Document merging

[danielloader]

Problem

Would it be in scope to be able to use this library to merge multiple PDFs?

Proposed Solution

import (
    "log"                                                                                                                                                                                                 
    "os"                                                                                                                                                                                                  
                                                                                                                                                                                                        
    "github.com/gpdf-dev/gpdf"                                                                                                                                                                            
)                                                                                                                                                                                                         
                                                                                                                                                                                                        
func main() {   
    // 1. Read existing PDFs from disk (or however they arrive)
    coverPage, _ := os.ReadFile("cover.pdf")                                                                                                                                                              
    attachment, _ := os.ReadFile("terms-and-conditions.pdf")                                                                                                                                              
                                                                                                                                                                                                        
    // 2. Generate a document with gpdf as normal                                                                                                                                                         
    generated, err := gpdf.NewDocument(                                                                                                                                                                   
        gpdf.WithPageSize(gpdf.A4),                                                                                                                                                                       
        gpdf.WithMargin(40, 40, 40, 60),
    ).                                                                                                                                                                                                    
        Row(30).Col(12).Text("Policy Certificate", gpdf.FontSize(18), gpdf.Bold()).
        AutoRow().Col(12).Text("Lorem ipsum...").                                                                                                                                                         
        Build()                                                                                                                                                                                           
    if err != nil {                                                                                                                                                                                       
        log.Fatal(err)                                                                                                                                                                                    
    }                                                                                                                                                                                                     
                
    // 3. Merge: cover + generated + attachment                                                                                                                                                           
    merged, err := gpdf.Merge(
        []gpdf.Source{                                                                                                                                                                                    
            {Data: coverPage},                                                                                                                                                                            
            {Data: generated},                                                                                                                                                                            
            {Data: attachment, Pages: gpdf.PageRange{From: 1, To: 3}}, // only first 3 pages                                                                                                              
        },                                                                                                                                                                                                
        gpdf.WithMergeMetadata("Policy Bundle", "Example Ltd", ""),                                                                                                                                       
    )                                                                                                                                                                                                     
    if err != nil {
        log.Fatal(err)                                                                                                                                                                                    
    }                                                                                                                                                                                                     
                                                                                                                                                                                                        
    os.WriteFile("output.pdf", merged, 0644)                                                                                                                                                              
}      

Alternatives Considered

No response

Scope

document (Layer 2: model)

[taiki-nd]

Implemented in #14. The API matches the proposed interface:

gpdf.Merge([]gpdf.Source{...}, gpdf.WithMergeMetadata(...))

Supports page range selection, metadata, and works with gpdf.Open() overlay.