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NAME
- ReadPixel
-
read the pen number value of the pixel at a specified x,y location within a certain RastPort.
SYNOPSIS
penno = ReadPixel( rp, x, y )
d0 a1 d0:16 d1:16
LONG ReadPixel( struct RastPort *, SHORT, SHORT );
LONG ReadPixel( struct RastPort *, SHORT, SHORT );
FUNCTION
Combine the bits from each of the bit-planes used to describe a particular RastPort into the pen number selector which that bit combination normally forms for the system hardware selection of pixel color.
INPUTS
- rp
-
pointer to a RastPort structure
- x
-
see next
- y
-
a point in the RastPort
RESULT
- penno
-
the pen number of the pixel at (x,y) is returned. -1 is returned if the pixel cannot be read for some reason.