ndg/lib/lvgl/docs/overview/color.md

Colors

The color module handles all color-related functions like changing color depth, creating colors from hex code, converting between color depths, mixing colors, etc.

The type lv_color_t is used to store a color. Its fields are set according to LV_COLOR_DEPTH in lv_conf.h. (See below)

You may set LV_COLOR_16_SWAP in lv_conf.h to swap bytes of RGB565 colors. You may need this when sending 16-bit colors via a byte-oriented interface like SPI. As 16-bit numbers are stored in little-endian format (lower byte at the lower address), the interface will send the lower byte first. However, displays usually need the higher byte first. A mismatch in the byte order will result in highly distorted colors.

Creating colors

RGB

Create colors from Red, Green and Blue channel values:

//All channels are 0-255
lv_color_t c = lv_color_make(red, green, blue);

//From hex code 0x000000..0xFFFFFF interpreted as RED + GREEN + BLUE
lv_color_t c = lv_color_hex(0x123456);

//From 3 digits. Same as lv_color_hex(0x112233)
lv_color_t c = lv_color_hex3(0x123);

HSV

Create colors from Hue, Saturation and Value values:

//h = 0..359, s = 0..100, v = 0..100
lv_color_t c = lv_color_hsv_to_rgb(h, s, v);

//All channels are 0-255
lv_color_hsv_t c_hsv = lv_color_rgb_to_hsv(r, g, b);


//From lv_color_t variable
lv_color_hsv_t c_hsv = lv_color_to_hsv(color);

Palette

LVGL includes Material Design's palette of colors. In this system all named colors have a nominal main color as well as four darker and five lighter variants.

The names of the colors are as follows:

• LV_PALETTE_RED
• LV_PALETTE_PINK
• LV_PALETTE_PURPLE
• LV_PALETTE_DEEP_PURPLE
• LV_PALETTE_INDIGO
• LV_PALETTE_BLUE
• LV_PALETTE_LIGHT_BLUE
• LV_PALETTE_CYAN
• LV_PALETTE_TEAL
• LV_PALETTE_GREEN
• LV_PALETTE_LIGHT_GREEN
• LV_PALETTE_LIME
• LV_PALETTE_YELLOW
• LV_PALETTE_AMBER
• LV_PALETTE_ORANGE
• LV_PALETTE_DEEP_ORANGE
• LV_PALETTE_BROWN
• LV_PALETTE_BLUE_GREY
• LV_PALETTE_GREY

To get the main color use lv_color_t c = lv_palette_main(LV_PALETTE_...).

For the lighter variants of a palette color use lv_color_t c = lv_palette_lighten(LV_PALETTE_..., v). v can be 1..5. For the darker variants of a palette color use lv_color_t c = lv_palette_darken(LV_PALETTE_..., v). v can be 1..4.

Modify and mix colors

The following functions can modify a color:

// Lighten a color. 0: no change, 255: white
lv_color_t c = lv_color_lighten(c, lvl);

// Darken a color. 0: no change, 255: black
lv_color_t c = lv_color_darken(lv_color_t c, lv_opa_t lvl);

// Lighten or darken a color. 0: black, 128: no change 255: white
lv_color_t c = lv_color_change_lightness(lv_color_t c, lv_opa_t lvl);


// Mix two colors with a given ratio 0: full c2, 255: full c1, 128: half c1 and half c2
lv_color_t c = lv_color_mix(c1, c2, ratio);

Built-in colors

lv_color_white() and lv_color_black() return 0xFFFFFF and 0x000000 respectively.

Opacity

To describe opacity the lv_opa_t type is created from uint8_t. Some special purpose defines are also introduced:

• LV_OPA_TRANSP Value: 0, means no opacity making the color completely transparent
• LV_OPA_10 Value: 25, means the color covers only a little
• LV_OPA_20 ... OPA_80 follow logically
• LV_OPA_90 Value: 229, means the color near completely covers
• LV_OPA_COVER Value: 255, means the color completely covers (full opacity)

You can also use the LV_OPA_* defines in lv_color_mix() as a mixing ratio.

Color types

The following variable types are defined by the color module:

• lv_color1_t Monochrome color. Also has R, G, B fields for compatibility but they are always the same value (1 byte)
• lv_color8_t A structure to store R (3 bit),G (3 bit),B (2 bit) components for 8-bit colors (1 byte)
• lv_color16_t A structure to store R (5 bit),G (6 bit),B (5 bit) components for 16-bit colors (2 byte)
• lv_color32_t A structure to store R (8 bit),G (8 bit), B (8 bit) components for 24-bit colors (4 byte)
• lv_color_t Equal to lv_color1/8/16/24_t depending on the configured color depth setting
• lv_color_int_t uint8_t, uint16_t or uint32_t depending on the color depth setting. Used to build color arrays from plain numbers.
• lv_opa_t A simple uint8_t type to describe opacity.

The lv_color_t, lv_color1_t, lv_color8_t, lv_color16_t and lv_color32_t types have four fields:

• ch.red red channel
• ch.green green channel
• ch.blue blue channel
• full* red + green + blue as one number

You can set the current color depth in lv_conf.h, by setting the LV_COLOR_DEPTH define to 1 (monochrome), 8, 16 or 32.

Convert color

You can convert a color from the current color depth to another. The converter functions return with a number, so you have to use the full field to map a converted color back into a structure:

lv_color_t c;
c.red   = 0x38;
c.green = 0x70;
c.blue  = 0xCC;

lv_color1_t c1;
c1.full = lv_color_to1(c);	/*Return 1 for light colors, 0 for dark colors*/

lv_color8_t c8;
c8.full = lv_color_to8(c);	/*Give a 8 bit number with the converted color*/

lv_color16_t c16;
c16.full = lv_color_to16(c); /*Give a 16 bit number with the converted color*/

lv_color32_t c24;
c32.full = lv_color_to32(c);	/*Give a 32 bit number with the converted color*/

API

.. doxygenfile:: lv_color.h
  :project: lvgl