How to remove the white background along the contour with GD?

Question

PHP

It is necessary to cut off the white background on the layout of the building. There are a lot of images, so doing in Photoshop is not an option. I just can’t get around the contour of the image, it turns out just like this:

The original is like this,

there are more complicated options with all sorts of dotted lines

Help solve this problem. On the server only GD, Imageck is not available.
So far I've created the following
sandbox.onlinephpfunctions.com/code/3066bf1757e5fc...
UPD: dimensions can also be removed from the image

Answer 1

I don't think this is possible with GD. But with OpenCV - it is quite possible.