In Scene I of Act II at Belmont, the second of the suitors has arrived, the Prince of Morocco, and Portia explains to him the conditions set by her father. When he declares that his love is as true as any of the men from the North, Portia explains that regarding her ability to choose a suitor, she is "scanted," or limited, by the restrictions that her father has set down in his will. In an apparent attempt to avoid any argument about his "complexion," about which the Prince seems defensive, Portia tells the prince that she is "scanted," or made to obey her father's will that demands that she marry whoever chooses the casket from the three that gives his permission for the suitor to marry his daughter--"who wins me by the means I told you." 

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Just to add an explanation for the end of her speech to the Prince of Morocco, so that the reader understands the lines under question in the context in which they are placed, Portia tells her second suitor that she considers him

...as fair
As any corner I have looked on yet
For my affection. (2.1.20-22)

In other words, the prince would stand as much chance as any of the other suitors who have asked to marry Portia. This remark carries with it a certain irony, however, since Portia has not yet really been attracted to anyone sent to her and greatly resents the provisions of her father's will.