMat signature (CV _ MAT _ MAGIC _ VAL) containing the type of elements and flags

step

Full row length in bytes

refcount

Underlying data reference counter

data

Pointers to the actual matrix data

rows

Number of rows

cols

Number of columns

Matrices are stored row by row. All of the rows are aligned by 4 bytes.

CvMatND

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CvMatND

Multi-dimensional dense multi-channel array.

typedef struct CvMatND
{
    int type;
    int dims;

    int* refcount;

    union
    {
        uchar* ptr;
        short* s;
        int* i;
        float* fl;
        double* db;
    } data;

    struct
    {
        int size;
        int step;
    }
    dim[CV_MAX_DIM];

} CvMatND;

type

A CvMatND signature (CV _ MATND _ MAGIC _ VAL), combining the type of elements and flags

dims

The number of array dimensions

refcount

Underlying data reference counter

data

Pointers to the actual matrix data

dim

For each dimension, the pair (number of elements, distance between elements in bytes)

CvSparseMat

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CvSparseMat

Multi-dimensional sparse multi-channel array.

typedef struct CvSparseMat
{
    int type;
    int dims;
    int* refcount;
    struct CvSet* heap;
    void** hashtable;
    int hashsize;
    int total;
    int valoffset;
    int idxoffset;
    int size[CV_MAX_DIM];

} CvSparseMat;

type

A CvSparseMat signature (CV _ SPARSE _ MAT _ MAGIC _ VAL), combining the type of elements and flags.

dims

Number of dimensions

refcount

Underlying reference counter. Not used.

heap

A pool of hash table nodes

hashtable

The hash table. Each entry is a list of nodes.

hashsize

Size of the hash table

total

Total number of sparse array nodes

valoffset

The value offset of the array nodes, in bytes

idxoffset

The index offset of the array nodes, in bytes

size

Array of dimension sizes

IplImage

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IplImage

IPL image header

typedef struct _IplImage
{
    int  nSize;
    int  ID;
    int  nChannels;
    int  alphaChannel;
    int  depth;
    char colorModel[4];
    char channelSeq[4];
    int  dataOrder;
    int  origin;
    int  align;
    int  width;
    int  height;
    struct _IplROI *roi;
    struct _IplImage *maskROI;
    void  *imageId;
    struct _IplTileInfo *tileInfo;
    int  imageSize;
    char *imageData;
    int  widthStep;
    int  BorderMode[4];
    int  BorderConst[4];
    char *imageDataOrigin;
}
IplImage;

nSize

sizeof(IplImage)

ID

Version, always equals 0

nChannels

Number of channels. Most OpenCV functions support 1-4 channels.

alphaChannel

Ignored by OpenCV

depth

Channel depth in bits + the optional sign bit ( IPL_DEPTH_SIGN ). The supported depths are:

IPL_DEPTH_8U

Unsigned 8-bit integer

IPL_DEPTH_8S

Signed 8-bit integer

IPL_DEPTH_16U

Unsigned 16-bit integer

IPL_DEPTH_16S

Signed 16-bit integer

IPL_DEPTH_32S

Signed 32-bit integer

IPL_DEPTH_32F

Single-precision floating point

IPL_DEPTH_64F

Double-precision floating point

colorModel

Ignored by OpenCV. The OpenCV function CvtColor requires the source and destination color spaces as parameters.

channelSeq

Ignored by OpenCV

dataOrder

0 = IPL_DATA_ORDER_PIXEL - interleaved color channels, 1 - separate color channels. CreateImage only creates images with interleaved channels. For example, the usual layout of a color image is:

origin

0 - top-left origin, 1 - bottom-left origin (Windows bitmap style)

align

Alignment of image rows (4 or 8). OpenCV ignores this and uses widthStep instead.

width

Image width in pixels

height

Image height in pixels

roi

Region Of Interest (ROI). If not NULL, only this image region will be processed.

maskROI

Must be NULL in OpenCV

imageId

Must be NULL in OpenCV

tileInfo

Must be NULL in OpenCV

imageSize

Image data size in bytes. For interleaved data, this equals

imageData

A pointer to the aligned image data

widthStep

The size of an aligned image row, in bytes

BorderMode

Border completion mode, ignored by OpenCV

BorderConst

Border completion mode, ignored by OpenCV

imageDataOrigin

A pointer to the origin of the image data (not necessarily aligned). This is used for image deallocation.

The IplImage structure was inherited from the Intel Image Processing Library, in which the format is native. OpenCV only supports a subset of possible IplImage formats, as outlined in the parameter list above.

In addition to the above restrictions, OpenCV handles ROIs differently. OpenCV functions require that the image size or ROI size of all source and destination images match exactly. On the other hand, the Intel Image Processing Library processes the area of intersection between the source and destination images (or ROIs), allowing them to vary independently.

CvArr

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CvArr

Arbitrary array

typedef void CvArr;

The metatype CvArr is used only as a function parameter to specify that the function accepts arrays of multiple types, such as IplImage*, CvMat* or even CvSeq* sometimes. The particular array type is determined at runtime by analyzing the first 4 bytes of the header.