first commit

libraries/lvgl/examples/widgets/canvas/lv_example_canvas_2.py

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+CANVAS_WIDTH   = 50
+CANVAS_HEIGHT  = 50
+LV_COLOR_CHROMA_KEY = lv.color_hex(0x00ff00)
+
+def LV_IMG_BUF_SIZE_ALPHA_1BIT(w, h):
+    return int(((w / 8) + 1) * h)
+
+def LV_IMG_BUF_SIZE_INDEXED_1BIT(w, h):
+    return LV_IMG_BUF_SIZE_ALPHA_1BIT(w, h) + 4 * 2
+
+def LV_CANVAS_BUF_SIZE_INDEXED_1BIT(w, h):
+    return LV_IMG_BUF_SIZE_INDEXED_1BIT(w, h)
+
+#
+# Create a transparent canvas with Chroma keying and indexed color format (palette).
+#
+
+# Create a button to better see the transparency
+btn=lv.btn(lv.scr_act())
+
+# Create a buffer for the canvas
+cbuf= bytearray(LV_CANVAS_BUF_SIZE_INDEXED_1BIT(CANVAS_WIDTH, CANVAS_HEIGHT))
+
+# Create a canvas and initialize its palette
+canvas = lv.canvas(lv.scr_act())
+canvas.set_buffer(cbuf, CANVAS_WIDTH, CANVAS_HEIGHT, lv.img.CF.INDEXED_1BIT)
+canvas.set_palette(0, LV_COLOR_CHROMA_KEY)
+canvas.set_palette(1, lv.palette_main(lv.PALETTE.RED))
+
+# Create colors with the indices of the palette
+c0 = lv.color_t()
+c1 = lv.color_t()
+
+c0.full = 0
+c1.full = 1
+
+# Red background (There is no dedicated alpha channel in indexed images so LV_OPA_COVER is ignored)
+canvas.fill_bg(c1, lv.OPA.COVER)
+
+# Create hole on the canvas
+for y in range(10,30):
+    for x in range(5,20):
+        canvas.set_px(x, y, c0)