Get BLOB image from mysql database via JSON

Question

I have an image stored as BLOB in my MySQL database. I am returning the image back to the android app via PHP JSON array like this: $row_array['image'] = base64_encode($row['image']); Now I am getting the value in android like this String image = c.getString(TAG_IMAGE); where c is a JSON Object. Then I tried decoding it

byte[] b = Base64.decode(image, 0);

Bitmap bmp = BitmapFactory.decodeByteArray(b, 0, b.length);

But this just gives me a null pointer exception and crashes. What am I doing wrong here?

Logcat:

05-16 15:40:47.469: E/AndroidRuntime(30925): FATAL EXCEPTION: main
05-16 15:40:47.469: E/AndroidRuntime(30925): java.lang.NullPointerException
05-16 15:40:47.469: E/AndroidRuntime(30925):    at com.example.shareity.ListNew$JSONParse.onPostExecute(ListNew.java:254)
05-16 15:40:47.469: E/AndroidRuntime(30925):    at com.example.shareity.ListNew$JSONParse.onPostExecute(ListNew.java:1)
05-16 15:40:47.469: E/AndroidRuntime(30925):    at android.os.AsyncTask.finish(AsyncTask.java:631)
05-16 15:40:47.469: E/AndroidRuntime(30925):    at android.os.AsyncTask.access$600(AsyncTask.java:177)
05-16 15:40:47.469: E/AndroidRuntime(30925):    at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:644)
05-16 15:40:47.469: E/AndroidRuntime(30925):    at android.os.Handler.dispatchMessage(Handler.java:99)
05-16 15:40:47.469: E/AndroidRuntime(30925):    at android.os.Looper.loop(Looper.java:137)
05-16 15:40:47.469: E/AndroidRuntime(30925):    at android.app.ActivityThread.main(ActivityThread.java:4745)
05-16 15:40:47.469: E/AndroidRuntime(30925):    at java.lang.reflect.Method.invokeNative(Native Method)
05-16 15:40:47.469: E/AndroidRuntime(30925):    at java.lang.reflect.Method.invoke(Method.java:511)
05-16 15:40:47.469: E/AndroidRuntime(30925):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
05-16 15:40:47.469: E/AndroidRuntime(30925):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
05-16 15:40:47.469: E/AndroidRuntime(30925):    at dalvik.system.NativeStart.main(Native Method)

Post the exception. Is it on Base64.decode (there is no data in image) or in BitmapFactory.decodeByteArray (the data could not be properly base64 decoded)? — JP Moresmau
– JP Moresmau, Commented May 16, 2015 at 15:42
@YohanBlake it might not look like anything more than "blah blah" to you, but your answer might be inside that "blah blah". If you post the exception output, someone might be able to help you find an answer from it. — Dan Getz
– Dan Getz, Commented May 16, 2015 at 16:15
Ok, now you can see in the 3rd line of the logcat, that it crashes when, on line 254 of ListNew.java, you try to use a value which is null. That might be a clue as to what's going on. Is that line one of the lines of code you already posted? — Dan Getz
– Dan Getz, Commented May 17, 2015 at 12:16

Community · Accepted Answer · 2021-01-18 12:34:40Z

4

Suppose the event is the table name , image is the column name that holds the BLOB Image and user_id is the id of the user/row . To extract the image from the BLOB, You should create an EXTRA PHP File. which would like something like this.

get_image.php

<?php 
$db = mysql_connect("localhost","user","password") or die(mysql_error()); 
mysql_select_db("shareity",$db) or die(mysql_error()); 
$userId = $_GET['eid']; 
$query = "SELECT image FROM event WHERE eid='$userId'"; 
$result = mysql_query($query) or die(mysql_error()); 
$photo = mysql_fetch_array($result); 
header('Content-Type:image/jpeg'); 
echo $photo['image']; 
?>

Now,get_image.php is like an image. if you pass a user_id through GET to the get_image.php will throw the user_image.

So when ever you encode the json from server side,add a field which append the user id with the get_image.php like this

{
 'ID':1,
 'userName':'John',
 'image_url':'http://your-host-name/get_image.php?ID=1'
}

So from the Android, you can decode the image like this

try {
    URL url = new URL("http://your-host-name/get_image.php?ID=1");
    HttpURLConnection connection = (HttpURLConnection) url.openConnection();
    connection.setDoInput(true);
    connection.connect();
    InputStream input = connection.getInputStream();
    Bitmap myBitmap = BitmapFactory.decodeStream(input);
} catch (IOException e) {
    // Log exception
    return null;
}

More clarification can be fnd here

edited Jan 18, 2021 at 12:34

CommunityBot

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answered May 16, 2015 at 15:40

theapache64

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5 Comments

Yohan Blake Over a year ago

can you please tell me what to include in my original php file in order to get the JSON result { "image_url":"http://example.com/myImageDecoder.php?id=1" }?

Yohan Blake Over a year ago

it has to be $row_array['image'] = something ; Can you please tell me what to add there?

theapache64 Over a year ago

Yeah, $con holds the db connection.Let me ask you some question. what is the table name and column name which holds the image as BLOB data-type ?

Yohan Blake Over a year ago

Table name is event. Column name is image

theapache64 Over a year ago

Let us continue this discussion in chat.

Salman C · Accepted Answer · 2015-06-29 17:52:02Z

1

<?php 
$db = mysql_connect("localhost","user","password") or die(mysql_error()); 
mysql_select_db("shareity",$db) or die(mysql_error()); 
$userId = $_GET['eid']; 
$query = "SELECT image FROM event WHERE eid='$userId'"; 
$result = mysql_query($query) or die(mysql_error()); 
$photo = mysql_fetch_array($result); 
header('Content-Type:image/jpeg'); 
echo $photo['image']; 
?>

answered Jun 29, 2015 at 17:52

Salman C

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