lv_canvas.h

Defines

LV_CANVAS_BUF_SIZE_TRUE_COLOR(w, h)
LV_CANVAS_BUF_SIZE_TRUE_COLOR_CHROMA_KEYED(w, h)
LV_CANVAS_BUF_SIZE_TRUE_COLOR_ALPHA(w, h)
LV_CANVAS_BUF_SIZE_ALPHA_1BIT(w, h)
LV_CANVAS_BUF_SIZE_ALPHA_2BIT(w, h)
LV_CANVAS_BUF_SIZE_ALPHA_4BIT(w, h)
LV_CANVAS_BUF_SIZE_ALPHA_8BIT(w, h)
LV_CANVAS_BUF_SIZE_INDEXED_1BIT(w, h)
LV_CANVAS_BUF_SIZE_INDEXED_2BIT(w, h)
LV_CANVAS_BUF_SIZE_INDEXED_4BIT(w, h)
LV_CANVAS_BUF_SIZE_INDEXED_8BIT(w, h)

Functions

lv_obj_t *lv_canvas_create(lv_obj_t *parent)

Create a canvas object

Parameters:

parent -- pointer to an object, it will be the parent of the new canvas

Returns:

pointer to the created canvas

void lv_canvas_set_buffer(lv_obj_t *canvas, void *buf, lv_coord_t w, lv_coord_t h, lv_color_format_t cf)

Set a buffer for the canvas.

Parameters:

  • buf -- a buffer where the content of the canvas will be. The required size is (lv_img_color_format_get_px_size(cf) * w) / 8 * h) It can be allocated with lv_malloc() or it can be statically allocated array (e.g. static lv_color_t buf[100*50]) or it can be an address in RAM or external SRAM

  • canvas -- pointer to a canvas object

  • w -- width of the canvas

  • h -- height of the canvas

  • cf -- color format. LV_IMG_CF_...

void lv_canvas_set_px(lv_obj_t *obj, lv_coord_t x, lv_coord_t y, lv_color_t color, lv_opa_t opa)
void lv_canvas_set_palette(lv_obj_t *canvas, uint8_t id, lv_color32_t c)

Set the palette color of a canvas with index format. Valid only for LV_IMG_CF_INDEXED1/2/4/8

Parameters:

  • canvas -- pointer to canvas object

  • id -- the palette color to set:

    • for LV_IMG_CF_INDEXED1: 0..1

    • for LV_IMG_CF_INDEXED2: 0..3

    • for LV_IMG_CF_INDEXED4: 0..15

    • for LV_IMG_CF_INDEXED8: 0..255

  • c -- the color to set

void lv_canvas_get_px(lv_obj_t *obj, lv_coord_t x, lv_coord_t y, lv_color_t *color, lv_opa_t *opa)
lv_img_dsc_t *lv_canvas_get_img(lv_obj_t *canvas)

Get the image of the canvas as a pointer to an lv_img_dsc_t variable.

Parameters:

canvas -- pointer to a canvas object

Returns:

pointer to the image descriptor.

void lv_canvas_copy_buf(lv_obj_t *canvas, const void *to_copy, lv_coord_t x, lv_coord_t y, lv_coord_t w, lv_coord_t h)

Copy a buffer to the canvas

Parameters:

  • canvas -- pointer to a canvas object

  • to_copy -- buffer to copy. The color format has to match with the canvas's buffer color format

  • x -- left side of the destination position

  • y -- top side of the destination position

  • w -- width of the buffer to copy

  • h -- height of the buffer to copy

void lv_canvas_transform(lv_obj_t *canvas, lv_img_dsc_t *img, int16_t angle, uint16_t zoom, lv_coord_t offset_x, lv_coord_t offset_y, int32_t pivot_x, int32_t pivot_y, bool antialias)

Transform and image and store the result on a canvas.

Parameters:

  • canvas -- pointer to a canvas object to store the result of the transformation.

  • img -- pointer to an image descriptor to transform. Can be the image descriptor of an other canvas too (lv_canvas_get_img()).

  • angle -- the angle of rotation (0..3600), 0.1 deg resolution

  • zoom -- zoom factor (256 no zoom);

  • offset_x -- offset X to tell where to put the result data on destination canvas

  • offset_y -- offset X to tell where to put the result data on destination canvas

  • pivot_x -- pivot X of rotation. Relative to the source canvas Set to source width / 2 to rotate around the center

  • pivot_y -- pivot Y of rotation. Relative to the source canvas Set to source height / 2 to rotate around the center

  • antialias -- apply anti-aliasing during the transformation. Looks better but slower.

void lv_canvas_blur_hor(lv_obj_t *canvas, const lv_area_t *area, uint16_t r)

Apply horizontal blur on the canvas

Parameters:

  • canvas -- pointer to a canvas object

  • area -- the area to blur. If NULL the whole canvas will be blurred.

  • r -- radius of the blur

void lv_canvas_blur_ver(lv_obj_t *canvas, const lv_area_t *area, uint16_t r)

Apply vertical blur on the canvas

Parameters:

  • canvas -- pointer to a canvas object

  • area -- the area to blur. If NULL the whole canvas will be blurred.

  • r -- radius of the blur

void lv_canvas_fill_bg(lv_obj_t *canvas, lv_color_t color, lv_opa_t opa)

Fill the canvas with color

Parameters:

  • canvas -- pointer to a canvas

  • color -- the background color

  • opa -- the desired opacity

void lv_canvas_draw_rect(lv_obj_t *canvas, lv_coord_t x, lv_coord_t y, lv_coord_t w, lv_coord_t h, const lv_draw_rect_dsc_t *draw_dsc)

Draw a rectangle on the canvas

Parameters:

  • canvas -- pointer to a canvas object

  • x -- left coordinate of the rectangle

  • y -- top coordinate of the rectangle

  • w -- width of the rectangle

  • h -- height of the rectangle

  • draw_dsc -- descriptor of the rectangle

void lv_canvas_draw_text(lv_obj_t *canvas, lv_coord_t x, lv_coord_t y, lv_coord_t max_w, lv_draw_label_dsc_t *draw_dsc, const char *txt)

Draw a text on the canvas.

Parameters:

  • canvas -- pointer to a canvas object

  • x -- left coordinate of the text

  • y -- top coordinate of the text

  • max_w -- max width of the text. The text will be wrapped to fit into this size

  • draw_dsc -- pointer to a valid label descriptor lv_draw_label_dsc_t

  • txt -- text to display

void lv_canvas_draw_img(lv_obj_t *canvas, lv_coord_t x, lv_coord_t y, const void *src, const lv_draw_img_dsc_t *draw_dsc)

Draw an image on the canvas

Parameters:

  • canvas -- pointer to a canvas object

  • x -- left coordinate of the image

  • y -- top coordinate of the image

  • src -- image source. Can be a pointer an lv_img_dsc_t variable or a path an image.

  • draw_dsc -- pointer to a valid label descriptor lv_draw_img_dsc_t

void lv_canvas_draw_line(lv_obj_t *canvas, const lv_point_t points[], uint32_t point_cnt, const lv_draw_line_dsc_t *draw_dsc)

Draw a line on the canvas

Parameters:

  • canvas -- pointer to a canvas object

  • points -- point of the line

  • point_cnt -- number of points

  • draw_dsc -- pointer to an initialized lv_draw_line_dsc_t variable

void lv_canvas_draw_polygon(lv_obj_t *canvas, const lv_point_t points[], uint32_t point_cnt, const lv_draw_rect_dsc_t *draw_dsc)

Draw a polygon on the canvas

Parameters:

  • canvas -- pointer to a canvas object

  • points -- point of the polygon

  • point_cnt -- number of points

  • draw_dsc -- pointer to an initialized lv_draw_rect_dsc_t variable

void lv_canvas_draw_arc(lv_obj_t *canvas, lv_coord_t x, lv_coord_t y, lv_coord_t r, int32_t start_angle, int32_t end_angle, const lv_draw_arc_dsc_t *draw_dsc)

Draw an arc on the canvas

Parameters:

  • canvas -- pointer to a canvas object

  • x -- origo x of the arc

  • y -- origo y of the arc

  • r -- radius of the arc

  • start_angle -- start angle in degrees

  • end_angle -- end angle in degrees

  • draw_dsc -- pointer to an initialized lv_draw_line_dsc_t variable

Variables

const lv_obj_class_t lv_canvas_class
struct lv_canvas_t

Public Members

lv_img_t img
lv_img_dsc_t dsc