How to use the JPEG decoder to display an image

How-to
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1

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Description

How do I use the new JPEG decoder in lvgl to display an Image on the screen?

What MCU/Processor/Board and compiler are you using?

ESP32-WROOM

What LVGL version are you using?

8.3.7

What do you want to achieve?

Display an image on the screen

What have you tried so far?

I have tried to use the decoder using the lv_img functions that are supposed to automatically use the decoder. I have defined the LV_USE_SJPG, the screens are being loaded but I can’t figure out how to display images on my 240x240 screen (GC9A01). Thanks!

Code to reproduce

void setup(){
//Initialized buffer and initialized lvgl

 lv_obj_t* main_screen = lv_obj_create(NULL);

  lv_scr_load(main_screen);

  lv_obj_set_style_bg_color(main_screen,lv_palette_main(LV_PALETTE_AMBER),0); // This is a check to screen has been loaded.

  lv_obj_t *img_obj = lv_img_create(main_screen);
  lv_img_set_src(img_obj,"space.jpg");
  lv_obj_set_pos(img_obj,0,0);
  lv_obj_set_size(img_obj,100,100);

  lv_scr_load(main_screen);
}

void loop(){
lv_task_handler();
}
2

Please check out the docs here: JPG decoder — LVGL documentation

3

Thank you for replying. I looked at the documentation provided as well as the documentation in the link and included the file system.

‘’‘/API for fopen, fread, etc/
#define LV_USE_FS_STDIO 1
#if LV_USE_FS_STDIO
#define LV_FS_STDIO_LETTER ‘\0’ /Set an upper cased letter on which the drive will accessible (e.g. ‘A’)/
#define LV_FS_STDIO_PATH “A” /Set the working directory. File/directory paths will be appended to it./
#define LV_FS_STDIO_CACHE_SIZE 0 />0 to cache this number of bytes in lv_fs_read()/
#endif’‘’

I also used the file system and tried to use the same functions as the example.

‘’'lv_obj_t *img_obj = lv_img_create(lv_scr_act());

lv_img_set_src(img_obj,“A:src/space.jpg”);

lv_scr_load(main_screen);‘’’

However, it did not work, I created an arc as a dummy widget to check if I had not initialized the screen correctly (happens a lot since I am still learning) but it appeared and was responsive to input. I am trying to figure out if it has to do with the file system structure of my project (using platformIO).

Thanks for replying back!

4

The official website has instructions for using JPEG decoders.