Font Designer


The Font Designer module is a graphical tool (Eclipse plugin) that runs within the MicroEJ IDE used to build and edit MicroUI fonts. It stores fonts in a platform-independent format.

Functional Description

Font Generation

Font Generation

Font Management

Create a MicroEJ Font

To create a MicroEJ font, follow the steps below:

  1. Open the Eclipse wizard: File > New > Other… > MicroEJ > MicroEJ Font.
  2. Select a directory and a name.
  3. Click Finish.

Once the font is created, a new editor is opened: the MicroEJ Font Designer.

Edit a MicroEJ Font

You can edit your font with the MicroEJ Font Designer (by double-clicking on a *.ejf file or after running the new MicroEJ Font wizard).

This editor is divided into three main parts:

  • The top left part manages the main font properties.
  • The top right part manages the character to embed in your font.
  • The bottom part allows you to edit a set of characters or an individual character.

Main Properties

The main font properties are:

  • font size: height and width (in pixels).
  • baseline (in pixels).
  • space character size (in pixels).
  • styles and filters.
  • identifiers.

Refer to the following sections for more information about these properties.

Font Height

A font has a fixed height. This height includes the white pixels at the top and at the bottom of each character simulating line spacing in paragraphs.

Font Height

Font Height

Font Width: Proportional and Monospace Fonts

A monospace font is a font in which all characters have the same width. For example a ‘!’ representation will be the same width as a ‘w’ (they will be in the same size rectangle of pixels). In a proportional font, a ‘w’ will be wider than a ‘!’.

A monospace font usually offers a smaller memory footprint than a proportional font because the Font Designer does not need to store the size of each character. As a result, this option can be useful if the difference between the size of the smallest character and the biggest one is small.


Characters have a baseline: an imaginary line on top of which the characters seem to stand. Note that characters can be partly under the line, for example, ‘g’ or ‘}’.

The Baseline

The Baseline

Space Character

The Space character (0x20) is a specific character because it has no filled pixels. From the Main Properties Menu you can fix the space character size in pixels.


When the font is monospace, the space size is equal to the font width.


Font Designer allows creating a font file that holds several combinations of built-in styles (styles hardcoded in pixels map) and runtime styles (styles rendered dynamically at runtime). However, since MicroUI 3, a MicroUI font holds only one style: PLAIN, BOLD, ITALIC or BOLD + ITALIC.

Font Designer features three drop-downs, one for each of BOLD, ITALIC, and UNDERLINED. Each drop-down has three options: None, Built-in and Dynamic. The font options must be adjusted to be compatible with MicroUI 3:

  • The style option Dynamic (that targets the runtime style) is forbidden; select None instead.
  • The syle UNDERLINED is forbidden; select None instead.

The styles options Built-in tag the font as bold, italic, or bold and italic. This style can be retrieved by the MicroEJ Application thanks the methods Font.isBold() and Font.isItalic(). Adjust the styles options according to the font:

  • The font is a plain font: select None option for each style.
  • The font is a bold font: select Built-in for the style bold and None for the other styles.
  • The font is an italic font: select Built-in for the style italic and None for the other styles.
  • The font is a bold and italic font: select Built-in for the styles bold and italic and None for UNDERLINED.


When a font holds a dynamic style or when the style UNDERLINED is not None, an error at MicroEJ application compile-time is thrown (incompatible font file).


A number of identifiers can be attached to a MicroUI font. At least one identifier is required to specify the font. Identifiers are a mechanism for specifying the contents of the font – the set or sets of characters it contains. The identifier may be a standard identifier (for example, LATIN) or a user-defined identifier. Identifiers are numbers, but standard identifiers, which are in the range 0 to 80, are typically associated with a handy name. A user-defined identifier is an identifier with a value of 81 or higher.

Character List

The list of characters can be populated through the import button, which allows you to import characters from system fonts, images or another MicroEJ font.

Import from System Font

This page allows you to select the system font to use (left part) and the range of characters. There are predefined ranges of characters below the font selection, as well as a custom selection picker (for example 0x21 to 0xfe for Latin characters).

The right part displays the selected characters with the selected font. If the background color of a displayed character is red, it means that the character is too large for the defined height, or in the case of a monospace font, it means the character is too high or too wide. You can then adjust the font properties (font size and style) to ensure that characters will not be truncated.

When your selection is done, click the Finish button to import this selection into your font.

Import from Images

This page allows the loading of images from a directory. The images must be named as follows: 0x[UTF-8].[extension].

When your selection is done, click the Finish button to import the images into your font.

Character Editor

When a single character is selected in the list, the character editor is opened.

Character Editor

Character Editor

You can define specific properties, such as left and right space, or index. You can also draw the character pixel by pixel - a left-click in the grid draws the pixel, a right-click erases it.

The changes are not saved until you click the Apply button. When changes are applied to a character, the editor shows that the font has changed, so you can now save it.

The same part of the editor is also used to edit a set of characters selected in the top right list. You can then edit the common editable properties (left and right space) for all those characters at the same time.

Working With Anti-Aliased Fonts

By default, when characters are imported from a system font, each pixel is either fully opaque or fully transparent. Fully opaque pixels show as black squares in the character grid in the right-hand part of the character editor; fully transparent pixels show as white squares.

However, the pixels stored in an ejf file can take one of 256 grayscale values. A fully-transparent pixel has the value 255 (the RGB value for white), and a fully-opaque pixel has the value 0 (the RGB value for black). These grayscale values are shown in parentheses at the end of the text in the Current alpha field when the mouse cursor hovers over a pixel in the grid. That field also shows the transparency level of the pixel, as a percentage, where 100% means fully opaque.

It is possible to achieve better-looking characters by using a combination of fully-opaque and partially-transparent pixels. This technique is called anti-aliasing. Anti-aliased characters can be imported from system fonts by checking the anti aliasing box in the import dialog. The ‘&’ character shown in the screenshot above was imported using anti aliasing, and you can see the various gray levels of the pixels.

When the Font Generator converts an ejf file into the raw format used at runtime, it can create fonts with characters that have 1, 2, 4 or 8 bits-per-pixel (bpp). If the raw font has 8 bpp, then no conversion is necessary and the characters will render with the same quality as seen in the character editor. However, if the raw font has less than 8 bpp (the default is 1 bpp) any gray pixels in the input file are compressed to fit, and the final rendering will be of lower quality (but less memory will be required to hold the font).

It is useful to be able to see the effects of this compression, so the character editor provides radio buttons that allow the user to preview the character at 1, 2, 4, or 8 bpp. Furthermore, when 2, 4 or 8 bpp is selected, a slider allows the user to select the transparency level of the pixels drawn when the left mouse button is clicked in the grid.

Previewing a Font

You can preview your font by pressing the Preview… button, which opens the Preview wizard. In the Preview wizard, press the Select File button, and select a text file which contains text that you want to see rendered using your font. Characters that are in the selected text file but not available in the font will be shown as red rectangles.

Font Preview

Font Preview

Removing Unused Characters

In order to reduce the size of a font file, you can reduce the number of characters in your font to be only those characters used by your application. To do this, create a file which contains all the characters used by your application (for example, concatenating all your NLS files is a good starting point). Then open the Preview wizard as described above, selecting that file. If you select the check box Delete unused on finish, then those characters that are in the font but not in the text file will be deleted from the font when you press the Finish button, leaving your font containing the minimum number of characters. As this font will contain only characters used by a specific application, it is best to prepare a “complete” font, and then apply this technique to a copy of that font to produce an application specific cut-down version of the font.

Use a MicroEJ Font

A MicroEJ Font must be converted to a format which is specific to the targeted platform. The Font Generator tool performs this operation for all fonts specified in the list of fonts configured in the application launch.


No dependency.


The Font Designer module is already installed in the MicroEJ environment.


Create a new ejf font file or open an existing one in order to open the Font Designer plugin.