happybits

Thanks follower

I've read his posts about GIF and referred to it at the end of my article. But I didn't know about "GIF Encoder" and "GIF Explorer" - interesting!

Aha, thanx for the info, I didn't know. So the canvas width and height should be the same as the width and height?

Thanks a lot JohnFen.

One reason for writing the post and trying to create GIF-images from binary, was to come as close as possible to GIF format and especially the LZW-algorithm. To understand it in an intuitive way. To get a bit closer to the minds who created the algorithm in the first place.

atoav: this sounds like at great exercise. Have you written any public article about that?

The main reason for writing this article was * My curiosity - what secret is behind all strange bytes in a graphical file * To spend some time doing something weird, that I know have zero effect of my career and no chance of giving and benefits or profit in the future.

81 in hex is 10000001 in binary, so I think this part is correct

Thanks mikecx, it was a typo, I've changed the text to "Next is the Global Packed Field, which in this case is 00..."

CUSTOMER

Hackerman, I need an impressive icon for my website. It should be 5x5 pixels big and look like a rabbit. Can you please draw it for me?

HACKERMAN

Draw!? Bah! I don’t need any graphic program for that. I am Hackerman. I will code it for you. You will get the image next week.

CUSTOMER

Next week?? But…

HACKERMAN

No buts! I just need to read about how the GIF file format works, then I can create the image in no time.

[TIME PASSES]

After spending some evenings, Hackerman gets the main idea of how the GIF file format works and the compression algorithm called LZW. With that knowledge, he succeeded in creating the image within an hour.

Hackerman calculated that the binary of the image should be as follows:

47 49 46 38 39 61 00 00 00 00 70 00 00 2c 00 00 00 00 05 00 05 00 81 11 11 11 FF FF FF D5 D7 D9 00 00 00 07 0F 80 01 00 83 01 82 84 85 88 82 8A 85 02 85 81 00 3b

So he just opened his code editor, saved the file as rabbit.gif, and sent it to his customer. Boom! Easy-peasy!

Do you want understand the GIF-file format and be as cool as Hackerman?