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Exercise - Bitmap Editor

1.1 Bitmap average colour.

Write a console program that reads an image (bmp or JPEG) and computes the average color.

Details

  • The file name should be read from console as a parameter.
  • Define a ImageStructure Java class that retains all image information: filename, dimensions, BufferedImage Java class.
  • The pixel information should be read from the BufferedImage Java class as a matrix of (r,g,b) entities.
  • Define a function that receives as parameter the BMP file and returns the ImageStructure class.
  • Define a function that receives the ImageStructure and returns a Color class representing the average of the colors in the image's pixel matrix.
  • The average will be computed as AveragePixelColor(R,G,B)=Color(Avg(<all R's>), Avg(<all G's>), Avg(<all B's>))
  • Print the average to the console.
  • Package your application as a JAR.

Example

$ java -jar image_comp_average.jar image.png
;;=> (233,204,123)

Further reading

1.2 Bitmap grayscale

Build a console program that reads a coloured image and saves it in grayscale form.

Details

  • Use the image_comp_avg.jar defined above to read the image; add the JAR as dependency to your new project.
  • Build a function that takes as parameter a ImageStructure object and saves it, returning a boolean indicating if the save was successful or an error occured.
  • Test that your save works: load an image and save it and then compare them to make sure they look the same; compare sizes also.
  • Build a function that takes as parameter a ImageStructure and applies grayscale transform on it, returning a new ImageStructure.
  • Apply your grayscale function to the inital image.
  • Save the image to disk.
  • Check out the result.
  • Compare your result with a grayscale image obtained from an image manipulation software.
  • Package your application as JAR.

Example

$ java -jar image_grayscale.jar initial_image.jpg
;; => Results written to grayscale_image.jpg

Further reading

1.3 Swing image editor

Build a Swing interface that allows 2D image manipulation: load image, save image, apply grayscale transform on the image.

Details

  • Build a JFrame interface with a menu to load/save image.
  • After image loading draw the image on a 2D Canvas.
  • Add a menu entry for Transformation with a Grayscale child menu.
  • Use the functions defined in the above JARs to add actions to menu entries.
  • When a Transformation is applied show the results in realtime in the Canvas.
  • Maintain the state of the Canvas in memory (clean/dirty) and add a Dialog to ask the user to save the modified image on exit.
  • Package your application as an executable JAR, so you can run it with 2click (at least on Win, not sure if that works on Linux).

Further reading