Raster-Font

C library that produces font characters in bitmaps that scan horizontally or vertically. Fonts are embeded as header files, and individual characters are delivered in the desired raster pattern. Developed on Espressif ESP-IDF toolchain, debugged seperately on Eclipse CDT.

Fonts

The fonts are grouped by character set, with the custom GLCD5x7 font always included and first.

The character sets to be compiled into the library are defined in fonts.h. Depending on the active charactersets, the index of a particular font may change. If all are chosen, these are the available fonts:

Num	Description	Size	Char Set
0	glcd_5x7	5x7
1	bitocra_4x7_ascii	4x7	ascii
2	roboto_8pt_ascii	8x11	ascii
3	roboto_10pt_ascii	11x14	ascii
4	tahoma_8pt_ascii	10x11	ascii
5	bitocra_6x11_iso8859_1	6x11	iso8859_1
6	bitocra_7x13_iso8859_1	7x13	iso8859_1
7	terminus_6x12_iso8859_1	6x12	iso8859_1
8	terminus_8x14_iso8859_1	8x14	iso8859_1
9	terminus_10x18_iso8859_1	10x18	iso8859_1
10	terminus_11x22_iso8859_1	11x22	iso8859_1
11	terminus_12x24_iso8859_1	12x24	iso8859_1
12	terminus_14x28_iso8859_1	14x28	iso8859_1
13	terminus_16x32_iso8859_1	16x32	iso8859_1
14	terminus_bold_8x14_iso8859_1	8x14	iso8859_1
15	terminus_bold_10x18_iso8859_1	10x18	iso8859_1
16	terminus_bold_11x22_iso8859_1	11x22	iso8859_1
17	terminus_bold_12x24_iso8859_1	12x24	iso8859_1
18	terminus_bold_14x28_iso8859_1	14x28	iso8859_1
19	terminus_bold_16x32_iso8859_1	16x32	iso8859_1
20	terminus_6x12_koi8_r	6x12	koi8_r
21	terminus_8x14_koi8_r	8x14	koi8_r
22	terminus_14x28_koi8_r	14x28	koi8_r
23	terminus_16x32_koi8_r	16x32	koi8_r
24	terminus_bold_8x14_koi8_r	8x14	koi8_r
25	terminus_bold_14x28_koi8_r	14x28	koi8_r
26	terminus_bold_16x32_koi8_r	16x32	koi8_r

Features

• Left-Right Top-Bottom rasterization
• Top-Bottom Left-Right rasterization (on the fly)
• Position offset - can shift the bitmap in the byte data along the rasterization axis

The original fonts are Left-Right Top-Bottom scanned, but on-the-fly Top-Bottom Left-Right rasterization is provided to allow paged type bitmapps to be supported directly in-library.

The position offset moved the bitmap along the major raster axis so that the output can be directly ORed with the destination bitmap without the need to calculate any required shift at the byte-boundary by the implementing app.

Architecture and Operation

The library contains two parts - the font manager, which is an instance of a given font and raster orientation, and the codified fonts. The fonts themselves are codified as individual C Header files containing arrays of bitmapped character byte data scanning left-right, top-bottom.

The font manager contains a fixed index of the available fonts and retrieves the character data for a particular font by calling a routing in that fonts' header. The font manager can then transform the L-R/T-B rasterization of the charater to some other rasterization as needed: In the case of my SSD1306 driver, it wants T-B/L-R rasterized fonts to allow the SSD1306 paged memory to be written to more effectively as it's also organized T-B/L-R.

This is not a dynamic library, in that it doesn't read the available fonts and index them automagically - to make a font available it has to be scanned, codified and coded into the index. One point to note is that some of the fonts processed for Baoshi's code have character indexes that are 1-out because of C arrays are index from zero and the first non-null character is one: The fist font_char_desc_t entries should be a dummy to compensate to allow a direct character-number to character-representation mapping.

Example

In paged display bitmap such as that in the SD1306, to rasterize a 5-bit high character at Y 21 means the character crosses a page boundry, starting in page 2 (21/8) and ending in page 3 (26/8). Using 21 as the offset the resulting bitmap is split into two rows that can be ORed directly into Page 2 and Page 3.

   /*
    * Create a font manager for glcd_5x7 to raster to an 
    * SSD1306 driving a 128x64 oled
    */
   Font_Manager fm( 3, Font_Manager::TBLR );    
    
   uint8_t x = 40;
   uint8_t y = 21;
   uint8_t page = y / 8;
   std::string s = "@test";

   
   /*
    * Raster an ampersand at the major raster axis (Y for TBLR) position y
    * and grab the bitmap data
    */
   Font_Manager::bitmap b = fm.rasterize( s,  y ); 
   uint8_t * d = b.data; 

	for ( yy = page; i < ( page + b.height ); i++ )
	/*
	 * For each page
	 */
    {
       uint8_t * oled = getOledAtCoord( x, yy * 8 );  // Oled memory buffer address at x, paged y
       
        for ( int xx = x; j < (x + b.width ); j++ )
        /*
         * for each column, OR the bit map into the oled buffer
         */
        {
            *oled++ |= *d++;
        }
    }

Integration and use can be seen in ESP32-SSD1306-Driver

Future Features

Thinking about what could be added:

• LRU Character cache for TBLR fonts

Versions

• 1.0.0 First release with 27 fonts, verticle and horizontal rasterization, position offset
• 0.1.0 Initial commit and pre-release

History and References

This repo is a fork of Baoshi's ESP-I2C-OLED repo, discarding the i2C/SSD1306 code, and developing font management code only. This move came from work on my own SSD1306 driver fork, but in organizing the font usage to better integrate with the bitmapped memory architecture of the SSD1306 I decide to just break this out into a seperate repo for re-use.

Looking through the various forks of the SSD1306 and similar drivers, you find plenty of font bitmaps you can you, such as the set from ubirch I've also borrowed here.

License

Raster-Font - Copyright 2019 technosf [http://github.com/technosf]

Licensed under the GNU LESSER GENERAL PUBLIC LICENSE, Version 3.0 or greater (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

         http://www.gnu.org/licenses/lgpl-3.0.en.html         

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.