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Graphics Programming

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# Lecture Notes - PowerPoint PPT Presentation

Graphics Programming In this class we will cover: Drawing lines, rectangles, and ellipses Copying an area Drawing an image Drawing Lines, Rectangles and Ellipses Java2D oraganizes geometric shapes in OO fashion. There are classes to represent lines, rectangles and ellipses. Line2D

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### Graphics Programming

In this class we will cover:
• Drawing lines, rectangles, and ellipses
• Copying an area
• Drawing an image
Drawing Lines, Rectangles and Ellipses
• Java2D oraganizes geometric shapes in OO fashion. There are classes to represent lines, rectangles and ellipses.
• Line2D
• Rectangle2D
• Ellipse2D
• These all implement the Shape interface
Drawing Shapes
• To draw a shape, you first create an object of a class that implements the Shape interface and then call the draw method of the Graphics2D class. Rectangle 2D rect = . . .;g2.draw(rect);
• There are two versions of each Shape class
• one with float coordinates (conserves memory)
• one with double coordinates (easier to use)
• Example:Rectangle2D rect = new Rectangle2D.Double(10.0, 25.0, 22.5, 20.0);
Drawing Rectangles
• Rectangles are simple to construct
• Requires four arguments
• x- and y-coordinates of the upper-left corner
• the width and the height
• The Rectangle2D class has over 20 useful methods including:
• get Width
• getHeight
• getCenterX
• getCenterY
Drawing Rectangles
• Sometimes you don’t have the top-left corner readily available.
• It is possible to have two diagonal corners of a rectangle that are not the top-left corner and the bottom-right corner.
• To create a rectangle in this case use the setFrameFromDiagonal method.Rectangle2D rect = new Rectangle2D.Double();rect.setFrameFromDiagonal(px, py, qx, qy);
• If you have a Point2D object, you can also create a rectangle by callingRectangle2D rect = new Rectangle2D.Double(p1, p2);
Drawing Ellipses
• The class Ellipse2D is inherited from the same Rectangle class that Rectangle2D is.
• because of the bounding box surrounding the ellipse
• So, creating an Ellipse2D object is very similar to creating a Rectangle2D object.Ellipse2D e = new Ellipse2D.Double(px, py, qx, qy)where px, py are the x- and y-coordinates of the top-left cornerand qx, qy are the x- and y-coordinates of the bottom-right cornerof the bounding box of the ellipse
Drawing Lines
• To construct a line, simple use the Line2D class.
• It too, requires 4 arguments (the x and y coordinates of the start and end positions)
• These coordinates can be 2 Point2D objects or 2 pairs of numbers.Line2D line = new Line2D.Double(start, end) orLine2D line = new Line2D.Double(px, py, qx, qy)
Filling Shapes
• You can fill the interior of closed shape objects with a color.
• Simply call the fill instead of draw method on the Graphics object.Rectangle2D rect = new Rectangle2D.Double(x, y, x2, y2);g2.setPaint(Color.red);g2.fill(rect);
Images
• You can display images on the Graphics object.
• You can use images stored locally or someplace on the Internet.
• If an image is stored locally call:String filename = “…”;Image image = ImageIO.read(new File(filename));
• If an image is on the Internet, use the url:String filename = “…”;Image image = ImageIO.read(new URL(url);
• To draw the image:g.drawImage(image, x, y, null)
Copying an Area
• copyArea() method - Use to copy an area
• Requires 6 parameters
• x-coordinate and y-coordinate of the upper-left corner of the area to be copied
• Width and height of the area to be copied
• The horizontal and vertical displacement of the destination of the copy
More on Graphics
• We have just begun to touch on the various graphics shapes available. You can also draw:
• arcs
• polygons
• three-dimensional shpes
• Java 2D also lets you create higher-quality two-dimensional graphics, images, and text using:
• fill patterns such as gradients
• strokes that define the width and style of a drawing stroke
• anti-aliasing, a graphics technique for producing smoother on-screen graphics
• For more info see: http://java.sun.com/docs/books/tutorial/2d/display/strokeandfill.html
Example
• So, let’s put all of this together in an example:
• See:http://www2.bc.edu/~bernier/MC697/LectureNotes/DrawShapesTest.java