adding type annotations and png example script

adafruit_imageload/png.py

@@ -13,16 +13,22 @@
 
 """
 
+try:
+    # pylint: disable=unused-import
+    import typing
+    from .displayio_types import PaletteConstructor, BitmapConstructor
+except ImportError:
+    pass
+
 import struct
 import zlib
 
-
 __version__ = "0.0.0-auto.0"
 __repo__ = "https://github.com/adafruit/Adafruit_CircuitPython_ImageLoad.git"
 
 
 def load(
-    file, *, bitmap, palette=None
+    file: str, *, bitmap: BitmapConstructor, palette: PaletteConstructor = None
 ):  # pylint: disable=too-many-locals,too-many-branches
     """Loads a PNG image from the open ``file``.
 

examples/imageload_png_simpletest.py

@@ -0,0 +1,43 @@
+# SPDX-FileCopyrightText: 2022 Tim Cocks
+# SPDX-License-Identifier: MIT
+
+import board
+import displayio
+from vectorio import Rectangle
+import adafruit_imageload
+
+# built-in display
+display = board.DISPLAY
+
+# load png image
+image, palette = adafruit_imageload.load("images/test_image.png")
+
+# Set the transparency index color to be hidden
+palette.make_transparent(0)
+
+# make tilegrid for the loaded image
+tile_grid = displayio.TileGrid(image, pixel_shader=palette)
+tile_grid.x = display.width // 2 - tile_grid.tile_width // 2
+tile_grid.y = display.height // 2 - tile_grid.tile_height // 2
+
+# make a blank background
+bg_palette = displayio.Palette(1)
+bg_palette[0] = 0xFFFFFF
+rect = Rectangle(
+    pixel_shader=bg_palette, width=display.width, height=display.height, x=0, y=0
+)
+
+# make a group to show on the display
+group = displayio.Group()
+
+# add background
+group.append(rect)
+# add loaded image tilegrid
+group.append(tile_grid)
+
+# show our group
+board.DISPLAY.show(group)
+
+# loop forever so it stays on the display
+while True:
+    pass

examples/images/test_image.png.license

@@ -0,0 +1,2 @@
+# SPDX-FileCopyrightText: 2022 ladyada for Adafruit Industries
+# SPDX-License-Identifier: MIT