Note: both the container chunk (`aDAT`) and every chunk within (`fCTL`, `IDAT`s, `fEND`) must specify the length of its own data field and the CRC over its own chunk name + chunk data as required by section 5.3 of the PNG Specification.
= 3. Interaction with other PNG chunks =
== 3.1. `PLTE` and `tRNS` chunks ==
Should `PLTE` or `tRNS` chunks be valid for the PNG stream's color type, any `PLTE` or `tRNS` specified in the enclosing stream is to be treated as a global palette or transparency, and applied to each frame. Individual frames may override the global values by including their own `PLTE` or `tRNS` between
their `IHDR` and `IDAT` chunks; such a local palette or transparency only applies to the frame where it is specified.
A local palette or transparency should have no effect on any content in the canvas other than the frame currently being rendered. Specifically, palette
animation is not supported -- the RGBA values of previously rendered content still visible on the canvas are not to be changed by a local palette.
== 3.2. Colour space chunks ==
Colour space chunks, as defined in section 11.3.3 of the PNG specification, shall only be valid in the enclosing stream and apply to all the frames within the stream. Any Colour space chunks within individual frames should be ignored by a decoder.
== 3.3. Other chunks ==
Chunks other than those specifically mentioned here should apply to the overall stream's canvas area, including chunks such as `bKGD`, `hIST`, `oFFs`, etc.
= 4. Revisions to this Specification ==
