Thanks Jim, This is a really good explanation. Obviously I had trouble grasping the coordinate system fully. This also helps to explain (to me) line2D.Float etc as the coordinates can be a float value where as pixels are defined units.
The fact that line width of 1 drew the additional pixel just wrongly confirm my errant thinking. At least a bug was uncovered if not already known. Thanks again! Lew > Hi Lew, > > You are describing the default behavior which assumes > CAP_SQUARE. > > The line itself is infinitely thin and goes from one > coordinate to the > next, don't think of pixels. So, 20,60 to 20,60 goes > nowhere - it has a > length of 0. 20,60 to 21,60 goes a total distance of > 1 unit and has a > length of 1. > > Now with CAP_SQUARE, the first line is extended by > lw/2 off the front > and back so it extends a total of lw in the > "direction" of the line > (ignore for now that a 0-length line has no > direction), and obviously it > extends lw perpendicular to the line (and centered on > the line). If > lw=1 then it is a 1x1 square - but only with > CAP_SQUARE. > > Also with CAP_SQUARE, the second line is extended by > the same lw/2 off > both ends, and so it is 1 unit long and extends > another lw units so it > is a total of lw+1 long or 2 units long for a lw=1 > line. It extends lw > perpendicular as well so it is a 2x1 line. > > With CAP_BUTT, there are no extensions so the > 0-length line is only 0 > units long and the 1-length line is only 1 units > long... > > ...jim > > [EMAIL PROTECTED] wrote: > > Thanks Jim, > > After all the time I've spent on this it seems I > still do not full understand it! > > > > Everything I have read on this seems to confirms my > thinking, it just doesn't translate when using line > widths > 1. > > My understanding is (or was) that the arguments to > the Line2D methods , as either x,y coordinates or > Points set the "endpoints" of the line. > > > > If I draw a line (with line width of 1) from > coordinates 20,60 to 20,60 it would cover 1 pixel > below and to the right of the coordinate which would > be the pixel 20,60 (current user space). > > > > So as 20,60 & 21,60 are two distinct coordinate > points , if I draw a line using these coordinates as > the endpoints, I expected to get a 2 pixel line > length (and did with line width of 1). > > > > Similarly if i set 2 Points to the coordinates > above and use .. > > setLine(Point2D p1, Point2D p2) it would cover 2 > pixels. ( and does with line width of 1 but not with > a width > 1 > > > > From the Sun APi Class Line2D docs .. > > " setLine(Point2D p1, Point2D p2) Sets the > location of the end points of this Line2D to the > specified Point2D coordinates." > > > > Without wishing to take the discussion away from > the points above, the end cap options raise another > issue.. > > If I had set CAP_SQUARE or ROUND with a line width > of 1, where would it decide to add the additional > pixel? Normally half the line width and adding it to > each end point? > > I guess this issue happens any time the line width > is an odd pixel number. > > > > ....Lew > > [Message sent by forum member 'aussielew' > (aussielew)] > > > > > http://forums.java.net/jive/thread.jspa?messageID=2920 > 07 > > > > > ====================================================== > ===================== > > To unsubscribe, send email to [EMAIL PROTECTED] > and include in the body > > of the message "signoff JAVA2D-INTEREST". For > general help, send email to > > [EMAIL PROTECTED] and include in the body of > the message "help". > > ====================================================== > ===================== > To unsubscribe, send email to [EMAIL PROTECTED] > and include in the body > of the message "signoff JAVA2D-INTEREST". For > general help, send email to > [EMAIL PROTECTED] and include in the body of the > message "help". [Message sent by forum member 'aussielew' (aussielew)] http://forums.java.net/jive/thread.jspa?messageID=292214 =========================================================================== To unsubscribe, send email to [EMAIL PROTECTED] and include in the body of the message "signoff JAVA2D-INTEREST". For general help, send email to [EMAIL PROTECTED] and include in the body of the message "help".
