The transparent color or the transparency of the palette color, the format depends on the image color type:
0 (Greyscale): number - the shade of grey that will use alpha 0.2 (Truecolor): [number, number, number] - the color rgb that will use alpha 0.3 (Indexed): [number, ...] - The alpha value of palette entries, this may not include all
palette entries.The type of metadata, this is typically the name of the chunk from which is originates.
A metadata entry that defines "simple transparency," allowing transparency within non-alpha color types. The transparency defined in this chunk is applied automatically to the data during decoding.