/// <summary>
/// Reads the <see cref="BmpInfoHeader"/> from the stream.
/// </summary>
private void ReadInfoHeader()
{
#if NETCOREAPP2_1
Span <byte> buffer = stackalloc byte[BmpInfoHeader.MaxHeaderSize];
#else
byte[] buffer = new byte[BmpInfoHeader.MaxHeaderSize];
#endif
this.stream.Read(buffer, 0, BmpInfoHeader.HeaderSizeSize); // read the header size
int headerSize = BinaryPrimitives.ReadInt32LittleEndian(buffer);
if (headerSize < BmpInfoHeader.CoreSize)
{
throw new NotSupportedException($"ImageSharp does not support this BMP file. HeaderSize: {headerSize}.");
}
int skipAmount = 0;
if (headerSize > BmpInfoHeader.MaxHeaderSize)
{
skipAmount = headerSize - BmpInfoHeader.MaxHeaderSize;
headerSize = BmpInfoHeader.MaxHeaderSize;
}
// read the rest of the header
this.stream.Read(buffer, BmpInfoHeader.HeaderSizeSize, headerSize - BmpInfoHeader.HeaderSizeSize);
if (headerSize == BmpInfoHeader.CoreSize)
{
// 12 bytes
this.infoHeader = BmpInfoHeader.ParseCore(buffer);
}
else if (headerSize == BmpInfoHeader.Os22ShortSize)
{
// 16 bytes
this.infoHeader = BmpInfoHeader.ParseOs22Short(buffer);
}
else if (headerSize >= BmpInfoHeader.Size)
{
// >= 40 bytes
this.infoHeader = BmpInfoHeader.Parse(buffer);
}
else
{
throw new NotSupportedException($"ImageSharp does not support this BMP file. HeaderSize: {headerSize}.");
}
// Resolution is stored in PPM.
var meta = new ImageMetaData
{
ResolutionUnits = PixelResolutionUnit.PixelsPerMeter
};
if (this.infoHeader.XPelsPerMeter > 0 && this.infoHeader.YPelsPerMeter > 0)
{
meta.HorizontalResolution = this.infoHeader.XPelsPerMeter;
meta.VerticalResolution = this.infoHeader.YPelsPerMeter;
}
else
{
// Convert default metadata values to PPM.
meta.HorizontalResolution = Math.Round(UnitConverter.InchToMeter(ImageMetaData.DefaultHorizontalResolution));
meta.VerticalResolution = Math.Round(UnitConverter.InchToMeter(ImageMetaData.DefaultVerticalResolution));
}
this.metaData = meta;
short bitsPerPixel = this.infoHeader.BitsPerPixel;
BmpMetaData bmpMetaData = this.metaData.GetFormatMetaData(BmpFormat.Instance);
// We can only encode at these bit rates so far.
if (bitsPerPixel.Equals((short)BmpBitsPerPixel.Pixel24) ||
bitsPerPixel.Equals((short)BmpBitsPerPixel.Pixel32))
{
bmpMetaData.BitsPerPixel = (BmpBitsPerPixel)bitsPerPixel;
}
// skip the remaining header because we can't read those parts
this.stream.Skip(skipAmount);
}
/// <summary>
/// Encodes the image to the specified stream from the <see cref="ImageFrame{TPixel}"/>.
/// </summary>
/// <typeparam name="TPixel">The pixel format.</typeparam>
/// <param name="image">The <see cref="ImageFrame{TPixel}"/> to encode from.</param>
/// <param name="stream">The <see cref="Stream"/> to encode the image data to.</param>
public void Encode<TPixel>(Image<TPixel> image, Stream stream)
where TPixel : struct, IPixel<TPixel>
{
Guard.NotNull(image, nameof(image));
Guard.NotNull(stream, nameof(stream));
ImageMetaData metaData = image.MetaData;
BmpMetaData bmpMetaData = metaData.GetFormatMetaData(BmpFormat.Instance);
this.bitsPerPixel = this.bitsPerPixel ?? bmpMetaData.BitsPerPixel;
short bpp = (short)this.bitsPerPixel;
int bytesPerLine = 4 * (((image.Width * bpp) + 31) / 32);
this.padding = bytesPerLine - (int)(image.Width * (bpp / 8F));
// Set Resolution.
int hResolution = 0;
int vResolution = 0;
if (metaData.ResolutionUnits != PixelResolutionUnit.AspectRatio)
{
if (metaData.HorizontalResolution > 0 && metaData.VerticalResolution > 0)
{
switch (metaData.ResolutionUnits)
{
case PixelResolutionUnit.PixelsPerInch:
hResolution = (int)Math.Round(UnitConverter.InchToMeter(metaData.HorizontalResolution));
vResolution = (int)Math.Round(UnitConverter.InchToMeter(metaData.VerticalResolution));
break;
case PixelResolutionUnit.PixelsPerCentimeter:
hResolution = (int)Math.Round(UnitConverter.CmToMeter(metaData.HorizontalResolution));
vResolution = (int)Math.Round(UnitConverter.CmToMeter(metaData.VerticalResolution));
break;
case PixelResolutionUnit.PixelsPerMeter:
hResolution = (int)Math.Round(metaData.HorizontalResolution);
vResolution = (int)Math.Round(metaData.VerticalResolution);
break;
}
}
}
var infoHeader = new BmpInfoHeader(
headerSize: BmpInfoHeader.Size,
height: image.Height,
width: image.Width,
bitsPerPixel: bpp,
planes: 1,
imageSize: image.Height * bytesPerLine,
clrUsed: 0,
clrImportant: 0,
xPelsPerMeter: hResolution,
yPelsPerMeter: vResolution);
var fileHeader = new BmpFileHeader(
type: 19778, // BM
offset: 54,
reserved: 0,
fileSize: 54 + infoHeader.ImageSize);
#if NETCOREAPP2_1
Span<byte> buffer = stackalloc byte[40];
#else
byte[] buffer = new byte[40];
#endif
fileHeader.WriteTo(buffer);
stream.Write(buffer, 0, BmpFileHeader.Size);
infoHeader.WriteTo(buffer);
stream.Write(buffer, 0, 40);
this.WriteImage(stream, image.Frames.RootFrame);
stream.Flush();
}
