How to convert an image from URL to hex string?

Question

I am downloading an image from URL as follows:

BufferedImage image = null;
URL url = new URL("http://www.ex.com/image/pic.jpg");
image = ImageIO.read(url);

I would like to convert it to something like the following hex string format:

89504E470D0A1A0A0000000D4948445200000124000001150802000000C6BD0FB3000000017352474200AECE1CE9000000097048597300000EC400000EC401952B0E1B000050B849444154785EED7D0B745CD759EE09E5618742A5C6F1833CB01A6E630587565E2154EE0D579203756DE823764B1ACAEB5A70EBAB2C08588EDB

But I don't know how to do that. How can I do that?

I think this looks more like some sort of hex encoding - each byte being represented by a two digit hex value — Andreas Fester, Mar 27 '13 at 12:54
You mean ... The URL `http://www.ex.com/image/pic.jpg` returns a `plain/text` content with the given string in hex format? This is quite strange. Where exactly did you get that hex string from? Did you print that yourself somehow or are you seeing that somewhere? Is so, how exactly or where exactly? — BalusC, Mar 27 '13 at 12:57
no, I want to get string like the above hex string from any given image. — becks, Mar 27 '13 at 12:58
Oh, you want to convert an image to hex string, not to convert hex string to image. — BalusC, Mar 27 '13 at 13:09

score 3 · Answer 1 · edited May 23 '17 at 12:13

3

You could do a combination of the following:

Get byte array of image: Java- Convert bufferedimage to byte[] without writing to disk
Get hex string of byte array: How to convert a byte array to a hex string in Java?

edited May 23 '17 at 12:13

Community

1
1

answered Mar 27 '13 at 12:58

Vincent van der Weele

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score 3 · Answer 2 · answered Mar 27 '13 at 12:59

To read a image into a byte array:

ByteArrayOutputStream baos = new ByteArrayOutputStream();
ImageIO.write( image, "jpg", baos );
baos.flush();
byte[] imageInByte = baos.toByteArray();
baos.close();

And to show it as String:

public static String bytesToHex(byte[] bytes) {
    final char[] hexArray = {'0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F'};
    char[] hexChars = new char[bytes.length * 2];
    int v;
    for ( int j = 0; j < bytes.length; j++ ) {
        v = bytes[j] & 0xFF;
        hexChars[j * 2] = hexArray[v >>> 4];
        hexChars[j * 2 + 1] = hexArray[v & 0x0F];
    }
    return new String(hexChars);
}

score 2 · Accepted Answer · answered Mar 27 '13 at 13:10

Just get the image in byte[] flavor the usual Java I/O way and feed that in turn to DataTypeConverter#printHexBinary() to get a hex string out of it.

ByteArrayOutputStream output = new ByteArrayOutputStream();

try (InputStream input = new URL("http://example.com/some.jpg").openStream()) {
    byte[] buffer = new byte[10240];
    for (int length = 0; (length = input.read(buffer)) > 0;) {
         output.write(buffer, 0, length);
    }
}

String hex = DatatypeConverter.printHexBinary(output.toByteArray());
// ...

Note that you don't need the whole Java 2D API (ImageIO et.al.) for this. This is only useful if you actually intend to manipulate the image (resize, crop, skew, etc).

Andreas Fester · Answer 4 · 2013-03-27T13:15:25.307

0

In addition to the other answers, once you have read the image, you can also use the existing javax.xml.bind.DatatypeConverter class to convert the byte array to a hex string. Ideally use the approach from @BalusC to save memory and directly read the image into a byte array, and then simply do

String s = javax.xml.bind.DatatypeConverter.printHexBinary(byteArray);

edited Mar 27 '13 at 13:15

answered Mar 27 '13 at 13:08

Andreas Fester

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How to convert an image from URL to hex string?

4 Answers4