mirror of
https://github.com/hajimehoshi/ebiten.git
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113 lines
2.5 KiB
Go
113 lines
2.5 KiB
Go
package graphics
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type AffineMatrixElement float64
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type AffineMatrix struct {
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elements []AffineMatrixElement
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dimension int
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}
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func NewAffineMatrix(dimension int) *AffineMatrix {
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if dimension < 0 {
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panic("invalid dimension")
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}
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matrix := &AffineMatrix{}
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elementsNumber := dimension * (dimension - 1)
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matrix.elements = make([]AffineMatrixElement, elementsNumber)
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matrix.dimension = dimension
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return matrix
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}
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func IdentityAffineMatrix(dimension int) *AffineMatrix {
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if dimension < 0 {
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panic("invalid dimension")
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}
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matrix := NewAffineMatrix(dimension)
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for i := 0; i < dimension-1; i++ {
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for j := 0; j < dimension; j++ {
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if i == j {
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matrix.elements[i*dimension+j] = 1
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} else {
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matrix.elements[i*dimension+j] = 0
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}
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}
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}
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return matrix
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}
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func (matrix *AffineMatrix) Clone() *AffineMatrix {
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result := NewAffineMatrix(matrix.dimension)
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copy(result.elements, matrix.elements)
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return result
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}
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func (matrix *AffineMatrix) Element(i, j int) AffineMatrixElement {
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dimension := matrix.dimension
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if i < 0 || dimension <= i {
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panic("out of range index i")
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}
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if j < 0 || dimension <= j {
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panic("out of range index j")
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}
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if i == dimension-1 {
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if j == dimension-1 {
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return 1
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}
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return 0
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}
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return matrix.elements[i*dimension+j]
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}
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func (matrix *AffineMatrix) SetElement(i, j int, element AffineMatrixElement) {
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dimension := matrix.dimension
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if i < 0 || dimension-1 <= i {
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panic("out of range index i")
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}
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if j < 0 || dimension <= j {
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panic("out of range index j")
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}
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matrix.elements[i*dimension+j] = element
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}
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func (matrix *AffineMatrix) IsIdentity() bool {
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dimension := matrix.dimension
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for i := 0; i < dimension-1; i++ {
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for j := 0; j < dimension; j++ {
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element := matrix.elements[i*dimension+j]
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if i == j && element != 1 {
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return false
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} else if i != j && element != 0 {
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return false
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}
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}
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}
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return true
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}
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/*
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* TODO: The arguments' names are strange even though they are not wrong.
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*/
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func (rhs *AffineMatrix) Concat(lhs *AffineMatrix) *AffineMatrix {
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dimension := lhs.dimension
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if dimension != rhs.dimension {
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panic("diffrent-sized matrices can't be concatenated")
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}
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result := NewAffineMatrix(dimension)
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for i := 0; i < dimension-1; i++ {
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for j := 0; j < dimension; j++ {
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var element AffineMatrixElement = 0.0
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for k := 0; k < dimension-1; k++ {
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element += lhs.elements[i*dimension+k] *
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rhs.elements[k*dimension+j]
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}
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if j == dimension-1 {
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element += lhs.elements[i*dimension+dimension-1]
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}
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result.elements[i*dimension+j] = element
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}
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}
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return result
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}
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