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Sample Java 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 Java PDF Library.
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//---------------------------------------------------------------------------------------
// Copyright (c) 2001-2019 by PDFTron Systems Inc. All Rights Reserved.
// Consult legal.txt regarding legal and license information.
//---------------------------------------------------------------------------------------
package com.pdftron.android.pdfnetsdksamples.samples;
import com.pdftron.android.pdfnetsdksamples.OutputListener;
import com.pdftron.android.pdfnetsdksamples.PDFNetSample;
import com.pdftron.android.pdfnetsdksamples.R;
import com.pdftron.android.pdfnetsdksamples.util.Utils;
import com.pdftron.common.Matrix2D;
import com.pdftron.common.PDFNetException;
import com.pdftron.pdf.ColorPt;
import com.pdftron.pdf.ColorSpace;
import com.pdftron.pdf.Element;
import com.pdftron.pdf.ElementBuilder;
import com.pdftron.pdf.ElementWriter;
import com.pdftron.pdf.Font;
import com.pdftron.pdf.GState;
import com.pdftron.pdf.Image;
import com.pdftron.pdf.PDFDoc;
import com.pdftron.pdf.PDFDocViewPrefs;
import com.pdftron.pdf.PDFDraw;
import com.pdftron.pdf.Page;
import com.pdftron.pdf.ocg.Config;
import com.pdftron.pdf.ocg.Context;
import com.pdftron.pdf.ocg.Group;
import com.pdftron.pdf.ocg.OCMD;
import com.pdftron.sdf.Obj;
import com.pdftron.sdf.SDFDoc;
import java.util.ArrayList;
/**
* This sample demonstrates how to create layers in PDF.
* The sample also shows how to extract and render PDF layers in documents
* that contain optional content groups (OCGs)
* <p>
* With the introduction of PDF version 1.5 came the concept of Layers.
* Layers, or as they are more formally known Optional Content Groups (OCGs),
* refer to sections of content in a PDF document that can be selectively
* viewed or hidden by document authors or consumers. This capability is useful
* in CAD drawings, layered artwork, maps, multi-language documents etc.
* <p>
* Couple of notes regarding this sample:
* ---------------------------------------
* - This sample is using CreateLayer() utility method to create new OCGs.
* CreateLayer() is relatively basic, however it can be extended to set
* other optional entries in the 'OCG' and 'OCProperties' dictionary. For
* a complete listing of possible entries in OC dictionary please refer to
* section 4.10 'Optional Content' in the PDF Reference Manual.
* - The sample is grouping all layer content into separate Form XObjects.
* Although using PDFNet is is also possible to specify Optional Content in
* Content Streams (Section 4.10.2 in PDF Reference), Optional Content in
* XObjects results in PDFs that are cleaner, less-error prone, and faster
* to process.
*/
public class PDFLayersTest extends PDFNetSample {
private static OutputListener mOutputListener;
private static ArrayList<String> mFileList = new ArrayList<>();
public PDFLayersTest() {
setTitle(R.string.sample_pdflayers_title);
setDescription(R.string.sample_pdflayers_description);
}
@Override
public void run(OutputListener outputListener) {
super.run(outputListener);
mOutputListener = outputListener;
mFileList.clear();
printHeader(outputListener);
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 ------------------------------------
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 the 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...
if (false) // set to true to enable 'ocmd' example.
{
// 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, OCMD.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(PDFDocViewPrefs.e_UseOC);
doc.save(Utils.createExternalFile("pdf_layers.pdf", mFileList).getAbsolutePath(), SDFDoc.SaveMode.LINEARIZED, null);
doc.close();
mOutputListener.println("Done.");
} catch (Exception e) {
mOutputListener.printError(e.getStackTrace());
}
// The following is a code snippet shows how to selectively render
// and export PDF layers.
try {
PDFDoc doc = new PDFDoc(Utils.createExternalFile("pdf_layers.pdf", mFileList).getAbsolutePath());
doc.initSecurityHandler();
if (doc.hasOC() == false) {
mOutputListener.println("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.
Page page = doc.getPage(1); // Get the first page in the document.
pdfdraw.export(page, Utils.createExternalFile("pdf_layers_default.png", mFileList).getAbsolutePath());
// output "pdf_layers_default.png"
// 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 = (int) ocgs.size();
for (i = 0; i < sz; ++i) {
Group ocg = new Group(ocgs.getAt(i));
ctx.resetStates(false);
ctx.setState(ocg, true);
String fname = "pdf_layers_" + ocg.getName() + ".png";
mOutputListener.println(fname);
pdfdraw.export(page, Utils.createExternalFile(fname, mFileList).getAbsolutePath());
// output "pdf_layers_" + ocg.getName() + ".png"
}
}
// Now draw content that is not part of any layer...
ctx.setNonOCDrawing(true);
ctx.setOCDrawMode(Context.e_NoOC);
pdfdraw.export(page, Utils.createExternalFile("pdf_layers_non_oc.png", mFileList).getAbsolutePath());
// output "pdf_layers_non_oc.png"
}
doc.close();
mOutputListener.println("Done.");
} catch (Exception e) {
mOutputListener.printError(e.getStackTrace());
}
for (String file : mFileList) {
addToFileList(file);
}
printFooter(outputListener);
}
// A utility function used to add new Content Groups (Layers) to the document.
static Group createLayer(PDFDoc doc, String layer_name) throws PDFNetException {
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
static Obj createGroup1(PDFDoc doc, Obj layer) throws PDFNetException {
ElementWriter writer = new ElementWriter();
writer.begin(doc);
// Create an Image that can be reused in the document or on the same page.
Image img = Image.create(doc.getSDFDoc(), (Utils.getAssetTempFile(INPUT_PATH + "peppers.jpg").getAbsolutePath()));
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.
return grp_obj;
}
// Creates some content (a path in the shape of a heart) and associate it with the vector layer
static Obj createGroup2(PDFDoc doc, Obj layer) throws PDFNetException {
ElementWriter writer = new ElementWriter();
writer.begin(doc);
// 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 Obj createGroup3(PDFDoc doc, Obj layer) throws PDFNetException {
ElementWriter writer = new ElementWriter();
writer.begin(doc);
// 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, Font.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;
}
}