backend/internal/service/skin_renderer/renderer.go

package skin_renderer

import (
	"bytes"
	"image"
	"image/color"
	"image/png"
	"math"
)

// SkinRenderer 皮肤渲染器
type SkinRenderer struct {
	playerSkin    image.Image
	isNewSkinType bool
	isAlex        bool
	hdRatio       int

	// 旋转参数
	ratio    float64
	headOnly bool
	hR       float64 // 水平旋转角度
	vR       float64 // 垂直旋转角度
	hrh      float64 // 头部水平旋转
	vrll     float64 // 左腿垂直旋转
	vrrl     float64 // 右腿垂直旋转
	vrla     float64 // 左臂垂直旋转
	vrra     float64 // 右臂垂直旋转
	layers   bool    // 是否渲染第二层

	// 计算后的三角函数值
	cosAlpha, sinAlpha float64
	cosOmega, sinOmega float64

	// 边界
	minX, maxX, minY, maxY float64

	// 各部件的旋转角度
	membersAngles map[string]angleSet

	// 可见面
	visibleFaces map[string]faceVisibility
	frontFaces   []string
	backFaces    []string

	// 多边形
	polygons map[string]map[string][]*Polygon
}

type angleSet struct {
	cosAlpha, sinAlpha float64
	cosOmega, sinOmega float64
}

type faceVisibility struct {
	front []string
	back  []string
}

var allFaces = []string{"back", "right", "top", "front", "left", "bottom"}

// NewSkinRenderer 创建皮肤渲染器
func NewSkinRenderer(ratio float64, headOnly bool, horizontalRotation, verticalRotation float64) *SkinRenderer {
	return &SkinRenderer{
		ratio:    ratio,
		headOnly: headOnly,
		hR:       horizontalRotation,
		vR:       verticalRotation,
		hrh:      0,
		vrll:     0,
		vrrl:     0,
		vrla:     0,
		vrra:     0,
		layers:   true,
	}
}

// NewSkinRendererFull 创建带完整参数的皮肤渲染器
func NewSkinRendererFull(ratio float64, headOnly bool, hR, vR, hrh, vrll, vrrl, vrla, vrra float64, layers bool) *SkinRenderer {
	return &SkinRenderer{
		ratio:    ratio,
		headOnly: headOnly,
		hR:       hR,
		vR:       vR,
		hrh:      hrh,
		vrll:     vrll,
		vrrl:     vrrl,
		vrla:     vrla,
		vrra:     vrra,
		layers:   layers,
	}
}

// Render 渲染皮肤
func (r *SkinRenderer) Render(skinData []byte, isAlex bool) (image.Image, error) {
	// 解码皮肤图像
	img, err := png.Decode(bytes.NewReader(skinData))
	if err != nil {
		return nil, err
	}

	r.playerSkin = img
	r.isAlex = isAlex

	// 计算 HD 比例
	sourceWidth := img.Bounds().Dx()
	sourceHeight := img.Bounds().Dy()

	// 防止内存溢出，限制最大尺寸
	if sourceWidth > 256 {
		r.playerSkin = resizeImage(img, 256, sourceHeight*256/sourceWidth)
	}

	r.hdRatio = r.playerSkin.Bounds().Dx() / 64

	// 检查是否为新版皮肤格式（64x64）
	if r.playerSkin.Bounds().Dx() == r.playerSkin.Bounds().Dy() {
		r.isNewSkinType = true
	}

	// 转换为 RGBA
	r.playerSkin = convertToRGBA(r.playerSkin)

	// 处理背景透明
	r.makeBackgroundTransparent()

	// 计算角度
	r.calculateAngles()

	// 确定可见面
	r.facesDetermination()

	// 生成多边形
	r.generatePolygons()

	// 部件旋转
	r.memberRotation()

	// 创建投影
	r.createProjectionPlan()

	// 渲染图像
	return r.displayImage(), nil
}

// makeBackgroundTransparent 处理背景透明
func (r *SkinRenderer) makeBackgroundTransparent() {
	rgba, ok := r.playerSkin.(*image.RGBA)
	if !ok {
		return
	}

	// 检查左上角 8x8 区域是否为纯色
	var tempColor color.RGBA
	needRemove := true
	first := true

	for y := 0; y < 8; y++ {
		for x := 0; x < 8; x++ {
			c := rgba.RGBAAt(x, y)

			// 如果已有透明度，不需要处理
			if c.A < 128 {
				needRemove = false
				break
			}

			if first {
				tempColor = c
				first = false
			} else if c != tempColor {
				needRemove = false
				break
			}
		}
		if !needRemove {
			break
		}
	}

	if !needRemove {
		return
	}

	// 将该颜色设为透明
	bounds := rgba.Bounds()
	for y := bounds.Min.Y; y < bounds.Max.Y; y++ {
		for x := bounds.Min.X; x < bounds.Max.X; x++ {
			c := rgba.RGBAAt(x, y)
			if c.R == tempColor.R && c.G == tempColor.G && c.B == tempColor.B {
				rgba.SetRGBA(x, y, color.RGBA{0, 0, 0, 0})
			}
		}
	}
}

// calculateAngles 计算旋转角度
func (r *SkinRenderer) calculateAngles() {
	// 转换为弧度
	alpha := r.vR * math.Pi / 180
	omega := r.hR * math.Pi / 180

	r.cosAlpha = math.Cos(alpha)
	r.sinAlpha = math.Sin(alpha)
	r.cosOmega = math.Cos(omega)
	r.sinOmega = math.Sin(omega)

	r.membersAngles = make(map[string]angleSet)

	// 躯干不旋转
	r.membersAngles["torso"] = angleSet{
		cosAlpha: 1, sinAlpha: 0,
		cosOmega: 1, sinOmega: 0,
	}

	// 头部旋转
	omegaHead := r.hrh * math.Pi / 180
	r.membersAngles["head"] = angleSet{
		cosAlpha: 1, sinAlpha: 0,
		cosOmega: math.Cos(omegaHead), sinOmega: math.Sin(omegaHead),
	}
	r.membersAngles["helmet"] = r.membersAngles["head"]

	// 右臂旋转
	alphaRightArm := r.vrra * math.Pi / 180
	r.membersAngles["rightArm"] = angleSet{
		cosAlpha: math.Cos(alphaRightArm), sinAlpha: math.Sin(alphaRightArm),
		cosOmega: 1, sinOmega: 0,
	}

	// 左臂旋转
	alphaLeftArm := r.vrla * math.Pi / 180
	r.membersAngles["leftArm"] = angleSet{
		cosAlpha: math.Cos(alphaLeftArm), sinAlpha: math.Sin(alphaLeftArm),
		cosOmega: 1, sinOmega: 0,
	}

	// 右腿旋转
	alphaRightLeg := r.vrrl * math.Pi / 180
	r.membersAngles["rightLeg"] = angleSet{
		cosAlpha: math.Cos(alphaRightLeg), sinAlpha: math.Sin(alphaRightLeg),
		cosOmega: 1, sinOmega: 0,
	}

	// 左腿旋转
	alphaLeftLeg := r.vrll * math.Pi / 180
	r.membersAngles["leftLeg"] = angleSet{
		cosAlpha: math.Cos(alphaLeftLeg), sinAlpha: math.Sin(alphaLeftLeg),
		cosOmega: 1, sinOmega: 0,
	}

	r.minX, r.maxX = 0, 0
	r.minY, r.maxY = 0, 0
}

// facesDetermination 确定可见面
func (r *SkinRenderer) facesDetermination() {
	r.visibleFaces = make(map[string]faceVisibility)

	parts := []string{"head", "torso", "rightArm", "leftArm", "rightLeg", "leftLeg"}

	for _, part := range parts {
		angles := r.membersAngles[part]

		// 创建测试立方体点
		cubePoints := r.createCubePoints()

		var maxDepthPoint *Point
		var maxDepthFaces []string

		for _, cp := range cubePoints {
			point := cp.point
			point.PreProject(0, 0, 0, angles.cosAlpha, angles.sinAlpha, angles.cosOmega, angles.sinOmega)
			point.Project(r.cosAlpha, r.sinAlpha, r.cosOmega, r.sinOmega, &r.minX, &r.maxX, &r.minY, &r.maxY)

			if maxDepthPoint == nil {
				maxDepthPoint = point
				maxDepthFaces = cp.faces
			} else {
				_, _, z1 := maxDepthPoint.GetDestCoord()
				_, _, z2 := point.GetDestCoord()
				if z1 > z2 {
					maxDepthPoint = point
					maxDepthFaces = cp.faces
				}
			}
		}

		r.visibleFaces[part] = faceVisibility{
			back:  maxDepthFaces,
			front: diffFaces(allFaces, maxDepthFaces),
		}
	}

	// 确定全局前后面
	cubePoints := r.createCubePoints()
	var maxDepthPoint *Point
	var maxDepthFaces []string

	for _, cp := range cubePoints {
		point := cp.point
		point.Project(r.cosAlpha, r.sinAlpha, r.cosOmega, r.sinOmega, &r.minX, &r.maxX, &r.minY, &r.maxY)

		if maxDepthPoint == nil {
			maxDepthPoint = point
			maxDepthFaces = cp.faces
		} else {
			_, _, z1 := maxDepthPoint.GetDestCoord()
			_, _, z2 := point.GetDestCoord()
			if z1 > z2 {
				maxDepthPoint = point
				maxDepthFaces = cp.faces
			}
		}
	}

	r.backFaces = maxDepthFaces
	r.frontFaces = diffFaces(allFaces, maxDepthFaces)
}

type cubePoint struct {
	point *Point
	faces []string
}

func (r *SkinRenderer) createCubePoints() []cubePoint {
	return []cubePoint{
		{NewPoint(0, 0, 0), []string{"back", "right", "top"}},
		{NewPoint(0, 0, 1), []string{"front", "right", "top"}},
		{NewPoint(0, 1, 0), []string{"back", "right", "bottom"}},
		{NewPoint(0, 1, 1), []string{"front", "right", "bottom"}},
		{NewPoint(1, 0, 0), []string{"back", "left", "top"}},
		{NewPoint(1, 0, 1), []string{"front", "left", "top"}},
		{NewPoint(1, 1, 0), []string{"back", "left", "bottom"}},
		{NewPoint(1, 1, 1), []string{"front", "left", "bottom"}},
	}
}

func diffFaces(all, exclude []string) []string {
	excludeMap := make(map[string]bool)
	for _, f := range exclude {
		excludeMap[f] = true
	}

	var result []string
	for _, f := range all {
		if !excludeMap[f] {
			result = append(result, f)
		}
	}
	return result
}

func contains(slice []string, item string) bool {
	for _, s := range slice {
		if s == item {
			return true
		}
	}
	return false
}

// memberRotation 部件旋转
func (r *SkinRenderer) memberRotation() {
	hd := float64(r.hdRatio)

	// 头部和头盔旋转
	angles := r.membersAngles["head"]
	for _, face := range r.polygons["head"] {
		for _, poly := range face {
			poly.PreProject(4*hd, 8*hd, 2*hd, angles.cosAlpha, angles.sinAlpha, angles.cosOmega, angles.sinOmega)
		}
	}
	for _, face := range r.polygons["helmet"] {
		for _, poly := range face {
			poly.PreProject(4*hd, 8*hd, 2*hd, angles.cosAlpha, angles.sinAlpha, angles.cosOmega, angles.sinOmega)
		}
	}

	if r.headOnly {
		return
	}

	// 右臂旋转
	angles = r.membersAngles["rightArm"]
	for _, face := range r.polygons["rightArm"] {
		for _, poly := range face {
			poly.PreProject(-2*hd, 8*hd, 2*hd, angles.cosAlpha, angles.sinAlpha, angles.cosOmega, angles.sinOmega)
		}
	}

	// 左臂旋转
	angles = r.membersAngles["leftArm"]
	for _, face := range r.polygons["leftArm"] {
		for _, poly := range face {
			poly.PreProject(10*hd, 8*hd, 2*hd, angles.cosAlpha, angles.sinAlpha, angles.cosOmega, angles.sinOmega)
		}
	}

	// 右腿旋转
	angles = r.membersAngles["rightLeg"]
	zOffset := 4 * hd
	if angles.sinAlpha < 0 {
		zOffset = 0
	}
	for _, face := range r.polygons["rightLeg"] {
		for _, poly := range face {
			poly.PreProject(2*hd, 20*hd, zOffset, angles.cosAlpha, angles.sinAlpha, angles.cosOmega, angles.sinOmega)
		}
	}

	// 左腿旋转
	angles = r.membersAngles["leftLeg"]
	zOffset = 4 * hd
	if angles.sinAlpha < 0 {
		zOffset = 0
	}
	for _, face := range r.polygons["leftLeg"] {
		for _, poly := range face {
			poly.PreProject(6*hd, 20*hd, zOffset, angles.cosAlpha, angles.sinAlpha, angles.cosOmega, angles.sinOmega)
		}
	}
}

// createProjectionPlan 创建投影
func (r *SkinRenderer) createProjectionPlan() {
	for _, piece := range r.polygons {
		for _, face := range piece {
			for _, poly := range face {
				if !poly.IsProjected() {
					poly.Project(r.cosAlpha, r.sinAlpha, r.cosOmega, r.sinOmega, &r.minX, &r.maxX, &r.minY, &r.maxY)
				}
			}
		}
	}
}

// displayImage 渲染最终图像
func (r *SkinRenderer) displayImage() image.Image {
	width := r.maxX - r.minX
	height := r.maxY - r.minY
	ratio := r.ratio * 2

	srcWidth := int(ratio*width) + 1
	srcHeight := int(ratio*height) + 1

	img := image.NewRGBA(image.Rect(0, 0, srcWidth, srcHeight))

	// 按深度顺序绘制
	displayOrder := r.getDisplayOrder()

	for _, order := range displayOrder {
		for piece, faces := range order {
			for _, face := range faces {
				if polys, ok := r.polygons[piece][face]; ok {
					for _, poly := range polys {
						poly.AddToImage(img, r.minX, r.minY, ratio)
					}
				}
			}
		}
	}

	// 抗锯齿：2x 渲染后缩小
	realWidth := srcWidth / 2
	realHeight := srcHeight / 2
	destImg := resizeImage(img, realWidth, realHeight)

	return destImg
}

// getDisplayOrder 获取绘制顺序
func (r *SkinRenderer) getDisplayOrder() []map[string][]string {
	var displayOrder []map[string][]string

	if contains(r.frontFaces, "top") {
		if contains(r.frontFaces, "right") {
			displayOrder = append(displayOrder, map[string][]string{"leftLeg": r.backFaces})
			displayOrder = append(displayOrder, map[string][]string{"leftLeg": r.visibleFaces["leftLeg"].front})
			displayOrder = append(displayOrder, map[string][]string{"rightLeg": r.backFaces})
			displayOrder = append(displayOrder, map[string][]string{"rightLeg": r.visibleFaces["rightLeg"].front})
			displayOrder = append(displayOrder, map[string][]string{"leftArm": r.backFaces})
			displayOrder = append(displayOrder, map[string][]string{"leftArm": r.visibleFaces["leftArm"].front})
			displayOrder = append(displayOrder, map[string][]string{"torso": r.backFaces})
			displayOrder = append(displayOrder, map[string][]string{"torso": r.visibleFaces["torso"].front})
			displayOrder = append(displayOrder, map[string][]string{"rightArm": r.backFaces})
			displayOrder = append(displayOrder, map[string][]string{"rightArm": r.visibleFaces["rightArm"].front})
		} else {
			displayOrder = append(displayOrder, map[string][]string{"rightLeg": r.backFaces})
			displayOrder = append(displayOrder, map[string][]string{"rightLeg": r.visibleFaces["rightLeg"].front})
			displayOrder = append(displayOrder, map[string][]string{"leftLeg": r.backFaces})
			displayOrder = append(displayOrder, map[string][]string{"leftLeg": r.visibleFaces["leftLeg"].front})
			displayOrder = append(displayOrder, map[string][]string{"rightArm": r.backFaces})
			displayOrder = append(displayOrder, map[string][]string{"rightArm": r.visibleFaces["rightArm"].front})
			displayOrder = append(displayOrder, map[string][]string{"torso": r.backFaces})
			displayOrder = append(displayOrder, map[string][]string{"torso": r.visibleFaces["torso"].front})
			displayOrder = append(displayOrder, map[string][]string{"leftArm": r.backFaces})
			displayOrder = append(displayOrder, map[string][]string{"leftArm": r.visibleFaces["leftArm"].front})
		}

		displayOrder = append(displayOrder, map[string][]string{"helmet": r.backFaces})
		displayOrder = append(displayOrder, map[string][]string{"head": r.backFaces})
		displayOrder = append(displayOrder, map[string][]string{"head": r.visibleFaces["head"].front})
		displayOrder = append(displayOrder, map[string][]string{"helmet": r.visibleFaces["head"].front})
	} else {
		displayOrder = append(displayOrder, map[string][]string{"helmet": r.backFaces})
		displayOrder = append(displayOrder, map[string][]string{"head": r.backFaces})
		displayOrder = append(displayOrder, map[string][]string{"head": r.visibleFaces["head"].front})
		displayOrder = append(displayOrder, map[string][]string{"helmet": r.visibleFaces["head"].front})

		if contains(r.frontFaces, "right") {
			displayOrder = append(displayOrder, map[string][]string{"leftArm": r.backFaces})
			displayOrder = append(displayOrder, map[string][]string{"leftArm": r.visibleFaces["leftArm"].front})
			displayOrder = append(displayOrder, map[string][]string{"torso": r.backFaces})
			displayOrder = append(displayOrder, map[string][]string{"torso": r.visibleFaces["torso"].front})
			displayOrder = append(displayOrder, map[string][]string{"rightArm": r.backFaces})
			displayOrder = append(displayOrder, map[string][]string{"rightArm": r.visibleFaces["rightArm"].front})
			displayOrder = append(displayOrder, map[string][]string{"leftLeg": r.backFaces})
			displayOrder = append(displayOrder, map[string][]string{"leftLeg": r.visibleFaces["leftLeg"].front})
			displayOrder = append(displayOrder, map[string][]string{"rightLeg": r.backFaces})
			displayOrder = append(displayOrder, map[string][]string{"rightLeg": r.visibleFaces["rightLeg"].front})
		} else {
			displayOrder = append(displayOrder, map[string][]string{"rightArm": r.backFaces})
			displayOrder = append(displayOrder, map[string][]string{"rightArm": r.visibleFaces["rightArm"].front})
			displayOrder = append(displayOrder, map[string][]string{"torso": r.backFaces})
			displayOrder = append(displayOrder, map[string][]string{"torso": r.visibleFaces["torso"].front})
			displayOrder = append(displayOrder, map[string][]string{"leftArm": r.backFaces})
			displayOrder = append(displayOrder, map[string][]string{"leftArm": r.visibleFaces["leftArm"].front})
			displayOrder = append(displayOrder, map[string][]string{"rightLeg": r.backFaces})
			displayOrder = append(displayOrder, map[string][]string{"rightLeg": r.visibleFaces["rightLeg"].front})
			displayOrder = append(displayOrder, map[string][]string{"leftLeg": r.backFaces})
			displayOrder = append(displayOrder, map[string][]string{"leftLeg": r.visibleFaces["leftLeg"].front})
		}
	}

	return displayOrder
}

// 辅助函数

func convertToRGBA(img image.Image) *image.RGBA {
	if rgba, ok := img.(*image.RGBA); ok {
		return rgba
	}

	bounds := img.Bounds()
	rgba := image.NewRGBA(bounds)
	for y := bounds.Min.Y; y < bounds.Max.Y; y++ {
		for x := bounds.Min.X; x < bounds.Max.X; x++ {
			rgba.Set(x, y, img.At(x, y))
		}
	}
	return rgba
}

func resizeImage(img image.Image, width, height int) *image.RGBA {
	bounds := img.Bounds()
	srcW := bounds.Dx()
	srcH := bounds.Dy()

	dst := image.NewRGBA(image.Rect(0, 0, width, height))

	for y := 0; y < height; y++ {
		for x := 0; x < width; x++ {
			srcX := bounds.Min.X + x*srcW/width
			srcY := bounds.Min.Y + y*srcH/height
			dst.Set(x, y, img.At(srcX, srcY))
		}
	}

	return dst
}

// getPixelColor 从皮肤图像获取像素颜色
func (r *SkinRenderer) getPixelColor(x, y int) color.RGBA {
	if x < 0 || y < 0 {
		return color.RGBA{}
	}
	bounds := r.playerSkin.Bounds()
	if x >= bounds.Dx() || y >= bounds.Dy() {
		return color.RGBA{}
	}

	c := r.playerSkin.At(bounds.Min.X+x, bounds.Min.Y+y)
	r32, g32, b32, a32 := c.RGBA()
	return color.RGBA{
		R: uint8(r32 >> 8),
		G: uint8(g32 >> 8),
		B: uint8(b32 >> 8),
		A: uint8(a32 >> 8),
	}
}