Displaying blob data from a Firebird database using PHP

Question

So, I have this Firebird database, with a "photo" column which I'm trying to display.

Here is what I've done so far:

• Since the content type is unknown (I'm not the one who created the database, and there is no column indicating the type).

• From the first 20 character of the blob data I guess it's a bmp:

  "01 00 00 01 36 65 01 00 42 4D 36 65 01 00 00 00"

  The "42 4D" is in every photo I get.

Here's a sample code:

// Before this : code to connect, run a query to get the table and fetch the result as object ( everything works fine until here)

$blob_data = ibase_blob_info($row->PHOTO);
$blob_hndl = ibase_blob_open($row->PHOTO);

$bl = ibase_blob_get($blob_hndl, $blob_data[0]);
header('Content-type : image/x-xbitmap');
ibase_blob_echo($row->PHOTO);
 
echo "<dt><strong>Technician Image:</strong></dt><dd>" . 
     '<img src="data:image/x-xbitmap  ;base64,'.
     base64_encode($bl).
      '" width="290" height="290">' . "</dd>";

$filename = $bl ? dirname(__FILE__)."/img/product__$NUM.bmp" : dirname(__FILE__)."/img/no_pic.bmp";

if ($bl) fwrite(fopen($filename, 'w'), $bl);

As you can see I've tried to :

• Display the blob data using "ibase_blob_echo"
• Display the blob using img tag
• Save it as a file

First one show raw data of the blob, the second nothing and the third result in a corrupted file.

Concerning the Content-type header I've tried

• image/bmp ,x-portable-bitmap, x-xbitmap , jpg, gif, png

Now I'm out of ideas.

Answer 1

As a bitmap has 0x42 0x4D at position 0, and then 4 bytes of file size (0x36 0x65 0x01 0x00). In the dump you posted both bytes 5 - 8 (before the BMP header) and bytes 11-14 (filesize after BMP header) are the same, so it look like the blob has (guess work):

• 4 bytes: some kind of application specific image type nr (?)
• 4 bytes: file size (same as after the 0x42 0x4D)
• Actual bitmap file

You might want to check if skipping the first 8 bytes is enough to get it to work, then I'd check if this is generic across all files (maybe there is more than one file type!)