# how to detect corner of image and find coordinate of corner - I need M-file code

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KURNIAWAN on 21 Jun 2012
Please help , i had tried to find corner and coordinate of corner automatically,,, but still have problem to solve,, can u help me to make code-mfile,, i still confuse how to find corner and find coordinate automatically,, i have image tile square , how to detect 4 corner of tile ceramic and find value of coorninate 4 corner of tile ,
this link of image of tile : <http://tinypic.com/view.php?pic=2czer0o&s=6>
tile before croping and warping : <http://tinypic.com/view.php?pic=k4yyyd&s=6>

Sean de Wolski on 21 Jun 2012
doc cornermetric
as a place to start?

#### 1 Comment

KURNIAWAN on 21 Jun 2012
how to detect edge corner? and find of coordinate

matlab_image on 21 Jun 2012

Walter Roberson on 21 Jun 2012
Unfortunately we do not know if the poster is using a version of MATLAB new enough to have the "corner" routine. The poster was asked in one of the numerous threads the poster has started on this topic, but did not answer.
KURNIAWAN on 21 Jun 2012
i confuse with harris corner detector http://www.mathworks.com/matlabcentral/fileexchange/9272-harris-corner-detector/content/Harris.m
in m-file use imag.mat... how if i use image to process

Image Analyst on 21 Jun 2012
I thought from your prior messages on this tile that you needed the corners to know how to warp the image. Now it looks like you're saying that you warped it somehow without the corners. But unfortunately you warped it incorrectly so that it's still not square.
But if it were the binary image, you could simply use find() in the first and last row of the binary image to find the corners.
upperLeftCornerX = find(binaryImage(1,:), 1, 'first');
upperRightCornerX = find(binaryImage(1,:), 1, 'last');
lowerLeftCornerX = find(binaryImage(end,:), 1, 'first');
lowerRightCornerX = find(binaryImage(end,:), 1, 'last');
but again, you must already have the corners to do that incorrect warping so why not just do it correctly, using the code I gave you in the other posting? There is no need to correct the skewness only part way and then try to warp it again to get it all the way fixed.

KURNIAWAN on 21 Jun 2012
this the problem : <http://tinypic.com/view.php?pic=9a9vdu&s=6>
so if the coordinate 4 corner automatically find, then i know defect of distance edge
KURNIAWAN on 21 Jun 2012
can u help me image analyst.. in whole code..
Image Analyst on 21 Jun 2012
No until sometime this weekend, but by then you'll probably have it all solved.