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Editorial Team
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Asked: 2026-05-17T16:45:21+00:00

I have been through these related questions: How to convert numbers between hexadecimal and

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I have been through these related questions:

But I did not get an answer probably because I do not understand 64bit or 16bit values.

I had posted a question on Picasa and face detection, to use the face detection that Picasa does to get individual pics from a photo containing many pictures. Automatic Face detection using API

In an answer @Joel Martinez linked to an answer on picasa help which said:

The number encased in rect64() is a 64-bit hexadecimal number.

  • Break that up into four 16-bit numbers.
  • Divide each by the maximum unsigned 16-bit number (65535) and you’ll have four
    numbers between 0 and 1.

the full text

@oedious wrote:- This is going to be
somewhat technical, so hang on. * The
number encased in rect64() is a 64-bit
hexadecimal number. * Break that up
into four 16-bit numbers. * Divide
each by the maximum unsigned 16-bit
number (65535) and you’ll have four
numbers between 0 and 1. * The four
numbers remaining give you relative
coordinates for the face rectangle:
(left, top, right, bottom). * If you
want to end up with absolute
coordinates, multiple the left and
right by the image width and the top
and bottom by the image height.

A sample picasa.ini file:

[1.jpg]
backuphash=65527
faces=rect64(5520c092dfb2f8d),615eec1bb18bdec5;rect64(dcc2ccf1fd63e93e),bc209d92a3388dc3;rect64(52524b7c785e6cf6),242908faa5044cb3
crop=rect64(0)

How do I get the 4 numbers from the 64 bit hex?

I am sorry people, currently I do not understand the answers. I guess I will have to learn some C++ (I am a PHP & Java Web Developer with weakness in Math) before I can jump in and write a something which will cut up an image into multiple images with the help of some co-ordinates. I am looking into CodeLab and creating plugins for Paint.net too

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1 Answer

  1. Editorial Team

    Here is the algorithm:

    The remainder of the division by 0x10000 (65536) will give you the first number.

    Take the result then divide by 0x10000 (65536) again, the remainder will give you the second number.

    Take the result the divide by 0x10000 (65536) again, the remainder will give you the third number.

    The result is the fourth number.

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