private byte[] colorDiff; // delta-encoded change in color, then RL-encoded
#endregion Fields
#region Constructors
/// <summary>
/// Creates a FrameDiff object as the difference between two frames.
/// </summary>
/// <param name="oldFrame"></param>
/// <param name="newFrame"></param>
internal MifFrameDiff(MifFrame oldFrame, MifFrame newFrame)
{
if (oldFrame == null)
throw new ArgumentNullException("oldFrame");
if (newFrame == null)
throw new ArgumentNullException("newFrame");
if (oldFrame.colorData != null && newFrame.colorData != null)
{
this.colorDiff = MifDeltaEncoding.Encode(
oldFrame.colorData, newFrame.colorData, true);
memoryUsed1 += colorDiff.Length;
this.colorDiff = MifRunLengthEncoding.Encode(colorDiff, 2);
memoryUsed2 += colorDiff.Length;
}
if (oldFrame.alphaData != null && newFrame.alphaData != null)
{
this.alphaDiff = MifDeltaEncoding.Encode(
oldFrame.alphaData, newFrame.alphaData, true);
memoryUsed1 += alphaDiff.Length;
this.alphaDiff = MifRunLengthEncoding.Encode(alphaDiff, 1);
memoryUsed2 += alphaDiff.Length;
}
}
/// <summary>
/// Read a frame.
/// </summary>
public MifFrame ReadFrame(MifHeader header, MifFrame prevFrame)
{
MifFrame frame = new MifFrame();
// Read Delay field if present.
if (header.Flags.HasFlag(MifFlags.HasDelay))
{
frame.delay = ReadInt32();
}
// Read primary channels.
frame.colorData = new byte[2 * header.ImageWidth * header.ImageHeight];
if (prevFrame != null && prevFrame.colorData != null)
{
prevFrame.colorData.CopyTo(frame.colorData, 0);
ReadPixelData(header, frame.colorData, false);
}
else
{
ReadPixelData(header, frame.colorData, true);
}
// Read alpha channel if present.
if (header.Flags.HasFlag(MifFlags.HasAlpha))
{
frame.alphaData = new byte[header.ImageWidth * header.ImageHeight];
if (prevFrame != null && prevFrame.alphaData != null)
{
prevFrame.alphaData.CopyTo(frame.alphaData, 0);
ReadPixelData(header, frame.alphaData, false);
}
else
{
ReadPixelData(header, frame.alphaData, true);
}
}
return frame;
}
internal void UpdateFrame(MifFrame frame)
{
if (frame == null)
throw new ArgumentNullException("frame");
if (frame.colorData != null && this.colorDiff != null)
{
byte[] actualColorDiff = MifRunLengthEncoding.Decode(this.colorDiff, 2);
MifDeltaEncoding.Decode(frame.colorData, actualColorDiff, true);
}
if (frame.alphaData != null && this.alphaDiff != null)
{
byte[] actualAlphaDiff = MifRunLengthEncoding.Decode(this.alphaDiff, 1);
MifDeltaEncoding.Decode(frame.alphaData, actualAlphaDiff, true);
}
}