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Go / Guides / Extract layer
To extract PDF layers or OCG (optional content group) from a document.
doc := NewPDFDoc(filename)
page = doc.GetPage(1)
init_cfg := doc.GetOCGConfig()
ctx := NewContext(init_cfg)
pdfdraw := NewPDFDraw()
pdfdraw.SetImageSize(1000, 1000)
pdfdraw.SetOCGContext(ctx) // Render the page using the given OCG context.
// Disable drawing of content that is not optional (i.e. is not part of any layer).
ctx.SetNonOCDrawing(false)
// Now render each layer in the input document to a separate image.
ocgs := doc.GetOCGs() // Get the array of all OCGs in the document.
if ocgs != nil{
sz := ocgs.Size()
i := int64(0)
for i < sz{
ocg := NewGroup(ocgs.GetAt(i))
ctx.ResetStates(false)
ctx.SetState(ocg, true)
fname := "pdf_layers_" + ocg.GetName() + ".png"
fmt.Println(fname)
pdfdraw.Export(page, outputPath + fname)
i = i + 1
}
}
// Now draw content that is not part of any layer...
ctx.SetNonOCDrawing(true)
ctx.SetOCDrawMode(ContextE_NoOC)
pdfdraw.Export(page, outputPath + "pdf_layers_non_oc.png")
PDF layers (OCG)
Full sample code which demonstrates how to create, extract, render PDF layers.
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