Java Hacks

Each directory of this repository contains a program in Java that is shown how to be compiled via CLI with a build.bat for Windows machines (in other machines just copy and paste the individual commands in this batch file or convert it the another shell script) to obtain a jar application that functions as a tool or example.

SVGspecular - Phong shading for SVG radial gradients

This is a single class program that creates an SVG file containing a square with a non-linear radial gradient based on Phong shading function for specular highlights (function $cos^n(angle)$​). The program produces a complete standalone SVG file.

The SVG has a number of stop colors $N$ determined by the user. Other parameters, such as the exponent of Phong's function (the $n$ of $cos^n(angle)$, not $N$), can also be supplied by the user following the program name as usually done in CLI mode.

Overall algorithm

The program takes the initial color $\vec{C_0}$ (which is generally white in the center of a the radial gradient) and the last color $\vec{C_1}$ (which is any color to be continued outside the radial gradient), and linearly interpolates the color $\vec{C}$ for each stop color based on a multidimensional parametric line equation, where the value of the parameter $t$ is given by the result of applying an $angle$ $\alpha$ to the function $cos^n(angle)$. In other words, this procedure is shown below:

$$\begin{aligned} &t = cos^n(\alpha)\\\ &\vec{C} = \vec{C_1}+ (\vec{C_0} - \vec{C_1}) \cdot t\\\ &\\\ \end{aligned}$$

Notice that the individual color components need to be processed independently. For simplicity and easier comprehension, the colors are dealt here as a sort of 3D (or 4D, including the alpha channel) vector representation. Indeed, colors can be represented as vectors where each color component corresponds to a different dimension.

Check the complete algorithm here

SVGfix - TreeMap Example

This program copies the color information from CSS classes and plugs them into the respective paths using SVG fill attribute instead of CSS.

It's an example of application using TreeMap JRE class to create a tree functioning as a symbol table to keep colors of SVG paths initially defined by CSS classes at the beginning of the SVG file as done by some versions of Illustrator when saving the file as SVG.

Once the program reads the colors between <defs><style> and </style></defs> from file input.svg, storing the the colors preceeded by a fill command in string format and using the class name as the key to access it in the TreeMap, it then prints in the command prompt (usually redirected to a file) the SVG with colors applied directly to the corresponding path (via fill attribute) that used the corresponding class to define the color.

This program is a simple hack and it may copy other commands when multiple classes with the same name are used but only the last reference will be taken into account for each path. Complex configurations, like CSS classes separated by commas sharing the same attribute (color or another attribute) will cause an error.

When an error is detected while using the TreeMap, the program says which class was not found and dumps all the keys of the tree for debugging purposes.

SVGinktxt - Mini parser for Texts and Automatization of CLI Debbuging

The actual class is called "SVGinktxt." More details about it can be found in the SVGinktxt README file. This program implements a small parser for texts in SVG coming from Inkscape. It erases the matrix that appears at each text line, by just applying the matrix to the coordinates of the first item in the line. For simplification and because the y coordinate first item in these cases is always negative, I just search for the negative value. Since Inkscape uses an entire matrix only to translate a negative y to a positive y, all I have to do is to extract the y translation from the matrix, make the matrix disappear, and add that value to the negative y in the first element of the line.

Notice that doing that, the matrix becomes an identity matrix which is what allows us to delete it. Inkscape typically generates one text item per line. This item posesses only one y coordinate and a list of x coordinates, one for each glyph in the text item. This is generally used to justify texts.

In certain versions of Illustrator text justifications don't always come out well. For some reason when the file is converted to SVG a line that was perfectly well justified on-screen can sometimes be divided at its last word, with a hyphen at the end of the line and the rest of the word appearing on the next line. This messes up with the intended formatting where the words were chosen to fit well in the paragraph. Something that looked beautiful and harmonious, becomes ugly and awkward.

The easy solution for this problem is to convert the whole file on Illustrator to PDF, import the PDF file into Inkscape and save the file as SVG. The problem is that Inkscape is too verbose and also makes use of internal variables where the name "inkscape" appears everywhere. The perfect solution in this case is to locate the text in the file generated by Inkscape and copy it into the file generated by Illustrator. It's often easier to erase the whole text in the file generated by Illustrator and substitute it by the text copied from the file generated by Inkscape.

New versions of Inkscape make this procedure almost straightforward. The only strange thing is the use of one matrix per line only to do a translation in the y coordinate. SVGinktxt is used to remove those matrices from all Inkscape text items.

On the other hand, the main interest of this class is not exactly its use case, but in the way the parser was written. It uses a methodololy that makes it ressemble a BNF grammar. This is done with just simple programming rules that are explained in the SVGinktxt README file.

Another insteresting topic discussed there is the automatization of CLI Java debugger setup which was used in this project to release the burden of manually setting it by hand.

UTF-8

This project allows to read UTF-8 encoded UNICODE files. It implements an infinite buffer file reader where one can recover the text word by word, which is converted from UTF-8, skipping blanks. The blanks can be recovered since they are all counted (feature used in the test program). By skipping blanks the reader is able to identify the start and the end of the words because they are different than blank. The fact that the text is encoded is totally transparent to the reader. The test program reads an UTF-8 testing file and prints it over the console. A batch file is provided to help running the jar. The source files are also given and they are all for free with no license of any kind.