how to crop image in codeigniter using image manipulation class?

[eluser]Laith99[/eluser]
Hello

i'm using codeigniter to build a project and right now i need to create a thumb depending on user choice. like he will give me X1,Y1,X2,Y2,X3,Y3,X4,Y4 i want to crop the image depending on that 4 points. i checked the image manipulation class. the crop function seems to be very strange. any help please ?

something like this

P1 = (100,100)
P2 = (100,200)
P3 = (200,100)
P4 = (200,200)