Added TIFF image file format and its ISO standard to normative references. Added ability to allow implementations to support additional image file formats.

Author: mikebmcl

source/image-file-format.tex

@@ -5,19 +5,21 @@
 \rSec1 [\iotwod.imagefileformat.summary] {\tcode{image_file_format} summary}
 
 \pnum
-The \tcode{image_file_format} enum class specifies the data format that an \tcode{image_surface} object shall be constructed from or shall be saved to.
+The \tcode{image_file_format} enum class specifies the data format that an \tcode{image_surface} object is constructed from or saved to. This allows data in a format that is required to be supported to be read or written regardless of its extension.
 
 \pnum
-This allows data in a format that is required to be supported to be read or written regardless of its extension.
+It also has a value that allows implementations to support additional file formats if it recognizes them.
 
 \rSec1 [\iotwod.imagefileformat.synopsis] {\tcode{image_file_format} synopsis}
 
 \indexlibrary{\idxcode{image_file_format}}
 \begin{codeblock}
 namespace std::experimental::io2d::v1 {
   enum class image_file_format {
+    unknown,
     png,
-    jpg
+    jpg,
+    tiff
   };
 }
 \end{codeblock}
@@ -38,10 +40,16 @@
  & \rhdr{Meaning}
  \\ \capsep
  \endhead
+ \tcode{unknown}
+ & The format is unknown because it is not an image file format that is required to be supported. It may be known and supported by the implementation.
+ \\
  \tcode{png}
- & The data is in the PNG format.
+ & The PNG format.
  \\
  \tcode{jpg}
- & The data is in the JPEG format.
+ & The JPEG format.
+ \\
+ \tcode{tiff}
+ & The TIFF format.
  \\
 \end{libreqtab2}

source/image-surface.tex

@@ -84,17 +84,23 @@
 \pnum
 The data of \tcode{f} is processed into uncompressed raster graphics data as specified by the value of \tcode{i}.
 
+\pnum
+If \tcode{i} is \tcode{image_file_format::unknown}, it is \impldefplain{image_surface!constructor} whether the surface is created in the image file format, if any, that the implementation associates with \tcode{p.extension()} provided that \tcode{p.has_extension() == true}. If \tcode{p.has_extension() == false}, the implementation does not associate an image file format with \tcode{p.extension()}, or the implementation does not support reading in graphics data in that image file format, the error specified below occurs.
+
 \pnum
 The resulting uncompressed raster graphics data is then transformed into the data format specified by \tcode{fmt}. If the format specified by \tcode{fmt} only contains an alpha channel, the values of the color channels, if any, of the \underlyingimagesurface are \unspecnorm. If the format specified by \tcode{fmt} only contains color channels and the resulting uncompressed raster graphics data is in a premultiplied format, then the value of each color channel for each pixel shall be divided by the value of the alpha channel for that pixel. The visual data shall then be set as the visual data of the \underlyingimagesurface.
 
 \pnum
 \throws
-As specified in Error reporting [\iotwod.fs.err.report] in \cppseventeen.
+As specified in Error reporting [\iotwod.err.report].
 
 \pnum
 \errors
 Any error that could result from trying to access \tcode{f}, open \tcode{f} for reading, or reading data from \tcode{f}.
 
+\pnum
+\tcode{errc::not_supported} if \tcode{image_file_format::unknown} is passed as an argument and the implementation is unable to determine the file format or does not support saving in the image file format it determined.
+
 \pnum
 Other errors, if any, produced by this function are \impldefplain{image_surface!data}.
 \end{itemdescr}
@@ -115,19 +121,25 @@
 
 \pnum
 \effects
-Any pending rendering and composing operations (\ref{\iotwod.surface.rendering}) shall be performed.
+Any pending rendering and composing operations (\ref{\iotwod.surface.rendering}) are performed.
 
 \pnum
 The visual data of the \underlyingimagesurface is written to \tcode{p} in the data format specified by \tcode{i}.
 
+\pnum
+If \tcode{i} is \tcode{image_file_format::unknown}, it is \impldefplain{image_surface!save} whether the surface is saved in the image file format, if any, that the implementation associates with \tcode{p.extension()} provided that \tcode{p.has_extension() == true}. If \tcode{p.has_extension() == false}, the implementation does not associate an image file format with \tcode{p.extension()}, or the implementation does not support saving in that image file format, the error specified below occurs.
+
 \pnum
 \throws
-As specified in Error reporting [\iotwod.fs.err.report] in \cppseventeen.
+As specified in Error reporting [\iotwod.err.report].
 
 \pnum
 \errors
 Any error that could result from trying to create \tcode{f}, access \tcode{f}, or write data to \tcode{f}.
 
+\pnum
+\tcode{errc::not_supported} if \tcode{image_file_format::unknown} is passed as an argument and the implementation is unable to determine the file format or does not support saving in the image file format it determined.
+
 \pnum
 Other errors, if any, produced by this function are \impldefplain{image_surface!data}.
 \end{itemdescr}

source/normative-references.tex

@@ -16,6 +16,7 @@
 Multiple-Octet Coded Character Set (UCS) --- Part 1: Architecture and Basic 
 Multilingual Plane}
 \item ISO/IEC 10918-1, \doccite{Information technology -- Digital compression and coding of continuous-tone still images: Requirements and guidelines}
+\item ISO 12639, \doccite{Graphic technology -- Prepress digital data exchange -- Tag image file format for image technology (TIFF/IT)}
 \item ISO/IEC 15948 \doccite{Information technology -- Computer graphics and image processing -- Portable Network Graphics (PNG) Functional specification}
 \item ISO/IEC TR 19769:2004, \doccite{Information technology --- Programming 
 languages, their environments and system software interfaces --- Extensions for 
@@ -35,6 +36,8 @@
 \pnum
 The compressed image data format described in ISO/IEC 10918-1 is hereinafter called the \indexdefn{format!JPEG}\term{JPEG format}.
 
+\pnum
+The tag image file format described in ISO 12639 is hereinafter called the \indexdefn{format!TIFF}\term{TIFF format}.
 \pnum
 The datastream and associated file format described in ISO/IEC 15948 is hereinafter called the \indexdefn{format!PNG}\term{PNG format}.