This object is returned by
chunks property from TPNGObject.
TPNGList provides access to all the chunks inside the current image.
Count property returns the number of
items, Item[Index: Cardinal] property
returns a TChunk using the index position (from 0 to Count - 1). Check the
name from the returned TChunk using the name
property and typecast using the appropriate class. For instance, if name
property returns 'IHDR', typecast the returned TChunk as TChunkIHDR.