Cheat Engine

--Pillboi-- · Posted: Mon Aug 20, 2007 2:40 pm Post subject: Comparing Pictures In C

If anyone knows how, can you please tell me how to take a picture and compare it to another picture, to find what part of the picture it is, in ANSI C. For instance, if you had a picture of an island, and another picture of a palm tree. And find out were the exact photo of the palm tree is in the picture of the island. I would also like to know, how to let a user upload a picture and use that to be found. Thanks.

Edit: 1137 post. That's close to 1337! Kinda. In a way.

appalsap · Posted: Mon Aug 20, 2007 2:43 pm Post subject:

memcmp

--Pillboi-- · Posted: Mon Aug 20, 2007 2:47 pm Post subject:

Thanks for the quick answer, but that just compares parts of two strings, how do you use that for a picture, and about the uploading?

appalsap · Posted: Mon Aug 20, 2007 2:49 pm Post subject:

It does not compare two strings, strcmp is for comparing two strings. You would map the pictures into memory and use memcmp on them.

--Pillboi-- · Posted: Mon Aug 20, 2007 2:52 pm Post subject:

Ok, thanks, I'll try reading up on it. If I have any problems, I'll ask. But remember, I only know very simple C. I don't even know pointers yet! If I understand everything, I'll try, and if I have any problems then, then I'll also ask! Anyway, thanks again!

oib111 · Posted: Mon Aug 20, 2007 7:41 pm Post subject:

You don't know C. So your prificient in...delphi...asm...?

--Pillboi-- · Posted: Tue Aug 21, 2007 2:46 am Post subject:

Nope, I know absolutely no delphi. As for asm, I have only learnt auto-assembly, as that is all I have had a need for, and, I would say, I was good at aa. I mean, I also know some languages which aren't really languages, but they are, such as, DOS, qbasic and a bit more than basic html.

nog_lorp · Posted: Tue Aug 21, 2007 7:19 am Post subject:

Appalsap: memcmp won't work well for this, because of how the images wrap in memory, and the fact that you would have to do comparisons starting at every byte of the original image.

You would have to use bitmap library (it would be much harder with a compressed image format such as jpeg or png or gif) and compare the first pixel of the inset to each pixel of the original. Then if one matches, move on to the second pixel, continue until
A) test fails
B) image wraps

If the test fails pick back up one after the first pixel that was correct.
If the image wraps, start testing one pixel below the first pixel that was correct.

It might be sufficient to only test a few rows.

--Pillboi-- · Posted: Tue Aug 21, 2007 11:10 am Post subject:

Well, with what I am thinking of, the initial picture is huge, but the smaller picture is only about 200 pixels tall. So then, how would you compare two pixels colours? How do you even find the colour of a specific pixel? Thanks.