/// <summary>
/// Processes the Start of Frame marker. Specified in section B.2.2.
/// </summary>
/// <param name="remaining">The remaining bytes in the segment block.</param>
private void ProcessStartOfFrameMarker(int remaining)
{
if (this.ComponentCount != 0)
{
throw new ImageFormatException("Multiple SOF markers");
}
switch (remaining)
{
case 6 + (3 * 1): // Grayscale image.
this.ComponentCount = 1;
break;
case 6 + (3 * 3): // YCbCr or RGB image.
this.ComponentCount = 3;
break;
case 6 + (3 * 4): // YCbCrK or CMYK image.
this.ComponentCount = 4;
break;
default:
throw new ImageFormatException("Incorrect number of components");
}
this.InputProcessor.ReadFull(this.Temp, 0, remaining);
// We only support 8-bit precision.
if (this.Temp[0] != 8)
{
throw new ImageFormatException("Only 8-Bit precision supported.");
}
int height = (this.Temp[1] << 8) + this.Temp[2];
int width = (this.Temp[3] << 8) + this.Temp[4];
this.ImageSizeInPixels = new Size(width, height);
if (this.Temp[5] != this.ComponentCount)
{
throw new ImageFormatException("SOF has wrong length");
}
this.Components = new OrigComponent[this.ComponentCount];
for (int i = 0; i < this.ComponentCount; i++)
{
byte componentIdentifier = this.Temp[6 + (3 * i)];
var component = new OrigComponent(componentIdentifier, i);
component.InitializeCoreData(this);
this.Components[i] = component;
}
int h0 = this.Components[0].HorizontalSamplingFactor;
int v0 = this.Components[0].VerticalSamplingFactor;
this.ImageSizeInMCU = this.ImageSizeInPixels.DivideRoundUp(8 * h0, 8 * v0);
foreach (OrigComponent component in this.Components)
{
component.InitializeDerivedData(this);
}
this.ColorSpace = this.DeduceJpegColorSpace();
}