Geekblok

You’ve probably heard about storing secret messages in JPEGs by means of steganography. But what if you have entire documents that you’d like to hide? As proof of concept, I showed this example to my coworkers.

We start out with a random JPEG, taken from my Flickr account:

Now we create a simple zip file with a text document in it:

$ zip test.zip test.txt

And we cat the two files together:

$ cat fotobok.jpg test.zip > fotobok-test.jpg

File indeed recognizes this as an image:

$ file fotobok-test.jpg
fotobok-test.jpg: JPEG image data, JFIF standard 1.01

And you can see it here too:

The only difference now is that we can unzip the file aswell:

$ unzip fotobok-test.jpg
Archive: fotobok-test.jpg

warning [fotobok-test.jpg]: 19881 extra bytes at beginning or within zipfile

(attempting to process anyway)

extracting: test.txt

Tada! Our highly secret test.txt is back!

Web2.0 is all about reflections and rounded corners, or so it seems. We’ve seen how to make reflections online before, so now it’s time to get rounded corners without Photoshop or GIMP.

The website RoundPic does this for you, and does it quite fast too! First you upload an image, or give them an URI to download and and click later, you have rounded corners. Woohoo!.

Let’s see the results. I gave them a photo of the Insomnium concert I recently attended and within a few seconds, the metal band was a little less frightening, with rounded corners.

ImproveYourImages.com is a simple looking website that can improve your images (hence the domain name, I figure). The three examples tell us that you can

# Restore true original colors
# Correct color temperature

# Adjust poor lighting

Especially the last one looks interesting to a bad photographer like me, so let’s test our own images on this!

Read more »

As some of you might know, there is interesting Exif header information in most of the jpeg images. On a unixlike system this information can be extracted from the original using jhead.

bq. $ jhead dsc02985.jpg
File name : dsc02985.jpg

File size : 1546562 bytes

File date : 2006:01:18 09:49:24

Camera make : SONY

Camera model : CYBERSHOT

Date/Time : 2002:07:06 14:18:37

Resolution : 2240 × 1680

Flash used : No

Focal length : 7.1mm

Exposure time: 0.0024 s (1/410)

Aperture : f/4.0

ISO equiv. : 100

Exposure : LandscapeMode

As can be seen I took this picture with my Sony Cybershot camera. Not too interesting. Another feature of jhead is that one can also extract thumbnails from the Exif header.

Read more »

Besides a website name that has less vowels than needed and ends with a ‘R’, a good old web2.0 site should have a logo with reflection (as BOK pointed out in Web2.0 - logo creator).

The technique behind this is fairly simple and can be done with software like Photoshop or GIMP. You basically duplicate the layer with the logo, then flip it horizontally and fade it out. But if you don’t have this software installed, Reflection Maker can help you to do this online.

The interface is quite easy and straightforward. Simply give it an URL, or upload an image. Set the background color and specify the size of the reflection. Hit generate and you’re all set.