Develop Reference

How to store image from Android app to MySQL

I store the images to SQLite by converting the bitmap to byte array.
Should I do the same thing? Getting the byte array from bitmap, then to JSON, then to PHP, and finally to MySQL.
If yes, how can I do that? I could store strings to MySQL from the app, but couldn't do it on byte arrays.

just convert the byte array into Base64 ... base64 technically is a string, so JSON it to your webservice, there convert it back from Base64 ... and the rest is history
here is a link for converting image to Base64 in android : How to convert a image into Base64 string?
btw, other guys are right it's not so efficient to store the image itself inthe db, storing a reference would be much better ... unless you do not want your images to be right on the sd card, which is something else, security wise !

You can refer to this SO discussion that talks about uploading files to a server using Android.
As a matter of fact it is not recommended to store binary data into relational databases. Refer this SO Discussion. Rather a recommended way would be store the binary data on a server disk location as a file and simply place the path of the file within the database. This would prevent any corruption of data due to discrepancies in the database character set and encodings.

As you are willing to use another solution that is more good, i am explaining you the below procedure.
Instead of storing the image in the database, create a directory specifically for the images, after you successfully upload the image store the path of that image in your database. After that use that path to refer that image.

You can upload image via POST method, and then store reference in the database (ex:- images/img1.bmp)
Whenever you needed you can get file reference using http request(you need to code php for that request handling)
You can access image by using your servers public ip or domain for example : mydomain.com/app1/images/img1.bmp
This is just a one way to do it, so if you think about implementing look for file upload examples via POST
Hope this helps

Use Multipart file upload to send file to your web service (Use libraries like Android Asynchronous Http Client to make the job easy).Then you can encode the file in to Base64 and store in the database as text ,but it is not a best practice to store image files in database, you should save the image as file in the server and keep the path in MySql.

public static String imgToBase64(Bitmap bitmap) {
ByteArrayOutputStream out = null;
try {
out = new ByteArrayOutputStream();
// compress image
bitmap.compress(Bitmap.CompressFormat.JPEG, 20, out);
out.flush();
out.close();
byte[] imgBytes = out.toByteArray();
return Base64.encodeToString(imgBytes, Base64.DEFAULT);
} catch (Exception e) {
return null;
} finally {
try {
out.flush();
out.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}

Blob information modified when retrieving image from DB using plain JDBC

I am working on a small POC (which will be integrated into a bigger application) which consists of
Problem Context
reading an image in a simple java application program,
Convert image into a byte array byte[] imageEncodedBytes = baos.toByteArray()
storing it into a remote DB2 database (technology used was not imp, so I am using plain jdbc for now)
Reading it back from the DB and
converting it back to ensure that the re-creation of the image works. ( I am able to open the new re-created image in any image viewer)
Issues
The issues occur at step 5.
I read the image using a select query into a Result Set.
use the rs.getBlob("ColumnName") to get the blob value.
Fetch the byte array from the blob value using byte[] decodedArray = myBlob.getBytes(1, (int)myBlob.length())
Create the image from the obtained byte array.
At Step 3 the byte array decodedArray obtained from the blob differs from the byte array 'imageEncodedBytes' that I get when I read the image.
As a consequence, the following code to create the image from the byte array decodedArray fails.
ByteArrayInputStream bais = new ByteArrayInputStream(decodedArray);
//Writing to image
BufferedImage imag=ImageIO.read(bais); // Line of failure. No registered provider able to read bais
ImageIO.write(imag, "jpg", new File(dirName,"snap.jpg"));
References and Other data for issue investigation
I have referred the following links for verification
1. Inserting image in DB2
2. This Link here offers insight, but yet I was not able to determine, how to register the ImageReader.
4. When inserting the image to DB2 I am using - the following query
Statement st = conn.createStatement();
st.executeUpdate("INSERT INTO PHOTO (ID,PHOTO_NM,PHOTO_IM, THMBNL_IM) " + "VALUES (1,'blob("+bl+")',blob('"+bl+"')")
As an alternative to fetching blob value from the result set I have also used binaryStream = rs.getBinaryStream("PHOTO_IM") to get the binary stream and then get byte array from the binary stream. even in this case, the decodedArray is different from imageEncodedBytes
Please assist, I may be missing something extremely trivial here, but I am not able to figure out what. Any help/pointers will be greatly helpful. Thanks in advance.

The resolution is sort of a workaround that I have worked on.
I have used the jdbcTemplates to resolve the issue. The lobHandler Object of the jdbc template provides an easy way to manage the blobs.
Steps to resolve using the Spring Lob Handler
) Created a Data Source
) configured the Jdbc template to use the data source
) use the lobHandler code to execute the insert query
Code below
jdbcTemplate = new JdbcTemplate(dataSource);
jdbcTemplate.execute("INSERT INTO PHOTO (PHOTO_IM) VALUES (?)",
new AbstractLobCreatingPreparedStatementCallback(lobHandler) {
protected void setValues(PreparedStatement ps, LobCreator lobCreator) {
try {
lobCreator.setBlobAsBinaryStream(ps, 1, bean.getImageOrig(), bean.getImageLength());
} catch (java.sql.SQLException e) {
e.printStackTrace();
}
}
}
);
references
1. ) Stack Overflow Link - Spring JDBC Template Insert Blob
2. ) Stack Overflow Link - Close InputStream
3. ) Spring Doc for LobHandler

Load Image OpenCV (JavaCV) from byte[] not a file

I have image data coming in from over a socket connection as a byte[]. All examples I have seen using cvLoadImage() is passed a file name. Do I have to save every image to file and re-open it to do the processing? This seems to have a lot of overhead for what needs to happen, is it possible to load the image from the byte[] data?

Simple solution in the end, you can use the following method to create an Image from a BufferedImage which solved my problem:
IplImage src = IplImage.createFrom(buffered);

Assuming the data is encoded in some standard format like JPG or PNG, and assuming you are using JavaCV, for a byte array b, this works as well:
IplImage image = cvDecodeImage(cvMat(1, b.length, CV_8UC1, new BytePointer(b)));

How can I turn an ImageIcon back into a blob?

I've stored a Blob (PNG file) into the database like so:
File file = new File( "image.png" );
FileInputStream fis = new FileInputStream( file );
statement.setBinaryStream( 1, fis, (int) file.length() );
Currently I use this process to get the Blob image from the DB and convert it back into an image for use:
Blob blob = results.getBlob( 1 );
ImageIcon imageIcon = new ImageIcon( blob.getBytes( 1L, (int) blob.length() ) );
However, i need a method to put the image back into the database (after i've altered it) from the ImageIcon without creating a file, storing it to the disk then reading it back in with the FileInputSteam.
edit for clarity
Well, say i've got that image stored inside a Label as an ImageIcon. The only way i know how to put that into the database is to read from a FileInputStream, but that would involve pointlessly making a file of the image. So how would i read the Image from ImageIcon back out as a BinaryStream or Blob back to the database?

I'd try something like this
PixelGrabber pg = new PixelGrabber(imageIcon.getImage(),0,0, w,h,true);
pg.grabPixels();
// You may need to wait here until all pixels are copied (see ImageObserver)
Object buffer = pg.getPixels();
See http://download.oracle.com/javase/1.4.2/docs/api/java/awt/image/PixelGrabber.html
You may need to tweak it appropriately and specify correct w and h.

In the Blob API:
setBinaryStream(long pos) returns an OutputStream
"Retrieves a stream that can be used to write to the BLOB value that this Blob object represents." So you can write your bits directly to that stream.
I'm not quite sure how to get the pixels from your modified ImageIcon. If you can cast it to a BufferedImage, that class has a getRGB method.

How do I retrieve images within Postgres into Matlab using Java?

I have been given a bit of a strange task, there are around 1500-2000 jpeg images all of around 1-50kb in size. They are currently stored in a simple database I made with Postgres. It's been a long time since I used Matlab and Postgres heavily so any help or suggestions is really appreciated!
I need to get the images that are stored in the database, out of the database into Java. The last step is retrieve the image from Java into Matlab so that the image is stored in the same way in which the imread function works in Matlab. The imread function reads an image in and creates a n by m by 3 matrix array of uint8 values which denote the pixel intensities of RGB.
Atm I have got the image in and out of the database in Java, currently storing the image in a bytea column data type. Is the best data type to use?
How can I get the data back out from the database, so that it is either the constructed jpeg image which I put in or is in the requested matrix array format?
Currently I do not understand the retrieved data. It is in a byte array of around 70,000 elements containing values between -128 to 128. Help!?!
Note: The database toolkit is unavailable to me
ANOTHER UPDATE: I have solved the problem related to the post regarding'UTF-8' encoding error.
If anyone stumbles upon this page, any answer posted will be tried as soon as I can! I really do appreciate your thoughts and answers. Thanks again.

When you say you have the image in a bytea column, how exactly is it stored? Is it storing the bytes of the JPEG file's contents, or an array of RGB pixel values, or something else? "Bytea" is just a binary string, which can store data in pretty much any format.
I'm assuming it's the JPEG contents. In that case what you can do is retrieve the jpeg contents via Java, save them to a temporary file, and call imread() on the temp file.
Those [-128,127] values are values of signed bytes Java. Even without the Database Toolbox, you can call regular JDBC or other Java code that uses it. The Java method you used to get those values - call it from Matlab (with your JAR on the classpath), and it should return that array as an int8 array, or something you can convert to one.
Given that in a Matlab variable named "bytes", you can write it out to a temp file with something like this.
file = [tempname() '.jpg'];
fid = fopen(file, 'wb');
fwrite(fid, bytes, 'int8');
fclose(fid);
By specifying 'int8' precision, I think you can skip the step of converting them to unsigned bytes, which is a more common convention. Writing int8s as 'int8' or uint8s as 'uint8' will produce the same file. If you do need to convert them to unsigned, use Matlab's typecast() function.
unsigned_bytes = typecast(bytes, 'uint8');
At that point you can call imread on the temp file and then delete it.
img = imread(file);
delete(file);

Problem solved :-)
I have managed to get the bytes stored within the bytea column within the database into a byte array. Then through creating a temp file ( using ByteArrayInputStream and Reader object to form a BufferedImage object which I write to a file) send this back into Matlab in an array.
Then process the data I retrieved and read from the temporary file in Matlab. Once the data is within Matlab all the temp files are deleted.
The code to process the ResultSet to create a temp image from a byte array received from the databases bytea column is shown below:
private static void processImageResultSet(ResultSet rs) throws SQLException, FileNotFoundException, IOException{
int i = 0; //used as a count and to name various temp files
while(rs.next()){ //loop through result sets
byte[] b = rs.getBytes(1); //the bytea column result
String location = getFileName(rs.getString(2)); //the name of the jpg file
ByteArrayInputStream bis = new ByteArrayInputStream(b); //creates stream storing byts
//To make individual names of temporary files unique the current time and date is stored
SimpleDateFormat df = new SimpleDateFormat("'Date 'yyyy-MM-dd HH'H'-mm'M'-ss'secs'-SS'ms'"); //formats date string
Calendar cal = Calendar.getInstance(); //gets instance of calendar time
String fileDate = df.format(cal.getTime()); //gets the time and date as a String
Iterator<?> readers = ImageIO.getImageReadersByFormatName("jpg"); //creates a reader object, that will read jpg codec compression format
Object source = bis; //object to store stream of bytes from database
ImageReader reader = (ImageReader) readers.next();
ImageInputStream iis = ImageIO.createImageInputStream(source); //creates image input stream from object source which stores byte stream
reader.setInput(iis, true); //sets the reader object to read image input stream
ImageReadParam param = reader.getDefaultReadParam();
Image image = reader.read(0, param);
BufferedImage bufferedImage = new BufferedImage(image.getWidth(null), image.getHeight(null), BufferedImage.TYPE_INT_RGB); //creates buffered image
Graphics2D g2 = bufferedImage.createGraphics();
g2.drawImage(image, null, null);
File imageFile = new File(location + " " + fileDate + " " + i + ".jpg"); //creates image file
ImageIO.write(bufferedImage, "jpg", imageFile); //writes buffered image object to created file
i++; //counts number of results from query within the ResultSet
}
}

Do you have access to the Database Toolbox in MATLAB? If so, you should be able to directly connect to a PostgreSQL database using the DATABASE function and then import and export data using the FETCH function or the QUERYBUILDER GUI. This may be easier than first going through Java.