unipdf 是 AGPL 或付费：迁移到 gpdf 的完整指南

// API key (metered)
import "github.com/unidoc/unipdf/v3/common/license"

func init() {
    if err := license.SetMeteredKey(os.Getenv("UNIDOC_API_KEY")); err != nil {
        log.Fatal(err)
    }
}

// 离线许可证文件
func init() {
    licenseKey, _ := os.ReadFile("/etc/unidoc/license.txt")
    if err := license.SetLicenseKey(string(licenseKey), "Acme Corp"); err != nil {
        log.Fatal(err)
    }
}

package main

import (
    "log"
    "os"

    "github.com/unidoc/unipdf/v3/common/license"
    "github.com/unidoc/unipdf/v3/creator"
)

func init() {
    if err := license.SetMeteredKey(os.Getenv("UNIDOC_API_KEY")); err != nil {
        log.Fatal(err)
    }
}

func main() {
    c := creator.New()
    c.SetPageSize(creator.PageSizeA4)

    p := c.NewParagraph("Hello, World!")
    p.SetFontSize(24)
    if err := c.Draw(p); err != nil {
        log.Fatal(err)
    }

    if err := c.WriteToFile("hello.pdf"); err != nil {
        log.Fatal(err)
    }
}

package main

import (
    "log"
    "os"

    "github.com/gpdf-dev/gpdf"
    "github.com/gpdf-dev/gpdf/document"
    "github.com/gpdf-dev/gpdf/template"
)

func main() {
    doc := gpdf.NewDocument(
        gpdf.WithPageSize(document.A4),
        gpdf.WithMargins(document.UniformEdges(document.Mm(20))),
    )

    page := doc.AddPage()
    page.AutoRow(func(r *template.RowBuilder) {
        r.Col(12, func(c *template.ColBuilder) {
            c.Text("Hello, World!", template.FontSize(24), template.Bold())
        })
    })

    data, err := doc.Generate()
    if err != nil {
        log.Fatal(err)
    }
    if err := os.WriteFile("hello.pdf", data, 0o644); err != nil {
        log.Fatal(err)
    }
}

table := c.NewTable(4)
table.SetColumnWidths(0.5, 0.15, 0.15, 0.2)

headerStyle := c.NewTextStyle()
headerStyle.Font, _ = model.NewStandard14Font("Helvetica-Bold")
headerStyle.FontSize = 11
headerStyle.Color = creator.ColorWhite

drawHeaderCell := func(text string) {
    cell := table.NewCell()
    cell.SetBackgroundColor(creator.ColorRGBFromHex("#1A237E"))
    cell.SetBorder(creator.CellBorderSideAll, creator.CellBorderStyleSingle, 0.5)

    p := c.NewStyledParagraph()
    chunk := p.Append(text)
    chunk.Style = headerStyle
    cell.SetContent(p)
}

for _, h := range []string{"项目", "数量", "单价", "金额"} {
    drawHeaderCell(h)
}

for _, row := range items {
    for _, cellText := range row {
        cell := table.NewCell()
        cell.SetBorder(creator.CellBorderSideAll, creator.CellBorderStyleSingle, 0.3)

        p := c.NewParagraph(cellText)
        p.SetFontSize(11)
        cell.SetContent(p)
    }
}

if err := c.Draw(table); err != nil {
    log.Fatal(err)
}

page.AutoRow(func(r *template.RowBuilder) {
    r.Col(12, func(c *template.ColBuilder) {
        c.Table(
            []string{"项目", "数量", "单价", "金额"},
            [][]string{
                {"前端开发", "40 小时", "¥1,500", "¥60,000"},
                {"后端开发", "60 小时", "¥1,500", "¥90,000"},
                {"UI 设计", "20 小时", "¥1,200", "¥24,000"},
            },
            template.ColumnWidths(50, 15, 15, 20),
            template.TableHeaderStyle(
                template.Bold(),
                template.TextColor(pdf.White),
                template.BgColor(pdf.RGBHex(0x1A237E)),
            ),
            template.TableStripe(pdf.RGBHex(0xF5F5F5)),
        )
    })
})

font, err := model.NewCompositePdfFontFromTTFFile("NotoSansSC-Regular.ttf")
if err != nil {
    log.Fatal(err)
}

c := creator.New()
c.SetPageSize(creator.PageSizeA4)

style := c.NewTextStyle()
style.Font = font
style.FontSize = 14

p := c.NewStyledParagraph()
p.Append("你好，世界。").Style = style
if err := c.Draw(p); err != nil {
    log.Fatal(err)
}

c.WriteToFile("zh.pdf")

package main

import (
    _ "embed"
    "log"
    "os"

    "github.com/gpdf-dev/gpdf"
    "github.com/gpdf-dev/gpdf/document"
    "github.com/gpdf-dev/gpdf/template"
)

//go:embed NotoSansSC-Regular.ttf
var notoSC []byte

func main() {
    doc := gpdf.NewDocument(
        gpdf.WithPageSize(document.A4),
        gpdf.WithMargins(document.UniformEdges(document.Mm(20))),
        gpdf.WithFont("NotoSansSC", notoSC),
        gpdf.WithDefaultFont("NotoSansSC", 14),
    )

    page := doc.AddPage()
    page.AutoRow(func(r *template.RowBuilder) {
        r.Col(12, func(c *template.ColBuilder) {
            c.Text("你好，世界。")
            c.Text("床前明月光，疑是地上霜。")
            c.Text("北京市朝阳区建国门外大街 1 号")
        })
    })

    data, _ := doc.Generate()
    if err := os.WriteFile("zh.pdf", data, 0o644); err != nil {
        log.Fatal(err)
    }
}

c.DrawHeader(func(block *creator.Block, args creator.HeaderFunctionArgs) {
    p := c.NewParagraph("ACME 公司")
    p.SetFontSize(12)
    p.SetPos(40, 30)
    block.Draw(p)
})

c.DrawFooter(func(block *creator.Block, args creator.FooterFunctionArgs) {
    p := c.NewParagraph(fmt.Sprintf("第 %d 页 / 共 %d 页", args.PageNum, args.TotalPages))
    p.SetFontSize(8)
    p.SetPos(0, 20)
    p.SetTextAlignment(creator.TextAlignmentCenter)
    block.Draw(p)
})

doc := gpdf.NewDocument(
    gpdf.WithPageSize(document.A4),
    gpdf.WithMargins(document.UniformEdges(document.Mm(20))),
)

doc.Header(func(p *template.PageBuilder) {
    p.AutoRow(func(r *template.RowBuilder) {
        r.Col(12, func(c *template.ColBuilder) {
            c.Text("ACME 公司", template.Bold(), template.FontSize(12))
            c.Line(template.LineColor(pdf.Gray(0.7)))
            c.Spacer(document.Mm(4))
        })
    })
})

doc.Footer(func(p *template.PageBuilder) {
    p.AutoRow(func(r *template.RowBuilder) {
        r.Col(6, func(c *template.ColBuilder) {
            c.Text("ACME 公司",
                template.FontSize(8), template.TextColor(pdf.Gray(0.5)))
        })
        r.Col(6, func(c *template.ColBuilder) {
            c.PageNumber(template.AlignRight(),
                template.FontSize(8), template.TextColor(pdf.Gray(0.5)))
        })
    })
})

for i := 0; i < 10; i++ {
    page := doc.AddPage()
    page.AutoRow(func(r *template.RowBuilder) {
        r.Col(12, func(c *template.ColBuilder) {
            c.Text(fmt.Sprintf("第 %d 页正文。", i+1))
        })
    })
}

// 先用 creator 渲染内容，然后用 model.PdfWriter 重新编码以附加加密。
// 许可证检查在这里触发。
c := creator.New()
// ... 绘制内容 ...

var buf bytes.Buffer
if err := c.Write(&buf); err != nil {
    log.Fatal(err)
}

reader, err := model.NewPdfReader(bytes.NewReader(buf.Bytes()))
if err != nil {
    log.Fatal(err)
}

writer := model.NewPdfWriter()
encryptOpts := &model.EncryptOptions{Algorithm: model.RC4_128bit, Permissions: model.PermPrinting}
if err := writer.Encrypt([]byte("user-pwd"), []byte("owner-pwd"), encryptOpts); err != nil {
    log.Fatal(err)
}

for i := 1; i <= reader.NumPage; i++ {
    page, _ := reader.GetPage(i)
    writer.AddPage(page)
}

f, _ := os.Create("encrypted.pdf")
defer f.Close()
writer.Write(f)

doc := gpdf.NewDocument(
    gpdf.WithPageSize(document.A4),
    gpdf.WithMargins(document.UniformEdges(document.Mm(20))),
    gpdf.WithEncryption(
        gpdf.AES256,
        "user-pwd",
        "owner-pwd",
        gpdf.PermPrinting|gpdf.PermCopyContent,
    ),
)

page := doc.AddPage()
page.AutoRow(func(r *template.RowBuilder) {
    r.Col(12, func(c *template.ColBuilder) {
        c.Text("机密")
    })
})

data, _ := doc.Generate()
os.WriteFile("encrypted.pdf", data, 0o644)

go get github.com/gpdf-dev/gpdf