private void WriteGraphicControlBlock(sGif gif, TimeSpan frameDelay)
{
WriteShort(GraphicControlExtensionBlockIdentifier); // Identifier
WriteByte(GraphicControlExtensionBlockSize); // Block Size
WriteByte(0x00);
WriteShort(Convert.ToInt32(frameDelay.TotalMilliseconds / 10)); // Setting frame delay
WriteByte(0); // Transparent color index
WriteByte(0); // Terminator
}
/// <summary>
/// Adds a frame to this animation.
/// </summary>
/// <param name="img">The image to add</param>
/// <param name="x">The positioning x offset this image should be displayed at.</param>
/// <param name="y">The positioning y offset this image should be displayed at.</param>
public void AddFrame(Image img)
{
using (var gifStream = new MemoryStream())
{
sGif gif = new sGif(img);
if (_isFirstImage) // Steal the global color table info
{
InitHeader(gif);
}
WriteGraphicControlBlock(gif, FrameDelay);
WriteImageBlock(gif, !_isFirstImage, 0, 0);
}
_isFirstImage = false;
}
private void _AddFramePart(sFramePart part, bool firstPart)
{
using (var gifStream = new MemoryStream())
{
sGif gif = new sGif(part.Image, _isFirstImage);
if (_isFirstImage) // Steal the global color table info
{
InitHeader(gif);
}
WriteGraphicControlBlock(gif, (firstPart ? FrameDelay : TimeSpan.FromSeconds(0)));
WriteImageBlock(gif, !_isFirstImage, part.X, part.Y);
}
_isFirstImage = false;
}
private void WriteImageBlock(sGif gif, bool includeColorTable, int x, int y)
{
WriteByte(ImageSeperator); // Separator
WriteShort(x); // Position X
WriteShort(y); // Position Y
WriteShort(gif.CanvasWidth);
WriteShort(gif.CanvasHeight);
if (includeColorTable) // If first frame, use global color table - else use local
{
WriteByte((((int)gif.PackedField & 0x70) >> 4) | 0x80); // Enabling local color table
WriteByte(gif.ColorTable);
}
else
{
WriteByte(0); // Disabling local color table
}
WriteByte(gif.Data);
}
private void InitHeader(sGif gif)
{
// File Header
WriteString(FileType);
WriteString(FileVersion);
WriteShort(gif.CanvasWidth); // Initial Logical Width
WriteShort(gif.CanvasHeight); // Initial Logical Height
WriteByte(gif.PackedField); // Global Color Table Info
WriteByte(0); // Background Color Index
WriteByte(0); // Pixel aspect ratio
WriteByte(gif.ColorTable);
// App Extension Header
WriteShort(ApplicationExtensionBlockIdentifier);
WriteByte(ApplicationBlockSize);
WriteString(ApplicationIdentification);
WriteByte(3); // Application block length
WriteByte(1);
WriteShort(0); // Repeat count for images.
WriteByte(0); // terminator
}
