Canvas alpha buffer set bg color

Description

Hey all :slight_smile: working with canvas for the first and I am having trouble setting the bg color for an alpha color buffer. The canvas is only black despite setting in via lv_canvas_fill_bg(canvas, lv_color_white(), LV_OPA_0);

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

Teensy MM

What LVGL version are you using?

8.1

Code to reproduce

lv_color_t canvas_buf[LV_CANVAS_BUF_SIZE_ALPHA_4BIT(CANVAS_WIDTH, CANVAS_HEIGHT)];
lv_obj_t *canvas = lv_canvas_create(NULL);
lv_canvas_set_buffer(canvas, canvas_buf, CANVAS_WIDTH, CANVAS_HEIGHT, LV_IMG_CF_ALPHA_4BIT);
lv_canvas_fill_bg(canvas, lv_color_white(), LV_OPA_0);

And then in an interrupt I am setting pixel OPA based on some indexing. OPA setting is working great, it is just the black color that I am having trouble with.

So turns out the alpha buffer makes the canvas behave more like an image I guess. I can set the color using styles using something like:

    lv_style_init(&img_style);
    lv_style_set_img_recolor(&img_style, lv_color_white());