Investigate if we need to implement ZIP compression support
pastelmind opened this issue · comments
Adobe's PSD file format document claims that there are four compression methods for image channels: uncompressed (0), RLE (1), ZIP (2), ZIP with prediction (3). However, I have yet to find a PSD file that uses compression methods 2 and 3. If they do exist, we may have to support them as well.
What to do
- Attempt to find or obtain a PSD file that uses compression methods 2 and 3
- Find other PSD parsers that support methods 2 or 3
- Decide if we want to implement ZIP compression support
Prior art
- PSD.rb (Ruby), PSD.js (CoffeeScript): Does not support ZIP compression. The author mentions that he could not produce a PSD file that uses ZIP compression.
- chinedufn/psd (Rust): Does not support ZIP compression (source)
- NtreevSoft/psd-parser (C#): Does not support ZIP compression (source)
- gopsd (Go): Does not support ZIP compression (source)
- libpsd (C): Does support ZIP compression (source), and uses ZLIB to do so. According to the comments in source code, "Photoshop CS and CS2 use ZIP compression".