Simplify setimage()

Author: radarhere

src/PIL/ImageFile.py

@@ -799,16 +799,13 @@ def setimage(
 
         if extents:
             x0, y0, x1, y1 = extents
-        else:
-            x0, y0, x1, y1 = (0, 0, 0, 0)
 
-        if x0 == 0 and x1 == 0:
-            self.state.xsize, self.state.ysize = self.im.size
-        else:
             self.state.xoff = x0
             self.state.yoff = y0
             self.state.xsize = x1 - x0
             self.state.ysize = y1 - y0
+        else:
+            self.state.xsize, self.state.ysize = self.im.size
 
         if self.state.xsize <= 0 or self.state.ysize <= 0:
             msg = "Size must be positive"