private static Bitmap SingleImagePlaneToRgbBitmap(FitsHeaderDataUnit hdu,
HistogramStretch histogramStretch = null)
{
// FITS section 3.3.2 lowest numbered axis varies most rapidly
var xAxis = hdu.MandatoryKeywords.LengthOfAxis[0];
var yAxis = hdu.MandatoryKeywords.LengthOfAxis[1];
var bytesPerPixel = 3; // 24 bits per pixel, 8, 8, 8 RGB
var pixelData = new byte[yAxis * xAxis * bytesPerPixel];
var dataArray = PrimaryDataExtractor.ExtractDataArray(hdu);
/*
* Establish the range of values for the histogram stretch.
* Use the values passed in via histogramStretch if they were provided.
* Otherwise, if there is Blacnlpoint and WhitePoint information in the FITS header, use that.
* Otherwise, using the Minimum and Maximum data values obtained from the data array.
*/
var histogram = histogramStretch ?? hdu.Header.HeaderRecords.BindProperties <HistogramStretch>();
if (histogramStretch == null)
{
if (!hdu.Header.HeaderRecords.Any(p => p.Keyword == "CBLACK"))
{
histogram.BlackPoint = dataArray.Cast <double>().Min();
}
if (!hdu.Header.HeaderRecords.Any(p => p.Keyword == "CWHITE"))
{
histogram.WhitePoint = dataArray.Cast <double>().Max();
}
}
using (var outStream = new MemoryStream(pixelData, writable: true))
using (var writer = new BinaryWriter(outStream))
{
for (var y = 0; y < yAxis; y++)
{
for (var x = 0; x < xAxis; x++)
{
//ToDo: only linear histogram stretch currently supported. In future support other histogram shapes.
var displayValue = (byte)dataArray[x, y]
.Constrain(histogram.BlackPoint, histogram.WhitePoint)
.MapToRange(histogram.BlackPoint, histogram.WhitePoint, byte.MinValue, byte.MaxValue);
writer.Write(displayValue); // Red channel
writer.Write(displayValue); // Green channel
writer.Write(displayValue); // Blue channel
}
}
}
var bitmap = ByteToImage24bpp(xAxis, yAxis, pixelData);
return(bitmap);
}
/// <summary>
/// Converts the data array in this HDU to a Windows bitmap.
/// </summary>
/// <param name="hdu">The hdu.</param>
/// <param name="histogram">
/// The histogram stretch configuration. Optional. If this parameter is provided, then it is used to stretch
/// the histogram of the displayed image. If not provided, then the FITS header will be examined for CBLACK
/// and CWHITE keywords and those will be used if present. If none of the above is found, then the default
/// is to use the minimum and maximum data values obtained from the data array.
/// </param>
/// <returns>Bitmap.</returns>
/// <exception cref="NotSupportedException">Thrown if the image is neither greyscale or RGB</exception>
public static Bitmap ToWindowsBitmap(this FitsHeaderDataUnit hdu, HistogramStretch histogram = null)
{
var bitmapKind = DetermineBitmapKind(hdu);
switch (bitmapKind)
{
case ImageKind.Monocrome:
return(SingleImagePlaneToRgbBitmap(hdu, histogram));
case ImageKind.RGB:
throw new NotSupportedException(
"Currently only monochrome images are supported. Feel free to clone the code and add this feature.");
default:
throw new NotSupportedException(
"Unknown image type - only single layer (monochrome) and triple layer (RGB) images are supported");
}
}
