https://github.com/lvgl/lv_lib_split_jpg
JPG decoder for LVGL
https://github.com/lvgl/lv_lib_split_jpg
embedded jpg lvgl
Last synced: 7 months ago
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JPG decoder for LVGL
- Host: GitHub
- URL: https://github.com/lvgl/lv_lib_split_jpg
- Owner: lvgl
- License: mit
- Created: 2020-09-04T12:11:53.000Z (about 5 years ago)
- Default Branch: master
- Last Pushed: 2021-10-19T16:15:40.000Z (almost 4 years ago)
- Last Synced: 2025-04-03T13:45:55.943Z (7 months ago)
- Topics: embedded, jpg, lvgl
- Language: C
- Homepage:
- Size: 758 KB
- Stars: 32
- Watchers: 5
- Forks: 12
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
# JPG decoder for LVGL
**This repository is merged into the lvgl repository. See https://docs.lvgl.io/master/libs/sjpg.html**
## Overview
- lv_lib_split_jpg supports both normal jpg and the custom sjpg formats.
- Decoding normal jpg consumes RAM with the site fo the whole uncompressed image (recommended only for devices with more RAM)
- sjpg is a custom format based on "normal" JPG and specially made for lvgl.
- sjpg is 'split-jpeg' which is a bundle of small jpeg fragments with an sjpg header.
- sjpg size will be almost comparable to the jpg file or might be a slightly larger.
- lv_sjpg can open and handle multiple files at same time.
- File read from disk (fread) and c-array is implemented.
- SJPEG frame fragment cache enables fast fetching of lines if availble in cache.
- By default the sjpg image cache will be xres * 2 * 16 bytes (can be modified)
- Currently only 16 bit image format is supported (to do)
## Getting started
- Clone this repository next to lvgl with `git clone https://github.com/lvgl/lv_lib_split_jpg.git`
- If you need to open (S)JPG files use [lv_fs_if](https://github.com/lvgl/lv_fs_if) or add your own [file system drivers](https://docs.lvgl.io/latest/en/html/overview/file-system.html).
- With `lv_fs_if` add these line to the end of `lv_conf.h` to enable "PC file system" handling
```c
#define LV_USE_FS_IF 1
#if LV_USE_FS_IF
# define LV_FS_IF_FATFS '\0'
# define LV_FS_IF_PC 'S'
#endif
```
- For fast simulatneous multi jpg/sjpg rendering in expense of additional RAM, you can modify `LV_IMG_CACHE_DEF_SIZE` to 2 or above if testing in simulator or using it in devices like raspberry pi etc.
- To open large JPG image a lot of dymaic memory is required. Be sure to set `LV_MEM_SIZE` to large enough value. In simulator `(4 * 1024 * 1024)` shiuld be a good start.
## Example code
```c
#include
#include "lv_lib_split_jpg/lv_sjpg.h"
LV_IMG_DECLARE( small_image_sjpg );
LV_IMG_DECLARE( wallpaper_jpg );
void demo_jpg_sjpg( void )
{
lv_fs_if_init();
lv_obj_t * img1;
lv_obj_t * img2;
lv_split_jpeg_init();
img1 = lv_img_create(lv_scr_act(), NULL);
img2 = lv_img_create(lv_scr_act(), NULL);
//jpg from c array
lv_img_set_src( img1, &wallpaper_jpg);
//sjpg from file (with lv_fs)
//On Windows
lv_img_set_src(img2, "S.\\lv_lib_split_jpg\\example\\images\\small_image.sjpg");
//On Linux
//lv_img_set_src(img2, "S/lv_lib_split_jpg/example/images/small_image.sjpg");
}
```
## Converter
# Converting JPG to C array
- Use lvgl online tool https://lvgl.io/tools/imageconverter
- Color format = RAW, output format = C Array
# Converting JPG to SJPG
python3 and PIL library required
To create SJPG from JPG:
1. Drag and drop a jpeg image on top of the jpg_to_sjpg.py
2. Run the python script on shell with jpeg filename as argument. It should generate filename.c and filename.sjpg files.
```sh
python3 jpg_to_sjpg.py wallpaper.jpg
```
Expected result:
```sh
Conversion started...
Input:
walpaper.jpg
RES = 640 x 480
Output:
Time taken = 1.66 sec
bin size = 77.1 KB
walpaper.sjpg (bin file)
walpaper.c (c array)
All good!
```