Sunday, December 11, 2011

How do the coded letters in the vitals of a .jpg picture works?

I opened a .jpg image in a particular notepad and it showed certain symbols, numbers and letters... So I decided to randomly remove '; 脕W煤k脨y'; from the ';text-converted image'; and see how would the image look. When I saved the text and then opened the file in .jpg format again, the whole image was totally bright.



So I need to know how do ALL the letters that we see in the text format of an image works? How can we edit the image i.e. change its size, add something in it, etc... by editing those letters?How do the coded letters in the vitals of a .jpg picture works?
You can't really.

The text you see is just notepad trying to represent the picture data as text, it is just gibberish. The chances of you making a valid change to an image in notepad are ridiculously small. Plus JPEG is actually a compression format, so the data you see in notepad is a compressed version of the image. Because it is compressed, viewers decompress the image before showing it to you. The compression makes it even less likely for you to make a valid change because the viewer expect a very specific structure to the image data and any change you make is most likely to screw this structure up. It would be like zipping a text file, editing the compressed file and the trying to extract the file again. You're not going to succeed.

So bottom line, if you want to edit an image, use image editing software, they exist for a reason.

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