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// Copyright 2025-2026 肖其顿 (XIAO QI DUN)
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package threed
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import (
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"bytes"
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"context"
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"errors"
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"fmt"
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"image"
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"image/color"
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"image/jpeg"
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"image/png"
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"io"
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baseimage "github.com/xiaoqidun/ofdgo/internal/base/image"
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"golang.org/x/image/tiff"
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)
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// U3DTextureResolver 由调用方按原始URL读取外部纹理，地址解析、访问策略和读取限额由调用方控制
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// 返回的数据在本次绘制结束前不得修改；失败时尝试下一候选地址，取消及超时错误立即返回
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// 入参: ctx 取消上下文, url 绝对或相对地址
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// 返回: []byte 压缩图像数据, error 读取错误
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type U3DTextureResolver func(ctx context.Context, url string) ([]byte, error)
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// u3dImageReader 在图像解码器读取压缩数据时检查取消状态
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type u3dImageReader struct {
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ctx context.Context
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data *bytes.Reader
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}
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// Read 读取顺序图像数据
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// 入参: p 接收缓冲
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// 返回: int 已读字节数, error 读取或取消错误
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func (r *u3dImageReader) Read(p []byte) (int, error) {
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if err := r.ctx.Err(); err != nil {
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return 0, err
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}
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return r.data.Read(p)
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}
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// ReadAt 读取指定偏移的图像数据
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// 入参: p 接收缓冲, offset 字节偏移
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// 返回: int 已读字节数, error 读取或取消错误
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func (r *u3dImageReader) ReadAt(p []byte, offset int64) (int, error) {
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if err := r.ctx.Err(); err != nil {
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return 0, err
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}
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return r.data.ReadAt(p, offset)
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}
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// texture 按需合成纹理并缓存，空名称使用ECMA-363第8.4.1节规定的默认纹理
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// 入参: name 纹理名称
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// 返回: *image.NRGBA64 非预乘纹理, error 资源、解码、预算或取消错误
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func (r *Renderer) texture(name string) (*image.NRGBA64, error) {
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if err := r.ctx.Err(); err != nil {
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return nil, err
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}
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if cached := r.textures[name]; cached != nil {
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return cached, nil
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}
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if err := r.Reserve(1, 256); err != nil {
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return nil, err
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}
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var pixels *image.NRGBA64
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if name == "" {
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if err := r.Reserve(64, 8); err != nil {
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return nil, err
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}
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pixels = image.NewNRGBA64(image.Rect(0, 0, 8, 8))
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for y := range 8 {
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for x := range 8 {
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c := color.NRGBA64{65535, 65535, 65535, 65535}
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if x/4 != y/4 {
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c.G, c.B = 26214, 13107
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}
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pixels.SetNRGBA64(x, y, c)
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}
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}
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} else {
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index, exists := r.textureIndex[name]
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if !exists {
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return nil, fmt.Errorf("missing U3D texture %q", name)
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}
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var err error
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pixels, err = r.decodeTexture(&r.model.Textures[index])
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if err != nil {
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return nil, fmt.Errorf("U3D texture %q: %w", name, err)
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}
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}
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if r.textures == nil {
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r.textures = make(map[string]*image.NRGBA64)
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}
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r.textures[name] = pixels
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return pixels, nil
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}
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// decodeTexture 合成各续图像指定的通道，保留十六位颜色与非预乘透明度
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// 入参: texture 纹理资源
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// 返回: *image.NRGBA64 合成图像, error 格式、预算或取消错误
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func (r *Renderer) decodeTexture(texture *U3DTexture) (*image.NRGBA64, error) {
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switch texture.ImageType {
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case 1, 14, 15, 16, 17:
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default:
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return nil, fmt.Errorf("invalid image type")
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}
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if texture.Width == 0 || texture.Height == 0 || len(texture.Images) == 0 || len(texture.Images) > 4 {
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return nil, fmt.Errorf("invalid image dimensions or channel count")
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}
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var covered uint8
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for _, source := range texture.Images {
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if source.Compression < 1 || source.Compression > 4 {
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return nil, fmt.Errorf("invalid image compression")
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}
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channels := u3dTextureChannels(source.Channels)
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if source.Channels == 0 || source.Channels&^uint8(31) != 0 || channels&covered != 0 || channels&^u3dTextureChannels(texture.ImageType) != 0 {
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return nil, fmt.Errorf("invalid image channels")
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}
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covered |= channels
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if source.External && (r.resolveTexture == nil || len(source.URLs) == 0) {
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return nil, fmt.Errorf("external texture image requires resolution")
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}
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if !source.External && uint64(len(source.Data)) != uint64(source.ByteCount) {
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return nil, fmt.Errorf("invalid image data length")
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}
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}
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if covered != u3dTextureChannels(texture.ImageType) {
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return nil, fmt.Errorf("incomplete image channels")
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}
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if err := r.Reserve(uint64(texture.Width)*uint64(texture.Height), 8); err != nil {
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return nil, err
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}
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pixels := image.NewNRGBA64(image.Rect(0, 0, int(texture.Width), int(texture.Height)))
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for y := range pixels.Rect.Dy() {
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if err := r.ctx.Err(); err != nil {
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return nil, err
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}
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for x := range pixels.Rect.Dx() {
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if x%4096 == 0 {
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if err := r.ctx.Err(); err != nil {
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return nil, err
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}
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}
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pixels.SetNRGBA64(x, y, color.NRGBA64{65535, 65535, 65535, 65535})
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}
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}
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for _, source := range texture.Images {
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if err := r.textureSource(pixels, source); err != nil {
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return nil, err
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}
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}
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return pixels, r.ctx.Err()
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}
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// textureSource 读取内置通道或按顺序尝试外部地址，不修改模型中的图像声明
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// 入参: pixels 目标纹理, source 通道图像
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// 返回: error 读取、解码、预算或取消错误
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func (r *Renderer) textureSource(pixels *image.NRGBA64, source U3DTextureImage) error {
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if !source.External {
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return r.textureChannels(pixels, source)
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}
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if r.resolveTexture == nil || len(source.URLs) == 0 {
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return fmt.Errorf("external texture image requires resolution")
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}
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var last error
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for _, address := range source.URLs {
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if err := r.ctx.Err(); err != nil {
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return err
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}
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data, err := r.resolveTexture(r.ctx, address)
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if r.ctx.Err() != nil {
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return r.ctx.Err()
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}
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if err == nil {
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source.Data = data
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err = r.textureChannels(pixels, source)
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source.Data = nil
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}
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if canceled := r.ctx.Err(); canceled != nil {
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return canceled
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}
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if err == nil || errors.Is(err, context.Canceled) || errors.Is(err, context.DeadlineExceeded) {
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return err
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}
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last = fmt.Errorf("external texture image %q: %w", address, err)
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}
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return last
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}
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// textureChannels 解码并合成一幅续图像，临时预算包括像素、分块及压缩数据开销
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// 入参: pixels 目标纹理, source 通道图像
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// 返回: error 格式、预算或取消错误
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func (r *Renderer) textureChannels(pixels *image.NRGBA64, source U3DTextureImage) error {
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var config func(io.Reader) (image.Config, error)
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var decode func(io.Reader) (image.Image, error)
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switch source.Compression {
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case 1, 3:
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config, decode = jpeg.DecodeConfig, jpeg.Decode
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case 2:
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config, decode = png.DecodeConfig, png.Decode
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case 4:
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config, decode = tiff.DecodeConfig, tiff.Decode
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default:
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return fmt.Errorf("invalid image compression")
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}
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budget := r.remaining
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defer func() { r.remaining = budget }()
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if err := r.Reserve(uint64(len(source.Data)), 4); err != nil {
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return err
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}
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if err := r.Reserve(1, 1<<20); err != nil {
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return err
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}
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reader := &u3dImageReader{ctx: r.ctx, data: bytes.NewReader(source.Data)}
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cfg, err := config(reader)
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if err != nil {
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return err
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}
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if cfg.Width != pixels.Rect.Dx() || cfg.Height != pixels.Rect.Dy() {
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return fmt.Errorf("image dimensions differ from texture declaration")
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}
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if source.Compression == 3 && cfg.ColorModel != color.GrayModel || source.Compression == 1 && cfg.ColorModel != color.YCbCrModel {
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return fmt.Errorf("invalid JPEG texture color model")
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}
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w, h := uint64(cfg.Width)+16, uint64(cfg.Height)+16
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if source.Compression == 4 {
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w, h = max(w, 1024), max(h, 1024)
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}
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if err := r.Reserve(w*h, 32); err != nil {
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return err
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}
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reader.data.Reset(source.Data)
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img, err := decode(reader)
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if err != nil {
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return err
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}
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if img.Bounds() != pixels.Bounds() {
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return fmt.Errorf("invalid decoded image dimensions")
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}
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channels := u3dTextureChannels(source.Channels)
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grayAlpha := source.Channels == 1 && (cfg.ColorModel == color.GrayModel || cfg.ColorModel == color.Gray16Model)
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for y := range cfg.Height {
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for x := range cfg.Width {
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if x%4096 == 0 {
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if err := r.ctx.Err(); err != nil {
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return err
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}
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}
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value := baseimage.NRGBA64At(img, x, y)
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current := pixels.NRGBA64At(x, y)
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if channels&8 != 0 {
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current.R = value.R
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}
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if channels&4 != 0 {
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current.G = value.G
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}
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if channels&2 != 0 {
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current.B = value.B
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}
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if channels&1 != 0 {
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current.A = value.A
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if grayAlpha {
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current.A = value.R
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}
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}
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pixels.SetNRGBA64(x, y, current)
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}
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}
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return r.ctx.Err()
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}
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Reference in new issue
Block a user