private void WriteColorTable(MemoryStream sourceImage)
{
sourceImage.Position = 13;
var header = new byte[768];
sourceImage.Read(header, 0, header.Length);
GifStream.Write(header, 0, header.Length);
}
private void GenerateHeader(MemoryStream firstFrame)
{
firstFrame.Position = 0;
var header = new byte[781]; // Header Block + Logical Screen Descriptor + max Global Color Table size
firstFrame.Read(header, 0, header.Length);
GifStream.Write(header, 0, header.Length);
}
public HttpResponseMessage Get()
{
var response = Request.CreateResponse();
GifStream gifStream = new GifStream(new GameGenerator(), 1000, false);
Action <Stream, HttpContent, TransportContext> writeToStream = gifStream.WriteToStream;
response.Content = new PushStreamContent(writeToStream, new MediaTypeHeaderValue("image/gif"));
return(response);
}
public HttpResponseMessage Get(string timeZone = "Central Standard Time")
{
var response = Request.CreateResponse();
GifStream gifStream = new GifStream(new ClockGenerator(timeZone), 1000, false);
Action <Stream, HttpContent, TransportContext> writeToStream = gifStream.WriteToStream;
response.Content = new PushStreamContent(writeToStream, new MediaTypeHeaderValue("image/gif"));
return(response);
}
public async Task AddFrame(Image frame, int x, int y)
{
using (var sourceImage = new MemoryStream())
{
frame.Save(sourceImage, ImageFormat.Gif);
if (FirstFrame)
{
GenerateHeader(sourceImage);
FirstFrame = false;
}
sourceImage.Position = 789; //Position of the Image Descriptor
var header = new byte[11];
sourceImage.Read(header, 0, header.Length);
WriteByte(header[0]);
WriteShort(x);
WriteShort(y);
WriteShort(frame.Width);
WriteShort(frame.Height);
if (UseLocalColorTable)
{
sourceImage.Position = 10;
WriteByte(sourceImage.ReadByte() & 0x3f | 0x80);
WriteColorTable(sourceImage);
}
else
{
WriteByte(header[9] & 0x07 | 0x07);
}
WriteByte(header[10]); //LZW Minimum Code Size
// Read image data
sourceImage.Position = 800;
var dataLength = sourceImage.ReadByte();
while (dataLength > 0)
{
var imgData = new byte[dataLength];
sourceImage.Read(imgData, 0, dataLength);
GifStream.WriteByte(Convert.ToByte(dataLength));
await GifStream.WriteAsync(imgData, 0, dataLength);
dataLength = sourceImage.ReadByte();
}
GifStream.WriteByte(0);
}
}
private void WriteByte(int value)
{
GifStream.WriteByte(Convert.ToByte(value));
}
private async Task WriteString(string value)
{
await GifStream.WriteAsync(value.ToArray().Select(c => (byte)c).ToArray(), 0, value.Length);
}
private void WriteShort(int value)
{
GifStream.WriteByte(Convert.ToByte(value & 0xff));
GifStream.WriteByte(Convert.ToByte((value >> 8) & 0xff));
}
