I have seen it in older versions, but that option is gone. I modified V9.3 based on the old version and I can use it with the help of STM32 CLUT table. This means we get 256 different colors(8bpp) and we can simply reference the color. I know it’s a low level, but it can be useful if you have little memory and simple usage.
In v9 we really don’t have an 8bit color rendering support in software render. We have 1 bit indexed and L8 tough as target color formats, and when I1/2/4/8 is used as source formats (with images) they are converted to ARGB8888 in advance.
Adding I8 seems seems reasonable to me with these limitations:
- Support only opacity > 128 will be full covering and opacity <= 128 will be transparent
- Allow blending only I8 images
To do this a file similar to this needs to added. Are you interested in contributing with such a feature?
Unfortunately, I don’t delve into the subject that deeply. This would be mostly a STM32+LTDC specific thing. LTDC has many advantages, it manages 2 layers. Hardware parallel 16bit, but the first layer can be set to L8, while the second layer can remain RGB565. So lvgl draws into the buffer (first layer). With the second layer we can display images, these are stored in an array and there is no extra work, only an address needs to be set. The arrays can be stored in external qspi flash memory, which takes up little space on the pcb and uses few mcu pins. So you don’t have to give up the color image because of 8bpp. RGB332 is not enough for anti-aliasing, so my attention was definitely focused on the monochrome font, only the 0x00 and 0xff bpp values work.
LTDC is set to L8 and expects a value of 0-255 per pixel, RGB332 is 3bit red+3bit green+2bit blue, but its binary value can match the pre-written CLUT table. The CLUT table is stored as 8bit address+8bit red+8bit green+8bit blue, so division is required.
I can’t actively participate, but I’m happy to share what I’ve achieved so far with the community.
These are the external necessary things, besides that, you only need to modify lvgl, but that can be easily copied from an older version. It’s okay if it’s not included in the new version, I put it here in case it might be useful to someone.
//main.c
#include "color_table_rgb332.h"
HAL_LTDC_ConfigCLUT(&hltdc, (uint32_t*)my_rgb332, 256, LTDC_LAYER_1);
HAL_LTDC_EnableCLUT(&hltdc, LTDC_LAYER_1);
//color_table_rgb332.h
/* RGB332, 3bit RED + 3bit GREEN + 2bit BLUE
* 8bit per pixel
* palette address = color bin number
* palette data RED 8bit + GREEN 8bit + BLUE 8bit
* ----------------------------------------------------
* RED BIN 000, 001, 010, 011, 100, 101, 110, 111
* 256/8 -> 0, 36, 73, 109, 146, 182, 219, 255
* HEX 0, 24, 49, 6D, 92, B6, DB, FF
* -----------------------------------------------------
* GREEN BIN 000, 001, 010, 011, 100, 101, 110, 111
* 256/8 -> 0, 36, 73, 109, 146, 182, 219, 255
* HEX 0, 24, 49, 6D, 92, B6, DB, FF
* -----------------------------------------------------
* BLUE BIN 00, 01, 10, 11
* 256/4 -> 0, 85, 170, 255
* HEX 0, 55, AA, FF
* -----------------------------------------------------
*/
#include <stdint.h>
const uint32_t my_rgb332[256] = {
0x000000, //0 000-000-00
0x000055, //1 000-000-01
0x0000AA, //2 000-000-10
0x0000FF, //3 000-000-11
0x002400, //4 000-001-00
0x002455, //5 000-001-01
0x0024AA, //6 000-001-10
0x0024FF, //7 000-001-11
0x004900, //8 000-010-00
0x004955, //9 000-010-01
0x0049AA, //10 000-010-10
0x0049FF, //11 000-010-11
0x006D00, //12 000-011-00
0x006D55, //13 000-011-01
0x006DAA, //14 000-011-10
0x006DFF, //15 000-011-11
0x009200, //16 000-100-00
0x009255, //17 000-100-01
0x0092AA, //18 000-100-10
0x0092FF, //19 000-100-11
0x00B600, //20 000-101-00
0x00B655, //21 000-101-01
0x00B6AA, //22 000-101-10
0x00B6FF, //23 000-101-11
0x00DB00, //24 000-110-00
0x00DB55, //25 000-110-01
0x00DBAA, //26 000-110-10
0x00DBFF, //27 000-110-11
0x00FF00, //28 000-111-00
0x00FF55, //29 000-111-01
0x00FFAA, //30 000-111-10
0x00FFFF, //31 000-111-11
0x240000, //32 001-000-00
0x240055, //33 001-000-01
0x2400AA, //34 001-000-10
0x2400FF, //35 001-000-11
0x242400, //36 001-001-00
0x242455, //37 001-001-01
0x2424AA, //38 001-001-10
0x2424FF, //39 001-001-11
0x244900, //40 001-010-00
0x244955, //41 001-010-01
0x2449AA, //42 001-010-10
0x2449FF, //43 001-010-11
0x246D00, //44 001-011-00
0x246D55, //45 001-011-01
0x246DAA, //46 001-011-10
0x246DFF, //47 001-011-11
0x249200, //48 001-100-00
0x249255, //49 001-100-01
0x2492AA, //50 001-100-10
0x2492FF, //51 001-100-11
0x24B600, //52 001-101-00
0x24B655, //53 001-101-01
0x24B6AA, //54 001-101-10
0x24B6FF, //55 001-101-11
0x24DB00, //56 001-110-00
0x24DB55, //57 001-110-01
0x24DBAA, //58 001-110-10
0x24DBFF, //59 001-110-11
0x24FF00, //60 001-111-00
0x24FF55, //61 001-111-01
0x24FFAA, //62 001-111-10
0x24FFFF, //63 001-111-11
0x490000, //64 010-000-00
0x490055, //65 010-000-01
0x4900AA, //66 010-000-10
0x4900FF, //67 010-000-11
0x492400, //68 010-001-00
0x492455, //69 010-001-01
0x4924AA, //70 010-001-10
0x4924FF, //71 010-001-11
0x494900, //72 010-010-00
0x494955, //73 010-010-01
0x4949AA, //74 010-010-10
0x4949FF, //75 010-010-11
0x496D00, //76 010-011-00
0x496D55, //77 010-011-01
0x496DAA, //78 010-011-10
0x496DFF, //79 010-011-11
0x499200, //80 010-100-00
0x499255, //81 010-100-01
0x4992AA, //82 010-100-10
0x4992FF, //83 010-100-11
0x49B600, //84 010-101-00
0x49B655, //85 010-101-01
0x49B6AA, //86 010-101-10
0x49B6FF, //87 010-101-11
0x49DB00, //88 010-110-00
0x49DB55, //89 010-110-01
0x49DBAA, //90 010-110-10
0x49DBFF, //91 010-110-11
0x49FF00, //92 010-111-00
0x49FF55, //93 010-111-01
0x49FFAA, //94 010-111-10
0x49FFFF, //95 010-111-11
0x6D0000, //96 011-000-00*
0x6D0055, //97 011-000-01
0x6D00AA, //98 011-000-10
0x6D00FF, //99 011-000-11
0x6D2400, //100 011-001-00
0x6D2455, //101 011-001-01
0x6D24AA, //102 011-001-10
0x6D24FF, //103 011-001-11
0x6D4900, //104 011-010-00
0x6D4955, //105 011-010-01
0x6D49AA, //106 011-010-10
0x6D49FF, //107 011-010-11
0x6D6D00, //108 011-011-00
0x6D6D55, //109 011-011-01
0x6D6DAA, //110 011-011-10
0x6D6DFF, //111 011-011-11
0x6D9200, //112 011-100-00
0x6D9255, //113 011-100-01
0x6D92AA, //114 011-100-10
0x6D92FF, //115 011-100-11
0x6DB600, //116 011-101-00
0x6DB655, //117 011-101-01
0x6DB6AA, //118 011-101-10
0x6DB6FF, //119 011-101-11
0x6DDB00, //120 011-110-00
0x6DDB55, //121 011-110-01
0x6DDBAA, //122 011-110-10
0x6DDBFF, //123 011-110-11
0x6DFF00, //124 011-111-00
0x6DFF55, //125 011-111-01
0x6DFFAA, //126 011-111-10
0x6DFFFF, //127 011-111-11
0x920000, //128 100-000-00
0x920055, //129 100-000-01
0x9200AA, //130 100-000-10
0x9200FF, //131 100-000-11
0x922400, //132 100-001-00
0x922455, //133 100-001-01
0x9224AA, //134 100-001-10
0x9224FF, //135 100-001-11
0x924900, //136 100-010-00
0x924955, //137 100-010-01
0x9249AA, //138 100-010-10
0x9249FF, //139 100-010-11
0x926D00, //140 100-011-00
0x926D55, //141 100-011-01
0x926DAA, //142 100-011-10
0x926DFF, //143 100-011-11
0x929200, //144 100-100-00
0x929255, //145 100-100-01
0x9292AA, //146 100-100-10
0x9292FF, //147 100-100-11
0x92B600, //148 100-101-00
0x92B655, //149 100-101-01
0x92B6AA, //150 100-101-10
0x92B6FF, //151 100-101-11
0x92DB00, //152 100-110-00
0x92DB55, //153 100-110-01
0x92DBAA, //154 100-110-10
0x92DBFF, //155 100-110-11
0x92FF00, //156 100-111-00
0x92FF55, //157 100-111-01
0x92FFAA, //158 100-111-10
0x92FFFF, //159 100-111-11
0xB60000, //160 101-000-00
0xB60055, //161 101-000-01
0xB600AA, //162 101-000-10
0xB600FF, //163 101-000-11
0xB62400, //164 101-001-00
0xB62455, //165 101-001-01
0xB624AA, //166 101-001-10
0xB624FF, //167 101-001-11
0xB64900, //168 101-010-00
0xB64955, //169 101-010-01
0xB649AA, //170 101-010-10
0xB649FF, //171 101-010-11
0xB66D00, //172 101-011-00
0xB66D55, //173 101-011-01
0xB66DAA, //174 101-011-10
0xB66DFF, //175 101-011-11
0xB69200, //176 101-100-00
0xB69255, //177 101-100-01
0xB692AA, //178 101-100-10
0xB692FF, //179 101-100-11
0xB6B600, //180 101-101-00
0xB6B655, //181 101-101-01
0xB6B6AA, //182 101-101-10
0xB6B6FF, //183 101-101-11
0xB6DB00, //184 101-110-00
0xB6DB55, //185 101-110-01
0xB6DBAA, //186 101-110-10
0xB6DBFF, //187 101-110-11
0xB6FF00, //188 101-111-00
0xB6FF55, //189 101-111-01
0xB6FFAA, //190 101-111-10
0xB6FFFF, //191 101-111-11
0xDB0000, //192 110-000-00
0xDB0055, //193 110-000-01
0xDB00AA, //194 110-000-10
0xDB00FF, //195 110-000-11
0xDB2400, //196 110-001-00
0xDB2455, //197 110-001-01
0xDB24AA, //198 110-001-10
0xDB24FF, //199 110-001-11
0xDB4900, //200 110-010-00
0xDB4955, //201 110-010-01
0xDB49AA, //202 110-010-10
0xDB49FF, //203 110-010-11
0xDB6D00, //204 110-011-00
0xDB6D55, //205 110-011-01
0xDB6DAA, //206 110-011-10
0xDB6DFF, //207 110-011-11
0xDB9200, //208 110-100-00
0xDB9255, //209 110-100-01
0xDB92AA, //210 110-100-10
0xDB92FF, //211 110-100-11
0xDBB600, //212 110-101-00
0xDBB655, //213 110-101-01
0xDBB6AA, //214 110-101-10
0xDBB6FF, //215 110-101-11
0xDBDB00, //216 110-110-00
0xDBDB55, //217 110-110-01
0xDBDBAA, //218 110-110-10
0xDBDBFF, //219 110-110-11
0xDBFF00, //220 110-111-00
0xDBFF55, //221 110-111-01
0xDBFFAA, //222 110-111-10
0xDBFFFF, //223 110-111-11
0xFF0000, //224 111-000-00
0xFF0055, //225 111-000-01
0xFF00AA, //226 111-000-10
0xFF00FF, //227 111-000-11
0xFF2400, //228 111-001-00
0xFF2455, //229 111-001-01
0xFF24AA, //230 111-001-10
0xFF24FF, //231 111-001-11
0xFF4900, //232 111-010-00
0xFF4955, //233 111-010-01
0xFF49AA, //234 111-010-10
0xFF49FF, //235 111-010-11
0xFF6D00, //236 111-011-00
0xFF6D55, //237 111-011-01
0xFF6DAA, //238 111-011-10
0xFF6DFF, //239 111-011-11
0xFF9200, //240 111-100-00
0xFF9255, //241 111-100-01
0xFF92AA, //242 111-100-10
0xFF92FF, //243 111-100-11
0xFFB600, //244 111-101-00
0xFFB655, //245 111-101-01
0xFFB6AA, //246 111-101-10
0xFFB6FF, //247 111-101-11
0xFFDB00, //248 111-110-00
0xFFDB55, //249 111-110-01
0xFFDBAA, //250 111-110-10
0xFFDBFF, //251 111-110-11
0xFFFF00, //252 111-111-00
0xFFFF55, //253 111-111-01
0xFFFFAA, //254 111-111-10
0xFFFFFF, //255 111-111-11
};
Thanks!
Unfortunately (or fortunately) we have a lot of customer and partner support things to work on now so can’t jump into it, but we will keep it on our radar.
If more requests come we will prioritize it for sure.
If you change you mind and get interested in working on it, just let us know.
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