Finding a smaller image inside a larger image

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4.00/5 (1 vote)

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Hi, I have been searching for a method that can locate the X and Y position of a smaller image inside a larger image (cropped screenshot) (only if the smaller image exists, sometimes it doesnt), i have found some solutions but i couldnt get any of them to work the way i needed

this is the my larger image
http://imageshack.us/photo/my-images/21/canchk.png/
and this is my smaller image
http://imageshack.us/photo/my-images/842/mycan.png/

Basically i need a method that i can call like this
findImagePos(SmallImage,LargeImage,X_array_varible, Y_array_varible, number_of_images_found_varible)

if no image is found then the number_of_images_found_varible would be 0
else number_of_images_found_varible would equal how many images where found
and X_array_varible[0] would have the X position of the first found image
and Y_array_varible[0] would have the Y position of the first found image
etc....

Thanks for any help

Posted 29-Jun-11 4:44am

Member 8034122

Updated 29-Jun-11 5:19am

v3

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2 solutions

Solution 1

You mean thumbnail image ?
In this case here a link that can help you :
create thumbnail

Posted 29-Jun-11 4:50am

Yuri Vital

Comments

Member 8034122 29-Jun-11 10:53am

no I need to FIND the smaller image in the larger image, not create a thumbnail, if you look at my attached images you can see what I mean, I need to find the mycan.png in the canchk.png

Yuri Vital 29-Jun-11 10:54am

Did you even read the link ?
It use the function : photoImg.GetThumbnailImage(50, 40, null, new System.IntPtr())) who retrieve the thumbnail !

Member 8034122 29-Jun-11 10:57am

yes I did, from what I can tell that is just cropping a smaller image from a larger image

Yuri Vital 29-Jun-11 11:01am

And what you need realy ?
Pattern recognition ?
Border detection ?

If you want image manipulation, you can use the library AForge
http://code.google.com/p/aforge/

Member 8034122 29-Jun-11 11:01am

i want to FIND the smaller image in the larger image i need the X and Y relative to the uppper left (0,0) of the larger image, not create a smaller image from the larger image, i updated my question, i hope i explained it more clearly

Yuri Vital 29-Jun-11 11:13am

in exemple you provided, did you have to find "mycan.png" in "canchk.png"
or to detect all sub-image in "canchk.png" ?

Member 8034122 29-Jun-11 11:20am

yes thats exactly what I need just need to find "mycan.png" in "canchk.png", also I reupdated my question

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Yuri Vital · Accepted Answer · 2011-06-29T05:46:00

Solution 2

I think that AForge can help you, look here Template matching

Posted 29-Jun-11 5:46am

Yuri Vital

Comments

Yuri Vital 29-Jun-11 11:48am

[....]
foreach ( TemplateMatch m in matchings )
{
// you have the m.Rectangle property that indicate the position of the image

// do something else with matching
}
sourceImage.UnlockBits( data );

Member 8034122 29-Jun-11 11:59am

just been reading up on it and this seems like exactly what I need
awesome thanks alot

Yuri Vital 29-Jun-11 12:05pm

you are welcome !