Generate QR codes with custom dot shapes using zxing - java

I'm writing an application to generate QR codes with custom dot shapes. What's the best way to do this using zxing?
So far, I've dug through the source code and I see that the data bits are written in com.google.zxing.qrcode.encoder.MatrixUtil.embedDataBits(). I think I could add some code on to the end of this function which would allow me to mask the dots but I'm not sure how to do this in Java. I can't extend the class because it's declared as final. Would it be a good idea and if so how would I extend this method in that way?
The other option I've been looking at involves post-processing the image produced by QRCode but this is really complex I think as I'd have to find a way to discern the dots from the positioning squares.
Is there a better way to do what I'm looking to do? Is there another QR code library besides zxing which can do what I'm looking to do out of the box?
P.S. I want to note that this is not a duplicate of this question although the keywords are similar.


The following java code uses zxing to make a QR-code image with circular dots and a circular finder pattern (custom rendering style). This can be adapted to other custom render styles.
I use the Encoder class directly and bypass QRCodeWriter and MatrixToImageWriter to gain enough control to alter the rendering. To alter the finder pattern, I use the fact that the finder pattern is always 7 dots wide/tall. Otherwise I would have to create a custom version of MatrixUtil (and perhaps Encoder).
Example QR Code Image Generated:
public static void main(String[] args) {
try {
generateQRCodeImage("https://www.google.com", 300, 300, "./MyQRCode.png");
} catch (Exception e) {
e.printStackTrace();
}
}
private static void generateQRCodeImage(String text, int width, int height, String filePath) throws WriterException, IOException {
final Map<EncodeHintType, Object> encodingHints = new HashMap<>();
encodingHints.put(EncodeHintType.CHARACTER_SET, "UTF-8");
QRCode code = Encoder.encode(text, ErrorCorrectionLevel.H, encodingHints);
BufferedImage image = renderQRImage(code, width, height, 4);
try (FileOutputStream stream = new FileOutputStream(filePath)) {
stream.write(bufferedImageToBytes(image));
}
}
private static BufferedImage renderQRImage(QRCode code, int width, int height, int quietZone) {
BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
Graphics2D graphics = image.createGraphics();
graphics.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
graphics.setBackground(Color.white);
graphics.clearRect(0, 0, width, height);
graphics.setColor(Color.black);
ByteMatrix input = code.getMatrix();
if (input == null) {
throw new IllegalStateException();
}
int inputWidth = input.getWidth();
int inputHeight = input.getHeight();
int qrWidth = inputWidth + (quietZone * 2);
int qrHeight = inputHeight + (quietZone * 2);
int outputWidth = Math.max(width, qrWidth);
int outputHeight = Math.max(height, qrHeight);
int multiple = Math.min(outputWidth / qrWidth, outputHeight / qrHeight);
int leftPadding = (outputWidth - (inputWidth * multiple)) / 2;
int topPadding = (outputHeight - (inputHeight * multiple)) / 2;
final int FINDER_PATTERN_SIZE = 7;
final float CIRCLE_SCALE_DOWN_FACTOR = 21f/30f;
int circleSize = (int) (multiple * CIRCLE_SCALE_DOWN_FACTOR);
for (int inputY = 0, outputY = topPadding; inputY < inputHeight; inputY++, outputY += multiple) {
for (int inputX = 0, outputX = leftPadding; inputX < inputWidth; inputX++, outputX += multiple) {
if (input.get(inputX, inputY) == 1) {
if (!(inputX <= FINDER_PATTERN_SIZE && inputY <= FINDER_PATTERN_SIZE ||
inputX >= inputWidth - FINDER_PATTERN_SIZE && inputY <= FINDER_PATTERN_SIZE ||
inputX <= FINDER_PATTERN_SIZE && inputY >= inputHeight - FINDER_PATTERN_SIZE)) {
graphics.fillOval(outputX, outputY, circleSize, circleSize);
}
}
}
}
int circleDiameter = multiple * FINDER_PATTERN_SIZE;
drawFinderPatternCircleStyle(graphics, leftPadding, topPadding, circleDiameter);
drawFinderPatternCircleStyle(graphics, leftPadding + (inputWidth - FINDER_PATTERN_SIZE) * multiple, topPadding, circleDiameter);
drawFinderPatternCircleStyle(graphics, leftPadding, topPadding + (inputHeight - FINDER_PATTERN_SIZE) * multiple, circleDiameter);
return image;
}
private static void drawFinderPatternCircleStyle(Graphics2D graphics, int x, int y, int circleDiameter) {
final int WHITE_CIRCLE_DIAMETER = circleDiameter*5/7;
final int WHITE_CIRCLE_OFFSET = circleDiameter/7;
final int MIDDLE_DOT_DIAMETER = circleDiameter*3/7;
final int MIDDLE_DOT_OFFSET = circleDiameter*2/7;
graphics.setColor(Color.black);
graphics.fillOval(x, y, circleDiameter, circleDiameter);
graphics.setColor(Color.white);
graphics.fillOval(x + WHITE_CIRCLE_OFFSET, y + WHITE_CIRCLE_OFFSET, WHITE_CIRCLE_DIAMETER, WHITE_CIRCLE_DIAMETER);
graphics.setColor(Color.black);
graphics.fillOval(x + MIDDLE_DOT_OFFSET, y + MIDDLE_DOT_OFFSET, MIDDLE_DOT_DIAMETER, MIDDLE_DOT_DIAMETER);
}
Maven dependency:
<dependency>
<groupId>com.google.zxing</groupId>
<artifactId>core</artifactId>
<version>3.4.0</version>
</dependency>


I ended up forking zxing and using JitPack to include it with Maven. I implemented functionality for RGB masking and for drawing circles and outlined squares as dot shapes. Here is the repository: https://github.com/flotwig/zxing

Related

Create simple 2D image preview from panoramic HDR

Is there some really simple and basic code for making preview for HDR images (like getting 2D BufferedImage output or something)?
I am using this HDR image.
I tried this (it uses TwelveMonkeys), but no success at all (it simply stuck/frozen at ImageReader reader = readers.next();)
I edited it a bit to suit my needs like this, testing where it got broken/stuck/frozen...and it always happen after TEST 1, that is TEST 2 is never reached, tho no IllegalArgumentException is thrown - if I remove the if() section, then TEST 3 is never reached (I am using NetBeansIDE v12.4, Win7 x64):
public BufferedImage hdrToBufferedImage(File hdrFile) throws IOException {
BufferedImage bi = null;
// Create input stream
// I WROTE DOWN THE STRING FOR THIS EXAMPLE, normally it is taken from the hdrFile
// HDR image size is 23.7MB if it matters at all?
ImageInputStream input = ImageIO.createImageInputStream(new File("Z:/HDR/spiaggia_di_mondello_4k.hdr"));
try {
// Get the reader
Iterator<ImageReader> readers = ImageIO.getImageReaders(input);
System.err.println("=====>>> TEST 1");
if (!readers.hasNext()) {
throw new IllegalArgumentException("No reader for: " + hdrFile);
}
System.err.println("=====>>> TEST 2");
ImageReader reader = readers.next();
System.err.println("=====>>> TEST 3");
try {
reader.setInput(input);
// Disable default tone mapping
HDRImageReadParam param = (HDRImageReadParam) reader.getDefaultReadParam();
param.setToneMapper(new NullToneMapper());
// Read the image, using settings from param
bi = reader.read(0, param);
} finally {
// Dispose reader in finally block to avoid memory leaks
reader.dispose();
}
} finally {
// Close stream in finally block to avoid resource leaks
input.close();
}
// Get float data
float[] rgb = ((DataBufferFloat) bi.getRaster().getDataBuffer()).getData();
// Convert the image to something easily displayable
BufferedImage converted = new ColorConvertOp(null).filter(bi, new BufferedImage(bi.getWidth(), bi.getHeight(), BufferedImage.TYPE_INT_RGB));
return converted;
}

Well, if you don't mind occasional extreme halucinogenic oversaturation of some colors here and there (I was unable solving the issue - if anyone knows how to, please, feel free to update my code), you can try this (it is using JavaHDR) + I also added a bit of brightness and contrast to it as all HDR I tested looked too dark for the preview, so if you do not like that you can remove that part from the code:
public int rgbToInteger(int r, int g, int b) {
int rgb = r;
rgb = (rgb << 8) + g;
rgb = (rgb << 8) + b;
return rgb;
}
public BufferedImage hdrToBufferedImage(File hdrFile) throws IOException {
HDRImage hdr = HDREncoder.readHDR(hdrFile, true);
int width = hdr.getWidth();
int height = hdr.getHeight();
BufferedImage bi = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
for (int x = 0; x < width; x++) {
for (int y = 0; y < height; y++) {
int r = (int) (hdr.getPixelValue(x, y, 0) * 255);
int g = (int) (hdr.getPixelValue(x, y, 1) * 255);
int b = (int) (hdr.getPixelValue(x, y, 2) * 255);
bi.setRGB(x, y, rgbToInteger(r, g, b));
}
}
//***** YOU CAN REMOVE THIS SMALL SECTION IF YOU FEEL THE IMAGE IS TOO BRIGHT FOR YOU
float brightness = 2f;
float contrast = 20f;
RescaleOp rescaleOp = new RescaleOp(brightness, contrast, null);
rescaleOp.filter(bi, bi);
//*****
return bi;
}

I can compile and run the code you posted (changing the path obviously) without problems on my two macOS machines, testing on all the LTS Java versions (8, 11 and 17). In addition, I run code similar to this as part of the CI/CD pipeline of my project that tests on Windows and Linux as well. I think there is something wrong with the setup in your IDE or Java on your computer. I am not able to reproduce the "freeze"-situation you describe...
Here is the output of running the program (I also printed the resulting BufferedImage for verification):
=====>>> TEST 1
=====>>> TEST 2
=====>>> TEST 3
image = BufferedImage#5a42bbf4: type = 1 DirectColorModel: rmask=ff0000 gmask=ff00 bmask=ff amask=0 IntegerInterleavedRaster: width = 1024 height = 512 #Bands = 3 xOff = 0 yOff = 0 dataOffset[0] 0
Running with the code as-is (with the NullToneMapper and no post-processing), the image looks like this, due to unnormalized values:
Running with the default/built-in tone mapper, or simply reading the image with ImageIO.read(hdrFile) as suggested in the comments, the image will look like this:
Finally, playing a bit with the code using a custom global tone mapper; param.setToneMapper(new DefaultToneMapper(0.75f)), I get a result like this:

After a long discussion with #HaraldK and his code addition, I am posting the final correct code for this problem, that is in fact mix of #qraqatit code updated a bit with the #HaraldK addition that corrects wrong color tone mapping, here it is:
public int rgbToInteger(int r, int g, int b) {
int rgb = r;
rgb = (rgb << 8) + g;
rgb = (rgb << 8) + b;
return rgb;
}
public BufferedImage hdrToBufferedImage(File hdrFile) throws IOException {
HDRImage hdr = HDREncoder.readHDR(hdrFile, true);
int width = hdr.getWidth();
int height = hdr.getHeight();
BufferedImage bi = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
float colorToneCorrection = 0.75f;
for (int x = 0; x < width; x++) {
for (int y = 0; y < height; y++) {
float r = hdr.getPixelValue(x, y, 0);
int red = (int) ((r / (colorToneCorrection + r)) * 255);
float g = hdr.getPixelValue(x, y, 1);
int green = (int) ((g / (colorToneCorrection + g)) * 255);
float b = hdr.getPixelValue(x, y, 2);
int blue = (int) (int) ((b / (colorToneCorrection + b)) * 255);
bi.setRGB(x, y, rgbToInteger(red, green, blue));
}
}
//MAKE THE RESULTING IMAGE A BIT BRIGHTER
float brightness = 1.35f;
float contrast = 0f;
RescaleOp rescaleOp = new RescaleOp(brightness, contrast, null);
rescaleOp.filter(bi, bi);
return bi;
}

How to implement a the tile seamless algorithm in JAVA?

Tile seamless is an image operation that is available in GIMP. It transforms the image so that it can cover a surface smoothly with a repeatable pattern. The edges will not be visible and the pieces will fit perfectly when tiled together. It makes senses for grass, floors, walls, etc... As far as the example shown in the GIMP documentation though, it is not good (the Taj Mahal https://docs.gimp.org/2.10/en/gimp-filter-tile-seamless.html) but it gives an idea of how it works.
A transparent layer is applied over the image. It's a translation of half the size of the image (modulo image size) and the closer to the center, the more transparent it gets to show more of the original image. I took a look at the algorithm used in GIMP but it was pretty hard to read (https://gitlab.gnome.org/GNOME/gegl/-/blob/master/operations/common/tile-seamless.c).
So instead I remembered Pythagore to compute the distance to the center.
Then I apply a pro-rata to have an alpha between 0 and 255 :
0 => fully transparent => center
255 => fully opaque => corner
So here is the code :
public class TileSeamless {
public static BufferedImage createSeamlessTile(BufferedImage inputImage) {
int w = inputImage.getWidth();
int h = inputImage.getHeight();
BufferedImage seamlessTile = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB);
seamlessTile.getGraphics().drawImage(inputImage, 0, 0, null);
seamlessTile.getGraphics().drawImage(createLayerImage(inputImage), 0, 0, null);
return seamlessTile;
}
public static BufferedImage createLayerImage(BufferedImage inputImage) {
int w = inputImage.getWidth();
int h = inputImage.getHeight();
BufferedImage layerImage = new BufferedImage(w, h, BufferedImage.TYPE_INT_ARGB);
for (int x = 0; x < w; x++) {
for (int y = 0; y < h; y++) {
Color color = new Color(inputImage.getRGB((x + w / 2) % w, (y + h / 2) % h));
int alpha = (int) Math.round(255 * distanceToCenter(x, y, w, h) / distanceToCenter(0, 0, w, h));
Color newColor = new Color(color.getRed(), color.getGreen(), color.getBlue(), alpha);
layerImage.setRGB(x, y, newColor.getRGB());
}
}
return layerImage;
}
public static double distanceToCenter(int x, int y, int w, int h) {
double distanceToCenterX = x - w / 2d;
double distanceToCenterY = y - h / 2d;
return Math.sqrt(distanceToCenterX * distanceToCenterX + distanceToCenterY * distanceToCenterY);
}
public static void main(String[] args) throws IOException {
File inputFile = new File(args[0]);
File outputFile = new File(args[1]);
BufferedImage inputImage = ImageIO.read(inputFile);
BufferedImage seamlessTile = TileSeamless.createSeamlessTile(inputImage);
ImageIO.write(seamlessTile, "png", outputFile);
}
The result is not too bad. It looks a bit different from the one produced by GIMP.
It's a bit blury.
Any idea how I can have a slighly more neat result?

How can I load textures from a spritesheet in Java using Slick-Utils?

I'm creating a game using LWJGL and Slick Utils. I'm trying to load an animated texture as a set of frames contained in a single PNG image.
I have tried to figure out how to get subimages using Slick, but so far all I've been able to find on the subject is a way to do it outside of Slick using BufferedImages. I'd like to know if there is a way to do this using the Slick Utils library, since all of my image loading code in my project so far has been using Slick.

Sure, Slick provides a way to do this. If you look at org.newdawn.slick.SpriteSheet.initImpl() and later org.newdawn.slick.SpriteSheet.getSprite(), you will notice how org.newdawn.slick.Image.getSubImage() can be used to quickly extract specific portions of an existing image.
SpriteSheet.java
protected void initImpl() {
if (subImages != null) {
return;
}
int tilesAcross = ((getWidth()-(margin*2) - tw) / (tw + spacing)) + 1;
int tilesDown = ((getHeight()-(margin*2) - th) / (th + spacing)) + 1;
if ((getHeight() - th) % (th+spacing) != 0) {
tilesDown++;
}
subImages = new Image[tilesAcross][tilesDown];
for (int x=0;x<tilesAcross;x++) {
for (int y=0;y<tilesDown;y++) {
//extract parts of the main image and store them in an array as sprites
subImages[x][y] = getSprite(x,y);
}
}
}
/**
* Get a sprite at a particular cell on the sprite sheet
*
* #param x The x position of the cell on the sprite sheet
* #param y The y position of the cell on the sprite sheet
* #return The single image from the sprite sheet
*/
public Image getSprite(int x, int y) {
target.init();
initImpl();
if ((x < 0) || (x >= subImages.length)) {
throw new RuntimeException("SubImage out of sheet bounds: "+x+","+y);
}
if ((y < 0) || (y >= subImages[0].length)) {
throw new RuntimeException("SubImage out of sheet bounds: "+x+","+y);
}
//Call Image.getSubImage() to get a portion of the image
return target.getSubImage(x*(tw+spacing) + margin, y*(th+spacing) + margin,tw,th);
}
You should be able to use that as reference. I remember having fully ported the Tiled renderer bundled with Slick to Java2D once, using the old good PixelGrabber to extract sprites.
And if you decide to use SpriteSheet, you can find an example of use in org.newdawn.slick.tiled.Layer.render():
Layer.java
public void render(int x, int y, int sx, int sy, int width, int ty,
boolean lineByLine, int mapTileWidth, int mapTileHeight) {
for (int tileset = 0; tileset < map.getTileSetCount(); tileset++) {
TileSet set = null;
for (int tx = 0; tx < width; tx++) {
if ((sx + tx < 0) || (sy + ty < 0)) {
continue;
}
if ((sx + tx >= this.width) || (sy + ty >= this.height)) {
continue;
}
if (data[sx + tx][sy + ty][0] == tileset) {
if (set == null) {
set = map.getTileSet(tileset);
set.tiles.startUse();
}
int sheetX = set.getTileX(data[sx + tx][sy + ty][1]);
int sheetY = set.getTileY(data[sx + tx][sy + ty][1]);
int tileOffsetY = set.tileHeight - mapTileHeight;
//Call SpriteSheet.renderInUse() to render the sprite cached at slot [sheetX, sheetY]
set.tiles.renderInUse(x + (tx * mapTileWidth), y
+ (ty * mapTileHeight) - tileOffsetY, sheetX,
sheetY);
}
}
if (lineByLine) {
if (set != null) {
set.tiles.endUse();
set = null;
}
map.renderedLine(ty, ty + sy, index);
}
if (set != null) {
set.tiles.endUse();
}
}
}
SpriteSheet.java
public void renderInUse(int x,int y,int sx,int sy) {
//Draw the selected sprite at (x,y), using the width/height defined for this SpriteSheet
subImages[sx][sy].drawEmbedded(x, y, tw, th);
}
Hope this helps you.

Convolution Blur Filter doesn't work and brightens the image

I've read about Convolution Filters recently and decided to try it out. I wanted to make code that blurs the image but what it ends up doing is brightening it. I've been looking at my code for some time now and can't find any mistakes. Could anyone help?
Here is my code:
final static int filterHeight =3;
final static int filterWidth = 3;
static double filter[][] = new double[][]{
{1,1,1},
{1,1,1},
{1,1,1}
};
public static void main(String[] args) {
BufferedImage img;
BufferedImage result;
try
{ File in = new File("in.jpg");
File out = new File("out.jpg");
img = ImageIO.read(in);
Color[][] pixels = new Color[img.getWidth()][img.getHeight()];
for(int i=0;i<img.getWidth();i++){
for(int j=0;j<img.getHeight();j++){
pixels[i][j]=new Color(img.getRGB(i,j),true);
}
}
result = new BufferedImage(img.getWidth(), img.getHeight(), img.getType());
for(int x=0;x<img.getWidth();x++){
for(int y=0;y<img.getHeight();y++){
int r=0,g=0,b=0;
for(int i=0;i<filterWidth;i++){
for(int j=0;j<filterHeight;j++){
int imageX = (int)(x - filterWidth / 2 + i + img.getWidth()) % img.getWidth();
int imageY = (int)(y - filterHeight / 2 + j + img.getHeight()) % img.getHeight();
if(imageX<0 || imageY<0) System.out.println("ERROR: "+imageX+" "+imageY);
r+=pixels[imageX][imageY].getRed()*filter[i][j];
g+=pixels[imageX][imageY].getGreen()*filter[i][j];
b+=pixels[imageX][imageY].getBlue()*filter[i][j];
}
if(r>255) r=255;
if(r<0) r=0;
if(g>255) g=255;
if(g<0) g=0;
if(b>255) b=255;
if(b<0) b=0;
Color color = new Color(img.getRGB(x,y),true)
Color colorBlur = new Color(r,g,b,color.getAlpha());
result.setRGB(x, y, colorBlur.getRGB());
}
}
}
ImageIO.write(result, "JPG", out );
}
catch (IOException e)
{
e.printStackTrace();
}
And here is image before aplying filter:
And after:

There are two options in order to get the result you desire.
Either you create a filter matrix with a sum of 1 (Like #Spektre mentioned in his comment above) or multiply the pixel's new value with a factor of 1 / sum(filterMatrix).
For a nice beginner tutorial of the concept of blurring I would recommend:
Concept of Blurring - www.TutorialsPoint.com

How can I can insert an image or stamp on a pdf where there is free space available like a density scanner

I have a pdf file where-in I am adding a stamp to all it's pages.
But, the problem is, the stamp is added to the upper-left corner of each page. If, the page has text in that part, the stamp appears on the text.
My question is, is there any method by which I can read each page and if there is no text in that part add the stamp else search for nearest available free space, just like what a density scanner does?
I am using IText and Java 1.7.
The free space fider class and the distance calculation function are the same that is there in the accepted answer.
Following is the edited code I am using:
// The resulting PDF file
String RESULT = "K:\\DCIN_TER\\DCIN_EPU2\\CIRCUIT FROM BRANCH\\RAINBOW ORDERS\\" + jtfSONo.getText().trim() + "\\PADR Release\\Final PADR Release 1.pdf";
// Create a reader
PdfReader reader = new PdfReader("K:\\DCIN_TER\\DCIN_EPU2\\CIRCUIT FROM BRANCH\\RAINBOW ORDERS\\" + jtfSONo.getText().trim() + "\\PADR Release\\Final PADR Release.pdf");
// Create a stamper
PdfStamper stamper = new PdfStamper(reader, new FileOutputStream(RESULT));
// Loop over the pages and add a footer to each page
int n = reader.getNumberOfPages();
for(int i = 1; i <= n; i++)
{
Collection<Rectangle2D> rectangles = find(reader, 300, 100, n, stamper); // minimum width & height of a rectangle
Iterator itr = rectangles.iterator();
while(itr.hasNext())
{
System.out.println(itr.next());
}
if(!(rectangles.isEmpty()) && (rectangles.size() != 0))
{
Rectangle2D best = null;
double bestDist = Double.MAX_VALUE;
Point2D.Double point = new Point2D.Double(200, 400);
float x = 0, y = 0;
for(Rectangle2D rectangle: rectangles)
{
double distance = distance(rectangle, point);
if(distance < bestDist)
{
best = rectangle;
bestDist = distance;
x = (float) best.getX();
y = (float) best.getY();
int left = (int) best.getMinX();
int right = (int) best.getMaxX();
int top = (int) best.getMaxY();
int bottom = (int) best.getMinY();
System.out.println("x : " + x);
System.out.println("y : " + y);
System.out.println("left : " + left);
System.out.println("right : " + right);
System.out.println("top : " + top);
System.out.println("bottom : " + bottom);
}
}
getFooterTable(i, n).writeSelectedRows(0, -1, x, y, stamper.getOverContent(i)); // 0, -1 indicates 1st row, 1st column upto last row and last column
}
else
getFooterTable(i, n).writeSelectedRows(0, -1, 94, 140, stamper.getOverContent(i)); // bottom left corner
}
// Close the stamper
stamper.close();
// Close the reader
reader.close();
public Collection<Rectangle2D> find(PdfReader reader, float minWidth, float minHeight, int page, PdfStamper stamper) throws IOException
{
Rectangle cropBox = reader.getCropBox(page);
Rectangle2D crop = new Rectangle2D.Float(cropBox.getLeft(), cropBox.getBottom(), cropBox.getWidth(), cropBox.getHeight());
FreeSpaceFinder finder = new FreeSpaceFinder(crop, minWidth, minHeight);
PdfReaderContentParser parser = new PdfReaderContentParser(reader);
parser.processContent(page, finder);
System.out.println("finder.freeSpaces : " + finder.freeSpaces);
return finder.freeSpaces;
}
// Create a table with page X of Y, #param x the page number, #param y the total number of pages, #return a table that can be used as footer
public static PdfPTable getFooterTable(int x, int y)
{
java.util.Date date = new java.util.Date();
SimpleDateFormat sdf = new SimpleDateFormat("dd MMM yyyy");
String month = sdf.format(date);
System.out.println("Month : " + month);
PdfPTable table = new PdfPTable(1);
table.setTotalWidth(120);
table.setLockedWidth(true);
table.getDefaultCell().setFixedHeight(20);
table.getDefaultCell().setBorder(Rectangle.TOP);
table.getDefaultCell().setBorder(Rectangle.LEFT);
table.getDefaultCell().setBorder(Rectangle.RIGHT);
table.getDefaultCell().setBorderColorTop(BaseColor.BLUE);
table.getDefaultCell().setBorderColorLeft(BaseColor.BLUE);
table.getDefaultCell().setBorderColorRight(BaseColor.BLUE);
table.getDefaultCell().setBorderWidthTop(1f);
table.getDefaultCell().setBorderWidthLeft(1f);
table.getDefaultCell().setBorderWidthRight(1f);
table.getDefaultCell().setHorizontalAlignment(Element.ALIGN_CENTER);
Font font1 = new Font(FontFamily.HELVETICA, 10, Font.BOLD, BaseColor.BLUE);
table.addCell(new Phrase("CONTROLLED COPY", font1));
table.getDefaultCell().setFixedHeight(20);
table.getDefaultCell().setBorder(Rectangle.LEFT);
table.getDefaultCell().setBorder(Rectangle.RIGHT);
table.getDefaultCell().setBorderColorLeft(BaseColor.BLUE);
table.getDefaultCell().setBorderColorRight(BaseColor.BLUE);
table.getDefaultCell().setBorderWidthLeft(1f);
table.getDefaultCell().setBorderWidthRight(1f);
table.getDefaultCell().setHorizontalAlignment(Element.ALIGN_CENTER);
Font font = new Font(FontFamily.HELVETICA, 10, Font.BOLD, BaseColor.RED);
table.addCell(new Phrase(month, font));
table.getDefaultCell().setFixedHeight(20);
table.getDefaultCell().setBorder(Rectangle.LEFT);
table.getDefaultCell().setBorder(Rectangle.RIGHT);
table.getDefaultCell().setBorder(Rectangle.BOTTOM);
table.getDefaultCell().setBorderColorLeft(BaseColor.BLUE);
table.getDefaultCell().setBorderColorRight(BaseColor.BLUE);
table.getDefaultCell().setBorderColorBottom(BaseColor.BLUE);
table.getDefaultCell().setBorderWidthLeft(1f);
table.getDefaultCell().setBorderWidthRight(1f);
table.getDefaultCell().setBorderWidthBottom(1f);
table.getDefaultCell().setHorizontalAlignment(Element.ALIGN_CENTER);
table.addCell(new Phrase("BLR DESIGN DEPT.", font1));
return table;
}

is there any method by which I can read each page and if there is no text in that part add the stamp else search for nearest available free space, just like what a density scanner does?
iText does not offer that functionality out of the box. Depending of what kind of content you want to evade, though, you might consider either rendering the page to an image and looking for white spots in the image or doing text extraction with a strategy that tries to find locations without text.
The first alternative, analyzing a rendered version of the page, would be the focus of a separate question as an image processing library would have to be chosen first.
There are a number of situations, though, in which that first alternative is not the best way to go. E.g. if you only want to evade text but not necessarily graphics (like watermarks), or if you also want to evade invisible text (which usually can be marked in a PDF viewer and, therefore, interfere with your addition).
The second alternative (using text and image extraction abilities of iText) can be the more appropriate approach in such situations.
Here a sample RenderListener for such a task:
public class FreeSpaceFinder implements RenderListener
{
//
// constructors
//
public FreeSpaceFinder(Rectangle2D initialBox, float minWidth, float minHeight)
{
this(Collections.singleton(initialBox), minWidth, minHeight);
}
public FreeSpaceFinder(Collection<Rectangle2D> initialBoxes, float minWidth, float minHeight)
{
this.minWidth = minWidth;
this.minHeight = minHeight;
freeSpaces = initialBoxes;
}
//
// RenderListener implementation
//
#Override
public void renderText(TextRenderInfo renderInfo)
{
Rectangle2D usedSpace = renderInfo.getAscentLine().getBoundingRectange();
usedSpace.add(renderInfo.getDescentLine().getBoundingRectange());
remove(usedSpace);
}
#Override
public void renderImage(ImageRenderInfo renderInfo)
{
Matrix imageMatrix = renderInfo.getImageCTM();
Vector image00 = rect00.cross(imageMatrix);
Vector image01 = rect01.cross(imageMatrix);
Vector image10 = rect10.cross(imageMatrix);
Vector image11 = rect11.cross(imageMatrix);
Rectangle2D usedSpace = new Rectangle2D.Float(image00.get(Vector.I1), image00.get(Vector.I2), 0, 0);
usedSpace.add(image01.get(Vector.I1), image01.get(Vector.I2));
usedSpace.add(image10.get(Vector.I1), image10.get(Vector.I2));
usedSpace.add(image11.get(Vector.I1), image11.get(Vector.I2));
remove(usedSpace);
}
#Override
public void beginTextBlock() { }
#Override
public void endTextBlock() { }
//
// 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);
}
//
// members
//
public Collection<Rectangle2D> freeSpaces = null;
final float minWidth;
final float minHeight;
final static Vector rect00 = new Vector(0, 0, 1);
final static Vector rect01 = new Vector(0, 1, 1);
final static Vector rect10 = new Vector(1, 0, 1);
final static Vector rect11 = new Vector(1, 1, 1);
}
Using this FreeSpaceFinder you can find empty areas with given minimum dimensions in a method like this:
public Collection<Rectangle2D> find(PdfReader reader, float minWidth, float minHeight, int page) throws IOException
{
Rectangle cropBox = reader.getCropBox(page);
Rectangle2D crop = new Rectangle2D.Float(cropBox.getLeft(), cropBox.getBottom(), cropBox.getWidth(), cropBox.getHeight());
FreeSpaceFinder finder = new FreeSpaceFinder(crop, minWidth, minHeight);
PdfReaderContentParser parser = new PdfReaderContentParser(reader);
parser.processContent(page, finder);
return finder.freeSpaces;
}
For your task you now have to choose from the returned rectangles the one which suits you best.
Beware, this code still may have to be tuned to your requirements:
It ignores clip paths, rendering modes, colors, and covering objects. Thus, it considers all text and all bitmap images, whether they are actually visible or not.
It does not consider vector graphics (because the iText parser package does not consider them).
It is not very optimized.
Applied to this PDF page:
with minimum width 200 and height 50, you get these rectangles:
x y w h
000,000 000,000 595,000 056,423
000,000 074,423 595,000 168,681
000,000 267,304 314,508 088,751
000,000 503,933 351,932 068,665
164,296 583,598 430,704 082,800
220,803 583,598 374,197 096,474
220,803 583,598 234,197 107,825
000,000 700,423 455,000 102,396
000,000 700,423 267,632 141,577
361,348 782,372 233,652 059,628
or, more visually, here as rectangles on the page:
The paper plane is a vector graphic and, therefore, ignored.
Of course you could also change the PDF rendering code to not draw stuff you want to ignore and to visibly draw originally invisible stuff which you want to ignore, and then use bitmap image analysis nonetheless...
EDIT
In his comments the OP asked how to find the rectangle in the rectangle collection returned by find which is nearest to a given point.
First of all there not necessarily is the nearest rectangle, there may be multiple.
That been said, one can choose a nearest rectangle as follows:
First one needs to calculate a distance between point and rectangle, e.g.:
double distance(Rectangle2D rectangle, Point2D point)
{
double x = point.getX();
double y = point.getY();
double left = rectangle.getMinX();
double right = rectangle.getMaxX();
double top = rectangle.getMaxY();
double bottom = rectangle.getMinY();
if (x < left) // point left of rect
{
if (y < bottom) // and below
return Point2D.distance(x, y, left, bottom);
if (y > top) // and top
return Point2D.distance(x, y, left, top);
return left - x;
}
if (x > right) // point right of rect
{
if (y < bottom) // and below
return Point2D.distance(x, y, right, bottom);
if (y > top) // and top
return Point2D.distance(x, y, right, top);
return x - right;
}
if (y < bottom) // and below
return bottom - y;
if (y > top) // and top
return y - top;
return 0;
}
Using this distance measurement one can select a nearest rectangle using code like this for a Collection<Rectangle2D> rectangles and a Point2D point:
Rectangle2D best = null;
double bestDist = Double.MAX_VALUE;
for (Rectangle2D rectangle: rectangles)
{
double distance = distance(rectangle, point);
if (distance < bestDist)
{
best = rectangle;
bestDist = distance;
}
}
After this best contains a best rectangle.
For the sample document used above, this method returns the colored rectangles for the page corners and left and right centers:
EDIT TWO
Since iText 5.5.6, the RenderListener interface has been extended as ExtRenderListener to also be signaled about Path construction and path drawing operations. Thus, the FreeSpaceFinder above could also be extended to handle paths:
//
// Additional ExtRenderListener methods
//
#Override
public void modifyPath(PathConstructionRenderInfo renderInfo)
{
List<Vector> points = new ArrayList<Vector>();
if (renderInfo.getOperation() == PathConstructionRenderInfo.RECT)
{
float x = renderInfo.getSegmentData().get(0);
float y = renderInfo.getSegmentData().get(1);
float w = renderInfo.getSegmentData().get(2);
float h = renderInfo.getSegmentData().get(3);
points.add(new Vector(x, y, 1));
points.add(new Vector(x+w, y, 1));
points.add(new Vector(x, y+h, 1));
points.add(new Vector(x+w, y+h, 1));
}
else if (renderInfo.getSegmentData() != null)
{
for (int i = 0; i < renderInfo.getSegmentData().size()-1; i+=2)
{
points.add(new Vector(renderInfo.getSegmentData().get(i), renderInfo.getSegmentData().get(i+1), 1));
}
}
for (Vector point: points)
{
point = point.cross(renderInfo.getCtm());
Rectangle2D.Float pointRectangle = new Rectangle2D.Float(point.get(Vector.I1), point.get(Vector.I2), 0, 0);
if (currentPathRectangle == null)
currentPathRectangle = pointRectangle;
else
currentPathRectangle.add(pointRectangle);
}
}
#Override
public Path renderPath(PathPaintingRenderInfo renderInfo)
{
if (renderInfo.getOperation() != PathPaintingRenderInfo.NO_OP)
remove(currentPathRectangle);
currentPathRectangle = null;
return null;
}
#Override
public void clipPath(int rule)
{
// TODO Auto-generated method stub
}
Rectangle2D.Float currentPathRectangle = null;
(FreeSpaceFinderExt.java)
Using this class the result above is improved to
As you see the paper plane and the table background colorations now also are taken into account.

My other answer focuses on the original question, i.e. how to find free space with given minimum dimensions on a page.
Since that answer had been written, the OP provided code trying to make use of that original answer.
This answer deals with that code.
The code has a number of shortcoming.
The choice of free space on a page depends on the number of pages in the document.
The reason for this is to be found at the start of the loop over the pages:
for(int i = 1; i <= n; i++)
{
Collection<Rectangle2D> rectangles = find(reader, 300, 100, n, stamper);
...
The OP surely meant i, not n there. The code as is always looks for free space on the last document page.
The rectangles are lower than they should be.
The reason for this is to be found in the retrieval and use of the rectangle coordinates:
x = (float) best.getX();
y = (float) best.getY();
...
getFooterTable(i, n).writeSelectedRows(0, -1, x, y, stamper.getOverContent(i));
The Rectangle2D methods getX and getY return the coordinates of the lower left rectangle corner; the PdfPTable methods writeSelectedRows, on the other hand, require the upper left rectangle corner. Thus, getMaxY should be used instead of getY.

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