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GimpMatrix

GimpMatrix — Utilities to set up and manipulate 3x3 transformation matrices.

Synopsis




struct      GimpMatrix2;
struct      GimpMatrix3;
struct      GimpMatrix4;
void        gimp_matrix2_identity           (GimpMatrix2 *matrix);
void        gimp_matrix2_mult               (const GimpMatrix2 *matrix1,
                                             GimpMatrix2 *matrix2);
void        gimp_matrix3_identity           (GimpMatrix3 *matrix);
void        gimp_matrix3_mult               (const GimpMatrix3 *matrix1,
                                             GimpMatrix3 *matrix2);
void        gimp_matrix3_translate          (GimpMatrix3 *matrix,
                                             gdouble x,
                                             gdouble y);
void        gimp_matrix3_scale              (GimpMatrix3 *matrix,
                                             gdouble x,
                                             gdouble y);
void        gimp_matrix3_rotate             (GimpMatrix3 *matrix,
                                             gdouble theta);
void        gimp_matrix3_xshear             (GimpMatrix3 *matrix,
                                             gdouble amount);
void        gimp_matrix3_yshear             (GimpMatrix3 *matrix,
                                             gdouble amount);
void        gimp_matrix3_affine             (GimpMatrix3 *matrix,
                                             gdouble a,
                                             gdouble b,
                                             gdouble c,
                                             gdouble d,
                                             gdouble e,
                                             gdouble f);
void        gimp_matrix3_transform_point    (const GimpMatrix3 *matrix,
                                             gdouble x,
                                             gdouble y,
                                             gdouble *newx,
                                             gdouble *newy);
gdouble     gimp_matrix3_determinant        (const GimpMatrix3 *matrix);
void        gimp_matrix3_invert             (GimpMatrix3 *matrix);
gboolean    gimp_matrix3_is_diagonal        (const GimpMatrix3 *matrix);
gboolean    gimp_matrix3_is_identity        (const GimpMatrix3 *matrix);
gboolean    gimp_matrix3_is_simple          (const GimpMatrix3 *matrix);
void        gimp_matrix4_to_deg             (const GimpMatrix4 *matrix,
                                             gdouble *a,
                                             gdouble *b,
                                             gdouble *c);

Description

When doing image manipulation you will often need 3x3 transformation matrices that define translation, rotation, scaling, shearing and arbitrary perspective transformations using a 3x3 matrix. Here you'll find a set of utility functions to set up those matrices and to perform basic matrix manipulations and tests.

Details

struct GimpMatrix2

struct GimpMatrix2 {

  gdouble coeff[2][2];
};

A two by two matrix.

struct GimpMatrix3

struct GimpMatrix3 {

  gdouble coeff[3][3];
};

A three by three matrix.

struct GimpMatrix4

struct GimpMatrix4 {

  gdouble coeff[4][4];
};

A four by four matrix.

gimp_matrix2_identity ()

void        gimp_matrix2_identity           (GimpMatrix2 *matrix);

Sets the matrix to the identity matrix.

matrix : A matrix.

gimp_matrix2_mult ()

void        gimp_matrix2_mult               (const GimpMatrix2 *matrix1,
                                             GimpMatrix2 *matrix2);

Multiplies two matrices and puts the result into the second one.

matrix1 : The first input matrix.
matrix2 : The second input matrix which will be overwritten by the result.

gimp_matrix3_identity ()

void        gimp_matrix3_identity           (GimpMatrix3 *matrix);

Sets the matrix to the identity matrix.

matrix : A matrix.

gimp_matrix3_mult ()

void        gimp_matrix3_mult               (const GimpMatrix3 *matrix1,
                                             GimpMatrix3 *matrix2);

Multiplies two matrices and puts the result into the second one.

matrix1 : The first input matrix.
matrix2 : The second input matrix which will be overwritten by the result.

gimp_matrix3_translate ()

void        gimp_matrix3_translate          (GimpMatrix3 *matrix,
                                             gdouble x,
                                             gdouble y);

Translates the matrix by x and y.

matrix : The matrix that is to be translated.
x : Translation in X direction.
y : Translation in Y direction.

gimp_matrix3_scale ()

void        gimp_matrix3_scale              (GimpMatrix3 *matrix,
                                             gdouble x,
                                             gdouble y);

Scales the matrix by x and y

matrix : The matrix that is to be scaled.
x : X scale factor.
y : Y scale factor.

gimp_matrix3_rotate ()

void        gimp_matrix3_rotate             (GimpMatrix3 *matrix,
                                             gdouble theta);

Rotates the matrix by theta degrees.

matrix : The matrix that is to be rotated.
theta : The angle of rotation (in radians).

gimp_matrix3_xshear ()

void        gimp_matrix3_xshear             (GimpMatrix3 *matrix,
                                             gdouble amount);

Shears the matrix in the X direction.

matrix : The matrix that is to be sheared.
amount : X shear amount.

gimp_matrix3_yshear ()

void        gimp_matrix3_yshear             (GimpMatrix3 *matrix,
                                             gdouble amount);

Shears the matrix in the Y direction.

matrix : The matrix that is to be sheared.
amount : Y shear amount.

gimp_matrix3_affine ()

void        gimp_matrix3_affine             (GimpMatrix3 *matrix,
                                             gdouble a,
                                             gdouble b,
                                             gdouble c,
                                             gdouble d,
                                             gdouble e,
                                             gdouble f);

Applies the affine transformation given by six values to matrix. The six values form define an affine transformation matrix as illustrated below:

( a c e ) ( b d f ) ( 0 0 1 )

matrix : The input matrix.
a :
b :
c :
d :
e :
f :

gimp_matrix3_transform_point ()

void        gimp_matrix3_transform_point    (const GimpMatrix3 *matrix,
                                             gdouble x,
                                             gdouble y,
                                             gdouble *newx,
                                             gdouble *newy);

Transforms a point in 2D as specified by the transformation matrix.

matrix : The transformation matrix.
x : The source X coordinate.
y : The source Y coordinate.
newx : The transformed X coordinate.
newy : The transformed Y coordinate.

gimp_matrix3_determinant ()

gdouble     gimp_matrix3_determinant        (const GimpMatrix3 *matrix);

Calculates the determinant of the given matrix.

matrix : The input matrix.
Returns : The determinant.

gimp_matrix3_invert ()

void        gimp_matrix3_invert             (GimpMatrix3 *matrix);

Inverts the given matrix.

matrix : The matrix that is to be inverted.

gimp_matrix3_is_diagonal ()

gboolean    gimp_matrix3_is_diagonal        (const GimpMatrix3 *matrix);

Checks if the given matrix is diagonal.

matrix : The matrix that is to be tested.
Returns : TRUE if the matrix is diagonal.

gimp_matrix3_is_identity ()

gboolean    gimp_matrix3_is_identity        (const GimpMatrix3 *matrix);

Checks if the given matrix is the identity matrix.

matrix : The matrix that is to be tested.
Returns : TRUE if the matrix is the identity matrix.

gimp_matrix3_is_simple ()

gboolean    gimp_matrix3_is_simple          (const GimpMatrix3 *matrix);

Checks if we'll need to interpolate when applying this matrix as a transformation.

matrix : The matrix that is to be tested.
Returns : TRUE if all entries of the upper left 2x2 matrix are either 0 or 1

gimp_matrix4_to_deg ()

void        gimp_matrix4_to_deg             (const GimpMatrix4 *matrix,
                                             gdouble *a,
                                             gdouble *b,
                                             gdouble *c);

matrix :
a :
b :
c :

See Also

GimpVector2

GimpVector3

GimpVector4

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