generate_tiles(image_format='.png') saves as TIFF with .png extension

[freezurbern]

Hello,
I tried to generate tiles from a .tiff orthophoto into .png tiles but found the RasterIO metadata is not updated to use the png format.
Reproduce:

INPUT_PATH = "orthophoto.tiff"
OUTPUT_DIR = "raw-tiles"
gt = geotile.GeoTile(INPUT_PATH)
gt.generate_tiles(
    output_folder=OUTPUT_DIR, prefix="tile_",
    save_tiles=True, save_transform=True,
    image_format=".png", dtype="uint8",
)

Examine the output image to find the file type:

> file ./raw-tiles/tile_459.png
raw-tiles/tile_459.png: TIFF image data, ...

I believe the generate_tiles() image_format parameter should be used to set meta['driver'] before saving the tiles.