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How to improve quality of signature image embedded in pdf

I am working on an web application to embed signature to pdf document. I am using following library Zetakey Sign & Send.From the signature pad signature is captured using:
var dataURL = canvas.toDataURL("image/png",1);
And in the server side(first Base64 decoding of signature string):
public String createSignature(String mySignature,int width,int height) throws IOException {
String filePath = SIGNATURE_PATH +"signature_" + new Date().getTime() + ".png";
byte[] imageByteArray = decodeImage(mySignature);
try(FileOutputStream imageOutFile = new FileOutputStream(filePath)){
imageOutFile.write(imageByteArray);
}
try {
BufferedImage image = ImageIO.read(new File(filePath));
image = scaleImage(image, width, height);
ImageIO.write(image, "png", new File(filePath));
for(Iterator<ImageWriter> iw = ImageIO.getImageWritersByFormatName("png"); iw.hasNext();) {
ImageWriter writer = iw.next();
ImageWriteParam writeParam = writer.getDefaultWriteParam();
ImageTypeSpecifier typeSpecifier = ImageTypeSpecifier.createFromBufferedImageType(BufferedImage.TYPE_INT_RGB);
IIOMetadata metadata = writer.getDefaultImageMetadata(typeSpecifier, writeParam);
if(metadata.isReadOnly() || !metadata.isStandardMetadataFormatSupported()) {
continue;
}
setDPI(metadata,500,width,height);
try (ImageOutputStream stream = ImageIO.createImageOutputStream(new FileOutputStream(filePath))){
writer.setOutput(stream);
writer.write(metadata, new IIOImage(image, null, metadata), writeParam);
}
break;
}
} catch (IOException e) {
logger.error(e.getMessage());
}
return filePath;
}
private static void setDPI(IIOMetadata metadata, int value, int width, int height) throws IIOInvalidTreeException {
double dotsPerMilli = value/(INCH_TO_CM*10);
IIOMetadataNode horiz = new IIOMetadataNode("HorizontalPixelSize");
horiz.setAttribute(VAL, Double.toString(dotsPerMilli));
IIOMetadataNode vert = new IIOMetadataNode("VerticalPixelSize");
vert.setAttribute(VAL, Double.toString(dotsPerMilli));
IIOMetadataNode horizScreenSize = new IIOMetadataNode("HorizontalScreenSize");
horizScreenSize.setAttribute(VAL, Integer.toString(width));
IIOMetadataNode vertScreenSize = new IIOMetadataNode("VerticalScreenSize");
vertScreenSize.setAttribute(VAL, Integer.toString(height));
IIOMetadataNode dim = new IIOMetadataNode("Dimension");
dim.appendChild(horiz);
dim.appendChild(vert);
dim.appendChild(horizScreenSize);
dim.appendChild(vertScreenSize);
IIOMetadataNode root = new IIOMetadataNode("javax_imageio_1.0");
root.appendChild(dim);
metadata.mergeTree("javax_imageio_1.0", root);
}
public static BufferedImage scaleImage(BufferedImage original, int width, int height){
BufferedImage scaled = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
AffineTransform at = new AffineTransform();
at.scale(((float)width)/original.getWidth(), ((float)height)/original.getHeight());
Map<RenderingHints.Key, Object> map = new HashMap<>();
map.put(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);
map.put(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY);
map.put(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
RenderingHints hints = new RenderingHints(map);
AffineTransformOp scaleOp = new AffineTransformOp(at, hints);
scaled = scaleOp.filter(original, scaled);
return scaled;
}
But the quality of signature image printed on pdf is not at all satisfactory even after attempting 500 DPI.Am I missing something?

So, using the ZetaKey's live-demo, the signature capture returned an acceptable quality PNG image...
Consider the following things:
Can I just use the original, unaltered image?
If not, can I change the order of my transformations? (DPI -> Scale Vs Scale -> DPI )
Can I forgo scaling? (often the cause of resolution loss)
I suspect that you are losing image resolution because you're adjusting DPI after you scale the image.
Effects of Scaling and DPI:
Effects of Image Transformations (DPI)
Excerpt: (not directly related, but may give insight into problem)
Now suppose you want to print your image using a regular offset press, which can print up to 300dpi images. Suppose you try to print it exactly at the original image dimension in inches. The press needs 300 dots for every inch to do a good job. The image you are supplying has only 72 dots for every inch, so the press (or more accurately, the software that prepares the plates for the press) has to make up the missing dots. The result will be blurry or noisy because there will be a lot of "transitional" dots that the software will creatively add to fill the missing gaps.

BufferedImage color saturation

I'm writing a simple scanning application using jfreesane and Apache PDFBox.
Here is the scanning code:
InetAddress address = InetAddress.getByName("192.168.0.17");
SaneSession session = SaneSession.withRemoteSane(address);
List<SaneDevice> devices = session.listDevices();
SaneDevice device = devices.get(0);
device.open();
device.getOption("resolution").setIntegerValue(300);
BufferedImage bimg = device.acquireImage();
File file = new File("test_scan.png");
ImageIO.write(bimg, "png", file);
device.close();
And making PDF:
PDDocument document = new PDDocument();
float width = bimg.getWidth();
float height = bimg.getHeight();
PDPage page = new PDPage(new PDRectangle(width, height));
document.addPage(page);
PDImageXObject pdimg = LosslessFactory.createFromImage(document, bimg);
PDPageContentStream stream = new PDPageContentStream(document, page, PDPageContentStream.AppendMode.APPEND, true);
stream.drawImage(pdimg, 0, 0);
stream.close();
document.save(filename);
document.close();
And here is the result:
As you can see the PDF image is more "pale" (saturation? - sorry, I'm not good at color theory and don't know how to name it correctly).
What I have found out:
Printing BufferedImage to JLabel using JLabel(new ImageIcon(bimg))
constructor produces the same result as with PDF ("pale" colors)
so I guess PDFBox is not the reason.
Changing scanning resolution -
no effect.
bimg.getTransparency() returns 1 (OPAQUE)
bimg.getType() returns 0 (TYPE_CUSTOM)
PNG file:
http://s000.tinyupload.com/index.php?file_id=95648202713651192395
PDF file
http://s000.tinyupload.com/index.php?file_id=90369236997064329368

There was an issue in JFreeSane with colorspaces, it was fixed in version 0.97:
https://github.com/sjamesr/jfreesane/releases/tag/jfreesane-0.97

Changing image quality

I'm trying to create remote control application in Java. I'm using robot to capture my screen image, and then I need to send it to the server. However, because the image size may be too big for the sending to be quick as possible, I'm changing the image quality in the code.
The problem is with the code I have, after changing the image it automatically save it as file in my computer but I don't want it to. I want it to the change it without saving it to be able to send it to my server
The code:
Robot robot = null;
Rectangle rectangle = null;
GraphicsEnvironment gEnv=GraphicsEnvironment.getLocalGraphicsEnvironment();
GraphicsDevice gDev=gEnv.getDefaultScreenDevice();
//Get screen dimensions
Dimension dim = Toolkit.getDefaultToolkit().getScreenSize();
rectangle = new Rectangle(dim);
System.out.println(rectangle);
robot = new Robot(gDev);
BufferedImage image = robot.createScreenCapture(rectangle);
// FileInputStream inputStream = new FileInputStream(MyFile);
// BufferedImage originalImage = ImageIO.read(inputStream);
Iterator iter = ImageIO.getImageWritersByFormatName("jpeg");
ImageWriter writer = (ImageWriter)iter.next();
ImageWriteParam iwp = writer.getDefaultWriteParam();
iwp.setCompressionMode(ImageWriteParam.MODE_EXPLICIT);
float quality = 0.25f; // reduce quality by 50%
iwp.setCompressionQuality(quality);
File file = new File("Tester6.png");
FileImageOutputStream output = new FileImageOutputStream(file);
writer.setOutput(output);
IIOImage image1 = new IIOImage(image, null, null);
writer.write(null, image1, iwp);
writer.dispose();

Instead of creating a file, do:
ByteArrayOutputStream baos = new ByteArrayOutputStream();
ImageOutputStream ios = ImageIO.createImageOutputStream(baos);
writer.setOutput(ios);
You can then use baos.toByteArray() to get the bytes after you have called writer.write().

antialiasing in java image scaling library

I am currently using http://code.google.com/p/java-image-scaling/ this library to generate scaled images for my web app.But when I scale down the image to about 100x100 size there are some leftover artifacts visible in some images. Is this an issue with antialiasing? And how do I use antialiasing with this library.The api documentation doesn't say any thing about it.
Here is the code
File f = new File("C:\\Users\\ad min\\Pictures\\30-whisky-3d-wallpaper-1152x864.jpg");
BufferedImage src = ImageIO.read(f);
//ResampleOp resampleOp = new ResampleOp(76, 76);
ResampleOp resampleOp = new ResampleOp(200,200);
resampleOp.setUnsharpenMask(AdvancedResizeOp.UnsharpenMask.VerySharp);
BufferedImage rescaled = resampleOp.filter(src, null);
ImageIO.write(rescaled, "JPG", new File(
"C:\\Users\\ad min\\Pictures\\scaleddown.jpg"));
what am I doing wrong?

I finally didn't need antialiasing I simply used this code given in the foloowing link and it worked :) whewww
http://www.universalwebservices.net/web-programming-resources/java/adjust-jpeg-image-
compression-quality-when-saving-images-in-java
Iterator<ImageWriter> iter = ImageIO
.getImageWritersByFormatName("jpeg");
ImageWriter writer = (ImageWriter) iter.next();
// instantiate an ImageWriteParam object with default compression
// options
ImageWriteParam iwp = writer.getDefaultWriteParam();
iwp.setCompressionMode(ImageWriteParam.MODE_EXPLICIT);
iwp.setCompressionQuality(1); // an integer between 0 and 1
// 1 specifies minimum compression and maximum quality
File file = new File("C:\\Users\\ad min\\Pictures\\scaleddown.jpg");
FileImageOutputStream output = new FileImageOutputStream(file);
writer.setOutput(output);
IIOImage image = new IIOImage(rescaled, null, null);
writer.write(null, image, iwp);
writer.dispose();

Insufficient Data For An Image (PDF File Generation)

I'm using PDFBox to generate PDF files, however when I try to draw an image which I receive from an array of bytes I get the following error:
Insufficient data for an image
This is the basic structure of my code:
public ByteArrayOutputStream generatePDF() {
.. Variable Declaration
// Creating Document
document = new PDDocument();
// Creating Pages
for(int i = 0; i < arrayVar.length; i++) {
// Adding page to document
page = new PDPage();
// Creating FONT Attributes
fontNormal = PDType1Font.HELVETICA;
fontBold = PDType1Font.HELVETICA_BOLD;
// Building Front & Back Invoice Images
singleImageMap = // Getting Map With Array Of Bytes from Web Service Call;
if(singleImageMap != null && !singleImageMap.isEmpty()) {
arrayFront = Utils.readImage((byte[]) singleImageMap.get(Constants.WS_IMAGE_FRONT));
arrayBack = Utils.readImage((byte[]) singleImageMap.get(Constants.WS_IMAGE_BACK));
fileFront = new ByteArrayInputStream(arrayFront);
fileBack = new ByteArrayInputStream(arrayBack);
bufferedImageFront = ImageIO.read(fileFront);
bufferedImageBack = ImageIO.read(fileBack);
rescaledFrontImg = Scalr.resize(bufferedImageFront, 500);
rescaledBackImg = Scalr.resize(bufferedImageBack, 500);
front = new PDJpeg(document, rescaledFrontImg);
back = new PDJpeg(document, rescaledBackImg);
}
// Next we start a new content stream which will "hold" the to be created content.
contentStream = new PDPageContentStream(document, page);
// Let's define the content stream
contentStream.beginText();
contentStream.setFont(fontNormal, 8);
contentStream.moveTextPositionByAmount(200, 740);
contentStream.drawString("NAME: " + arrayVar[i].getParameter(Constants.NAME));
contentStream.endText();
if(front != null && back != null) {
contentStream.drawImage(front, 55, 500);
contentStream.drawImage(back, 55, 260);
}
// Add Page
document.addPage(page);
// Let's close the content stream
contentStream.close();
}
// Let's create OutputStream object
output = new ByteArrayOutputStream();
// Finally Let's save the PDF
document.save(output);
document.close();
return output;
}
Since I receive a PNG file from the Web Service I do the conversion to JPG with the following method:
public static byte[] readImage(byte[] file) throws Exception {
ImageInputStream is = ImageIO.createImageInputStream(new ByteArrayInputStream(file));
BufferedImage originalImage = ImageIO.read(is);
ByteArrayOutputStream baos = new ByteArrayOutputStream();
ImageIO.write(originalImage, "jpg", baos );
byte[] imageInByte = baos.toByteArray();
return imageInByte;
}
As per this link:
https://issues.apache.org/jira/browse/PDFBOX-849
It points out that the error is because the PDJepg object should be created before the creation of the contentStream, but that's what I do in my code.
I'm not sure if there is a problem with the structure of my code, or that maybe there is an error in the way I'm handling the image bytes I'm getting from the Web Service call.
Does anyone has an idea of what could be the problem?
UPDATE
I did what Zelter Ady and indeed the image that I'm getting from the Web Service is valid since I was able to generate a physical file with it, so the problem should be somewhere around the manipulation of the image, the thing is I don't know what I'm missing.

I've got the same problem. With some images, Acrobat failed to display pages with this message:
Insufficient data for an image
My problem came from the colorModel in some jpeg images.
To track which images weren't ok, i log the BufferedImage colorModel by log.warn(img.getColorModel());
[VisualLocatorServlet.doGet:142] ColorModel: #pixelBits = 24 numComponents = 3 color space = java.awt.color.ICC_ColorSpace#4b7fce transparency = 1 has alpha = false isAlphaPre = false
[VisualLocatorServlet.doGet:142] ColorModel: #pixelBits = 24 numComponents = 3 color space = java.awt.color.ICC_ColorSpace#4b7fce transparency = 1 has alpha = false isAlphaPre = false
[VisualLocatorServlet.doGet:142] ColorModel: #pixelBits = 8 numComponents = 1 color space = java.awt.color.ICC_ColorSpace#19ef899 transparency = 1 has alpha = false isAlphaPre = false
Obviously, failing images are 8-bits encoded.
To fix that, i did the following:
byte[] buffer = null;
ByteArrayOutputStream out = new ByteArrayOutputStream();
BufferedImage img = ImageIO.read(new URL(visual));
/* resample 8-bits to 24-bits if necessary to fix pdf corruption */
if(img.getColorModel().getNumColorComponents()==1){
log.warn("components #1"+img.getColorModel());
BufferedImage out = new BufferedImage(w, h, BufferedImage.TYPE_3BYTE_BGR);
Graphics2D g2 = out.createGraphics();
g2.setBackground(Color.WHITE);
g2.drawImage(i, 0, 0, null);
g2.dispose();
log.warn("redrawn image "+img.getColorModel());
}
ImageIO.write(img, "jpeg", out);
...
The main point is to recreate a BufferedImage in 24bits. (BufferedImage.TYPE_3BYTE_BGR).

This may be an issue on the Adobe viewer side rather than at creation time. There's a known issue with the latest Acrobat versions: “Insufficient data for an image” error after updating to 10.1.4 or 9.5.2:
http://blogs.adobe.com/dmcmahon/2012/08/21/acrobat-insufficient-data-for-an-image-error-after-updating-to-10-1-4-or-9-5-2/

Before the build of the pdf try to save the image in a file, just to see the image is complete and can be saved.
You may use something like this to test the received image:
System.IO.File.WriteAllBytes("c:\\tmp.png", (byte[]) singleImageMap.get(Constants.FRONT));
and then open the image in a imageviewer. If the image cannot be open, then u have an error here. If the image is ok.... at least you know that this part is ok!

Well after a lot of debugging I found that the problem was here:
front = new PDJpeg(document, rescaledFrontImg);
back = new PDJpeg(document, rescaledBackImg);
The PDJpeg class has two constructors:
PDJpeg(PDDocument doc, BufferedImage bi)
PDJpeg(PDDocument doc, InputStream is)
I was passing a BufferedImage and at some point that I still can't figure out, I assume all the bytes were not being completely sent thus I got the message "Insufficient Data For An Image".
Solution: I passed an InputStream instead of a BufferedImage.
I still don't know why I got that error using a BufferedImage maybe I needed to do some sort of .push()?

This code worked for me.
import java.awt.Dimension;
import java.awt.image.BufferedImage;
import org.apache.commons.imaging.Imaging;
import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.pdmodel.PDPage;
import org.apache.pdfbox.pdmodel.PDPageContentStream;
import org.apache.pdfbox.pdmodel.graphics.image.JPEGFactory;
import org.apache.pdfbox.pdmodel.graphics.image.PDImageXObject;
public void generatePdfFromTifPbox(File sourceFile, String destinationPath) throws Exception {
//sourceFile is tiff file, destinationPath is pdf destination path with pdf file name
PDDocument doc = new PDDocument();
List<BufferedImage> bimages = Imaging.getAllBufferedImages(sourceFile);
for (BufferedImage bi : bimages) {
PDPage page = new PDPage();
doc.addPage(page);
PDPageContentStream contentStream = new PDPageContentStream(doc, page);
try {
// the .08F can be tweaked. Go up for better quality,
// but the size of the PDF will increase
PDImageXObject image = JPEGFactory.createFromImage(doc, bi, 0.08f);
Dimension scaledDim = getScaledDimension(new Dimension(image.getWidth(), image.getHeight()),
new Dimension((int) page.getMediaBox().getWidth(), (int) page.getMediaBox().getHeight()));
contentStream.drawImage(image, 1, 1, scaledDim.width, scaledDim.height);
} finally {
contentStream.close();
}
}
doc.save(destinationPath);
}
private Dimension getScaledDimension(Dimension imgSize, Dimension boundary) {
int original_width = imgSize.width;
int original_height = imgSize.height;
int bound_width = boundary.width;
int bound_height = boundary.height;
int new_width = original_width;
int new_height = original_height;
// first check if we need to scale width
if (original_width > bound_width) {
// scale width to fit
new_width = bound_width;
// scale height to maintain aspect ratio
new_height = (new_width * original_height) / original_width;
}
// then check if we need to scale even with the new height
if (new_height > bound_height) {
// scale height to fit instead
new_height = bound_height;
// scale width to maintain aspect ratio
new_width = (new_height * original_width) / original_height;
}
return new Dimension(new_width, new_height);
}
Reference/Courtesy: http://www.paulzepernick.com/java/java-apache-pdfbox-convert-multipage-tiff-to-pdf/
Maven dependency:
<dependency>
<groupId>org.apache.pdfbox</groupId>
<artifactId>pdfbox</artifactId>
<version>2.0.3</version>
</dependency>
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-imaging</artifactId>
<version>1.0-alpha1</version>
</dependency>