RE: Show BMP image on display

JVKran — Wed, 12 May 2021 08:24:38 GMT

Hi Simon,

Thanks for pointing that out! Got that working almost instantly. That topic, however, doesn't really provide any information with regards to writing an image from the SD card to a display. Since I couldn't get the function form the GFX library working, I decided to write my own that takes the filename and rectangle as input.

ret_code_t display_c::show_image(nrf_gfx_rect_t const * p_rect, const char* file_name){
    UINT bytes_read;
    FIL f;
    if(f_open(&f, file_name, FA_READ) != FR_OK){
        NRF_LOG_WARNING("Opening \"%s\" failed.", file_name);
        return NRF_ERROR_NOT_FOUND;
    }

    if ((p_rect->x > nrf_gfx_width_get(&lcd)) || (p_rect->y > nrf_gfx_height_get(&lcd))){
        return NRF_ERROR_INVALID_PARAM;
    }

    uint16_t signature;
    f_read(&f, &signature, 2, &bytes_read);

    uint32_t size, creator_bytes, image_offset;
    f_read(&f, &size, 4, &bytes_read);
    f_read(&f, &creator_bytes, 4, &bytes_read);
    f_read(&f, &image_offset, 4, &bytes_read);

    f_lseek(&f, image_offset);

    uint16_t pixel;
    for (int32_t i = 0; i < p_rect->height; i++){
        for (uint32_t j = 0; j < p_rect->width; j++){
            f_read(&f, &pixel, 2, &bytes_read);
            lcd.lcd_pixel_draw(p_rect->x + j, p_rect->y + i, pixel);
        }
    }

    f_close(&f);
    NRF_LOG_WARNING("Image \"%s\" drawn.", file_name);
    return NRF_SUCCESS;
}

For anyone facing the same challenge; feel free to use it.

Kind regards,

Jochem

RE: Show BMP image on display

Simonr — Thu, 15 Apr 2021 05:58:33 GMT

I'm afraid what documentation we got regarding LCD control is limited to the GFX library and the GFX example project in our nRF5 SDK, so we don't have any examples for displaying data stored on an SD card I'm afraid. We do however have this thread on DevZone where control of an ST7789 LCD with an nRF52DK is the theme. This should be a similar screen to the one you're using, and has quite a bit of information on bitmaps with the ST-series LCDs, so I would suggest giving it a read to see if that helps with your understanding.

Best regards,

Simon