ebiten/internal/affine/geom.go

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// Copyright 2014 Hajime Hoshi
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package affine
import (
"math"
)
// GeoMDim is a dimension of a GeoM.
const GeoMDim = 3
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var (
geoMIdentityElements = []float64{
1, 0, 0,
0, 1, 0,
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}
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)
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// A GeoM represents a matrix to transform geometry when rendering an image.
//
// The initial value is identity.
type GeoM struct {
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// When elements is empty, this matrix is identity.
// elements is immutable and a new array must be created when updating.
elements []float64
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}
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func (g *GeoM) UnsafeElements() []float64 {
if g.elements == nil {
g.elements = geoMIdentityElements
}
return g.elements
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}
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// SetElement sets an element at (i, j).
func (g *GeoM) SetElement(i, j int, element float64) {
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if g.elements == nil {
g.elements = geoMIdentityElements
}
es := make([]float64, len(g.elements))
copy(es, g.elements)
es[i*GeoMDim+j] = element
g.elements = es
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}
// Concat multiplies a geometry matrix with the other geometry matrix.
// This is same as muptiplying the matrix other and the matrix g in this order.
func (g *GeoM) Concat(other GeoM) {
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if g.elements == nil {
g.elements = geoMIdentityElements
}
if other.elements == nil {
other.elements = geoMIdentityElements
}
g.elements = mul(other.elements, g.elements, GeoMDim)
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}
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// Add is deprecated.
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func (g *GeoM) Add(other GeoM) {
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if g.elements == nil {
g.elements = geoMIdentityElements
}
if other.elements == nil {
other.elements = geoMIdentityElements
}
g.elements = add(other.elements, g.elements, GeoMDim)
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}
// Scale scales the matrix by (x, y).
func (g *GeoM) Scale(x, y float64) {
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if g.elements == nil {
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g.elements = []float64{
x, 0, 0,
0, y, 0,
}
return
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}
es := make([]float64, len(g.elements))
copy(es, g.elements)
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for i := 0; i < GeoMDim; i++ {
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es[i] *= x
es[i+GeoMDim] *= y
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}
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g.elements = es
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}
// Translate translates the matrix by (x, y).
func (g *GeoM) Translate(tx, ty float64) {
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if g.elements == nil {
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g.elements = []float64{
1, 0, tx,
0, 1, ty,
}
return
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}
es := make([]float64, len(g.elements))
copy(es, g.elements)
es[2] += tx
es[2+GeoMDim] += ty
g.elements = es
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}
// Rotate rotates the matrix by theta.
func (g *GeoM) Rotate(theta float64) {
sin, cos := math.Sincos(theta)
g.Concat(GeoM{
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elements: []float64{
cos, -sin, 0,
sin, cos, 0,
},
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})
}
// ScaleGeo is deprecated as of 1.2.0-alpha. Use Scale instead.
func ScaleGeo(x, y float64) GeoM {
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g := GeoM{}
g.Scale(x, y)
return g
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}
// TranslateGeo is deprecated as of 1.2.0-alpha. Use Translate instead.
func TranslateGeo(tx, ty float64) GeoM {
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g := GeoM{}
g.Translate(tx, ty)
return g
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}
// RotateGeo is deprecated as of 1.2.0-alpha. Use Rotate instead.
func RotateGeo(theta float64) GeoM {
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g := GeoM{}
g.Rotate(theta)
return g
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}