Summarize supported features in README

README.md

@@ -4,3 +4,43 @@
 [![Further crate info](https://img.shields.io/crates/v/tiff.svg)](https://crates.io/crates/tiff)
 
 TIFF decoding and encoding library in pure Rust
+
+## Supported
+
+### Features
+- Baseline spec (other than formats and tags listed below as not supported)
+- Multipage
+- Incremental decoding
+
+### Formats
+This table lists photometric interpretations and sample formats which are supported for encoding and decoding. The entries are `ColorType` variants for which sample bit depths are supported. Only samples where all bit depths are equal are currently supported. For example, `RGB(8)` means that the bit depth [8, 8, 8] is supported and will be interpreted as an 8 bit per channel RGB color type.
+
+| `PhotometricInterpretation` | UINT Format | IEEEFP Format |
+|-|-|-|
+| `WhiteIsZero` | Gray(8), Gray(16) | |
+| `BlackIsZero` | Gray(8), Gray(16) | |
+| `RGB` | RGB(8), RGB(16), RGBA(8), RGBA(16) | |
+| `RGBPalette` | | |
+| `Mask` | | |
+| `CMYK` | CMYK(8) | |
+| `YCbCr` | | |
+| `CIELab` | | |
+
+### Compressions
+
+| | Decoding | Encoding |
+|-|-|-|
+| None | ✓ | ✓ |
+| LZW | ✓ | |
+| Deflate | ✓ | |
+| PackBits | ✓ | |
+
+
+## Not yet supported
+
+Formats and interpretations not listed above or with empty entries are unsupported.
+
+- Baseline tags
+  - `ExtraSamples`
+- Extension tags
+- BigTIFF