feat(signatureblock): optimize processing for signed documents with less space for signature block

Issue #73

add configuration property to stop signing process if
document has less space for new signature block and
new page is not allowed because document is already signed

5 files changed, 328 insertions, 305 deletions

diff --git a/build.gradle b/build.gradle
index 4d5f0d41..af7e5af3 100644
--- a/build.gradle
+++ b/build.gradle
@@ -46,6 +46,8 @@ subprojects {
   }
 
 	dependencies { 
+		compileOnly group: 'org.projectlombok', name: 'lombok', version: '1.18.24'    
+		annotationProcessor group: 'org.projectlombok', name: 'lombok', version: '1.18.24'
 		testImplementation 'junit:junit:4.13.2' 
 	}
 
@@ -58,7 +60,7 @@ subprojects {
 	    archives sourcesJar
 	}
 
-	sourceCompatibility = 1.7
+	sourceCompatibility = 1.8
 	compileJava.options.encoding = "UTF-8"
 	compileTestJava.options.encoding = "UTF-8"
 	project.ext{
diff --git a/pdf-as-common/src/main/resources/resources/messages/common.properties b/pdf-as-common/src/main/resources/resources/messages/common.properties
index 0a7f1787..d8695619 100644
--- a/pdf-as-common/src/main/resources/resources/messages/common.properties
+++ b/pdf-as-common/src/main/resources/resources/messages/common.properties
@@ -24,6 +24,8 @@ error.pdf.stamp.08=Failed to write the visual signature object
 error.pdf.stamp.09=no suitable placeholder found and STRICT matching mode requested
 error.pdf.stamp.10=no stamper available
 error.pdf.stamp.11=Failed to calculate page length
+error.pdf.stamp.12=Signature-block would be need a new page, but new pages are not allowed on already signed documents
+
 
 error.invalid.signature.parameter.01=Signature block parameter is invalid
 #Signature errors
diff --git a/pdf-as-lib/src/configuration/cfg/advancedconfig.properties b/pdf-as-lib/src/configuration/cfg/advancedconfig.properties
index c5fd06e9..9ba105d1 100644
--- a/pdf-as-lib/src/configuration/cfg/advancedconfig.properties
+++ b/pdf-as-lib/src/configuration/cfg/advancedconfig.properties
@@ -21,7 +21,6 @@
 

 #enable_placeholder_search=true

 

-

 #Aktiviert oder deaktiviert die Kompatibilität mit dem PAdES Signaturstandard manuell

 #sig_obj.PAdESCompatibility=[true|false]

 

@@ -42,6 +41,11 @@
 # MATCH_MODE_SORTED = 3

 #placeholder_mode=

 

+

+### stop processing it signature-block can not valid placed on document

+sigblock.placement.less.space.failing=false

+

+

 ##################

 # Signaturdienste

 

diff --git a/pdf-as-lib/src/main/java/at/gv/egiz/pdfas/lib/api/IConfigurationConstants.java b/pdf-as-lib/src/main/java/at/gv/egiz/pdfas/lib/api/IConfigurationConstants.java
index 4d6cef47..21a8e3b9 100644
--- a/pdf-as-lib/src/main/java/at/gv/egiz/pdfas/lib/api/IConfigurationConstants.java
+++ b/pdf-as-lib/src/main/java/at/gv/egiz/pdfas/lib/api/IConfigurationConstants.java
@@ -110,6 +110,8 @@ public interface IConfigurationConstants {
 	/**
 	 * Visual Signature placement
 	 */
+	
+	public static final String SIG_BLOCK_LESS_SPACE_STOPPING_WITH_ERROR = "sigblock.placement.less.space.failing";
 	public static final String BG_COLOR_DETECTION = "sigblock.placement.bgcolor.detection.enabled";
 	public static final String SIG_PLACEMENT_DEBUG_OUTPUT = "sigblock.placement.debug.file";
 
diff --git a/pdf-as-pdfbox-2/src/main/java/at/gv/egiz/pdfas/lib/impl/pdfbox2/positioning/Positioning.java b/pdf-as-pdfbox-2/src/main/java/at/gv/egiz/pdfas/lib/impl/pdfbox2/positioning/Positioning.java
index 52a865b1..13d1ebe6 100644
--- a/pdf-as-pdfbox-2/src/main/java/at/gv/egiz/pdfas/lib/impl/pdfbox2/positioning/Positioning.java
+++ b/pdf-as-pdfbox-2/src/main/java/at/gv/egiz/pdfas/lib/impl/pdfbox2/positioning/Positioning.java
@@ -3,19 +3,19 @@
  * PDF-AS has been contracted by the E-Government Innovation Center EGIZ, a
  * joint initiative of the Federal Chancellery Austria and Graz University of
  * Technology.
- * 
+ *
  * Licensed under the EUPL, Version 1.1 or - as soon they will be approved by
  * the European Commission - subsequent versions of the EUPL (the "Licence");
  * You may not use this work except in compliance with the Licence.
  * You may obtain a copy of the Licence at:
  * http://www.osor.eu/eupl/
- * 
+ *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the Licence is distributed on an "AS IS" basis,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the Licence for the specific language governing permissions and
  * limitations under the Licence.
- * 
+ *
  * This product combines work with different licenses. See the "NOTICE" text
  * file for details on the various modules and licenses.
  * The "NOTICE" text file is part of the distribution. Any derivative works
@@ -26,323 +26,336 @@ package at.gv.egiz.pdfas.lib.impl.pdfbox2.positioning;
 import java.awt.geom.AffineTransform;
 import java.awt.geom.Point2D;
 import java.io.IOException;
-import java.util.ArrayList;
-import java.util.List;
 
 import org.apache.pdfbox.pdmodel.PDDocument;
 import org.apache.pdfbox.pdmodel.PDPage;
-import org.apache.pdfbox.pdmodel.PDPageTree;
 import org.apache.pdfbox.pdmodel.common.PDRectangle;
-import org.apache.pdfbox.pdmodel.interactive.form.PDSignatureField;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
 
 import at.gv.egiz.pdfas.common.exceptions.PdfAsException;
 import at.gv.egiz.pdfas.common.settings.ISettings;
+import at.gv.egiz.pdfas.lib.api.IConfigurationConstants;
 import at.gv.egiz.pdfas.lib.impl.pdfbox2.utils.PdfBoxUtils;
 import at.gv.egiz.pdfas.lib.impl.stamping.IPDFVisualObject;
 import at.knowcenter.wag.egov.egiz.pdf.PositioningInstruction;
 import at.knowcenter.wag.egov.egiz.pdf.TablePos;
 import at.knowcenter.wag.egov.egiz.pdfbox2.pdf.PDFUtilities;
+import lombok.extern.slf4j.Slf4j;
 
 /**
  * Created with IntelliJ IDEA. User: afitzek Date: 8/29/13 Time: 4:30 PM To
  * change this template use File | Settings | File Templates.
  */
+@Slf4j
 public class Positioning {
 
-	private static final Logger logger = LoggerFactory
-			.getLogger(Positioning.class);
-
-	/**
-	 * The left/right margin.
-	 */
-	public static final float SIGNATURE_MARGIN_HORIZONTAL = 50f;
-
-	/**
-	 * The top/bottom margin.
-	 */
-	public static final float SIGNATURE_MARGIN_VERTICAL = 20f;
-
-	/**
-	 * Evalutates absolute positioning and prepares the PositioningInstruction
-	 * for placing the table.
-	 *
-	 * @param pos
-	 *            The absolute positioning parameter. If null it is sought in
-	 *            the profile definition.
-	 * @param signature_type
-	 *            The profile definition of the table to be written.
-	 * @param pdfDataSource
-	 *            The pdf.
-	 * @param pdf_table
-	 *            The pdf table to be written.
-	 * @param settings 
-	 * @return Returns the PositioningInformation.
-	 * @throws PdfAsException
-	 *             F.e.
-	 */
-	public static PositioningInstruction determineTablePositioning(
-			TablePos pos, String signature_type, PDDocument pdfDataSource,
-			IPDFVisualObject pdf_table, ISettings settings) throws PdfAsException {
-		return adjustSignatureTableandCalculatePosition(pdfDataSource,
-				pdf_table, pos, settings);
-	}
-
-	private static PDRectangle rotateBox(PDRectangle cropBox, int rotation) {
-		if (rotation != 0) {
-			Point2D upSrc = new Point2D.Float();
-
-			upSrc.setLocation(cropBox.getUpperRightX(),
-					cropBox.getUpperRightY());
-
-			Point2D llSrc = new Point2D.Float();
-			llSrc.setLocation(cropBox.getLowerLeftX(), cropBox.getLowerLeftY());
-			AffineTransform transform = new AffineTransform();
-			transform.setToIdentity();
-			if (rotation % 360 != 0) {
-				transform.setToRotation(Math.toRadians(rotation * -1), llSrc.getX(),
-						llSrc.getY());
-			}
-			Point2D upDst = new Point2D.Float();
-			transform.transform(upSrc, upDst);
-
-			Point2D llDst = new Point2D.Float();
-			transform.transform(llSrc, llDst);
-			
-			float y1 = (float) upDst.getY();
-			float y2 = (float) llDst.getY();
-			
-			if(y1 > y2) {
-				float t = y1;
-				y1 = y2;
-				y2 = t;
-			}
-			
-			if(y1 < 0) {
-				y2 = y2 + -1 * y1;
-				y1 = 0;
-			}
-			
-			float x1 = (float) upDst.getX();
-			float x2 = (float) llDst.getX();
-			
-			if(x1 > x2) {
-				float t = x1;
-				x1 = x2;
-				x2 = t;
-			}
-			
-			if(x1 < 0) {
-				x2 = x2 + -1 * x1;
-				x1 = 0;
-			}
-			
-			cropBox.setUpperRightX(x2);
-			cropBox.setUpperRightY(y2);
-			cropBox.setLowerLeftY(y1);
-			cropBox.setLowerLeftX(x1);
-		}
-		return cropBox;
-	}
-
-	/**
-	 * Sets the width of the table according to the layout of the document and
-	 * calculates the y position where the PDFPTable should be placed.
-	 *
-	 * @param pdfDataSource
-	 *            The PDF document.
-	 * @param pdf_table
-	 *            The PDFPTable to be placed.
-	 * @param settings 
-	 * @return Returns the position where the PDFPTable should be placed.
-	 * @throws PdfAsException
-	 *             F.e.
-	 */
-	public static PositioningInstruction adjustSignatureTableandCalculatePosition(
-			final PDDocument pdfDataSource, IPDFVisualObject pdf_table,
-			TablePos pos, ISettings settings) throws PdfAsException {
-		List<PDSignatureField> pdSignatureFieldList;
-		PdfBoxUtils.checkPDFPermissions(pdfDataSource);
-		int counter = 0;
-
-		try {
-			//count signature fields with signatures
-			pdSignatureFieldList = pdfDataSource.getSignatureFields();
-			for (PDSignatureField signatureField : pdSignatureFieldList)
-			{
-				if(signatureField.getSignature()!=null){
-					counter++;
-				}
-			}
-		} catch (IOException e) {
-			e.printStackTrace();
-		}
-		// get pages of currentdocument
-		int doc_pages = pdfDataSource.getNumberOfPages();
-		int page = doc_pages;
-		boolean make_new_page = pos.isNewPage();
-
-		//we cannot add new page if a document is already signed
-
-
-		if (!(pos.isNewPage() || pos.isPauto())) {
-			// we should posit signaturtable on this page
-			page = pos.getPage();
-			// System.out.println("XXXXPAGE="+page+" doc_pages="+doc_pages);
-				if (page > doc_pages ) {
-                    make_new_page = true;
-                    page = doc_pages;
-                }
-		}
-
-		if(make_new_page && counter!=0) {
-			make_new_page = false;
-		}
-
-		PDPage pdPage = pdfDataSource.getPage(page-1);
-
-		PDRectangle cropBox = pdPage.getCropBox();
-
-		// fallback to MediaBox if Cropbox not available!
-
-		if (cropBox == null) {
-			cropBox = pdPage.getCropBox();
-		}
-
-		if (cropBox == null) {
-			cropBox = pdPage.getCropBox();
-		}
-
-		// getPagedimensions
-		// Rectangle psize = reader.getPageSizeWithRotation(page);
-		// int page_rotation = reader.getPageRotation(page);
-
-		// Integer rotation = pdPage.getRotation();
-		// int page_rotation = rotation.intValue();
-
-		int rotation = pdPage.getRotation();
-
-		logger.debug("Original CropBox: " + cropBox.toString());
-		
-		cropBox = rotateBox(cropBox, rotation);
-		
-		logger.debug("Rotated CropBox: " + cropBox.toString());
-		
-		float page_width = cropBox.getWidth();
-		float page_height = cropBox.getHeight();
-
-		logger.debug("CropBox width: " + page_width);
-		logger.debug("CropBox heigth: " + page_height);
-		
-		// now we can calculate x-position
-		float pre_pos_x = SIGNATURE_MARGIN_HORIZONTAL;
-		if (!pos.isXauto()) {
-			// we do have absolute x
-			pre_pos_x = pos.getPosX();
-		}
-		// calculate width
-		// center
-		float pre_width = page_width - 2 * pre_pos_x;
-		if (!pos.isWauto()) {
-			// we do have absolute width
-			pre_width = pos.getWidth();
-			if (pos.isXauto()) { // center x
-				pre_pos_x = (page_width - pre_width) / 2;
-			}
-		}
-		final float pos_x = pre_pos_x;
-		final float width = pre_width;
-		// Signatur table dimensions are complete
-		pdf_table.setWidth(width);
-		pdf_table.fixWidth();
-		// pdf_table.setTotalWidth(width);
-		// pdf_table.setLockedWidth(true);
-
-		final float table_height = pdf_table.getHeight();
-		// now check pos_y
-		float pos_y = pos.getPosY();
-
-		// in case an absolute y position is already given OR
-		// if the table is related to an invisible signature
-		// there is no need for further calculations
-		// (fixed adding new page in case of invisible signatures)
-		if (!pos.isYauto() || table_height == 0) {
-			// we do have y-position too --> all parameters but page ok
-			if (make_new_page) {
-				page++;
-			}
-			return new PositioningInstruction(make_new_page, page, pos_x,
-					pos_y, pos.rotation);
-		}
-		// pos_y is auto
-		if (make_new_page) {
-			// ignore footer in new page
-                page++;
-			pos_y = page_height - SIGNATURE_MARGIN_VERTICAL;
-			return new PositioningInstruction(make_new_page, page, pos_x,
-					pos_y, pos.rotation);
-		}
-		// up to here no checks have to be made if Tablesize and Pagesize are
-		// fit
-		// Now we have to getfreespace in page and reguard footerline
-		float footer_line = pos.getFooterLine();
-
-//		float pre_page_length = PDFUtilities.calculatePageLength(pdfDataSource,
-//				page - 1, page_height - footer_line, /* page_rotation, */
-//				legacy32, legacy40);
-
-		 float pre_page_length = Float.NEGATIVE_INFINITY;
-		try {
-			pre_page_length = PDFUtilities.getMaxYPosition(pdfDataSource, page-1, pdf_table, SIGNATURE_MARGIN_VERTICAL, footer_line, settings);
-			//pre_page_length = PDFUtilities.getFreeTablePosition(pdfDataSource, page-1, pdf_table,SIGNATURE_MARGIN_VERTICAL);
-		} catch (IOException e) {
-			logger.warn("Could not determine page length, using -INFINITY");
-		} 
-		
-		if (pre_page_length == Float.NEGATIVE_INFINITY){
-			// we do have an empty page or nothing in area above footerline
-			pre_page_length = page_height;
-			// no text --> SIGNATURE_BORDER
-			pos_y = page_height - SIGNATURE_MARGIN_VERTICAL;
-			if (pos_y - footer_line <= table_height) {
-				if(counter!=0)
-					make_new_page = false;
-				else{
-					make_new_page = true;
-					page++;
-				}
-				if (!pos.isPauto()) {
-					// we have to correct pagenumber
-					page = pdfDataSource.getNumberOfPages();
-				}
-				// no text --> SIGNATURE_BORDER
-				pos_y = page_height - SIGNATURE_MARGIN_VERTICAL;
-			}
-			return new PositioningInstruction(make_new_page, page, pos_x,
-					pos_y, pos.rotation);
-		}
-		final float page_length = pre_page_length;
-		// we do have text take SIGNATURE_MARGIN
-		pos_y = page_height - page_length - SIGNATURE_MARGIN_VERTICAL;
-		if (pos_y - footer_line <= table_height) {
-			if(counter!=0){
-				make_new_page = false;
-			}
-			else{
-				make_new_page = true;
-				page++;
-			}
-			if (!pos.isPauto()) {
-				// we have to correct pagenumber in case of absolute page and
-				// not enough
-				// space
-				page = pdfDataSource.getNumberOfPages();
-			}
-			// no text --> SIGNATURE_BORDER
-			pos_y = page_height - SIGNATURE_MARGIN_VERTICAL;
-		}
-		return new PositioningInstruction(make_new_page, page, pos_x, pos_y,
-				pos.rotation);
-	}
+  /**
+   * The left/right margin.
+   */
+  public static final float SIGNATURE_MARGIN_HORIZONTAL = 50f;
+
+  /**
+   * The top/bottom margin.
+   */
+  public static final float SIGNATURE_MARGIN_VERTICAL = 20f;
+
+  /**
+   * Evalutates absolute positioning and prepares the PositioningInstruction for
+   * placing the table.
+   *
+   * @param pos            The absolute positioning parameter. If null it is
+   *                       sought in the profile definition.
+   * @param signature_type The profile definition of the table to be written.
+   * @param pdfDataSource  The pdf.
+   * @param pdf_table      The pdf table to be written.
+   * @param settings
+   * @return Returns the PositioningInformation.
+   * @throws PdfAsException F.e.
+   */
+  public static PositioningInstruction determineTablePositioning(
+      TablePos pos, String signature_type, PDDocument pdfDataSource,
+      IPDFVisualObject pdf_table, ISettings settings) throws PdfAsException {
+    return adjustSignatureTableandCalculatePosition(pdfDataSource,
+        pdf_table, pos, settings);
+  }
+
+  /**
+   * Sets the width of the table according to the layout of the document and
+   * calculates the y position where the PDFPTable should be placed.
+   *
+   * @param pdfDataSource The PDF document.
+   * @param pdf_table     The PDFPTable to be placed.
+   * @param settings
+   * @return Returns the position where the PDFPTable should be placed.
+   * @throws PdfAsException F.e.
+   */
+  public static PositioningInstruction adjustSignatureTableandCalculatePosition(
+      final PDDocument pdfDataSource, IPDFVisualObject pdf_table,
+      TablePos pos, ISettings settings) throws PdfAsException {
+    PdfBoxUtils.checkPDFPermissions(pdfDataSource);
+    final long numberOfExistingSignatures = getNumberOfExistingSignatures(pdfDataSource);
+
+    // get pages of currentdocument
+    final int doc_pages = pdfDataSource.getNumberOfPages();
+    int page = doc_pages;
+    boolean make_new_page = pos.isNewPage();
+
+
+    if (!(pos.isNewPage() || pos.isPauto())) {
+      // we should posit signaturtable on this page
+      page = pos.getPage();
+      if (page > doc_pages) {
+        log.debug("Document is shorter than requested page for signature block. Adding new page ...");
+        make_new_page = true;
+        page = doc_pages;
+        
+      }
+    }
+
+    make_new_page = checkIfNewPageIsAllowed(make_new_page, numberOfExistingSignatures, settings);
+    
+    
+    if(make_new_page && numberOfExistingSignatures!=0) {
+      make_new_page = false;
+      
+    }
+       
+    
+    final PDPage pdPage = pdfDataSource.getPage(page - 1);
+
+    PDRectangle cropBox = pdPage.getCropBox();
+
+    // fallback to MediaBox if Cropbox not available!
+
+    if (cropBox == null) {
+      cropBox = pdPage.getCropBox();
+    }
+
+    if (cropBox == null) {
+      cropBox = pdPage.getCropBox();
+    }
+
+    // getPagedimensions
+    // Rectangle psize = reader.getPageSizeWithRotation(page);
+    // int page_rotation = reader.getPageRotation(page);
+
+    // Integer rotation = pdPage.getRotation();
+    // int page_rotation = rotation.intValue();
+
+    final int rotation = pdPage.getRotation();
+
+    log.debug("Original CropBox: " + cropBox.toString());
+
+    cropBox = rotateBox(cropBox, rotation);
+
+    log.debug("Rotated CropBox: " + cropBox.toString());
+
+    final float page_width = cropBox.getWidth();
+    final float page_height = cropBox.getHeight();
+
+    log.debug("CropBox width: " + page_width);
+    log.debug("CropBox heigth: " + page_height);
+
+    // now we can calculate x-position
+    float pre_pos_x = SIGNATURE_MARGIN_HORIZONTAL;
+    if (!pos.isXauto()) {
+      // we do have absolute x
+      pre_pos_x = pos.getPosX();
+    }
+    // calculate width
+    // center
+    float pre_width = page_width - 2 * pre_pos_x;
+    if (!pos.isWauto()) {
+      // we do have absolute width
+      pre_width = pos.getWidth();
+      if (pos.isXauto()) { // center x
+        pre_pos_x = (page_width - pre_width) / 2;
+        
+      }
+    }
+    
+    final float pos_x = pre_pos_x;
+    final float width = pre_width;
+
+    // Signatur table dimensions are complete
+    pdf_table.setWidth(width);
+    pdf_table.fixWidth();
+
+    final float table_height = pdf_table.getHeight();
+    // now check pos_y
+    float pos_y = pos.getPosY();
+
+    // in case an absolute y position is already given OR
+    // if the table is related to an invisible signature
+    // there is no need for further calculations
+    // (fixed adding new page in case of invisible signatures)
+    if (!pos.isYauto() || table_height == 0) {
+      // we do have y-position too --> all parameters but page ok
+      if (make_new_page) {
+        page++;
+        
+      }      
+      return new PositioningInstruction(make_new_page, page, pos_x, pos_y, pos.rotation);
+      
+    }
+    
+    // pos_y is auto
+    if (make_new_page) {            
+      // ignore footer in new page
+      page++;
+      pos_y = page_height - SIGNATURE_MARGIN_VERTICAL;            
+      return new PositioningInstruction(make_new_page, page, pos_x, pos_y, pos.rotation);
+      
+    }
+    
+    // up to here no checks have to be made if Tablesize and Pagesize are
+    // fit
+    // Now we have to getfreespace in page and reguard footerline   
+    float pre_page_length = calculatePrePageLength(pdfDataSource, page, pdf_table, pos.getFooterLine(), settings);
+   
+    if (pre_page_length == Float.NEGATIVE_INFINITY) {
+      // we do have an empty page or nothing in area above footerline     
+      pos_y = page_height - SIGNATURE_MARGIN_VERTICAL;      
+      return buildPostitionInfoOnSubpage(pdfDataSource, make_new_page, page, pos_x, pos_y, pos.rotation, 
+          pos.getFooterLine(), table_height, pos, page_height, numberOfExistingSignatures, settings);
+           
+    } else {    
+      // we do have text take SIGNATURE_MARGIN
+      pos_y = page_height - pre_page_length - SIGNATURE_MARGIN_VERTICAL;
+      return buildPostitionInfoOnSubpage(pdfDataSource, make_new_page, page, pos_x, pos_y, pos.rotation, 
+          pos.getFooterLine(), table_height, pos, page_height, numberOfExistingSignatures, settings);
+    
+    }  
+  }
+
+  private static float calculatePrePageLength(PDDocument pdfDataSource, int page, IPDFVisualObject pdf_table, float footer_line, ISettings settings) {    
+    try {
+      return PDFUtilities.getMaxYPosition(pdfDataSource, page - 1, pdf_table,
+          SIGNATURE_MARGIN_VERTICAL, footer_line, settings);
+    
+    } catch (final IOException e) {
+      log.warn("Could not determine page length, using -INFINITY");
+      return Float.NEGATIVE_INFINITY;
+      
+    }
+  }
+
+  private static boolean isFailOnLessSpaceEnabled(ISettings settings) {    
+    String value = settings.getValue(IConfigurationConstants.SIG_BLOCK_LESS_SPACE_STOPPING_WITH_ERROR);    
+    return Boolean.valueOf(value);
+    
+  }
+  
+  private static boolean checkIfNewPageIsAllowed(boolean make_new_page, long numberOfExistingSignatures, ISettings settings) throws PdfAsException {
+    if(make_new_page && numberOfExistingSignatures!=0) {
+      log.info("Signature-block would be need a new page, but new pages are not allowed on already signed documents.");
+      if (isFailOnLessSpaceEnabled(settings)) {
+        throw new PdfAsException("error.pdf.stamp.12");
+        
+      } else {
+        log.info("Placing signature-block on last page without free-space checks ... ");
+        return false;
+        
+      }
+      
+    } else {
+      return make_new_page;
+      
+    }       
+  }
+  
+  private static PositioningInstruction buildPostitionInfoOnSubpage(PDDocument pdfDataSource, boolean make_new_page, int page, float pos_x, 
+      float pos_y, float rotation, float footer_line, float table_height, TablePos pos, float page_height, 
+      long numberOfExistingSignatures, ISettings settings) throws PdfAsException {
+    if (pos_y - footer_line <= table_height) {
+      
+      make_new_page = checkIfNewPageIsAllowed(true, numberOfExistingSignatures, settings);
+      if (make_new_page) {        
+        page++;
+        
+      }
+            
+      if (!pos.isPauto()) {
+        // we have to correct pagenumber
+        page = pdfDataSource.getNumberOfPages();
+        
+      }
+      // no text --> SIGNATURE_BORDER
+      pos_y = page_height - SIGNATURE_MARGIN_VERTICAL;
+      
+    }
+    
+    return new PositioningInstruction(make_new_page, page, pos_x, pos_y, pos.rotation);
+    
+  }
+
+  private static long getNumberOfExistingSignatures(PDDocument pdfDataSource) {
+    try {
+      return pdfDataSource.getSignatureFields().stream()
+          .filter(el -> el.getSignature() != null)
+          .count();
+
+    } catch (final IOException e) {
+      log.warn("Can not extract existing Signatures from PDF. Use it as 0", e);
+      return 0;
+
+    }
+  }
+
+  private static PDRectangle rotateBox(PDRectangle cropBox, int rotation) {
+    if (rotation != 0) {
+      final Point2D upSrc = new Point2D.Float();
+
+      upSrc.setLocation(cropBox.getUpperRightX(),
+          cropBox.getUpperRightY());
+
+      final Point2D llSrc = new Point2D.Float();
+      llSrc.setLocation(cropBox.getLowerLeftX(), cropBox.getLowerLeftY());
+      final AffineTransform transform = new AffineTransform();
+      transform.setToIdentity();
+      if (rotation % 360 != 0) {
+        transform.setToRotation(Math.toRadians(rotation * -1), llSrc.getX(),
+            llSrc.getY());
+      }
+      final Point2D upDst = new Point2D.Float();
+      transform.transform(upSrc, upDst);
+
+      final Point2D llDst = new Point2D.Float();
+      transform.transform(llSrc, llDst);
+
+      float y1 = (float) upDst.getY();
+      float y2 = (float) llDst.getY();
+
+      if (y1 > y2) {
+        final float t = y1;
+        y1 = y2;
+        y2 = t;
+      }
+
+      if (y1 < 0) {
+        y2 = y2 + -1 * y1;
+        y1 = 0;
+      }
+
+      float x1 = (float) upDst.getX();
+      float x2 = (float) llDst.getX();
+
+      if (x1 > x2) {
+        final float t = x1;
+        x1 = x2;
+        x2 = t;
+      }
+
+      if (x1 < 0) {
+        x2 = x2 + -1 * x1;
+        x1 = 0;
+      }
+
+      cropBox.setUpperRightX(x2);
+      cropBox.setUpperRightY(y2);
+      cropBox.setLowerLeftY(y1);
+      cropBox.setLowerLeftX(x1);
+    }
+    return cropBox;
+  }
+
 }