A metadata entry that defines the approximate color usage frequency in the palette. This entry
can only exist if there is also a palette. If a viewer of the png file cannot display all colors,
this chunk can help select a subset of the colors to use.
An array of approximately frequency of each palette entry, the exact scale of the frequency is
not standard and determined by the encoder of the image.
type
type:"hIST"
The type of metadata, this is typically the name of the chunk from which is originates.
A metadata entry that defines the approximate color usage frequency in the palette. This entry can only exist if there is also a palette. If a viewer of the png file cannot display all colors, this chunk can help select a subset of the colors to use.