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Sample C# code to use PDFTron SDK for creating and manipulating PDF layers (also known as Optional Content Groups - OCGs). These samples demonstrate how to create and extract layers, as well as to selectively render them (show, hide) in conforming PDF readers or printers. Learn more about our C# PDF Library.
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//
// Copyright (c) 2001-2020 by PDFTron Systems Inc. All Rights Reserved.
//
using System;
using System.IO;
using System.Threading.Tasks;
using Windows.Foundation;
using pdftron.Common;
using pdftron.PDF;
using pdftron.PDF.OCG;
using pdftron.SDF;
using PDFNetUniversalSamples.ViewModels;
namespace PDFNetSamples
{
public sealed class PDFLayersTest : Sample
{
public PDFLayersTest() :
base("PDFLayers", "This sample demonstrates how to create PDF layers (also known as Optional Content Groups - OCGs). The sample also shows how to extract and render PDF layers.")
{
}
public override IAsyncAction RunAsync()
{
return Task.Run(new System.Action(async () => {
WriteLine("--------------------------------");
WriteLine("Starting PDFLayers Test...");
WriteLine("--------------------------------\n");
try
{
PDFDoc doc = new PDFDoc();
// Create three layers...
Group image_layer = CreateLayer(doc, "Image Layer");
Group text_layer = CreateLayer(doc, "Text Layer");
Group vector_layer = CreateLayer(doc, "Vector Layer");
// Start a new page ------------------------------------
pdftron.PDF.Page page = doc.PageCreate();
ElementBuilder builder = new ElementBuilder(); // ElementBuilder is used to build new Element objects
ElementWriter writer = new ElementWriter(); // ElementWriter is used to write Elements to the page
writer.Begin(page); // begin writing to this page
// Add new content to the page and associate it with one of the layers.
Element element = builder.CreateForm(CreateGroup1(doc, image_layer.GetSDFObj()));
writer.WriteElement(element);
element = builder.CreateForm(CreateGroup2(doc, vector_layer.GetSDFObj()));
writer.WriteElement(element);
// Add the text layer to the page...
bool ocmdSample = false; // set to 'true' to enable 'ocmd' example.
if (ocmdSample)
{
// A bit more advanced example of how to create an OCMD text layer that
// is visible only if text, image and path layers are all 'ON'.
// An example of how to set 'Visibility Policy' in OCMD.
Obj ocgs = doc.CreateIndirectArray();
ocgs.PushBack(image_layer.GetSDFObj());
ocgs.PushBack(vector_layer.GetSDFObj());
ocgs.PushBack(text_layer.GetSDFObj());
OCMD text_ocmd = OCMD.Create(doc, ocgs, OCMDVisibilityPolicyType.e_AllOn);
element = builder.CreateForm(CreateGroup3(doc, text_ocmd.GetSDFObj()));
}
else {
element = builder.CreateForm(CreateGroup3(doc, text_layer.GetSDFObj()));
}
writer.WriteElement(element);
// Add some content to the page that does not belong to any layer...
// In this case this is a rectangle representing the page border.
element = builder.CreateRect(0, 0, page.GetPageWidth(), page.GetPageHeight());
element.SetPathFill(false);
element.SetPathStroke(true);
element.GetGState().SetLineWidth(40);
writer.WriteElement(element);
writer.End(); // save changes to the current page
doc.PagePushBack(page);
// Set the default viewing preference to display 'Layer' tab.
PDFDocViewPrefs prefs = doc.GetViewPrefs();
prefs.SetPageMode(PDFDocViewPrefsPageMode.e_UseOC);
string output_file_path = Path.Combine(OutputPath, "pdf_layers.pdf");
await doc.SaveAsync(output_file_path, SDFDocSaveOptions.e_linearized);
doc.Destroy();
WriteLine("Done. Results saved in " + output_file_path);
await AddFileToOutputList(output_file_path).ConfigureAwait(false);
}
catch (Exception e)
{
WriteLine(GetExceptionMessage(e));
}
// The following is a code snippet shows how to selectively render
// and export PDF layers.
try
{
PDFDoc doc = new PDFDoc(Path.Combine(OutputPath, "pdf_layers.pdf"));
doc.InitSecurityHandler();
if (!doc.HasOC())
{
WriteLine("The document does not contain 'Optional Content'");
}
else
{
Config init_cfg = doc.GetOCGConfig();
Context ctx = new Context(init_cfg);
PDFDraw pdfdraw = new PDFDraw();
pdfdraw.SetImageSize(1000, 1000);
pdfdraw.SetOCGContext(ctx); // Render the page using the given OCG context.
pdftron.PDF.Page page = doc.GetPage(1); // Get the first page in the document.
string output_file_path = Path.Combine(OutputPath, "pdf_layers_default.png");
pdfdraw.Export(page, output_file_path);
WriteLine("Exporting " + output_file_path);
await AddFileToOutputList(output_file_path).ConfigureAwait(false);
// 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.
Obj ocgs = doc.GetOCGs(); // Get the array of all OCGs in the document.
if (ocgs != null)
{
int i, sz = ocgs.Size();
for (i=0; i<sz; ++i)
{
Group ocg = new Group(ocgs.GetAt(i));
ctx.ResetStates(false);
ctx.SetState(ocg, true);
string fname = Path.Combine(OutputPath, "pdf_layers_" + ocg.GetName() + ".png");
WriteLine(fname);
pdfdraw.Export(page, fname);
WriteLine("Exporting " + fname);
await AddFileToOutputList(fname).ConfigureAwait(false);
}
}
// Now draw content that is not part of any layer...
ctx.SetNonOCDrawing(true);
ctx.SetOCDrawMode(ContextOCDrawMode.e_NoOC);
output_file_path = Path.Combine(OutputPath, "pdf_layers_non_oc.png");
pdfdraw.Export(page, output_file_path);
WriteLine("Exporting " + output_file_path);
await AddFileToOutputList(output_file_path).ConfigureAwait(false);
doc.Destroy();
WriteLine("Done.");
}
}
catch (Exception e)
{
WriteLine(GetExceptionMessage(e));
}
WriteLine("\n--------------------------------");
WriteLine("Done PDFLayers Test.");
WriteLine("--------------------------------\n");
})).AsAsyncAction();
}
// A utility function used to add new Content Groups (Layers) to the document.
Group CreateLayer(PDFDoc doc, String layer_name)
{
Group grp = Group.Create(doc, layer_name);
Config cfg = doc.GetOCGConfig();
if (cfg == null)
{
cfg = Config.Create(doc, true);
cfg.SetName("Default");
}
// Add the new OCG to the list of layers that should appear in PDF viewer GUI.
Obj layer_order_array = cfg.GetOrder();
if (layer_order_array == null)
{
layer_order_array = doc.CreateIndirectArray();
cfg.SetOrder(layer_order_array);
}
layer_order_array.PushBack(grp.GetSDFObj());
return grp;
}
// Creates some content (3 images) and associate them with the image layer
Obj CreateGroup1(PDFDoc doc, Obj layer)
{
ElementWriter writer = new ElementWriter();
writer.Begin(doc.GetSDFDoc());
// Create an Image that can be reused in the document or on the same page.
pdftron.PDF.Image img = pdftron.PDF.Image.Create(doc.GetSDFDoc(), Path.Combine(InputPath, "peppers.jpg"));
ElementBuilder builder = new ElementBuilder();
Element element = builder.CreateImage(img, new Matrix2D(img.GetImageWidth()/2, -145, 20, img.GetImageHeight()/2, 200, 150));
writer.WritePlacedElement(element);
GState gstate = element.GetGState(); // use the same image (just change its matrix)
gstate.SetTransform(200, 0, 0, 300, 50, 450);
writer.WritePlacedElement(element);
// use the same image again (just change its matrix).
writer.WritePlacedElement(builder.CreateImage(img, 300, 600, 200, -150));
Obj grp_obj = writer.End();
// Indicate that this form (content group) belongs to the given layer (OCG).
grp_obj.PutName("Subtype","Form");
grp_obj.Put("OC", layer);
grp_obj.PutRect("BBox", 0, 0, 1000, 1000); // Set the clip box for the content.
// As an example of further configuration, set the image layer to
// be visible on screen, but not visible when printed...
// The AS entry is an auto state array consisting of one or more usage application
// dictionaries that specify how conforming readers shall automatically set the
// state of optional content groups based on external factors.
Obj cfg = doc.GetOCGConfig().GetSDFObj();
Obj auto_state = cfg.FindObj("AS");
if (auto_state == null) auto_state = cfg.PutArray("AS");
Obj print_state = auto_state.PushBackDict();
print_state.PutArray("Category").PushBackName("Print");
print_state.PutName("Event", "Print");
print_state.PutArray("OCGs").PushBack(layer);
Obj layer_usage = layer.PutDict("Usage");
Obj view_setting = layer_usage.PutDict("View");
view_setting.PutName("ViewState", "ON");
Obj print_setting = layer_usage.PutDict("Print");
print_setting.PutName("PrintState", "OFF");
return grp_obj;
}
// Creates some content (a path in the shape of a heart) and associate it with the vector layer
static public Obj CreateGroup2(PDFDoc doc, Obj layer)
{
ElementWriter writer = new ElementWriter();
writer.Begin(doc.GetSDFDoc());
// Create a path object in the shape of a heart.
ElementBuilder builder = new ElementBuilder();
builder.PathBegin(); // start constructing the path
builder.MoveTo(306, 396);
builder.CurveTo(681, 771, 399.75, 864.75, 306, 771);
builder.CurveTo(212.25, 864.75, -69, 771, 306, 396);
builder.ClosePath();
Element element = builder.PathEnd(); // the path geometry is now specified.
// Set the path FILL color space and color.
element.SetPathFill(true);
GState gstate = element.GetGState();
gstate.SetFillColorSpace(ColorSpace.CreateDeviceCMYK());
gstate.SetFillColor(new ColorPt(1, 0, 0, 0)); // cyan
// Set the path STROKE color space and color.
element.SetPathStroke(true);
gstate.SetStrokeColorSpace(ColorSpace.CreateDeviceRGB());
gstate.SetStrokeColor(new ColorPt(1, 0, 0)); // red
gstate.SetLineWidth(20);
gstate.SetTransform(0.5, 0, 0, 0.5, 280, 300);
writer.WriteElement(element);
Obj grp_obj = writer.End();
// Indicate that this form (content group) belongs to the given layer (OCG).
grp_obj.PutName("Subtype","Form");
grp_obj.Put("OC", layer);
grp_obj.PutRect("BBox", 0, 0, 1000, 1000); // Set the clip box for the content.
return grp_obj;
}
// Creates some text and associate it with the text layer
static public Obj CreateGroup3(PDFDoc doc, Obj layer)
{
ElementWriter writer = new ElementWriter();
writer.Begin(doc.GetSDFDoc());
// Create a path object in the shape of a heart.
ElementBuilder builder = new ElementBuilder();
// Begin writing a block of text
Element element = builder.CreateTextBegin(Font.Create(doc.GetSDFDoc(), FontStandardType1Font.e_times_roman), 120);
writer.WriteElement(element);
element = builder.CreateTextRun("A text layer!");
// Rotate text 45 degrees, than translate 180 pts horizontally and 100 pts vertically.
Matrix2D transform = Matrix2D.RotationMatrix(-45 * (3.1415/ 180.0));
transform.Concat(1, 0, 0, 1, 180, 100);
element.SetTextMatrix(transform);
writer.WriteElement(element);
writer.WriteElement(builder.CreateTextEnd());
Obj grp_obj = writer.End();
// Indicate that this form (content group) belongs to the given layer (OCG).
grp_obj.PutName("Subtype","Form");
grp_obj.Put("OC", layer);
grp_obj.PutRect("BBox", 0, 0, 1000, 1000); // Set the clip box for the content.
return grp_obj;
}
}
}