LCD API

Introduction

The LCD API can be used to display BMP images or text onto the LCD screen. At the moment of writing, only BMP's in C array's are supported. Supported color schemes for BMP's are ARGB8888, RGB565, RGB888. Displayed text that is exceeds the LCD width size, will be wrapped onto the next line and a '-' character will be injected if the wrap occurs within a word.

Usage of LCD API

Generating BMP C header files

Resizing images

To resize an image to the desired size (width and height), one can use an image editor such as Photoshop, GIMP, ImageMagick, ... .

For example, using ImageMagick:

convert in.png -resize 10% BMP3:out.bmp
#OR (depending on the version of ImageMagick)
magick in.png -resize 50x50 out.png

The resize option can both be used to resize in percentages or in pixels.

The BMP3 option is used to convert the PNG to Bitmap version 3.0 (note that the BMP header will still be present in the output image).

Generating the C array

To easily generate a BMP C array (in the desired color scheme) from an image, lv_img_conv can be used.

See the installation instructions on Github or use the online version.

Example:

./lv_img_conv.js test.png -f -c CF_TRUE_COLOR

The command above will generate a .c file in which arrays can be found for RGB332, RGB565, ARGB8888. It is also possible to generate a binary BMP image file in ARGB8332, ARGB8565, ARGB8565_RBSWAP, ARGB8888.

./lv_img_conv.js logo_lvgl.png -f -c CF_TRUE_COLOR -t bin --binary-format ARGB8888

Using the LCD API

Initialization of LCD API

The lcd_init(bool bl_on) function initialises the LCD screen. The bl_on variable allows to enable or disable the LCD backlight.

#include "lcd_api.h"

...

void main(void) {
    ...
    lcd_init(true);
    ...
}

Drawing text on the screen

void lcd_display_text(const char* text, uint16_t x_pos, uint16_t y_pos, uint32_t color, uint32_t bg_color, sFONT *font);

#include "lcd_api.h"

...

void main(void) {
    ...
    lcd_init(true);
    ...
    lcd_display_text("This is a text string.", 10, 10, LCD_GREEN, LCD_BLACK, LCD_FONT16);
}

Display text on the LCD screen in a certain color. When text width exceeds BSP_LCD_GetXSize(), a text wrap will be performed. If the text wrap is between two will be injected.

Drawing a BMP (C-array) onto the screen

void lcd_draw_bmp(const void* p_src, uint32_t x_pos, uint32_t y_pos, uint32_t x_size, uint32_t y_size, uint32_t color_mode);

#include "lcd_api.h"
#include "test_image.h"

void main(void) {
  ...
  lcd_init(true);
  ...
  lcd_draw_bmp(bmp_array, 0, 0, 50, 50, LCD_ARGB8888);
}

Draw BMP image from C array to the LCD screen at position X, Y. In color mode ARGB8888, RGB888, RGB565 or ARGB1555 Supports ARGB8888, RGB565, RGB888 (see LCD_* defines in header file).

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