public void Initialize(ushort restartInterval, ushort[] subsamplingFactors)
{
_restartInterval = restartInterval;
// Make sure everything is initialized
if (_components.Length == 0)
{
throw new InvalidDataException();
}
foreach (ComponentInfo component in _components)
{
if (!component.IsInitialized)
{
throw new InvalidDataException();
}
}
var frameComponents = new JpegFrameComponentSpecificationParameters[_components.Length];
var scanComponents = new JpegScanComponentSpecificationParameters[_components.Length];
// Special case for YCbCr.
if (subsamplingFactors.Length == 2)
{
if (frameComponents.Length != 3)
{
// YCbCr image must have 3 components.
throw new InvalidDataException();
}
if (subsamplingFactors[0] != 1 && subsamplingFactors[0] != 2 && subsamplingFactors[0] != 4)
{
throw new InvalidDataException("Subsampling factor other than 1,2,4 is not supported.");
}
if (subsamplingFactors[1] != 1 && subsamplingFactors[1] != 2 && subsamplingFactors[1] != 4)
{
throw new InvalidDataException("Subsampling factor other than 1,2,4 is not supported.");
}
ushort maxFactor = Math.Max(subsamplingFactors[0], subsamplingFactors[1]);
frameComponents[0] = new JpegFrameComponentSpecificationParameters(0, (byte)maxFactor, (byte)maxFactor, 0);
frameComponents[1] = new JpegFrameComponentSpecificationParameters(1, (byte)(maxFactor / subsamplingFactors[0]), (byte)(maxFactor / subsamplingFactors[1]), 1);
frameComponents[2] = new JpegFrameComponentSpecificationParameters(2, (byte)(maxFactor / subsamplingFactors[0]), (byte)(maxFactor / subsamplingFactors[1]), 2);
}
else
{
for (int i = 0; i < frameComponents.Length; i++)
{
frameComponents[i] = new JpegFrameComponentSpecificationParameters((byte)i, 1, 1, (byte)i);
}
}
for (int i = 0; i < scanComponents.Length; i++)
{
scanComponents[i] = new JpegScanComponentSpecificationParameters((byte)i, (byte)i, (byte)i);
}
_frameHeader = new JpegFrameHeader(8, 0, 0, (byte)frameComponents.Length, frameComponents);
_scanHeader = new JpegScanHeader((byte)scanComponents.Length, scanComponents, 0, 0, 0, 0);
}
protected int InitDecodeComponents(JpegFrameHeader frameHeader, JpegScanHeader scanHeader, Span <JpegArithmeticDecodingComponent> components)
{
Debug.Assert(!(frameHeader.Components is null));
Debug.Assert(!(scanHeader.Components is null));
// Compute maximum sampling factor
int maxHorizontalSampling = 1;
int maxVerticalSampling = 1;
foreach (JpegFrameComponentSpecificationParameters currentFrameComponent in frameHeader.Components !)
{
maxHorizontalSampling = Math.Max(maxHorizontalSampling, currentFrameComponent.HorizontalSamplingFactor);
maxVerticalSampling = Math.Max(maxVerticalSampling, currentFrameComponent.VerticalSamplingFactor);
}
// Resolve each component
if (components.Length < scanHeader.NumberOfComponents)
{
throw new InvalidOperationException();
}
for (int i = 0; i < scanHeader.NumberOfComponents; i++)
{
JpegScanComponentSpecificationParameters scanComponenet = scanHeader.Components ![i];
