rectangle detection and extraction

Hello,

I have got this image example: http://tinypic.com/view.php?pic=ac535x&s=5

I would like to automatically extract the upper card. I tried edge detection, dilation/erosion and then fill holes. It didn't work as the edges resulted in only few points of the rectangle. I don't think this method was good, as some frames in the card were considered as edges.

Your help will be welcome. Thank you.

[Image Analyst]

What if the top card is much smaller than those below and fits completely inside them? What if some cards have complicating graphics/printing on them? You see, it can get very complicated in the general situation unless you define some constraint parameters to simplify it. This looks like a student project or homework, not a "real world" application - is it?

[Emilie]

Thanks for replying. Cards always have same size and will have no complicated graphics/printing on them.

[Emilie]

Hello, can any one help please?. I can't succeed in detecting the correct edge or coner of the left side. Many thanks in advance.

[Emilie]

Sorry, I mean difficulties in getting the right side!

[Emilie]

Here are image results (<http://tinypic.com/view.php?pic=352r8go&s=5> http://tinypic.com/view.php?pic=o0w3et&s=5)

while trying to find corners in order to crop the top card and using regionprops(BoundingBox). As you can the the right side isn't correct. I also tried canny edge detection and Hough to draw the lines but my results are bad too!. Any help, please. Thanks.