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Plotting dots on Canvas and adding/removing them

Posted on 2006-06-14
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Last Modified: 2010-03-31
I was able to create an applet with a canvas and an Image display over the canvas. I also created an interactive feature that lets me mark red dots over the canvas (on top of image). Now, I want to create a feature that also lets me remove an existing dot.. like how they do it in Flash editor, removing a vector graphics by highlighting or clicking it and pressing delete. Can anyone give me some techniques on how to do it?
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Question by:ibo
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5 Comments
 
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Expert Comment

by:CEHJ
ID: 16909035
You need to keep a list of dots to be painted. Add a MouseListener and if one of the dots, say, is right-clicked, remove it from the list and call repaint
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by:ibo
ID: 16909125
I already have a list of locations of the dots. The part missing is how to implement the "right-click to remove" feature. How do I go about that? Do I just read the location for a red pixel? I know it wont work because underneath is an image which can have any kind of picture/color. Also, the dot is not a 1x1 pixel, but can vary in size, ie. a filled circle with a radius of 5 pixels. Is there an exisiting technique how to implement this kind of problem? Im concerned with overlapping dots too.
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CEHJ earned 80 total points
ID: 16909138
What's underneath is immaterial. If the dots are not 1 pixel in diameter then you need to keep a record of their bounds. I suggest the following:

http://java.sun.com/j2se/1.5.0/docs/api/java/awt/Shape.html

See the contains method
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Author Comment

by:ibo
ID: 16909226
I think thats what im looking for.. to be able to determine that a marked point is inside the boundary of the dot.
hmm what if a location hits two (or more) intersecting dots? I guess Ill have to choose the latest dot plotted right?. Thanks.
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LVL 86

Expert Comment

by:CEHJ
ID: 16909272
:-)

>>I guess Ill have to choose the latest dot plotted right?. Thanks.

Possibly
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