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.
Sets SkMatrix to scale by (sx, sy). Returned matrix is:
| sx 0 0 | | 0 sy 0 | | 0 0 1 |
SkMatrix with scale
setScale postScale preScale
Sets SkMatrix to scale by (scale, scale). Returned matrix is:
| scale 0 0 | | 0 scale 0 | | 0 0 1 |
SkMatrix with scale
setScale postScale preScale
Sets SkMatrix to translate by (dx, dy). Returned matrix is:
| 1 0 dx | | 0 1 dy | | 0 0 1 |
SkMatrix with translation
setTranslate postTranslate preTranslate
Sets SkMatrix to:
| scaleX skewX transX | | skewY scaleY transY | | pers0 pers1 pers2 |
SkMatrix constructed from parameters
setAll set9 postConcat preConcat
Enumeration of bit fields for mask returned by getType. Used to identify the complexity of Matrix, to optimize performance.
after reset: kIdentity_Mask after postTranslate: kTranslate_Mask after postScale: kTranslate_Mask kScale_Mask after postScale: kTranslate_Mask kScale_Mask kAffine_Mask after setPolyToPoly: kTranslate_Mask kScale_Mask kAffine_Mask kPerspective_Mask
getType
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
identity flags hex: 0 decimal: 0 set all flags hex: f decimal: 15
TypeMask
Returns true if SkMatrix is identity. Identity matrix is:
| 1 0 0 | | 0 1 0 | | 0 0 1 |
true if SkMatrix has no effect
is identity: true is identity: false
reset() setIdentity getType
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
is scale-translate: true is scale-translate: true is scale-translate: true is scale-translate: true
setScale isTranslate setTranslate getType
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
is translate: true is translate: true is translate: false is translate: false
setTranslate getType
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
rectStaysRect: true rectStaysRect: true rectStaysRect: true rectStaysRect: true
preservesAxisAlignment preservesRightAngles
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
preservesAxisAlignment: true preservesAxisAlignment: true preservesAxisAlignment: true preservesAxisAlignment: true
rectStaysRect preservesRightAngles
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
setAll set9 MakeAll
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.
true if SkMatrix only rotates, uniformly scales, translates
isScaleTranslate preservesRightAngles rectStaysRect isFixedStepInX
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.
true if SkMatrix only rotates, scales, translates
isScaleTranslate isSimilarity rectStaysRect isFixedStepInX
Matrix organizes its values in row order. These members correspond to each value in Matrix.
get() set()
Affine arrays are in column major order to match the matrix used by PDF and XPS.
SetAffineIdentity asAffine setAffine
matrix[SkMatrix::kMScaleX] == 42 matrix[SkMatrix::kMScaleY] == 24
get set
Returns one matrix value. Asserts if index is out of range and SK_DEBUG is defined.
kMPersp0, kMPersp1, kMPersp2
value corresponding to index
matrix.get(SkMatrix::kMSkewX) == 42 matrix.get(SkMatrix::kMSkewY) == 24
operator[](int index) set
Returns scale factor multiplied by x-axis input, contributing to x-axis output. With mapPoints(), scales SkPoint along the x-axis.
horizontal scale factor
matrix.getScaleX() == 42
get getScaleY setScaleX setScale
Returns scale factor multiplied by y-axis input, contributing to y-axis output. With mapPoints(), scales SkPoint along the y-axis.
vertical scale factor
matrix.getScaleY() == 24
get getScaleX setScaleY setScale
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
matrix.getSkewY() == 24
get getSkewX setSkewY setSkew
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
matrix.getSkewX() == 42
get getSkewY setSkewX setSkew
Returns translation contributing to x-axis output. With mapPoints(), moves SkPoint along the x-axis.
horizontal translation factor
matrix.getTranslateX() == 42
get getTranslateY setTranslateX setTranslate
Returns translation contributing to y-axis output. With mapPoints(), moves SkPoint along the y-axis.
vertical translation factor
matrix.getTranslateY() == 24
get getTranslateX setTranslateY setTranslate
Returns factor scaling input x-axis relative to input y-axis.
input x-axis perspective factor
kMPersp0 getPerspY
Returns factor scaling input y-axis relative to input x-axis.
input y-axis perspective factor
kMPersp1 getPerspX
with identity matrix: x = 24 after skew x mod: x = 24 after 2nd skew x mod: x = 24 after dirty cache: x = 66
get dirtyMatrixTypeCache set
Sets SkMatrix value. Asserts if index is out of range and SK_DEBUG is defined. Safer than operator[]; internal cache is always maintained.
kMPersp0, kMPersp1, kMPersp2
with identity matrix: x = 24 after skew x mod: x = 24 after 2nd skew x mod: x = 66
operator[] get
Sets horizontal scale factor.
set setScale setScaleY
Sets vertical scale factor.
set setScale setScaleX
Sets vertical skew factor.
set setSkew setSkewX
Sets horizontal skew factor.
set setSkew setSkewX
Sets horizontal translation.
set setTranslate setTranslateY
Sets vertical translation.
set setTranslate setTranslateX
Sets input x-axis perspective factor, which causes mapXY() to vary input x-axis values inversely proportional to input y-axis values.
getPerspX set setAll set9 MakeAll
Sets input y-axis perspective factor, which causes mapXY() to vary input y-axis values inversely proportional to input x-axis values.
getPerspY set setAll set9 MakeAll
Sets all values from parameters. Sets matrix to:
| scaleX skewX transX | | skewY scaleY transY | | persp0 persp1 persp2 |
set9 MakeAll
Copies nine scalar values contained by SkMatrix into buffer, in member value ascending order: kMScaleX, kMSkewX, kMTransX, kMSkewY, kMScaleY, kMTransY, kMPersp0, kMPersp1, kMPersp2.
{4, 0, 3},
{0, 5, 4},
{0, 0, 1}
set9
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.
setAll get9 MakeAll
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.
m.isIdentity(): true
isIdentity 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.
m.isIdentity(): true
isIdentity reset
Sets SkMatrix to translate by (dx, dy).
setTranslateX setTranslateY
Sets SkMatrix to translate by (v.fX, v.fY).
setTranslateX setTranslateY MakeTrans
Sets SkMatrix to scale by sx and sy, about a pivot point at (px, py). The pivot point is unchanged when mapped with SkMatrix.
setScaleX setScaleY MakeScale preScale postScale
Sets SkMatrix to scale by sx and sy about at pivot point at (0, 0).
setScaleX setScaleY MakeScale preScale postScale
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.
setSinCos preRotate postRotate
Sets SkMatrix to rotate by degrees about a pivot point at (0, 0). Positive degrees rotates clockwise.
setSinCos preRotate postRotate
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.
setRotate setScale setRSXform
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.
setRotate setScale setRSXform
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).
reference to SkMatrix
setSinCos setScale setTranslate
Sets SkMatrix to skew by kx and ky, about a pivot point at (px, py). The pivot point is unchanged when mapped with SkMatrix.
setSkewX setSkewY preSkew postSkew
Sets SkMatrix to skew by kx and ky, about a pivot point at (0, 0).
setSkewX setSkewY preSkew postSkew
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 |
Concat preConcat postConcat SkCanvas::concat
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 A*dx+B*dy+C | Matrix * T(dx, dy) = | D E F | | 0 1 dy | = | D E D*dx+E*dy+F | | G H I | | 0 0 1 | | G H G*dx+H*dy+I |
postTranslate setTranslate MakeTrans
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 | | A*sx B*sy Adx+Bdy+C | Matrix * S(sx, sy, px, py) = | D E F | | 0 sy dy | = | D*sx E*sy Ddx+Edy+F | | G H I | | 0 0 1 | | G*sx H*sy Gdx+Hdy+I |
postScale setScale MakeScale
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 | | A*sx B*sy C | Matrix * S(sx, sy) = | D E F | | 0 sy 0 | = | D*sx E*sy F | | G H I | | 0 0 1 | | G*sx H*sy I |
postScale setScale MakeScale
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 Adx+Bdy+C | Matrix * R(degrees, px, py) = | D E F | | s c dy | = | Dc+Es -Ds+Ec Ddx+Edy+F | | G H I | | 0 0 1 | | Gc+Hs -Gs+Hc Gdx+Hdy+I |
postRotate setRotate
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 |
postRotate setRotate
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
dx = -kx * py dy = -ky * px
sets SkMatrix to:
| A B C | | 1 kx dx | | A+B*ky A*kx+B Adx+Bdy+C | Matrix * K(kx, ky, px, py) = | D E F | | ky 1 dy | = | D+E*ky D*kx+E Ddx+Edy+F | | G H I | | 0 0 1 | | G+H*ky G*kx+H Gdx+Hdy+I |
postSkew setSkew
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+B*ky A*kx+B C | Matrix * K(kx, ky) = | D E F | | ky 1 0 | = | D+E*ky D*kx+E F | | G H I | | 0 0 1 | | G+H*ky G*kx+H I |
postSkew setSkew
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 |
postConcat setConcat Concat
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 |
preTranslate setTranslate MakeTrans
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 | | sxJ+dxP sxK+dxQ sx*L+dx+R | S(sx, sy, px, py) * Matrix = | 0 sy dy | | M N O | = | syM+dyP syN+dyQ syO+dyR | | 0 0 1 | | P Q R | | P Q R |
preScale setScale MakeScale
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 |
preScale setScale MakeScale
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:
where
sets Matrix to:
true on successful scale
postScale MakeScale
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+dxP cK-sN+dxQ cL-sO+dx+R| R(degrees, px, py) * Matrix = |s c dy| |M N O| = |sJ+cM+dyP sK+cN+dyQ sL+cO+dy*R| |0 0 1| |P Q R| | P Q R|
preRotate setRotate
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 |
preRotate setRotate
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
dx = -kx * py dy = -ky * px
sets SkMatrix to:
| 1 kx dx| |J K L| |J+kxM+dxP K+kxN+dxQ L+kx*O+dx+R| K(kx, ky, px, py) * Matrix = |ky 1 dy| |M N O| = |kyJ+M+dyP kyK+N+dyQ kyL+O+dyR| | 0 0 1| |P Q R| | P Q R|
preSkew setSkew
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 |
preSkew setSkew
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 |
preConcat setConcat Concat
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.
setRectToRect MakeRectToRect setPolyToPoly
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 |
kCenter_ScaleToFit, kEnd_ScaleToFit
true if SkMatrix can represent SkRect mapping
src: 0, 0, 0, 0 dst: 0, 0, 0, 0 success: false [ 1.0000 0.0000 0.0000][ 0.0000 1.0000 0.0000][ 0.0000 0.0000 1.0000] src: 0, 0, 0, 0 dst: 5, 6, 8, 9 success: false [ 1.0000 0.0000 0.0000][ 0.0000 1.0000 0.0000][ 0.0000 0.0000 1.0000] src: 1, 2, 3, 4 dst: 0, 0, 0, 0 success: true [ 0.0000 0.0000 0.0000][ 0.0000 0.0000 0.0000][ 0.0000 0.0000 1.0000] src: 1, 2, 3, 4 dst: 5, 6, 8, 9 success: true [ 1.5000 0.0000 3.5000][ 0.0000 1.5000 3.0000][ 0.0000 0.0000 1.0000]
MakeRectToRect ScaleToFit setPolyToPoly SkRect::isEmpty
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 |
kCenter_ScaleToFit, kEnd_ScaleToFit
SkMatrix mapping src to dst
src: 0, 0, 0, 0 dst: 0, 0, 0, 0 [ 1.0000 0.0000 0.0000][ 0.0000 1.0000 0.0000][ 0.0000 0.0000 1.0000] src: 0, 0, 0, 0 dst: 5, 6, 8, 9 [ 1.0000 0.0000 0.0000][ 0.0000 1.0000 0.0000][ 0.0000 0.0000 1.0000] src: 1, 2, 3, 4 dst: 0, 0, 0, 0 [ 0.0000 0.0000 0.0000][ 0.0000 0.0000 0.0000][ 0.0000 0.0000 1.0000] src: 1, 2, 3, 4 dst: 5, 6, 8, 9 [ 1.5000 0.0000 3.5000][ 0.0000 1.5000 3.0000][ 0.0000 0.0000 1.0000]
setRectToRect ScaleToFit setPolyToPoly SkRect::isEmpty
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.
true if SkMatrix was constructed successfully
setRectToRect MakeRectToRect
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.
true if SkMatrix can be inverted
Concat
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.
ScaleX: 1 SkewY: 0 SkewX: 0 ScaleY: 1 TransX: 0 TransY: 0
setAffine asAffine
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.
true if SkMatrix does not contain perspective
ScaleX: 2 SkewY: 5 SkewX: 3 ScaleY: 6 TransX: 4 TransY: 7
setAffine SetAffineIdentity
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 |
ScaleX: 2 SkewY: 5 SkewX: 3 ScaleY: 6 TransX: 4 TransY: 7 [ 2.0000 3.0000 4.0000][ 5.0000 6.0000 7.0000][ 0.0000 0.0000 1.0000]
asAffine SetAffineIdentity
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.
mapXY mapHomogeneousPoints mapVectors
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
mapXY mapHomogeneousPoints mapVectors
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|
mapPoints mapXY mapVectors
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
mapPoints mapVectors
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
mapped SkPoint
mapPoints mapVectors
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.
mapVector mapPoints mapXY
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
mapVector mapPoints mapXY
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| A*dx+B*dy D*dx+E*dy Matrix * vec = |D E 0| |dy| = |A*dx+B*dy D*dx+E*dy G*dx+H*dy+I| = ----------- , ----------- |G H I| | 1| G*dx+H*dy+I G*dx+*dHy+I
mapVectors mapPoints mapXY
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| A*dx+B*dy D*dx+E*dy Matrix * vec = |D E 0| |dy| = |A*dx+B*dy D*dx+E*dy G*dx+H*dy+I| = ----------- , ----------- |G H I| | 1| G*dx+H*dy+I G*dx+*dHy+I
mapped vector
mapVectors mapPoints mapXY
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().
true if dst is equivalent to mapped src
mapPoints rectStaysRect
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().
true if result is equivalent to mapped rect
mapRectScaleTranslate mapPoints rectStaysRect
Returns bounds of src corners mapped by SkMatrix.
mapped bounds
mapRectToQuad mapRectScaleTranslate
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
mapRect mapRectScaleTranslate
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.
mapRect mapRectToQuad isScaleTranslate rectStaysRect
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.
average mapped radius
mapVector
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
[ 1.0000 0.0000 0.0000][ 0.0000 1.0000 0.0000][ 0.0000 0.0000 1.0000] isFixedStepInX: true [ 1.0000 0.0000 0.0000][ 0.0000 2.0000 0.0000][ 0.0000 0.0000 1.0000] isFixedStepInX: true [ 1.0000 0.0000 0.0000][ 0.0000 1.0000 0.0000][ 0.0000 0.1000 1.0000] isFixedStepInX: true [ 1.0000 0.0000 0.0000][ 0.0000 2.0000 0.0000][ 0.0000 0.1000 1.0000] isFixedStepInX: true [ 1.0000 0.0000 0.0000][ 0.0000 1.0000 0.0000][ 0.1000 0.0000 1.0000] isFixedStepInX: false [ 1.0000 0.0000 0.0000][ 0.0000 2.0000 0.0000][ 0.1000 0.0000 1.0000] isFixedStepInX: false [ 1.0000 0.0000 0.0000][ 0.0000 1.0000 0.0000][ 0.1000 0.1000 1.0000] isFixedStepInX: false [ 1.0000 0.0000 0.0000][ 0.0000 2.0000 0.0000][ 0.1000 0.1000 1.0000] isFixedStepInX: false
fixedStepInX getType
Returns vector representing a unit step on x-axis at y mapped through SkMatrix. If isFixedStepInX() is false, returned value is undefined.
vector advance of mapped unit step on x-axis
isFixedStepInX getType
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.
true if m and SkMatrix are represented by identical bit patterns
identity: a == b a.cheapEqualTo(b): true neg zero: a == b a.cheapEqualTo(b): false one NaN: a != b a.cheapEqualTo(b): false both NaN: a != b a.cheapEqualTo(b): true
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.
true if SkMatrix a and SkMatrix b are numerically equal
identity: a == b a.cheapEqualTo(b): true
cheapEqualTo 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.
true if SkMatrix a and SkMatrix b are numerically not equal
cheapEqualTo operator==(const SkMatrix& a, const SkMatrix& b)
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.
[ 0.7071 -0.7071 0.0000][ 0.7071 0.7071 0.0000][ 0.0000 0.0000 1.0000] [ 0.7071 -0.7071 0.0000][ 0.7071 0.7071 0.0000][ 0.0000 0.0000 1.0000] matrix != nearlyEqual
SkPath::dump
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
matrix.getMinScale() 24
getMaxScale getMinMaxScales
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
matrix.getMaxScale() 42
getMinScale getMinMaxScales
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.
true if scale factors were computed correctly
matrix.getMinMaxScales() false 2 2
getMinScale getMaxScale
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.
true if scale can be computed
[ 0.0000 -0.2500 0.0000][ 0.5000 0.0000 0.0000][ 0.0000 0.0000 1.0000] success: true scale: 0.5, 0.25 [ 0.0000 -0.5000 0.0000][ 2.0000 0.0000 0.0000][ 0.0000 0.0000 1.0000] [ 0.0000 -0.2500 0.0000][ 0.5000 0.0000 0.0000][ 0.0000 0.0000 1.0000]
setScale MakeScale
Returns reference to const identity SkMatrix. Returned SkMatrix is set to:
| 1 0 0 | | 0 1 0 | | 0 0 1 |
const identity SkMatrix
m1 == m2 m2 == m3
reset() setIdentity
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
scaleX 3.40282e+38
getType
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 |
SkMatrix computed from a times b
preConcat postConcat
Sets internal cache to unknown state. Use to force update after repeated modifications to SkMatrix element reference returned by operator[](int index).
with identity matrix: x = 24 after skew x mod: x = 24 after 2nd skew x mod: x = 24 after dirty cache: x = 66
operator[](int index) getType
Initializes SkMatrix with scale and translate elements.
| sx 0 tx | | 0 sy ty | | 0 0 1 |
[ 1.0000 0.0000 3.0000][ 0.0000 2.0000 4.0000][ 0.0000 0.0000 1.0000]
setScale preTranslate postTranslate
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
[ 1.0000 0.0000 nan][ 0.0000 1.0000 0.0000][ 0.0000 0.0000 1.0000] matrix is finite: false matrix != matrix
operator==