doc/guile-png.texi (<png-image>): Improve

doc/guile-png.texi

@@ -307,19 +307,102 @@ filters from the image; this is useful for debugging purposes
 @subsection <png-image>
 
 @deftp {Class} <png-image> @
-               [#:chunks='()] @
-               [#:data=(make <bytevector> 0)] @
-               [#:data-chunk-size=256]
+               [#:data=(make-bytevector 0)] @
+               [#:data-chunk-size=256] @
+               [#:width=0] @
+               [#:height=0] @
+               [#:bit-depth=8] @
+               [#:color-type=0] @
+               [#:compression-method=0] @
+               [#:filter-method=0] @
+               [#:interlace-method=0] @
+               [#:palette=0] @
+               [#:chunks='()]
 
 This class represents a decompressed PNG image.
 
 Constructor parameters:
 
-@table @asis
-@item #:data (data <bytevector>)
+@table @code
+@item #:data
+Value type: @code{<bytevector>}
+
 The image data as a continuous @code{<bytevector>}.
-@item #:data-chunk-size (size <number>)
+@item #:data-chunk-size
+Value type: @code{<number>}
+
 The data chunk size that will be used for image encoder.
+@item #:width
+Value type: @code{<number>}
+
+The image width.
+@item #:height
+Value type: @code{<number>}
+
+The image height.
+@item #:bit-depth
+Value type: @code{<number>}
+@item #:color-type
+Value type: @code{<number>} | @code{<symbol>}
+
+Color type is a single-byte integer that describes the interpretation of the
+image data.  Color type codes represent sums of the following values: 1
+(palette used), 2 (color used), and 4 (alpha channel used). Valid values are
+0, 2, 3, 4, and 6.
+
+The value can be either a number (the color type according to RFC) or a
+symbol.  The symbol mapping is as follows:
+@table @asis
+@item 0
+@code{grayscale}
+@item 2
+@code{rgb}
+@item 3
+@code{indexed}
+@item 4
+@code{grayscale+alpha}
+@item 6
+@code{rgb+alpha}
+@end table
+
+@item #:compression-method
+Value type: @code{<number>}
+
+Compression method is a single-byte integer that indicates the method used to
+compress the image data.  At present, only compression method 0
+(deflate/inflate compression with a 32K sliding window) is defined.
+
+@item #:filter-method
+Value type: @code{<number>}
+
+Filter method is a single-byte integer that indicates the preprocessing method
+applied to the image data before compression.  At present, only filter method
+0 (adaptive filtering with five basic filter types) is defined.
+
+@item #:interlace-method
+Value type: @code{<number>}
+
+Interlace method is a single-byte integer that indicates the transmission
+order of the image data.  Two values are currently defined: 0 (no interlace)
+or 1 (Adam7 interlace).
+
+@item #:palette
+Value type: @code{<vector>} of @code{<bytevector>}
+
+A vector of PNG image palette entries, each a three-byte bytevector in the
+form:
+
+@table @asis
+@item Red: 1 byte (0 = black, 255 = red)
+@item Green: 1 byte (0 = black, 255 = green)
+@item Blue:  1 byte (0 = black, 255 = blue)
+@end table
+
+@item #:chunks
+Value type: @code{<list>} of @code{<png-chunk>}
+
+Extra PNG chunks.
+
 @end table
 
 @end deftp