mirror of
https://github.com/xiaoqidun/ofdgo.git
synced 2026-10-29 08:46:55 +08:00
90 lines
3.2 KiB
Go
90 lines
3.2 KiB
Go
// 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 ofdgo
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import (
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"encoding/binary"
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"fmt"
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basefont "github.com/xiaoqidun/ofdgo/internal/base/font"
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)
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// SFNTBackend 提供独立的OpenType字体度量、轮廓和资源处理
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type SFNTBackend struct{}
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// sfntResourceMetrics 隔离资源解析器的度量实现
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type sfntResourceMetrics struct{ *basefont.SFNT }
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// Name 返回资源后端标识
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// 返回: string 后端标识
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func (SFNTBackend) Name() string { return "sfnt" }
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// OpenFontResource 提取独立字体并读取名称、样式和裁剪能力
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// CFF2使用默认实例的静态轮廓，不改变原字体文件
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// 入参: file 字体文件, index 集合索引
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// 返回: *FontResource 字体资源, error 解析错误
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func (SFNTBackend) OpenFontResource(file FontFile, index int) (*FontResource, error) {
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data, err := file.Face(index)
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if err != nil {
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return nil, err
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}
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data, err = basefont.DefaultCFF2Font(data)
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if err != nil {
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return nil, err
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}
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sfnt, err := basefont.ParseSFNT(data)
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if err != nil {
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return nil, err
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}
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name := basefont.SFNTName(sfnt, 6, 4, 1)
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if name == "" {
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return nil, fmt.Errorf("font has no name")
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}
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extension := ".ttf"
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if sfnt.IsCFF {
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extension = ".otf"
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}
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return &FontResource{
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FontMetrics: sfntResourceMetrics{sfnt}, Data: data, Extension: extension,
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Font: Font{FontName: name, FamilyName: basefont.SFNTName(sfnt, 16, 1), Charset: "unicode", Bold: binary.BigEndian.Uint16(sfnt.Tables["head"][44:])&1 != 0, Italic: binary.BigEndian.Uint16(sfnt.Tables["head"][44:])&2 != 0, FixedWidth: len(sfnt.Tables["post"]) >= 16 && binary.BigEndian.Uint32(sfnt.Tables["post"][12:]) != 0},
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CanSubset: basefont.Subsettable(sfnt),
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}, nil
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}
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// SubsetFont 裁剪新建字体并按要求保留显式字形编号
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// 入参: data 字体数据, glyphs 用字, preserve 是否保留编号
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// 返回: []byte 子集, error 裁剪错误
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func (SFNTBackend) SubsetFont(data []byte, glyphs []uint16, preserve bool) ([]byte, error) {
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return basefont.SubsetSFNT(data, glyphs, preserve)
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}
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// SubsetSourceFont 按全包引用裁剪原字体，不确定时保留原资源
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// 入参: data 字体数据, usage 用字信息
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// 返回: []byte 子集, error 裁剪错误
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func (SFNTBackend) SubsetSourceFont(data []byte, usage FontUsage) ([]byte, error) {
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u := &basefont.Usage{Characters: make(map[rune]bool), Glyphs: make(map[uint16]bool), Unsafe: usage.Unsafe}
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for _, char := range usage.Characters {
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u.Characters[char] = true
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}
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for _, glyph := range usage.Glyphs {
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u.Glyphs[glyph] = true
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}
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return basefont.SubsetSourceSFNT(data, u), nil
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}
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// Write 返回未改动元信息的字体数据
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// 返回: []byte 字体数据
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func (f sfntResourceMetrics) Write() []byte { return f.SFNT.Write() }
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