class SkMatrix { static SkMatrix MakeScale(SkScalar sx, SkScalar sy); static SkMatrix MakeScale(SkScalar scale); static SkMatrix MakeTrans(SkScalar dx, SkScalar dy); static SkMatrix MakeAll(SkScalar scaleX, SkScalar skewX, SkScalar transX, SkScalar skewY, SkScalar scaleY, SkScalar transY, SkScalar pers0, SkScalar pers1, SkScalar pers2); enum TypeMask { kIdentity_Mask = 0, kTranslate_Mask = 0x01, kScale_Mask = 0x02, kAffine_Mask = 0x04, kPerspective_Mask = 0x08, }; TypeMask getType() const; bool isIdentity() const; bool isScaleTranslate() const; bool isTranslate() const; bool rectStaysRect() const; bool preservesAxisAlignment() const; bool hasPerspective() const; bool isSimilarity(SkScalar tol = SK_ScalarNearlyZero) const; bool preservesRightAngles(SkScalar tol = SK_ScalarNearlyZero) const; static constexpr int kMScaleX = 0 static constexpr int kMSkewX = 1 static constexpr int kMTransX = 2 static constexpr int kMSkewY = 3 static constexpr int kMScaleY = 4 static constexpr int kMTransY = 5 static constexpr int kMPersp0 = 6 static constexpr int kMPersp1 = 7 static constexpr int kMPersp2 = 8 static constexpr int kAScaleX = 0 static constexpr int kASkewY = 1 static constexpr int kASkewX = 2 static constexpr int kAScaleY = 3 static constexpr int kATransX = 4 static constexpr int kATransY = 5 SkScalar operator[](int index) const; SkScalar get(int index) const; SkScalar getScaleX() const; SkScalar getScaleY() const; SkScalar getSkewY() const; SkScalar getSkewX() const; SkScalar getTranslateX() const; SkScalar getTranslateY() const; SkScalar getPerspX() const; SkScalar getPerspY() const; SkScalar& operator[](int index); void set(int index, SkScalar value); void setScaleX(SkScalar v); void setScaleY(SkScalar v); void setSkewY(SkScalar v); void setSkewX(SkScalar v); void setTranslateX(SkScalar v); void setTranslateY(SkScalar v); void setPerspX(SkScalar v); void setPerspY(SkScalar v); void setAll(SkScalar scaleX, SkScalar skewX, SkScalar transX, SkScalar skewY, SkScalar scaleY, SkScalar transY, SkScalar persp0, SkScalar persp1, SkScalar persp2); void get9(SkScalar buffer[9]) const; void set9(const SkScalar buffer[9]); void reset(); void setIdentity(); void setTranslate(SkScalar dx, SkScalar dy); void setTranslate(const SkVector& v); void setScale(SkScalar sx, SkScalar sy, SkScalar px, SkScalar py); void setScale(SkScalar sx, SkScalar sy); void setRotate(SkScalar degrees, SkScalar px, SkScalar py); void setRotate(SkScalar degrees); void setSinCos(SkScalar sinValue, SkScalar cosValue, SkScalar px, SkScalar py); void setSinCos(SkScalar sinValue, SkScalar cosValue); SkMatrix& setRSXform(const SkRSXform& rsxForm); void setSkew(SkScalar kx, SkScalar ky, SkScalar px, SkScalar py); void setSkew(SkScalar kx, SkScalar ky); void setConcat(const SkMatrix& a, const SkMatrix& b); void preTranslate(SkScalar dx, SkScalar dy); void preScale(SkScalar sx, SkScalar sy, SkScalar px, SkScalar py); void preScale(SkScalar sx, SkScalar sy); void preRotate(SkScalar degrees, SkScalar px, SkScalar py); void preRotate(SkScalar degrees); void preSkew(SkScalar kx, SkScalar ky, SkScalar px, SkScalar py); void preSkew(SkScalar kx, SkScalar ky); void preConcat(const SkMatrix& other); void postTranslate(SkScalar dx, SkScalar dy); void postScale(SkScalar sx, SkScalar sy, SkScalar px, SkScalar py); void postScale(SkScalar sx, SkScalar sy); bool postIDiv(int divx, int divy); void postRotate(SkScalar degrees, SkScalar px, SkScalar py); void postRotate(SkScalar degrees); void postSkew(SkScalar kx, SkScalar ky, SkScalar px, SkScalar py); void postSkew(SkScalar kx, SkScalar ky); void postConcat(const SkMatrix& other); enum ScaleToFit { kFill_ScaleToFit, kStart_ScaleToFit, kCenter_ScaleToFit, kEnd_ScaleToFit, }; bool setRectToRect(const SkRect& src, const SkRect& dst, ScaleToFit stf); static SkMatrix MakeRectToRect(const SkRect& src, const SkRect& dst, ScaleToFit stf); bool setPolyToPoly(const SkPoint src[], const SkPoint dst[], int count); bool invert(SkMatrix* inverse) const; static void SetAffineIdentity(SkScalar affine[6]); bool asAffine(SkScalar affine[6]) const; void setAffine(const SkScalar affine[6]); void mapPoints(SkPoint dst[], const SkPoint src[], int count) const; void mapPoints(SkPoint pts[], int count) const; void mapHomogeneousPoints(SkPoint3 dst[], const SkPoint3 src[], int count) const; void mapXY(SkScalar x, SkScalar y, SkPoint* result) const; SkPoint mapXY(SkScalar x, SkScalar y) const; void mapVectors(SkVector dst[], const SkVector src[], int count) const; void mapVectors(SkVector vecs[], int count) const; void mapVector(SkScalar dx, SkScalar dy, SkVector* result) const; SkVector mapVector(SkScalar dx, SkScalar dy) const; bool mapRect(SkRect* dst, const SkRect& src) const; bool mapRect(SkRect* rect) const; SkRect mapRect(const SkRect& src) const; void mapRectToQuad(SkPoint dst[4], const SkRect& rect) const; void mapRectScaleTranslate(SkRect* dst, const SkRect& src) const; SkScalar mapRadius(SkScalar radius) const; bool isFixedStepInX() const; SkVector fixedStepInX(SkScalar y) const; bool cheapEqualTo(const SkMatrix& m) const; friend bool operator==(const SkMatrix& a, const SkMatrix& b); friend bool operator!=(const SkMatrix& a, const SkMatrix& b); void dump() const; SkScalar getMinScale() const; SkScalar getMaxScale() const; bool getMinMaxScales(SkScalar scaleFactors[2]) const; bool decomposeScale(SkSize* scale, SkMatrix* remaining = nullptr) const; static const SkMatrix& I(); static const SkMatrix& InvalidMatrix(); static SkMatrix Concat(const SkMatrix& a, const SkMatrix& b); void dirtyMatrixTypeCache(); void setScaleTranslate(SkScalar sx, SkScalar sy, SkScalar tx, SkScalar ty); bool isFinite() const; };
Matrix holds a 3 by 3 matrix for transforming coordinates. This allows mapping Points and Vectors with translation, scaling, skewing, rotation, and perspective.
Matrix elements are in row major order. Matrix does not have a constructor, so it must be explicitly initialized. setIdentity initializes Matrix so it has no effect. setTranslate, setScale, setSkew, setRotate, set9 and setAll initializes all Matrix elements with the corresponding mapping.
Matrix includes a hidden variable that classifies the type of matrix to improve performance. Matrix is not thread safe unless getType is called first.
static SkMatrix MakeScale(SkScalar sx, SkScalar sy)
Sets SkMatrix to scale by (sx, sy). Returned matrix is:
| sx 0 0 | | 0 sy 0 | | 0 0 1 |
sx |
horizontal scale factor |
sy |
vertical scale factor |
SkMatrix with scale
static SkMatrix MakeScale(SkScalar scale)
Sets SkMatrix to scale by (scale, scale). Returned matrix is:
| scale 0 0 | | 0 scale 0 | | 0 0 1 |
scale |
horizontal and vertical scale factor |
static SkMatrix MakeTrans(SkScalar dx, SkScalar dy)
Sets SkMatrix to translate by (dx, dy). Returned matrix is:
| 1 0 dx | | 0 1 dy | | 0 0 1 |
dx |
horizontal translation |
dy |
vertical translation |
SkMatrix with translation
setTranslate postTranslate preTranslate
static SkMatrix MakeAll(SkScalar scaleX, SkScalar skewX, SkScalar transX, SkScalar skewY, SkScalar scaleY, SkScalar transY, SkScalar pers0, SkScalar pers1, SkScalar pers2)
Sets SkMatrix to:
| scaleX skewX transX | | skewY scaleY transY | | pers0 pers1 pers2 |
scaleX |
horizontal scale factor |
skewX |
horizontal skew factor |
transX |
horizontal translation |
skewY |
vertical skew factor |
scaleY |
vertical scale factor |
transY |
vertical translation |
pers0 |
input x-axis perspective factor |
pers1 |
input y-axis perspective factor |
pers2 |
perspective scale factor |
SkMatrix constructed from parameters
setAll set9 postConcat preConcat
enum TypeMask { kIdentity_Mask = 0, kTranslate_Mask = 0x01, kScale_Mask = 0x02, kAffine_Mask = 0x04, kPerspective_Mask = 0x08, };
Enumeration of bit fields for mask returned by getType. Used to identify the complexity of Matrix, to optimize performance.
Const | Value | Description |
---|---|---|
SkMatrix::kIdentity_Mask |
0 | all bits clear if Matrix is identity |
SkMatrix::kTranslate_Mask |
1 | set if Matrix has translation |
SkMatrix::kScale_Mask |
2 | set if Matrix scales x-axis or y-axis |
SkMatrix::kAffine_Mask |
4 | set if Matrix skews or rotates |
SkMatrix::kPerspective_Mask |
8 | set if Matrix has perspective |
TypeMask getType()const
Returns a bit field describing the transformations the matrix may perform. The bit field is computed conservatively, so it may include false positives. For example, when kPerspective_Mask is set, all other bits are set.
kIdentity_Mask, or combinations of: kTranslate_Mask, kScale_Mask,
kAffine_Mask, kPerspective_Mask
bool isIdentity()const
Returns true if SkMatrix is identity. Identity matrix is:
| 1 0 0 | | 0 1 0 | | 0 0 1 |
true if SkMatrix has no effect
bool isScaleTranslate()const
Returns true if SkMatrix at most scales and translates. SkMatrix may be identity, contain only scale elements, only translate elements, or both. SkMatrix form is:
| scale-x 0 translate-x | | 0 scale-y translate-y | | 0 0 1 |
true if SkMatrix is identity; or scales, translates, or both
setScale isTranslate setTranslate getType
bool isTranslate()const
Returns true if SkMatrix is identity, or translates. SkMatrix form is:
| 1 0 translate-x | | 0 1 translate-y | | 0 0 1 |
true if SkMatrix is identity, or translates
bool rectStaysRect()const
Returns true SkMatrix maps SkRect to another SkRect. If true, SkMatrix is identity, or scales, or rotates a multiple of 90 degrees, or mirrors on axes. In all cases, SkMatrix may also have translation. SkMatrix form is either:
| scale-x 0 translate-x | | 0 scale-y translate-y | | 0 0 1 |
or
| 0 rotate-x translate-x | | rotate-y 0 translate-y | | 0 0 1 |
for non-zero values of scale-x, scale-y, rotate-x, and rotate-y.
Also called preservesAxisAlignment(); use the one that provides better inline documentation.
true if SkMatrix maps one SkRect into another
preservesAxisAlignment preservesRightAngles
bool preservesAxisAlignment()const
Returns true SkMatrix maps SkRect to another SkRect. If true, SkMatrix is identity, or scales, or rotates a multiple of 90 degrees, or mirrors on axes. In all cases, SkMatrix may also have translation. SkMatrix form is either:
| scale-x 0 translate-x | | 0 scale-y translate-y | | 0 0 1 |
or
| 0 rotate-x translate-x | | rotate-y 0 translate-y | | 0 0 1 |
for non-zero values of scale-x, scale-y, rotate-x, and rotate-y.
Also called rectStaysRect(); use the one that provides better inline documentation.
true if SkMatrix maps one SkRect into another
rectStaysRect preservesRightAngles
bool hasPerspective()const
Returns true if the matrix contains perspective elements. SkMatrix form is:
| – – – | | – – – | | perspective-x perspective-y perspective-scale |
where perspective-x or perspective-y is non-zero, or perspective-scale is not one. All other elements may have any value.
true if SkMatrix is in most general form
bool isSimilarity(SkScalar tol = SK_ScalarNearlyZero)const
Returns true if SkMatrix contains only translation, rotation, reflection, and uniform scale. Returns false if SkMatrix contains different scales, skewing, perspective, or degenerate forms that collapse to a line or point.
Describes that the SkMatrix makes rendering with and without the matrix are visually alike; a transformed circle remains a circle. Mathematically, this is referred to as similarity of a Euclidean space, or a similarity transformation.
Preserves right angles, keeping the arms of the angle equal lengths.
tol |
to be deprecated |
true if SkMatrix only rotates, uniformly scales, translates
isScaleTranslate preservesRightAngles rectStaysRect isFixedStepInX
bool preservesRightAngles(SkScalar tol = SK_ScalarNearlyZero)const
Returns true if SkMatrix contains only translation, rotation, reflection, and scale. Scale may differ along rotated axes. Returns false if SkMatrix skewing, perspective, or degenerate forms that collapse to a line or point.
Preserves right angles, but not requiring that the arms of the angle retain equal lengths.
tol |
to be deprecated |
true if SkMatrix only rotates, scales, translates
isScaleTranslate isSimilarity rectStaysRect isFixedStepInX
static constexpr int kMScaleX = 0; static constexpr int kMSkewX = 1; static constexpr int kMTransX = 2; static constexpr int kMSkewY = 3; static constexpr int kMScaleY = 4; static constexpr int kMTransY = 5; static constexpr int kMPersp0 = 6; static constexpr int kMPersp1 = 7; static constexpr int kMPersp2 = 8;
Matrix organizes its values in row order. These members correspond to each value in Matrix.
Const | Value | Description |
---|---|---|
SkMatrix::kMScaleX |
0 | horizontal scale factor |
SkMatrix::kMSkewX |
1 | horizontal skew factor |
SkMatrix::kMTransX |
2 | horizontal translation |
SkMatrix::kMSkewY |
3 | vertical skew factor |
SkMatrix::kMScaleY |
4 | vertical scale factor |
SkMatrix::kMTransY |
5 | vertical translation |
SkMatrix::kMPersp0 |
6 | input x perspective factor |
SkMatrix::kMPersp1 |
7 | input y perspective factor |
SkMatrix::kMPersp2 |
8 | perspective bias |
Affine arrays are in column major order to match the matrix used by PDF and XPS.
Const | Value | Description |
---|---|---|
SkMatrix::kAScaleX |
0 | horizontal scale factor |
SkMatrix::kASkewY |
1 | vertical skew factor |
SkMatrix::kASkewX |
2 | horizontal skew factor |
SkMatrix::kAScaleY |
3 | vertical scale factor |
SkMatrix::kATransX |
4 | horizontal translation |
SkMatrix::kATransY |
5 | vertical translation |
SetAffineIdentity asAffine setAffine
SkScalar operator[](int index)const
SkScalar get(int index)const
Returns one matrix value. Asserts if index is out of range and SK_DEBUG is defined.
index |
one of: kMScaleX, kMSkewX, kMTransX, kMSkewY, kMScaleY, kMTransY, |
value corresponding to index
operator[](int index) set
SkScalar getScaleX()const
Returns scale factor multiplied by x-axis input, contributing to x-axis output. With mapPoints(), scales SkPoint along the x-axis.
horizontal scale factor
get getScaleY setScaleX setScale
SkScalar getScaleY()const
Returns scale factor multiplied by y-axis input, contributing to y-axis output. With mapPoints(), scales SkPoint along the y-axis.
vertical scale factor
get getScaleX setScaleY setScale
SkScalar getSkewY()const
Returns scale factor multiplied by x-axis input, contributing to y-axis output. With mapPoints(), skews SkPoint along the y-axis. Skewing both axes can rotate SkPoint.
vertical skew factor
SkScalar getSkewX()const
Returns scale factor multiplied by y-axis input, contributing to x-axis output. With mapPoints(), skews SkPoint along the x-axis. Skewing both axes can rotate SkPoint.
horizontal scale factor
SkScalar getTranslateX()const
Returns translation contributing to x-axis output. With mapPoints(), moves SkPoint along the x-axis.
horizontal translation factor
get getTranslateY setTranslateX setTranslate
SkScalar getTranslateY()const
Returns translation contributing to y-axis output. With mapPoints(), moves SkPoint along the y-axis.
vertical translation factor
get getTranslateX setTranslateY setTranslate
SkScalar getPerspX()const
Returns factor scaling input x-axis relative to input y-axis.
input x-axis perspective factor
SkScalar getPerspY()const
Returns factor scaling input y-axis relative to input x-axis.
input y-axis perspective factor
SkScalar& operator[](int index)
void set(int index, SkScalar value)
Sets SkMatrix value. Asserts if index is out of range and SK_DEBUG is defined. Safer than operator[]; internal cache is always maintained.
index |
one of: kMScaleX, kMSkewX, kMTransX, kMSkewY, kMScaleY, kMTransY, |
value |
scalar to store in SkMatrix |
operator[] get
void setScaleX(SkScalar v)
Sets horizontal scale factor.
v |
horizontal scale factor to store |
void setScaleY(SkScalar v)
Sets vertical scale factor.
v |
vertical scale factor to store |
void setSkewY(SkScalar v)
Sets vertical skew factor.
v |
vertical skew factor to store |
void setSkewX(SkScalar v)
Sets horizontal skew factor.
v |
horizontal skew factor to store |
void setTranslateX(SkScalar v)
Sets horizontal translation.
v |
horizontal translation to store |
set setTranslate setTranslateY
void setTranslateY(SkScalar v)
Sets vertical translation.
v |
vertical translation to store |
set setTranslate setTranslateX
void setPerspX(SkScalar v)
Sets input x-axis perspective factor, which causes mapXY() to vary input x-axis values inversely proportional to input y-axis values.
v |
perspective factor |
getPerspX set setAll set9 MakeAll
void setPerspY(SkScalar v)
Sets input y-axis perspective factor, which causes mapXY() to vary input y-axis values inversely proportional to input x-axis values.
v |
perspective factor |
getPerspY set setAll set9 MakeAll
void setAll(SkScalar scaleX, SkScalar skewX, SkScalar transX, SkScalar skewY, SkScalar scaleY, SkScalar transY, SkScalar persp0, SkScalar persp1, SkScalar persp2)
Sets all values from parameters. Sets matrix to:
| scaleX skewX transX | | skewY scaleY transY | | persp0 persp1 persp2 |
scaleX |
horizontal scale factor to store |
skewX |
horizontal skew factor to store |
transX |
horizontal translation to store |
skewY |
vertical skew factor to store |
scaleY |
vertical scale factor to store |
transY |
vertical translation to store |
persp0 |
input x-axis values perspective factor to store |
persp1 |
input y-axis values perspective factor to store |
persp2 |
perspective scale factor to store |
void get9(SkScalar buffer[9])const
Copies nine scalar values contained by SkMatrix into buffer, in member value ascending order: kMScaleX, kMSkewX, kMTransX, kMSkewY, kMScaleY, kMTransY, kMPersp0, kMPersp1, kMPersp2.
buffer |
storage for nine scalar values |
void set9(const SkScalar buffer[9])
Sets SkMatrix to nine scalar values in buffer, in member value ascending order: kMScaleX, kMSkewX, kMTransX, kMSkewY, kMScaleY, kMTransY, kMPersp0, kMPersp1, kMPersp2.
Sets matrix to:
| buffer[0] buffer[1] buffer[2] | | buffer[3] buffer[4] buffer[5] | | buffer[6] buffer[7] buffer[8] |
In the future, set9 followed by get9 may not return the same values. Since SkMatrix maps non-homogeneous coordinates, scaling all nine values produces an equivalent transformation, possibly improving precision.
buffer |
nine scalar values |
void reset()
Sets SkMatrix to identity; which has no effect on mapped SkPoint. Sets SkMatrix to:
| 1 0 0 | | 0 1 0 | | 0 0 1 |
Also called setIdentity(); use the one that provides better inline documentation.
void setIdentity()
Sets SkMatrix to identity; which has no effect on mapped SkPoint. Sets SkMatrix to:
| 1 0 0 | | 0 1 0 | | 0 0 1 |
Also called reset(); use the one that provides better inline documentation.
void setTranslate(SkScalar dx, SkScalar dy)
Sets SkMatrix to translate by (dx, dy).
dx |
horizontal translation |
dy |
vertical translation |
void setTranslate(const SkVector& v)
Sets SkMatrix to translate by (v.fX, v.fY).
v |
vector containing horizontal and vertical translation |
setTranslateX setTranslateY MakeTrans
void setScale(SkScalar sx, SkScalar sy, SkScalar px, SkScalar py)
Sets SkMatrix to scale by sx and sy, about a pivot point at (px, py). The pivot point is unchanged when mapped with SkMatrix.
sx |
horizontal scale factor |
sy |
vertical scale factor |
px |
pivot on x-axis |
py |
pivot on y-axis |
setScaleX setScaleY MakeScale preScale postScale
void setScale(SkScalar sx, SkScalar sy)
Sets SkMatrix to scale by sx and sy about at pivot point at (0, 0).
sx |
horizontal scale factor |
sy |
vertical scale factor |
setScaleX setScaleY MakeScale preScale postScale
void setRotate(SkScalar degrees, SkScalar px, SkScalar py)
Sets SkMatrix to rotate by degrees about a pivot point at (px, py). The pivot point is unchanged when mapped with SkMatrix.
Positive degrees rotates clockwise.
degrees |
angle of axes relative to upright axes |
px |
pivot on x-axis |
py |
pivot on y-axis |
setSinCos preRotate postRotate
void setRotate(SkScalar degrees)
Sets SkMatrix to rotate by degrees about a pivot point at (0, 0). Positive degrees rotates clockwise.
degrees |
angle of axes relative to upright axes |
setSinCos preRotate postRotate
void setSinCos(SkScalar sinValue, SkScalar cosValue, SkScalar px, SkScalar py)
Sets SkMatrix to rotate by sinValue and cosValue, about a pivot point at (px, py). The pivot point is unchanged when mapped with SkMatrix.
Vector (sinValue, cosValue) describes the angle of rotation relative to (0, 1). Vector length specifies scale.
sinValue |
rotation vector x-axis component |
cosValue |
rotation vector y-axis component |
px |
pivot on x-axis |
py |
pivot on y-axis |
void setSinCos(SkScalar sinValue, SkScalar cosValue)
Sets SkMatrix to rotate by sinValue and cosValue, about a pivot point at (0, 0).
Vector (sinValue, cosValue) describes the angle of rotation relative to (0, 1). Vector length specifies scale.
sinValue |
rotation vector x-axis component |
cosValue |
rotation vector y-axis component |
SkMatrix& setRSXform(const SkRSXform& rsxForm)
Sets SkMatrix to rotate, scale, and translate using a compressed matrix form.
Vector (rsxForm.fSSin, rsxForm.fSCos) describes the angle of rotation relative to (0, 1). Vector length specifies scale. Mapped point is rotated and scaled by vector, then translated by (rsxForm.fTx, rsxForm.fTy).
rsxForm |
compressed SkRSXform matrix |
reference to SkMatrix
setSinCos setScale setTranslate
void setSkew(SkScalar kx, SkScalar ky, SkScalar px, SkScalar py)
Sets SkMatrix to skew by kx and ky, about a pivot point at (px, py). The pivot point is unchanged when mapped with SkMatrix.
kx |
horizontal skew factor |
ky |
vertical skew factor |
px |
pivot on x-axis |
py |
pivot on y-axis |
setSkewX setSkewY preSkew postSkew
void setSkew(SkScalar kx, SkScalar ky)
Sets SkMatrix to skew by kx and ky, about a pivot point at (0, 0).
kx |
horizontal skew factor |
ky |
vertical skew factor |
setSkewX setSkewY preSkew postSkew
void setConcat(const SkMatrix& a, const SkMatrix& b)
Sets SkMatrix to SkMatrix a multiplied by SkMatrix b. Either a or b may be this.
Given:
| A B C | | J K L | a = | D E F |, b = | M N O | | G H I | | P Q R |
sets SkMatrix to:
| A B C | | J K L | | AJ+BM+CP AK+BN+CQ AL+BO+CR | a * b = | D E F | * | M N O | = | DJ+EM+FP DK+EN+FQ DL+EO+FR | | G H I | | P Q R | | GJ+HM+IP GK+HN+IQ GL+HO+IR |
a |
SkMatrix on left side of multiply expression |
b |
SkMatrix on right side of multiply expression |
Concat preConcat postConcat SkCanvas::concat
void preTranslate(SkScalar dx, SkScalar dy)
Sets SkMatrix to SkMatrix multiplied by SkMatrix constructed from translation (dx, dy). This can be thought of as moving the point to be mapped before applying SkMatrix.
Given:
| A B C | | 1 0 dx | Matrix = | D E F |, T(dx, dy) = | 0 1 dy | | G H I | | 0 0 1 |
sets SkMatrix to:
| A B C | | 1 0 dx | | A B Adx+Bdy+C | Matrix * T(dx, dy) = | D E F | | 0 1 dy | = | D E Ddx+Edy+F | | G H I | | 0 0 1 | | G H Gdx+Hdy+I |
dx |
x-axis translation before applying SkMatrix |
dy |
y-axis translation before applying SkMatrix |
postTranslate setTranslate MakeTrans
void preScale(SkScalar sx, SkScalar sy, SkScalar px, SkScalar py)
Sets SkMatrix to SkMatrix multiplied by SkMatrix constructed from scaling by (sx, sy) about pivot point (px, py). This can be thought of as scaling about a pivot point before applying SkMatrix.
Given:
| A B C | | sx 0 dx | Matrix = | D E F |, S(sx, sy, px, py) = | 0 sy dy | | G H I | | 0 0 1 |
where
dx = px - sx * px dy = py - sy * py
sets SkMatrix to:
| A B C | | sx 0 dx | | Asx Bsy A*dx+B*dy+C | Matrix * S(sx, sy, px, py) = | D E F | | 0 sy dy | = | Dsx Esy D*dx+Edy+F | | G H I | | 0 0 1 | | Gsx H*sy G*dx+H*dy+I |
sx |
horizontal scale factor |
sy |
vertical scale factor |
px |
pivot on x-axis |
py |
pivot on y-axis |
void preScale(SkScalar sx, SkScalar sy)
Sets SkMatrix to SkMatrix multiplied by SkMatrix constructed from scaling by (sx, sy) about pivot point (0, 0). This can be thought of as scaling about the origin before applying SkMatrix.
Given:
| A B C | | sx 0 0 | Matrix = | D E F |, S(sx, sy) = | 0 sy 0 | | G H I | | 0 0 1 |
sets SkMatrix to:
| A B C | | sx 0 0 | | Asx Bsy C | Matrix * S(sx, sy) = | D E F | | 0 sy 0 | = | Dsx Esy F | | G H I | | 0 0 1 | | Gsx Hsy I |
sx |
horizontal scale factor |
sy |
vertical scale factor |
void preRotate(SkScalar degrees, SkScalar px, SkScalar py)
Sets SkMatrix to SkMatrix multiplied by SkMatrix constructed from rotating by degrees about pivot point (px, py). This can be thought of as rotating about a pivot point before applying SkMatrix.
Positive degrees rotates clockwise.
Given:
| A B C | | c -s dx | Matrix = | D E F |, R(degrees, px, py) = | s c dy | | G H I | | 0 0 1 |
where
c = cos(degrees) s = sin(degrees) dx = s * py + (1 - c) * px dy = -s * px + (1 - c) * py
sets SkMatrix to:
| A B C | | c -s dx | | Ac+Bs -As+Bc A*dx+B*dy+C | Matrix * R(degrees, px, py) = | D E F | | s c dy | = | Dc+Es -Ds+Ec D*dx+E*dy+F | | G H I | | 0 0 1 | | Gc+Hs -Gs+Hc G*dx+H*dy+I |
degrees |
angle of axes relative to upright axes |
px |
pivot on x-axis |
py |
pivot on y-axis |
void preRotate(SkScalar degrees)
Sets SkMatrix to SkMatrix multiplied by SkMatrix constructed from rotating by degrees about pivot point (0, 0). This can be thought of as rotating about the origin before applying SkMatrix.
Positive degrees rotates clockwise.
Given:
| A B C | | c -s 0 | Matrix = | D E F |, R(degrees, px, py) = | s c 0 | | G H I | | 0 0 1 |
where
c = cos(degrees) s = sin(degrees)
sets SkMatrix to:
| A B C | | c -s 0 | | Ac+Bs -As+Bc C | Matrix * R(degrees, px, py) = | D E F | | s c 0 | = | Dc+Es -Ds+Ec F | | G H I | | 0 0 1 | | Gc+Hs -Gs+Hc I |
degrees |
angle of axes relative to upright axes |
void preSkew(SkScalar kx, SkScalar ky, SkScalar px, SkScalar py)
Sets SkMatrix to SkMatrix multiplied by SkMatrix constructed from skewing by (kx, ky) about pivot point (px, py). This can be thought of as skewing about a pivot point before applying SkMatrix.
Given:
| A B C | | 1 kx dx | Matrix = | D E F |, K(kx, ky, px, py) = | ky 1 dy | | G H I | | 0 0 1 |
where
sets SkMatrix to:
| A B C | | 1 kx dx | | A+Bky Akx+B A*dx+B*dy+C | Matrix * K(kx, ky, px, py) = | D E F | | ky 1 dy | = | D+Eky Dkx+E D*dx+Edy+F | | G H I | | 0 0 1 | | G+Hky G*kx+H G*dx+H*dy+I |
kx |
horizontal skew factor |
ky |
vertical skew factor |
px |
pivot on x-axis |
py |
pivot on y-axis |
void preSkew(SkScalar kx, SkScalar ky)
Sets SkMatrix to SkMatrix multiplied by SkMatrix constructed from skewing by (kx, ky) about pivot point (0, 0). This can be thought of as skewing about the origin before applying SkMatrix.
Given:
| A B C | | 1 kx 0 | Matrix = | D E F |, K(kx, ky) = | ky 1 0 | | G H I | | 0 0 1 |
sets SkMatrix to:
| A B C | | 1 kx 0 | | A+Bky Akx+B C | Matrix * K(kx, ky) = | D E F | | ky 1 0 | = | D+Eky Dkx+E F | | G H I | | 0 0 1 | | G+Hky Gkx+H I |
kx |
horizontal skew factor |
ky |
vertical skew factor |
void preConcat(const SkMatrix& other)
Sets SkMatrix to SkMatrix multiplied by SkMatrix other. This can be thought of mapping by other before applying SkMatrix.
Given:
| A B C | | J K L | Matrix = | D E F |, other = | M N O | | G H I | | P Q R |
sets SkMatrix to:
| A B C | | J K L | | AJ+BM+CP AK+BN+CQ AL+BO+CR | Matrix * other = | D E F | * | M N O | = | DJ+EM+FP DK+EN+FQ DL+EO+FR | | G H I | | P Q R | | GJ+HM+IP GK+HN+IQ GL+HO+IR |
other |
SkMatrix on right side of multiply expression |
void postTranslate(SkScalar dx, SkScalar dy)
Sets SkMatrix to SkMatrix constructed from translation (dx, dy) multiplied by SkMatrix. This can be thought of as moving the point to be mapped after applying SkMatrix.
Given:
| J K L | | 1 0 dx | Matrix = | M N O |, T(dx, dy) = | 0 1 dy | | P Q R | | 0 0 1 |
sets SkMatrix to:
| 1 0 dx | | J K L | | J+dx*P K+dx*Q L+dx*R | T(dx, dy) * Matrix = | 0 1 dy | | M N O | = | M+dy*P N+dy*Q O+dy*R | | 0 0 1 | | P Q R | | P Q R |
dx |
x-axis translation after applying SkMatrix |
dy |
y-axis translation after applying SkMatrix |
preTranslate setTranslate MakeTrans
void postScale(SkScalar sx, SkScalar sy, SkScalar px, SkScalar py)
Sets SkMatrix to SkMatrix constructed from scaling by (sx, sy) about pivot point (px, py), multiplied by SkMatrix. This can be thought of as scaling about a pivot point after applying SkMatrix.
Given:
| J K L | | sx 0 dx | Matrix = | M N O |, S(sx, sy, px, py) = | 0 sy dy | | P Q R | | 0 0 1 |
where
dx = px - sx * px dy = py - sy * py
sets SkMatrix to:
| sx 0 dx | | J K L | | sx*J+dx*P sx*K+dx*Q sx*L+dx+R | S(sx, sy, px, py) * Matrix = | 0 sy dy | | M N O | = | sy*M+dy*P sy*N+dy*Q sy*O+dy*R | | 0 0 1 | | P Q R | | P Q R |
sx |
horizontal scale factor |
sy |
vertical scale factor |
px |
pivot on x-axis |
py |
pivot on y-axis |
void postScale(SkScalar sx, SkScalar sy)
Sets SkMatrix to SkMatrix constructed from scaling by (sx, sy) about pivot point (0, 0), multiplied by SkMatrix. This can be thought of as scaling about the origin after applying SkMatrix.
Given:
| J K L | | sx 0 0 | Matrix = | M N O |, S(sx, sy) = | 0 sy 0 | | P Q R | | 0 0 1 |
sets SkMatrix to:
| sx 0 0 | | J K L | | sx*J sx*K sx*L | S(sx, sy) * Matrix = | 0 sy 0 | | M N O | = | sy*M sy*N sy*O | | 0 0 1 | | P Q R | | P Q R |
sx |
horizontal scale factor |
sy |
vertical scale factor |
bool postIDiv(int divx, int divy)
Sets Matrix to Matrix constructed from scaling by (1/divx, 1/divy), multiplied by Matrix.
Returns false if either divx or divy is zero.
Given:
| J K L | | sx 0 0 | Matrix = | M N O |, I(divx, divy) = | 0 sy 0 | | P Q R | | 0 0 1 |
where
sx = 1 / divx sy = 1 / divy
sets Matrix to:
| sx 0 0 | | J K L | | sx*J sx*K sx*L | I(divx, divy) * Matrix = | 0 sy 0 | | M N O | = | sy*M sy*N sy*O | | 0 0 1 | | P Q R | | P Q R |
divx |
integer divisor for inverse scale on x-axis |
divy |
integer divisor for inverse scale on y-axis |
true on successful scale
void postRotate(SkScalar degrees, SkScalar px, SkScalar py)
Sets SkMatrix to SkMatrix constructed from rotating by degrees about pivot point (px, py), multiplied by SkMatrix. This can be thought of as rotating about a pivot point after applying SkMatrix.
Positive degrees rotates clockwise.
Given:
| J K L | | c -s dx | Matrix = | M N O |, R(degrees, px, py) = | s c dy | | P Q R | | 0 0 1 |
where
c = cos(degrees) s = sin(degrees) dx = s * py + (1 - c) * px dy = -s * px + (1 - c) * py
sets SkMatrix to:
|c -s dx| |J K L| |cJ-sM+dx*P cK-sN+dx*Q cL-sO+dx+R| R(degrees, px, py) * Matrix = |s c dy| |M N O| = |sJ+cM+dy*P sK+cN+dy*Q sL+cO+dy*R| |0 0 1| |P Q R| | P Q R|
degrees |
angle of axes relative to upright axes |
px |
pivot on x-axis |
py |
pivot on y-axis |
void postRotate(SkScalar degrees)
Sets SkMatrix to SkMatrix constructed from rotating by degrees about pivot point (0, 0), multiplied by SkMatrix. This can be thought of as rotating about the origin after applying SkMatrix.
Positive degrees rotates clockwise.
Given:
| J K L | | c -s 0 | Matrix = | M N O |, R(degrees, px, py) = | s c 0 | | P Q R | | 0 0 1 |
where
c = cos(degrees) s = sin(degrees)
sets SkMatrix to:
| c -s dx | | J K L | | cJ-sM cK-sN cL-sO | R(degrees, px, py) * Matrix = | s c dy | | M N O | = | sJ+cM sK+cN sL+cO | | 0 0 1 | | P Q R | | P Q R |
degrees |
angle of axes relative to upright axes |
void postSkew(SkScalar kx, SkScalar ky, SkScalar px, SkScalar py)
Sets SkMatrix to SkMatrix constructed from skewing by (kx, ky) about pivot point (px, py), multiplied by SkMatrix. This can be thought of as skewing about a pivot point after applying SkMatrix.
Given:
| J K L | | 1 kx dx | Matrix = | M N O |, K(kx, ky, px, py) = | ky 1 dy | | P Q R | | 0 0 1 |
where
sets SkMatrix to:
| 1 kx dx| |J K L| |J+kx*M+dx*P K+kx*N+dx*Q L+kx*O+dx+R| K(kx, ky, px, py) * Matrix = |ky 1 dy| |M N O| = |ky*J+M+dy*P ky*K+N+dy*Q ky*L+O+dy*R| | 0 0 1| |P Q R| | P Q R|
kx |
horizontal skew factor |
ky |
vertical skew factor |
px |
pivot on x-axis |
py |
pivot on y-axis |
void postSkew(SkScalar kx, SkScalar ky)
Sets SkMatrix to SkMatrix constructed from skewing by (kx, ky) about pivot point (0, 0), multiplied by SkMatrix. This can be thought of as skewing about the origin after applying SkMatrix.
Given:
| J K L | | 1 kx 0 | Matrix = | M N O |, K(kx, ky) = | ky 1 0 | | P Q R | | 0 0 1 |
sets SkMatrix to:
| 1 kx 0 | | J K L | | J+kx*M K+kx*N L+kx*O | K(kx, ky) * Matrix = | ky 1 0 | | M N O | = | ky*J+M ky*K+N ky*L+O | | 0 0 1 | | P Q R | | P Q R |
kx |
horizontal skew factor |
ky |
vertical skew factor |
void postConcat(const SkMatrix& other)
Sets SkMatrix to SkMatrix other multiplied by SkMatrix. This can be thought of mapping by other after applying SkMatrix.
Given:
| J K L | | A B C | Matrix = | M N O |, other = | D E F | | P Q R | | G H I |
sets SkMatrix to:
| A B C | | J K L | | AJ+BM+CP AK+BN+CQ AL+BO+CR | other * Matrix = | D E F | * | M N O | = | DJ+EM+FP DK+EN+FQ DL+EO+FR | | G H I | | P Q R | | GJ+HM+IP GK+HN+IQ GL+HO+IR |
other |
SkMatrix on left side of multiply expression |
enum ScaleToFit { kFill_ScaleToFit, kStart_ScaleToFit, kCenter_ScaleToFit, kEnd_ScaleToFit, };
ScaleToFit describes how Matrix is constructed to map one Rect to another. ScaleToFit may allow Matrix to have unequal horizontal and vertical scaling, or may restrict Matrix to square scaling. If restricted, ScaleToFit specifies how Matrix maps to the side or center of the destination Rect.
Const | Value | Description |
---|---|---|
SkMatrix::kFill_ScaleToFit |
0 | Computes Matrix that scales about x-axis and y-axis independently, so that source Rect is mapped to completely fill destination Rect. The aspect ratio of source Rect may change. |
SkMatrix::kStart_ScaleToFit |
1 | Computes Matrix that maintains source Rect aspect ratio, mapping source Rect width or height to destination Rect. Aligns mapping to left and top edges of destination Rect. |
SkMatrix::kCenter_ScaleToFit |
2 | Computes Matrix that maintains source Rect aspect ratio, mapping source Rect width or height to destination Rect. Aligns mapping to center of destination Rect. |
SkMatrix::kEnd_ScaleToFit |
3 | Computes Matrix that maintains source Rect aspect ratio, mapping source Rect width or height to destination Rect. Aligns mapping to right and bottom edges of destination Rect. |
setRectToRect MakeRectToRect setPolyToPoly
bool setRectToRect(const SkRect& src, const SkRect& dst, ScaleToFit stf)
Sets SkMatrix to scale and translate src SkRect to dst SkRect. stf selects whether mapping completely fills dst or preserves the aspect ratio, and how to align src within dst. Returns false if src is empty, and sets SkMatrix to identity. Returns true if dst is empty, and sets SkMatrix to:
| 0 0 0 | | 0 0 0 | | 0 0 1 |
src |
SkRect to map from |
dst |
SkRect to map to |
stf |
one of: kFill_ScaleToFit, kStart_ScaleToFit, |
kCenter_ScaleToFit, kEnd_ScaleToFit
true if SkMatrix can represent SkRect mapping
MakeRectToRect ScaleToFit setPolyToPoly SkRect::isEmpty
static SkMatrix MakeRectToRect(const SkRect& src, const SkRect& dst, ScaleToFit stf)
Returns SkMatrix set to scale and translate src SkRect to dst SkRect. stf selects whether mapping completely fills dst or preserves the aspect ratio, and how to align src within dst. Returns the identity SkMatrix if src is empty. If dst is empty, returns SkMatrix set to:
| 0 0 0 | | 0 0 0 | | 0 0 1 |
src |
SkRect to map from |
dst |
SkRect to map to |
stf |
one of: kFill_ScaleToFit, kStart_ScaleToFit, |
kCenter_ScaleToFit, kEnd_ScaleToFit
setRectToRect ScaleToFit setPolyToPoly SkRect::isEmpty
bool setPolyToPoly(const SkPoint src[], const SkPoint dst[], int count)
Sets SkMatrix to map src to dst. count must be zero or greater, and four or less.
If count is zero, sets SkMatrix to identity and returns true. If count is one, sets SkMatrix to translate and returns true. If count is two or more, sets SkMatrix to map SkPoint if possible; returns false if SkMatrix cannot be constructed. If count is four, SkMatrix may include perspective.
src |
SkPoint to map from |
dst |
SkPoint to map to |
count |
number of SkPoint in src and dst |
true if SkMatrix was constructed successfully
bool invert(SkMatrix* inverse)const
Sets inverse to reciprocal matrix, returning true if SkMatrix can be inverted. Geometrically, if SkMatrix maps from source to destination, inverse SkMatrix maps from destination to source. If SkMatrix can not be inverted, inverse is unchanged.
inverse |
storage for inverted SkMatrix; may be nullptr |
true if SkMatrix can be inverted
static void SetAffineIdentity(SkScalar affine[6])
Fills affine with identity values in column major order. Sets affine to:
| 1 0 0 | | 0 1 0 |
Affine 3 by 2 matrices in column major order are used by OpenGL and XPS.
affine |
storage for 3 by 2 affine matrix |
bool asAffine(SkScalar affine[6])const
Fills affine in column major order. Sets affine to:
| scale-x skew-x translate-x | | skew-y scale-y translate-y |
If SkMatrix contains perspective, returns false and leaves affine unchanged.
affine |
storage for 3 by 2 affine matrix; may be nullptr |
true if SkMatrix does not contain perspective
void setAffine(const SkScalar affine[6])
Sets SkMatrix to affine values, passed in column major order. Given affine, column, then row, as:
| scale-x skew-x translate-x | | skew-y scale-y translate-y |
SkMatrix is set, row, then column, to:
| scale-x skew-x translate-x | | skew-y scale-y translate-y | | 0 0 1 |
affine |
3 by 2 affine matrix |
void mapPoints(SkPoint dst[], const SkPoint src[], int count)const
Maps src SkPoint array of length count to dst SkPoint array of equal or greater length. SkPoint are mapped by multiplying each SkPoint by SkMatrix. Given:
| A B C | | x | Matrix = | D E F |, pt = | y | | G H I | | 1 |
where
for (i = 0; i < count; ++i) { x = src[i].fX y = src[i].fY }
each dst SkPoint is computed as:
|A B C| |x| Ax+By+C Dx+Ey+F Matrix * pt = |D E F| |y| = |Ax+By+C Dx+Ey+F Gx+Hy+I| = ——- , ——- |G H I| |1| Gx+Hy+I Gx+Hy+I
src and dst may point to the same storage.
dst |
storage for mapped SkPoint |
src |
SkPoint to transform |
count |
number of SkPoint to transform |
mapXY mapHomogeneousPoints mapVectors
void mapPoints(SkPoint pts[], int count)const
Maps pts SkPoint array of length count in place. SkPoint are mapped by multiplying each SkPoint by SkMatrix. Given:
| A B C | | x | Matrix = | D E F |, pt = | y | | G H I | | 1 |
where
for (i = 0; i < count; ++i) { x = pts[i].fX y = pts[i].fY }
each resulting pts SkPoint is computed as:
|A B C| |x| Ax+By+C Dx+Ey+F Matrix * pt = |D E F| |y| = |Ax+By+C Dx+Ey+F Gx+Hy+I| = ——- , ——- |G H I| |1| Gx+Hy+I Gx+Hy+I
pts |
storage for mapped SkPoint |
count |
number of SkPoint to transform |
mapXY mapHomogeneousPoints mapVectors
void mapHomogeneousPoints(SkPoint3 dst[], const SkPoint3 src[], int count)const
Maps src SkPoint3 array of length count to dst SkPoint3 array, which must of length count or greater. SkPoint3 array is mapped by multiplying each SkPoint3 by SkMatrix. Given:
| A B C | | x | Matrix = | D E F |, src = | y | | G H I | | z |
each resulting dst SkPoint is computed as:
|A B C| |x| Matrix * src = |D E F| |y| = |Ax+By+Cz Dx+Ey+Fz Gx+Hy+Iz| |G H I| |z|
dst |
storage for mapped SkPoint3 array |
src |
SkPoint3 array to transform |
count |
items in SkPoint3 array to transform |
void mapXY(SkScalar x, SkScalar y, SkPoint* result)const
Maps SkPoint (x, y) to result. SkPoint is mapped by multiplying by SkMatrix. Given:
| A B C | | x | Matrix = | D E F |, pt = | y | | G H I | | 1 |
result is computed as:
|A B C| |x| Ax+By+C Dx+Ey+F Matrix * pt = |D E F| |y| = |Ax+By+C Dx+Ey+F Gx+Hy+I| = ——- , ——- |G H I| |1| Gx+Hy+I Gx+Hy+I
x |
x-axis value of SkPoint to map |
y |
y-axis value of SkPoint to map |
result |
storage for mapped SkPoint |
SkPoint mapXY(SkScalar x, SkScalar y)const
Returns SkPoint (x, y) multiplied by SkMatrix. Given:
| A B C | | x | Matrix = | D E F |, pt = | y | | G H I | | 1 |
result is computed as:
|A B C| |x| Ax+By+C Dx+Ey+F Matrix * pt = |D E F| |y| = |Ax+By+C Dx+Ey+F Gx+Hy+I| = ——- , ——- |G H I| |1| Gx+Hy+I Gx+Hy+I
x |
x-axis value of SkPoint to map |
y |
y-axis value of SkPoint to map |
mapped SkPoint
void mapVectors(SkVector dst[], const SkVector src[], int count)const
Maps src vector array of length count to vector SkPoint array of equal or greater length. Vectors are mapped by multiplying each vector by SkMatrix, treating SkMatrix translation as zero. Given:
| A B 0 | | x | Matrix = | D E 0 |, src = | y | | G H I | | 1 |
where
for (i = 0; i < count; ++i) { x = src[i].fX y = src[i].fY }
each dst vector is computed as:
|A B 0| |x| Ax+By Dx+Ey Matrix * src = |D E 0| |y| = |Ax+By Dx+Ey Gx+Hy+I| = ——- , ——- |G H I| |1| Gx+Hy+I Gx+Hy+I
src and dst may point to the same storage.
dst |
storage for mapped vectors |
src |
vectors to transform |
count |
number of vectors to transform |
void mapVectors(SkVector vecs[], int count)const
Maps vecs vector array of length count in place, multiplying each vector by SkMatrix, treating SkMatrix translation as zero. Given:
| A B 0 | | x | Matrix = | D E 0 |, vec = | y | | G H I | | 1 |
where
for (i = 0; i < count; ++i) { x = vecs[i].fX y = vecs[i].fY }
each result vector is computed as:
|A B 0| |x| Ax+By Dx+Ey Matrix * vec = |D E 0| |y| = |Ax+By Dx+Ey Gx+Hy+I| = ——- , ——- |G H I| |1| Gx+Hy+I Gx+Hy+I
vecs |
vectors to transform, and storage for mapped vectors |
count |
number of vectors to transform |
void mapVector(SkScalar dx, SkScalar dy, SkVector* result)const
Maps vector (dx, dy) to result. Vector is mapped by multiplying by SkMatrix, treating SkMatrix translation as zero. Given:
| A B 0 | | dx | Matrix = | D E 0 |, vec = | dy | | G H I | | 1 |
each result vector is computed as:
|A B 0| |dx| Adx+Bdy Ddx+Edy Matrix * vec = |D E 0| |dy| = |Adx+Bdy Ddx+Edy Gdx+Hdy+I| = ———– , ———– |G H I| | 1| Gdx+Hdy+I G*dx+*dHy+I
dx |
x-axis value of vector to map |
dy |
y-axis value of vector to map |
result |
storage for mapped vector |
SkVector mapVector(SkScalar dx, SkScalar dy)const
Returns vector (dx, dy) multiplied by SkMatrix, treating SkMatrix translation as zero. Given:
| A B 0 | | dx | Matrix = | D E 0 |, vec = | dy | | G H I | | 1 |
each result vector is computed as:
|A B 0| |dx| Adx+Bdy Ddx+Edy Matrix * vec = |D E 0| |dy| = |Adx+Bdy Ddx+Edy Gdx+Hdy+I| = ———– , ———– |G H I| | 1| Gdx+Hdy+I G*dx+*dHy+I
dx |
x-axis value of vector to map |
dy |
y-axis value of vector to map |
mapped vector
bool mapRect(SkRect* dst, const SkRect& src)const
Sets dst to bounds of src corners mapped by SkMatrix. Returns true if mapped corners are dst corners.
Returned value is the same as calling rectStaysRect().
dst |
storage for bounds of mapped SkPoint |
src |
SkRect to map |
true if dst is equivalent to mapped src
bool mapRect(SkRect* rect)const
Sets rect to bounds of rect corners mapped by SkMatrix. Returns true if mapped corners are computed rect corners.
Returned value is the same as calling rectStaysRect().
rect |
rectangle to map, and storage for bounds of mapped corners |
true if result is equivalent to mapped rect
mapRectScaleTranslate mapPoints rectStaysRect
SkRect mapRect(const SkRect& src)const
Returns bounds of src corners mapped by SkMatrix.
src |
rectangle to map |
mapped bounds
mapRectToQuad mapRectScaleTranslate
void mapRectToQuad(SkPoint dst[4], const SkRect& rect)const
Maps four corners of rect to dst. SkPoint are mapped by multiplying each rect corner by SkMatrix. rect corner is processed in this order: (rect.fLeft, rect.fTop), (rect.fRight, rect.fTop), (rect.fRight, rect.fBottom), (rect.fLeft, rect.fBottom).
rect may be empty: rect.fLeft may be greater than or equal to rect.fRight; rect.fTop may be greater than or equal to rect.fBottom.
Given:
| A B C | | x | Matrix = | D E F |, pt = | y | | G H I | | 1 |
where pt is initialized from each of (rect.fLeft, rect.fTop), (rect.fRight, rect.fTop), (rect.fRight, rect.fBottom), (rect.fLeft, rect.fBottom), each dst SkPoint is computed as:
|A B C| |x| Ax+By+C Dx+Ey+F Matrix * pt = |D E F| |y| = |Ax+By+C Dx+Ey+F Gx+Hy+I| = ——- , ——- |G H I| |1| Gx+Hy+I Gx+Hy+I
dst |
storage for mapped corner SkPoint |
rect |
SkRect to map |
void mapRectScaleTranslate(SkRect* dst, const SkRect& src)const
Sets dst to bounds of src corners mapped by SkMatrix. If matrix contains elements other than scale or translate: asserts if SK_DEBUG is defined; otherwise, results are undefined.
dst |
storage for bounds of mapped SkPoint |
src |
SkRect to map |
mapRect mapRectToQuad isScaleTranslate rectStaysRect
SkScalar mapRadius(SkScalar radius)const
Returns geometric mean radius of ellipse formed by constructing circle of size radius, and mapping constructed circle with SkMatrix. The result squared is equal to the major axis length times the minor axis length. Result is not meaningful if SkMatrix contains perspective elements.
radius |
circle size to map |
average mapped radius
bool isFixedStepInX()const
Returns true if a unit step on x-axis at some y-axis value mapped through SkMatrix can be represented by a constant vector. Returns true if getType() returns kIdentity_Mask, or combinations of: kTranslate_Mask, kScale_Mask, and kAffine_Mask.
May return true if getType() returns kPerspective_Mask, but only when SkMatrix does not include rotation or skewing along the y-axis.
true if SkMatrix does not have complex perspective
SkVector fixedStepInX(SkScalar y)const
Returns vector representing a unit step on x-axis at y mapped through SkMatrix. If isFixedStepInX() is false, returned value is undefined.
y |
position of line parallel to x-axis |
vector advance of mapped unit step on x-axis
bool cheapEqualTo(const SkMatrix& m)const
Returns true if SkMatrix equals m, using an efficient comparison.
Returns false when the sign of zero values is the different; when one matrix has positive zero value and the other has negative zero value.
Returns true even when both SkMatrix contain NaN.
NaN never equals any value, including itself. To improve performance, NaN values are treated as bit patterns that are equal if their bit patterns are equal.
m |
SkMatrix to compare |
true if m and SkMatrix are represented by identical bit patterns
operator==(const SkMatrix& a, const SkMatrix& b)
bool operator==(const SkMatrix& a, const SkMatrix& b)
Compares a and b; returns true if a and b are numerically equal. Returns true even if sign of zero values are different. Returns false if either SkMatrix contains NaN, even if the other SkMatrix also contains NaN.
a |
SkMatrix to compare |
b |
SkMatrix to compare |
true if SkMatrix a and SkMatrix b are numerically equal
cheapEqualTo operator!=(const SkMatrix& a, const SkMatrix& b)
bool operator!=(const SkMatrix& a, const SkMatrix& b)
Compares a and b; returns true if a and b are not numerically equal. Returns false even if sign of zero values are different. Returns true if either SkMatrix contains NaN, even if the other SkMatrix also contains NaN.
a |
SkMatrix to compare |
b |
SkMatrix to compare |
true if SkMatrix a and SkMatrix b are numerically not equal
cheapEqualTo operator==(const SkMatrix& a, const SkMatrix& b)
void dump()const
Writes text representation of SkMatrix to standard output. Floating point values are written with limited precision; it may not be possible to reconstruct original SkMatrix from output.
SkScalar getMinScale()const
Returns the minimum scaling factor of SkMatrix by decomposing the scaling and skewing elements. Returns -1 if scale factor overflows or SkMatrix contains perspective.
minimum scale factor
SkScalar getMaxScale()const
Returns the maximum scaling factor of SkMatrix by decomposing the scaling and skewing elements. Returns -1 if scale factor overflows or SkMatrix contains perspective.
maximum scale factor
bool getMinMaxScales(SkScalar scaleFactors[2])const
Sets scaleFactors[0] to the minimum scaling factor, and scaleFactors[1] to the maximum scaling factor. Scaling factors are computed by decomposing the SkMatrix scaling and skewing elements.
Returns true if scaleFactors are found; otherwise, returns false and sets scaleFactors to undefined values.
scaleFactors |
storage for minimum and maximum scale factors |
true if scale factors were computed correctly
bool decomposeScale(SkSize* scale, SkMatrix* remaining = nullptr)const
Decomposes Matrix into scale components and whatever remains. Returns false if Matrix could not be decomposed.
Sets scale to portion of Matrix that scale axes. Sets remaining to Matrix with scaling factored out. remaining may be passed as nullptr to determine if Matrix can be decomposed without computing remainder.
Returns true if scale components are found. scale and remaining are unchanged if Matrix contains perspective; scale factors are not finite, or are nearly zero.
On success: Matrix = scale * Remaining
.
scale |
axes scaling factors; may be nullptr |
remaining |
Matrix without scaling; may be nullptr |
true if scale can be computed
static const SkMatrix& I()
Returns reference to const identity SkMatrix. Returned SkMatrix is set to:
| 1 0 0 | | 0 1 0 | | 0 0 1 |
const identity SkMatrix
static const SkMatrix& InvalidMatrix()
Returns reference to a const SkMatrix with invalid values. Returned SkMatrix is set to:
| SK_ScalarMax SK_ScalarMax SK_ScalarMax | | SK_ScalarMax SK_ScalarMax SK_ScalarMax | | SK_ScalarMax SK_ScalarMax SK_ScalarMax |
const invalid SkMatrix
static SkMatrix Concat(const SkMatrix& a, const SkMatrix& b)
Returns SkMatrix a multiplied by SkMatrix b.
Given:
| A B C | | J K L | a = | D E F |, b = | M N O | | G H I | | P Q R |
sets SkMatrix to:
| A B C | | J K L | | AJ+BM+CP AK+BN+CQ AL+BO+CR | a * b = | D E F | * | M N O | = | DJ+EM+FP DK+EN+FQ DL+EO+FR | | G H I | | P Q R | | GJ+HM+IP GK+HN+IQ GL+HO+IR |
a |
SkMatrix on left side of multiply expression |
b |
SkMatrix on right side of multiply expression |
SkMatrix computed from a times b
void dirtyMatrixTypeCache()
Sets internal cache to unknown state. Use to force update after repeated modifications to SkMatrix element reference returned by operator[](int index).
operator[](int index) getType
void setScaleTranslate(SkScalar sx, SkScalar sy, SkScalar tx, SkScalar ty)
Initializes SkMatrix with scale and translate elements.
| sx 0 tx | | 0 sy ty | | 0 0 1 |
sx |
horizontal scale factor to store |
sy |
vertical scale factor to store |
tx |
horizontal translation to store |
ty |
vertical translation to store |
setScale preTranslate postTranslate
bool isFinite()const
Returns true if all elements of the matrix are finite. Returns false if any element is infinity, or NaN.
true if matrix has only finite elements
operator==