update asserts

examples/widgets/canvas/lv_example_canvas_2.c

@@ -0,0 +1,44 @@
+#include "../../../lvgl.h"
+#if LV_USE_CANVAS
+
+#define CANVAS_WIDTH  50
+#define CANVAS_HEIGHT  50
+
+/**
+ * Create a transparent canvas with Chroma keying and indexed color format (palette).
+ */
+void lv_example_canvas_2(void)
+{
+    /*Create a button to better see the transparency*/
+    lv_btn_create(lv_scr_act(), NULL);
+
+    /*Create a buffer for the canvas*/
+    static lv_color_t cbuf[LV_CANVAS_BUF_SIZE_INDEXED_1BIT(CANVAS_WIDTH, CANVAS_HEIGHT)];
+
+    /*Create a canvas and initialize its the palette*/
+    lv_obj_t * canvas = lv_canvas_create(lv_scr_act(), NULL);
+    lv_canvas_set_buffer(canvas, cbuf, CANVAS_WIDTH, CANVAS_HEIGHT, LV_IMG_CF_INDEXED_1BIT);
+    lv_canvas_set_palette(canvas, 0, LV_COLOR_CHROMA_KEY);
+    lv_canvas_set_palette(canvas, 1, LV_COLOR_RED);
+
+    /*Create colors with the indices of the palette*/
+    lv_color_t c0;
+    lv_color_t c1;
+
+    c0.full = 0;
+    c1.full = 1;
+
+    /*Red background (There is no dedicated alpha channel in indexed images so LV_OPA_COVER is ignored)*/
+    lv_canvas_fill_bg(canvas, c1, LV_OPA_COVER);
+
+    /*Create hole on the canvas*/
+    uint32_t x;
+    uint32_t y;
+    for( y = 10; y < 30; y++) {
+        for( x = 5; x < 20; x++) {
+            lv_canvas_set_px(canvas, x, y, c0);
+        }
+    }
+
+}
+#endif