| [Page 126 (continued)] In this chapter, we talk about several kinds of encodings of data (or objects). Color | An object that holds red, green, and blue values, each between 0 and 255. | Picture | Pictures are encodings of images, typically coming from a JPEG file or a bitmap (.bmp) file. | Pixel | A pixel is a dot in a Picture object. It has a color (red, green, and blue) and an (x, y) position associated with it. It remembers its own Picture object so that a change to the pixel changes the real dot in the picture. |
Picture Methods getHeight() | This method returns the height of the Picture object in pixels. | getPixel(int x, int y) | This method takes an x position and a y position (two numbers), and returns the Pixel object at that location in the Picture object it is invoked on. | getPixels() | Returns a one-dimensional array of Pixel objects in the Picture object it is invoked on. | getWidth() | This method returns the width of the Picture object in pixels. | writePictureTo(String fileName) | This method takes a file name (a string) as input, then writes the Picture object to the file as a JPEG. (Be sure to end the filename in ".jpg" or ".bmp" for the operating system to understand it well.) |
[Page 127]Pixel Methods getColor() | Returns the Color object for the Pixel object. | getred(), getGreen(), getBlue() | Each method returns the value (between 0 and 255) of the amount of redness, greenness, and blueness (respectively) in the Pixel object. | getX(), getY() | This method returns the x or y (respectively) position of where that Pixel object is in the picture. | setColor(Color color) | This method takes a Color object and sets the color for the Pixel object. | setRed(int value), setGreen(int value), setBlue(int value) | Each method takes a value (between 0 and 255) and sets the redness, greenness, or blueness (respectively) of the Pixel object to the given value. |
Color Methods new Color(int red,int green, int blue) | Takes three inputs: the red, green, and blue values (in that order), then creates and returns a Color object. | darker(),brighter() | The methods return a slightly darker or lighter (respectively) version of the Color object. |
ColorChooser Methods ColorChooser.pickAColor() | Displays a window with ways to pick a color. Find the color you want, and the method will return the Color object that you picked. |
There are a bunch of constants that are useful in this chapter. These are variables with pre-defined values. These values are colors: Color.black, Color.white, Color.blue, Color.red, Color.green, Color.gray, Color.darkGray, Color.pink, Color.yellow, Color.orange, Color.lightGray, Color.magenta, Color.cyan. You can also use Color.BLACK, Color.WHITE, and so on. Notice that these are not method calls but are public class variables (fields) so they can be accessed using ClassName.fieldName. |
