Update README

README.md

@@ -1,30 +1,70 @@
 # png_data -- Data as images
 
+## png_data -- Data to PNG
+
+![TeX Live english documentation](doc/texlive_en.png)
+
+`png_data` transforms a file as a png image.
+
+### Encoding
+`png_data -l rgb8 -e file.pdf -o output.png -c "(.pdf) documentation"`
+Where:
+ * `rgb8` is the RGB layout with 8 bits per pixel
+ * `file.pdf` is the file to store in the resulting image
+ * `output.png` the resulting png image
+
+**Available layouts**
+ * `rgb[8|16]` RGB with 8 or 16 bits per channel
+ * `rgba[8|16]` RGBA with 8 or 16 bits per channel (densest layout)
+ * `g[1|2|4|8|16]` Grayscale with 1-16 bits per channel
+ * `ga[1|2|4|8|16]` Grayscale Alpha with 1-16 bits per channel
+
+### Decoding
+`png_data -d output.png -o original.pdf`
+Where:
+ * `output.png` the encoded png image
+ * `original.pdf` the resulting decoded file
+
+### Getting header information
+`png_data -z output.png`
+ * `output.png` a `png_data` encoded image
+This will display the header of the encoded file, as well as the comment.
+
+
 ## png_embed -- Embed files into mostly innocent PNG
 
 ![Contains an embed](doc/with_embed.png)
 ![The embed](doc/embed.png)
 
+`png_embed` encodes a file into an existing png image making it possible to recover that file by passing the image around.
+
 ### Current algorithm:
  * `lo` Embeds data in the colors channels lowest bits.
 
 See [examples/test.sh](examples/test.sh) for usage.
 
 ### Encoding an image
-`png_embed -l lo2 -e embed.tar original.png -o output.png`
+`png_embed -l lo2 -e embed.tar original.png -o output.png -c "(.tar) archive"`
 Where:
- * `lo2` is the `Lo` algorithm using the 2 lowests bits
+ * `lo2` is the `Lo` algorithm using the 2 lowest bits
  * `embed.tar` the file to embed into the final image
  * `original.png` the original PNG file
  * `output.png` the resulting PNG file
+ * `"(.tar) archive"` an optional comment
 
 ### Decoding an image
 `png_embed -l lo2 -d image.png -o embed.tar`
 Where:
- * `lo2` is the `Lo` algorithm using the 2 lowests bits
+ * `lo2` is the `Lo` algorithm using the 2 lowest bits
  * `image.png` the PNG containing an embed
  * `embed.tar` the extracted embedded file
 
+### Getting header information
+`png_embed -l lo2 -z output.png`
+ * `lo2` is the `Lo` algorithm using the 2 lowest bits
+ * `output.png` a `png_embed` encoded image
+This will display the header of the encoded file, as well as the comment.
+
 # License
 
 png_data is licensed under the GNU AGPL version 3 or later. See [LICENSE.md](LICENSE.md) for more information.