ebiten/internal/affine/affine.go

// 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 (
	"github.com/hajimehoshi/ebiten/internal/endian"
)

var identityValues = map[int]string{
	ColorMDim: colorMValueString([ColorMDim - 1][ColorMDim]float64{
		{1, 0, 0, 0, 0},
		{0, 1, 0, 0, 0},
		{0, 0, 1, 0, 0},
		{0, 0, 0, 1, 0},
	}),
	GeoMDim: geoMValueString([GeoMDim - 1][GeoMDim]float64{
		{1, 0, 0},
		{0, 1, 0},
	}),
}

func uint64ToBytes(value uint64) []uint8 {
	result := make([]uint8, 8)
	if endian.IsLittle() {
		for i := 0; i < 8; i++ {
			result[i] = uint8(value)
			value >>= 8
		}
	} else {
		for i := 7; 0 <= i; i-- {
			result[i] = uint8(value)
			value >>= 8
		}
	}
	return result
}

type affine interface {
	dim() int
	element(i, j int) float64
	SetElement(i, j int, element float64)
}

// add is deprecated
func add(lhs, rhs, result affine) {
	dim := lhs.dim()
	if dim != rhs.dim() {
		panic("ebiten: different-sized matrices can't be multiplied")
	}

	for i := 0; i < dim-1; i++ {
		for j := 0; j < dim; j++ {
			v := lhs.element(i, j) + rhs.element(i, j)
			result.SetElement(i, j, v)
		}
	}
}

func mul(lhs, rhs, result affine) {
	dim := lhs.dim()
	if dim != rhs.dim() {
		panic("ebiten: different-sized matrices can't be multiplied")
	}

	for i := 0; i < dim-1; i++ {
		for j := 0; j < dim; j++ {
			element := float64(0)
			for k := 0; k < dim-1; k++ {
				element += lhs.element(i, k) *
					rhs.element(k, j)
			}
			if j == dim-1 {
				element += lhs.element(i, j)
			}
			result.SetElement(i, j, element)
		}
	}
}