/// <summary>
/// Writes a Logical Screen Descriptor to the supplied stream.
/// Also writes a global colour table if required.
/// </summary>
/// <param name="outputStream">
/// The stream to write to.
/// </param>
private void WriteLogicalScreenDescriptor( Stream outputStream )
{
bool hasGlobalColourTable = _strategy == ColourTableStrategy.UseGlobal;
int colourResolution = 7; // TODO: parameterise colourResolution?
bool globalColourTableIsSorted = false; // Sorting of colour tables is not currently supported
int backgroundColorIndex = 0; // TODO: parameterise backgroundColourIndex?
int pixelAspectRatio = 0; // TODO: parameterise pixelAspectRatio?
if( _strategy == ColourTableStrategy.UseGlobal )
{
if( _quantizerType == QuantizerType.UseSuppliedPalette )
{
// use supplied palette
_globalColourTable = new ColourTable();
string buildColourTableCounterText
= "Building colour table from supplied palette";
AddCounter( buildColourTableCounterText,
_palette.Count );
int paletteIndex = 0;
foreach( Color c in _palette )
{
_globalColourTable.Add( c );
MyProgressCounters[buildColourTableCounterText].Value
= paletteIndex;
paletteIndex++;
}
_globalColourTable.Pad();
RemoveCounter( buildColourTableCounterText );
}
else
{
// Analyse the pixels in all the images to build the
// global colour table.
Collection<Image> images = new Collection<Image>();
foreach( GifFrame thisFrame in _frames )
{
Image thisImage = thisFrame.TheImage;
images.Add( thisImage );
}
_pixelAnalysis = new PixelAnalysis( images );
_pixelAnalysis.ColourQuality = _quality;
_pixelAnalysis.Analyse();
_globalColourTable = _pixelAnalysis.ColourTable;
}
LogicalScreenDescriptor lsd =
new LogicalScreenDescriptor( _logicalScreenSize,
hasGlobalColourTable,
colourResolution,
globalColourTableIsSorted,
_globalColourTable.SizeBits,
backgroundColorIndex,
pixelAspectRatio );
lsd.WriteToStream( outputStream );
_globalColourTable.WriteToStream( outputStream );
}
else
{
LogicalScreenDescriptor lsd =
new LogicalScreenDescriptor( _logicalScreenSize,
hasGlobalColourTable,
colourResolution,
globalColourTableIsSorted,
7,
backgroundColorIndex,
pixelAspectRatio );
lsd.WriteToStream( outputStream );
}
}
/// <summary>
/// Creates a colour table directly from the distinct colours in the
/// supplied image(s).
/// </summary>
private void CreateDirectColourTable()
{
string buildColourTableCounterText
= "Creating colour table from images";
AddCounter( buildColourTableCounterText,
_distinctColours.Values.Count );
_colourTable = new ColourTable();
int distinctColourIndex = 0;
foreach( Color c in _distinctColours.Values )
{
MyProgressCounters[buildColourTableCounterText].Value
= distinctColourIndex;
_colourTable.Add( c );
distinctColourIndex++;
}
_colourTable.Pad();
RemoveCounter( buildColourTableCounterText );
}
private ColourTable SetActiveColourTable()
{
ColourTable act; // active colour table
if( _strategy == ColourTableStrategy.UseLocal )
{
if( _quantizerType == QuantizerType.UseSuppliedPalette )
{
if( _frames[_encodingFrame].Palette == null )
{
// TESTME: SetActiveColourTable - SetActiveColourTable, UseSuppliedPalette, no palette supplied
string message
= "You have opted to use a local colour table built "
+ "from a supplied palette, but frame "
+ _encodingFrame
+ "does not have a palette.";
throw new InvalidOperationException( message );
}
else
{
// Build local colour table from colours in the frame's
// supplied palette.
act = new ColourTable();
foreach( Color c in _frames[_encodingFrame].Palette )
{
act.Add( c );
}
act.Pad();
}
}
else
{
// Build local colour table based on colours in the image.
Image thisImage = _frames[_encodingFrame].TheImage;
_pixelAnalysis = new PixelAnalysis( thisImage,
_quantizerType );
_pixelAnalysis.ColourQuality = _quality;
_pixelAnalysis.Analyse();
// make local colour table active
act = _pixelAnalysis.ColourTable;
}
}
else
{
// make global colour table active
act = _globalColourTable;
}
return act;
}