1. Introduction

Application Fractal Browser is a study assignment for Java programming course (*:94x) at the Department of Computer and System Science (DSV) at Stockholm University. It is a Java application for rendering fractal images based on the Mandelbrot set. A characteristic feature of the fractal numbers is an ability to generate rich and complex graphical shapes. Application illustrates this feature by allowing to zoom in numerous times in the image area and observe new evolving unique patterns.

The purpose of Fractal Browser is to implement extended zooming, animation, and color editing features. These features may be used for creating customized wallpaper images, and presumably screen savers.

2. Application screen shot

3. Draw and browse

To create a new image, draw a rectangle in the image area and click Draw. To review created images, use arrow and double-arrow buttons. Once the image was rendered (it might be a time-consuming operation, depending on the image size and system resources), it is placed in the history buffer, offering a quick browsing capability. Coordinates x0, y0, x1, y1 represents the top left and bottom right corners of the image area being viewed (in fact, they are the real and the imaginary part of the complex numbers, representing these particular points).

Screen shots and examples:
1. Rectangle in the image area
2. Image after repainting

4. Color set

Color set menu allows to change image colors. There are four color sets that can be chosen:
'Active Element' (foreground: red, yellow, green, cyan, blue, magenta, red, background: black),
'Dark Edges' (foreground: dark red, red, yellow, green, cyan, blue, dark blue, background: black),
'Winter Sky' (foreground: dark gray, white, cyan, background: white),
'Editing...' (customized colors).

'Editing...' is in fact a color editing mode. It means that user can choose own colors in this color set (see 8. Edit color set). When application started, the first image is always painted with 'Active Element' colors. After choosing a color set, you have to click Draw to repaint the image. Image coordinates remain the same, only image colors are altered. Everytime the image is repainted, it is placed in the history for a quick viewing later on.

Screen shots and examples:
1. Image painted in 'Active Element' colors
2. Same image painted in 'Dark Edges' colors

5. Play history

Play history tool reviews all history images in one sequence, as animation. It starts with the first image (image 0) and ends with the last. Frames/sec menu allows to choose animation speed. 16 or 24 frames per second is regular speed for animations. When playing history first time, it might be a little slow (it depends on memory resources). To achieve normal speed just play it once more.

Play history is placed in the left part of the application window.

6. Multiple zoom

Multiple zoom option creates multiple images. To make a multiple zoom, draw rectangle in the image area and click Zoom. It draws a number of images with various size, changing from the current size to the rectangle size. How many images has to be drawn is indicated by the Frames menu. A less number of frames is also less time-consuming, but it makes wider jumps between images. A higher number of frames takes longer time to perform, but returns a better zooming effect when executing Play history. In fact, it is thought to use Multiple zoom to create fine animations. Multiple zoom can also be used in combination with different color sets (e.g. you change color set every 24-32 images).

Screen shots and examples:
1. Start position: image 0, with the rectangle, 8 frames
2. Result: Image 1
3. Result: Image 2
4. Result: Image 3
5. Result: Image 4
6. Result: Image 5
7. Result: Image 6
8. Result: Image 7
9. Result: Image 8

7. Clear history

Clear history tool allows user to edit history. Sometimes it is necessary to clear history from old images to get more space in the memory. Besides, it can also be practical to delete all temporar test images in order to create a 'clean' history for animation. This can be done in two ways. Clear Before deletes all images before the current image. Clear After deletes all images after the current image. If you want to delete all images in the history, but save the first one, click first the left double-arrow button (<<), and then Clear After. If you want to save only the last one, click the right double-arrow button (>>), and Clear Before.

Clear history is in the left part of the application window.

8. Edit color set

Edit color set feature allows user to create customized color sets in order to use them in the images. Section contains Color settings panel and Color sample bar. Color settings has 8 columns representing different levels of color scale. (Color scale is presented in Color sample.) Each column can have only one color. The 1st column means the begining of the scale, and the 7th is the end of it. The last, 8th column represents the background color (background color is the inside part of the oval figures). To use colors in the Edit color set, choose 'Editing...' in the Color set menu, and then click Draw.

A choise of 9 colors in Color settings is to some extent limiting. It would be interesting to have more colors to choose from, maybe as a regular RGB color panel. Nevertheless, the idea of dividing color mapping (color scale) into several levels proves to be quite productive. That allows different image parts to have different color settings without affecting the rest of the image.

Screen shots and examples:

1. Color set and image:

2. Color set and image:

3. Color set and example:

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