transparent canvas with chroma keying for little vGL

canvas with chroma keying for little vGL"/>

transparent canvas with chroma keying for little vGL

• 定义画布尺寸

  #define TRANSPARENT_CANVAS_WIDTH    50
  #define TRANSPARENT_CANVAS_HIGHT    50

• 创建一个button

  lv_btn_create(lv_scr_act(), NULL);

• 定义画布缓冲buffer，注意不能是局部的

  static lv_color_t cbuf[LV_CANVAS_BUF_SIZE_INDEXED_1BIT(TRANSPARENT_CANVAS_WIDTH,TRANSPARENT_CANVAS_HIGHT)];

• 创建画布对象

   lv_obj_t* canvas = lv_canvas_create(lv_scr_act(), NULL);

• 设置关联画布缓冲buffer

   lv_canvas_set_buffer(canvas, cbuf, TRANSPARENT_CANVAS_WIDTH, TRANSPARENT_CANVAS_HIGHT, LV_IMG_CF_INDEXED_1BIT);

•    设置透明和红色2个调色盘

      lv_canvas_set_palette(canvas, 0, LV_COLOR_TRANSP);lv_canvas_set_palette(canvas, 1, LV_COLOR_RED);

• 定义颜色变量C0,C1

      lv_color_t c0;lv_color_t c1;c0.full = 0;c1.full = 1;
  

• 绘制C0,C1

    lv_canvas_fill_bg(canvas, c1);uint32_t x, y;for (y = 10; y < 30; y++){for (x = 5; x < 20; x++){lv_canvas_set_px(canvas, x, y, c0);}}

• 完整的实现

#define TRANSPARENT_CANVAS_WIDTH    50
#define TRANSPARENT_CANVAS_HIGHT    50
void transparent_canvas_demo(void) {lv_btn_create(lv_scr_act(), NULL);static lv_color_t cbuf[LV_CANVAS_BUF_SIZE_INDEXED_1BIT(TRANSPARENT_CANVAS_WIDTH,TRANSPARENT_CANVAS_HIGHT)];lv_obj_t* canvas = lv_canvas_create(lv_scr_act(), NULL);lv_canvas_set_buffer(canvas, cbuf, TRANSPARENT_CANVAS_WIDTH, TRANSPARENT_CANVAS_HIGHT, LV_IMG_CF_INDEXED_1BIT);lv_canvas_set_palette(canvas, 0, LV_COLOR_TRANSP);lv_canvas_set_palette(canvas, 1, LV_COLOR_RED);lv_color_t c0;lv_color_t c1;c0.full = 0;c1.full = 1;lv_canvas_fill_bg(canvas, c1);uint32_t x, y;for (y = 10; y < 30; y++) {for (x = 5; x < 20; x++) {lv_canvas_set_px(canvas, x, y, c0);}}
}

• 调用transparent_canvas_demo函数，编译运行