使用 PDFBox 为签名字段查找空白 space（矩形）
Find blank space(rectangle) for signature field using PDFBox
当您想使用 PDFBox 创建一个可见的签名时，您需要创建一个 Rectangle2D 对象。
Rectangle2D humanRect = new Rectangle2D.Float(100, 200, 150, 50);
我想知道是否可以在文档（或 first/last 页面）中找到特定大小（宽 x 高）的所有空白（矩形）。
我想选择其中一个职位作为我的签名表。
我想在下面的例子中使用它：
Rectangle2D humanRect = new Rectangle2D.Float(foundX, foundY, width, height);
正如在对问题的评论中已经确认的那样，您本质上是在寻找 FreeSpaceFinder and FreeSpaceFinderExt classes for iText from this answer 到 PDFBox 的功能端口。这是本次回答的重点：
如果您想从带有 PDFBox 的页面的内容流指令中确定某些内容，您通常会创建一个基于 PDFStreamEngine 或其子classes 之一的 class .对于大多数不关注文本提取的内容，PDFGraphicsStreamEngine 是选择的基础 class。
基于此，我们基本上可以复制上述基于 classes:
的 iText 的功能
public class FreeSpaceFinder extends PDFGraphicsStreamEngine {
//
// constructors
//
public FreeSpaceFinder(PDPage page, float minWidth, float minHeight) {
this(page, page.getCropBox().toGeneralPath().getBounds2D(), minWidth, minHeight);
}
public FreeSpaceFinder(PDPage page, Rectangle2D initialBox, float minWidth, float minHeight) {
this(page, Collections.singleton(initialBox), minWidth, minHeight);
}
public FreeSpaceFinder(PDPage page, Collection<Rectangle2D> initialBoxes, float minWidth, float minHeight) {
super(page);
this.minWidth = minWidth;
this.minHeight = minHeight;
this.freeSpaces = initialBoxes;
}
//
// Result
//
public Collection<Rectangle2D> getFreeSpaces() {
return freeSpaces;
}
//
// Text
//
@Override
protected void showGlyph(Matrix textRenderingMatrix, PDFont font, int code, Vector displacement)
throws IOException {
super.showGlyph(textRenderingMatrix, font, code, displacement);
Shape shape = calculateGlyphBounds(textRenderingMatrix, font, code);
if (shape != null) {
Rectangle2D rect = shape.getBounds2D();
remove(rect);
}
}
/**
* Copy of <code>org.apache.pdfbox.examples.util.DrawPrintTextLocations.calculateGlyphBounds(Matrix, PDFont, int)</code>.
*/
private Shape calculateGlyphBounds(Matrix textRenderingMatrix, PDFont font, int code) throws IOException
{
GeneralPath path = null;
AffineTransform at = textRenderingMatrix.createAffineTransform();
at.concatenate(font.getFontMatrix().createAffineTransform());
if (font instanceof PDType3Font)
{
// It is difficult to calculate the real individual glyph bounds for type 3 fonts
// because these are not vector fonts, the content stream could contain almost anything
// that is found in page content streams.
PDType3Font t3Font = (PDType3Font) font;
PDType3CharProc charProc = t3Font.getCharProc(code);
if (charProc != null)
{
BoundingBox fontBBox = t3Font.getBoundingBox();
PDRectangle glyphBBox = charProc.getGlyphBBox();
if (glyphBBox != null)
{
// PDFBOX-3850: glyph bbox could be larger than the font bbox
glyphBBox.setLowerLeftX(Math.max(fontBBox.getLowerLeftX(), glyphBBox.getLowerLeftX()));
glyphBBox.setLowerLeftY(Math.max(fontBBox.getLowerLeftY(), glyphBBox.getLowerLeftY()));
glyphBBox.setUpperRightX(Math.min(fontBBox.getUpperRightX(), glyphBBox.getUpperRightX()));
glyphBBox.setUpperRightY(Math.min(fontBBox.getUpperRightY(), glyphBBox.getUpperRightY()));
path = glyphBBox.toGeneralPath();
}
}
}
else if (font instanceof PDVectorFont)
{
PDVectorFont vectorFont = (PDVectorFont) font;
path = vectorFont.getPath(code);
if (font instanceof PDTrueTypeFont)
{
PDTrueTypeFont ttFont = (PDTrueTypeFont) font;
int unitsPerEm = ttFont.getTrueTypeFont().getHeader().getUnitsPerEm();
at.scale(1000d / unitsPerEm, 1000d / unitsPerEm);
}
if (font instanceof PDType0Font)
{
PDType0Font t0font = (PDType0Font) font;
if (t0font.getDescendantFont() instanceof PDCIDFontType2)
{
int unitsPerEm = ((PDCIDFontType2) t0font.getDescendantFont()).getTrueTypeFont().getHeader().getUnitsPerEm();
at.scale(1000d / unitsPerEm, 1000d / unitsPerEm);
}
}
}
else if (font instanceof PDSimpleFont)
{
PDSimpleFont simpleFont = (PDSimpleFont) font;
// these two lines do not always work, e.g. for the TT fonts in file 032431.pdf
// which is why PDVectorFont is tried first.
String name = simpleFont.getEncoding().getName(code);
path = simpleFont.getPath(name);
}
else
{
// shouldn't happen, please open issue in JIRA
System.out.println("Unknown font class: " + font.getClass());
}
if (path == null)
{
return null;
}
return at.createTransformedShape(path.getBounds2D());
}
//
// Bitmaps
//
@Override
public void drawImage(PDImage pdImage) throws IOException {
Matrix ctm = getGraphicsState().getCurrentTransformationMatrix();
Rectangle2D unitSquare = new Rectangle2D.Float(0, 0, 1, 1);
Path2D path = new Path2D.Float(unitSquare);
path.transform(ctm.createAffineTransform());
remove(path.getBounds2D());
}
//
// Paths
//
@Override
public void appendRectangle(Point2D p0, Point2D p1, Point2D p2, Point2D p3) throws IOException {
currentPath.moveTo(p0.getX(), p0.getY());
currentPath.lineTo(p1.getX(), p1.getY());
currentPath.lineTo(p2.getX(), p2.getY());
currentPath.lineTo(p3.getX(), p3.getY());
currentPath.closePath();
}
@Override
public void clip(int windingRule) throws IOException {
// ignore
}
@Override
public void moveTo(float x, float y) throws IOException {
currentPath.moveTo(x, y);
}
@Override
public void lineTo(float x, float y) throws IOException {
currentPath.lineTo(x, y);
}
@Override
public void curveTo(float x1, float y1, float x2, float y2, float x3, float y3) throws IOException {
currentPath.curveTo(x1, y1, x2, y2, x3, y3);
}
@Override
public Point2D getCurrentPoint() throws IOException {
// To prevent many warnings...
return new Point2D.Float();
}
@Override
public void closePath() throws IOException {
currentPath.closePath();
}
@Override
public void endPath() throws IOException {
currentPath = new Path2D.Float();
}
@Override
public void strokePath() throws IOException {
// Better only remove the bounding boxes of the constituting strokes
remove(currentPath.getBounds2D());
currentPath = new Path2D.Float();
}
@Override
public void fillPath(int windingRule) throws IOException {
// Better only remove the bounding boxes of the constituting subpaths
remove(currentPath.getBounds2D());
currentPath = new Path2D.Float();
}
@Override
public void fillAndStrokePath(int windingRule) throws IOException {
// Better only remove the bounding boxes of the constituting subpaths
remove(currentPath.getBounds2D());
currentPath = new Path2D.Float();
}
@Override
public void shadingFill(COSName shadingName) throws IOException {
// ignore
}
//
// helpers
//
void remove(Rectangle2D usedSpace)
{
final double minX = usedSpace.getMinX();
final double maxX = usedSpace.getMaxX();
final double minY = usedSpace.getMinY();
final double maxY = usedSpace.getMaxY();
final Collection<Rectangle2D> newFreeSpaces = new ArrayList<Rectangle2D>();
for (Rectangle2D freeSpace: freeSpaces)
{
final Collection<Rectangle2D> newFragments = new ArrayList<Rectangle2D>();
if (freeSpace.intersectsLine(minX, minY, maxX, minY))
newFragments.add(new Rectangle2D.Double(freeSpace.getMinX(), freeSpace.getMinY(), freeSpace.getWidth(), minY-freeSpace.getMinY()));
if (freeSpace.intersectsLine(minX, maxY, maxX, maxY))
newFragments.add(new Rectangle2D.Double(freeSpace.getMinX(), maxY, freeSpace.getWidth(), freeSpace.getMaxY() - maxY));
if (freeSpace.intersectsLine(minX, minY, minX, maxY))
newFragments.add(new Rectangle2D.Double(freeSpace.getMinX(), freeSpace.getMinY(), minX - freeSpace.getMinX(), freeSpace.getHeight()));
if (freeSpace.intersectsLine(maxX, minY, maxX, maxY))
newFragments.add(new Rectangle2D.Double(maxX, freeSpace.getMinY(), freeSpace.getMaxX() - maxX, freeSpace.getHeight()));
if (newFragments.isEmpty())
{
add(newFreeSpaces, freeSpace);
}
else
{
for (Rectangle2D fragment: newFragments)
{
if (fragment.getHeight() >= minHeight && fragment.getWidth() >= minWidth)
{
add(newFreeSpaces, fragment);
}
}
}
}
freeSpaces = newFreeSpaces;
}
void add(Collection<Rectangle2D> rectangles, Rectangle2D addition)
{
final Collection<Rectangle2D> toRemove = new ArrayList<Rectangle2D>();
boolean isContained = false;
for (Rectangle2D rectangle: rectangles)
{
if (rectangle.contains(addition))
{
isContained = true;
break;
}
if (addition.contains(rectangle))
toRemove.add(rectangle);
}
rectangles.removeAll(toRemove);
if (!isContained)
rectangles.add(addition);
}
//
// hidden members
//
Path2D currentPath = new Path2D.Float();
Collection<Rectangle2D> freeSpaces = null;
final float minWidth;
final float minHeight;
}
使用此 FreeSpaceFinder 您可以使用如下方法找到具有给定最小尺寸的空白区域：
public Collection<Rectangle2D> find(PDDocument pdDocument, PDPage pdPage, float minWidth, float minHeight) throws IOException {
FreeSpaceFinder finder = new FreeSpaceFinder(pdPage, minWidth, minHeight);
finder.processPage(pdPage);
return finder.getFreeSpaces();
}
(DetermineFreeSpaces方法find)
应用于与最小宽度为 200 和高度为 50 的以 iText 为中心的解决方案相同的 PDF 页面，我们得到：
与 iText 变体的类似屏幕截图相比，我们发现这里有更多可能的矩形。
这是由于 iText 解决方案使用 font-level 上升器和下降器，而我们在这里使用单独的字形边界框。
当您想使用 PDFBox 创建一个可见的签名时，您需要创建一个 Rectangle2D 对象。
Rectangle2D humanRect = new Rectangle2D.Float(100, 200, 150, 50);
我想知道是否可以在文档（或 first/last 页面）中找到特定大小（宽 x 高）的所有空白（矩形）。 我想选择其中一个职位作为我的签名表。
我想在下面的例子中使用它：
Rectangle2D humanRect = new Rectangle2D.Float(foundX, foundY, width, height);
正如在对问题的评论中已经确认的那样，您本质上是在寻找 FreeSpaceFinder and FreeSpaceFinderExt classes for iText from this answer 到 PDFBox 的功能端口。这是本次回答的重点：
如果您想从带有 PDFBox 的页面的内容流指令中确定某些内容，您通常会创建一个基于 PDFStreamEngine 或其子classes 之一的 class .对于大多数不关注文本提取的内容，PDFGraphicsStreamEngine 是选择的基础 class。
基于此，我们基本上可以复制上述基于 classes:
的 iText 的功能public class FreeSpaceFinder extends PDFGraphicsStreamEngine {
//
// constructors
//
public FreeSpaceFinder(PDPage page, float minWidth, float minHeight) {
this(page, page.getCropBox().toGeneralPath().getBounds2D(), minWidth, minHeight);
}
public FreeSpaceFinder(PDPage page, Rectangle2D initialBox, float minWidth, float minHeight) {
this(page, Collections.singleton(initialBox), minWidth, minHeight);
}
public FreeSpaceFinder(PDPage page, Collection<Rectangle2D> initialBoxes, float minWidth, float minHeight) {
super(page);
this.minWidth = minWidth;
this.minHeight = minHeight;
this.freeSpaces = initialBoxes;
}
//
// Result
//
public Collection<Rectangle2D> getFreeSpaces() {
return freeSpaces;
}
//
// Text
//
@Override
protected void showGlyph(Matrix textRenderingMatrix, PDFont font, int code, Vector displacement)
throws IOException {
super.showGlyph(textRenderingMatrix, font, code, displacement);
Shape shape = calculateGlyphBounds(textRenderingMatrix, font, code);
if (shape != null) {
Rectangle2D rect = shape.getBounds2D();
remove(rect);
}
}
/**
* Copy of <code>org.apache.pdfbox.examples.util.DrawPrintTextLocations.calculateGlyphBounds(Matrix, PDFont, int)</code>.
*/
private Shape calculateGlyphBounds(Matrix textRenderingMatrix, PDFont font, int code) throws IOException
{
GeneralPath path = null;
AffineTransform at = textRenderingMatrix.createAffineTransform();
at.concatenate(font.getFontMatrix().createAffineTransform());
if (font instanceof PDType3Font)
{
// It is difficult to calculate the real individual glyph bounds for type 3 fonts
// because these are not vector fonts, the content stream could contain almost anything
// that is found in page content streams.
PDType3Font t3Font = (PDType3Font) font;
PDType3CharProc charProc = t3Font.getCharProc(code);
if (charProc != null)
{
BoundingBox fontBBox = t3Font.getBoundingBox();
PDRectangle glyphBBox = charProc.getGlyphBBox();
if (glyphBBox != null)
{
// PDFBOX-3850: glyph bbox could be larger than the font bbox
glyphBBox.setLowerLeftX(Math.max(fontBBox.getLowerLeftX(), glyphBBox.getLowerLeftX()));
glyphBBox.setLowerLeftY(Math.max(fontBBox.getLowerLeftY(), glyphBBox.getLowerLeftY()));
glyphBBox.setUpperRightX(Math.min(fontBBox.getUpperRightX(), glyphBBox.getUpperRightX()));
glyphBBox.setUpperRightY(Math.min(fontBBox.getUpperRightY(), glyphBBox.getUpperRightY()));
path = glyphBBox.toGeneralPath();
}
}
}
else if (font instanceof PDVectorFont)
{
PDVectorFont vectorFont = (PDVectorFont) font;
path = vectorFont.getPath(code);
if (font instanceof PDTrueTypeFont)
{
PDTrueTypeFont ttFont = (PDTrueTypeFont) font;
int unitsPerEm = ttFont.getTrueTypeFont().getHeader().getUnitsPerEm();
at.scale(1000d / unitsPerEm, 1000d / unitsPerEm);
}
if (font instanceof PDType0Font)
{
PDType0Font t0font = (PDType0Font) font;
if (t0font.getDescendantFont() instanceof PDCIDFontType2)
{
int unitsPerEm = ((PDCIDFontType2) t0font.getDescendantFont()).getTrueTypeFont().getHeader().getUnitsPerEm();
at.scale(1000d / unitsPerEm, 1000d / unitsPerEm);
}
}
}
else if (font instanceof PDSimpleFont)
{
PDSimpleFont simpleFont = (PDSimpleFont) font;
// these two lines do not always work, e.g. for the TT fonts in file 032431.pdf
// which is why PDVectorFont is tried first.
String name = simpleFont.getEncoding().getName(code);
path = simpleFont.getPath(name);
}
else
{
// shouldn't happen, please open issue in JIRA
System.out.println("Unknown font class: " + font.getClass());
}
if (path == null)
{
return null;
}
return at.createTransformedShape(path.getBounds2D());
}
//
// Bitmaps
//
@Override
public void drawImage(PDImage pdImage) throws IOException {
Matrix ctm = getGraphicsState().getCurrentTransformationMatrix();
Rectangle2D unitSquare = new Rectangle2D.Float(0, 0, 1, 1);
Path2D path = new Path2D.Float(unitSquare);
path.transform(ctm.createAffineTransform());
remove(path.getBounds2D());
}
//
// Paths
//
@Override
public void appendRectangle(Point2D p0, Point2D p1, Point2D p2, Point2D p3) throws IOException {
currentPath.moveTo(p0.getX(), p0.getY());
currentPath.lineTo(p1.getX(), p1.getY());
currentPath.lineTo(p2.getX(), p2.getY());
currentPath.lineTo(p3.getX(), p3.getY());
currentPath.closePath();
}
@Override
public void clip(int windingRule) throws IOException {
// ignore
}
@Override
public void moveTo(float x, float y) throws IOException {
currentPath.moveTo(x, y);
}
@Override
public void lineTo(float x, float y) throws IOException {
currentPath.lineTo(x, y);
}
@Override
public void curveTo(float x1, float y1, float x2, float y2, float x3, float y3) throws IOException {
currentPath.curveTo(x1, y1, x2, y2, x3, y3);
}
@Override
public Point2D getCurrentPoint() throws IOException {
// To prevent many warnings...
return new Point2D.Float();
}
@Override
public void closePath() throws IOException {
currentPath.closePath();
}
@Override
public void endPath() throws IOException {
currentPath = new Path2D.Float();
}
@Override
public void strokePath() throws IOException {
// Better only remove the bounding boxes of the constituting strokes
remove(currentPath.getBounds2D());
currentPath = new Path2D.Float();
}
@Override
public void fillPath(int windingRule) throws IOException {
// Better only remove the bounding boxes of the constituting subpaths
remove(currentPath.getBounds2D());
currentPath = new Path2D.Float();
}
@Override
public void fillAndStrokePath(int windingRule) throws IOException {
// Better only remove the bounding boxes of the constituting subpaths
remove(currentPath.getBounds2D());
currentPath = new Path2D.Float();
}
@Override
public void shadingFill(COSName shadingName) throws IOException {
// ignore
}
//
// helpers
//
void remove(Rectangle2D usedSpace)
{
final double minX = usedSpace.getMinX();
final double maxX = usedSpace.getMaxX();
final double minY = usedSpace.getMinY();
final double maxY = usedSpace.getMaxY();
final Collection<Rectangle2D> newFreeSpaces = new ArrayList<Rectangle2D>();
for (Rectangle2D freeSpace: freeSpaces)
{
final Collection<Rectangle2D> newFragments = new ArrayList<Rectangle2D>();
if (freeSpace.intersectsLine(minX, minY, maxX, minY))
newFragments.add(new Rectangle2D.Double(freeSpace.getMinX(), freeSpace.getMinY(), freeSpace.getWidth(), minY-freeSpace.getMinY()));
if (freeSpace.intersectsLine(minX, maxY, maxX, maxY))
newFragments.add(new Rectangle2D.Double(freeSpace.getMinX(), maxY, freeSpace.getWidth(), freeSpace.getMaxY() - maxY));
if (freeSpace.intersectsLine(minX, minY, minX, maxY))
newFragments.add(new Rectangle2D.Double(freeSpace.getMinX(), freeSpace.getMinY(), minX - freeSpace.getMinX(), freeSpace.getHeight()));
if (freeSpace.intersectsLine(maxX, minY, maxX, maxY))
newFragments.add(new Rectangle2D.Double(maxX, freeSpace.getMinY(), freeSpace.getMaxX() - maxX, freeSpace.getHeight()));
if (newFragments.isEmpty())
{
add(newFreeSpaces, freeSpace);
}
else
{
for (Rectangle2D fragment: newFragments)
{
if (fragment.getHeight() >= minHeight && fragment.getWidth() >= minWidth)
{
add(newFreeSpaces, fragment);
}
}
}
}
freeSpaces = newFreeSpaces;
}
void add(Collection<Rectangle2D> rectangles, Rectangle2D addition)
{
final Collection<Rectangle2D> toRemove = new ArrayList<Rectangle2D>();
boolean isContained = false;
for (Rectangle2D rectangle: rectangles)
{
if (rectangle.contains(addition))
{
isContained = true;
break;
}
if (addition.contains(rectangle))
toRemove.add(rectangle);
}
rectangles.removeAll(toRemove);
if (!isContained)
rectangles.add(addition);
}
//
// hidden members
//
Path2D currentPath = new Path2D.Float();
Collection<Rectangle2D> freeSpaces = null;
final float minWidth;
final float minHeight;
}
使用此 FreeSpaceFinder 您可以使用如下方法找到具有给定最小尺寸的空白区域：
public Collection<Rectangle2D> find(PDDocument pdDocument, PDPage pdPage, float minWidth, float minHeight) throws IOException {
FreeSpaceFinder finder = new FreeSpaceFinder(pdPage, minWidth, minHeight);
finder.processPage(pdPage);
return finder.getFreeSpaces();
}
(DetermineFreeSpaces方法find)
应用于与最小宽度为 200 和高度为 50 的以 iText 为中心的解决方案相同的 PDF 页面，我们得到：
与 iText 变体的类似屏幕截图相比，我们发现这里有更多可能的矩形。
这是由于 iText 解决方案使用 font-level 上升器和下降器，而我们在这里使用单独的字形边界框。