如何将db中存储的图像转换为十六进制为可见图像

Question

Context I have access to database. That database contains image data something like 0xFFD8FFE....................09090

Problem

I need those cryptic(hex) data to convert into visual image. I am not being able to find any way.

I have tried

$image = base64_decode(file_get_contents('img.txt'));
$db_img = imagecreatefromstring($image);
Header("Content-type: image/jpeg");
imagepng($db_img);

Here img.txt is file name containing the hex data.

It Doesn't work. How can I achieve this?

Answer 1

To turn a string like 0xFFD8FFE...09090 into actual binary data, you need to first get rid of the "0x" prefix, which is not part of the actual data, and then do a simply hex → bin conversion:

$data   = '0xFFD8FFE...09090';  // maybe from file_get_contents
$binary = hex2bin(substr($data, 2));

If you don't know what type of image it is then, the most efficient method to find out is probably the use of finfo:

$finfo = new finfo(FILEINFO_MIME);
$type  = $finfo->buffer($binary);

header('Content-Type: ' . $type);
echo $binary;

There's no need to use gd to reencode the image if $binary already is an image. You may want to inspect $type here a bit to verify that it's really the kind of file you expect before blindly outputting it.