/// <summary>
/// Generate BitmapFileHeader from first 14 bytes
/// </summary>
/// <param name="headerBytes"></param>
/// <returns>BitmapFileHeader or throws exception</returns>
public static BitmapFileHeader GetHeaderFromBytes(byte[] headerBytes)
{
if (headerBytes == null)
{
throw new ArgumentNullException(nameof(headerBytes));
}
if (headerBytes.Length != BitmapFileHeader.BitmapFileHeaderSizeInBytes)
{
throw new ArgumentOutOfRangeException($"{nameof( headerBytes )} should be {BitmapFileHeader.BitmapFileHeaderSizeInBytes} bytes in headerSize");
}
if (!System.BitConverter.IsLittleEndian)
{
Array.Reverse(headerBytes, 2, 4);
Array.Reverse(headerBytes, 10, 4);
}
var sizeBytes = BitConverter.ToUInt32(headerBytes, 2);
var offset = BitConverter.ToUInt32(headerBytes, 10);
var header = new BitmapFileHeader()
{
PixelDataOffset = offset,
FileSize = sizeBytes
};
return(header);
}
public static Bitmap ReadFileAsBitmap(string fileName, bool flipRows = false)
{
if (string.IsNullOrWhiteSpace(fileName))
{
throw new ArgumentNullException(nameof(fileName));
}
if (!File.Exists(fileName))
{
throw new Exception($"File {fileName} not found");
}
var fileInfo = new FileInfo(fileName);
if (fileInfo.Length <= BitmapFileHeader.BitmapFileHeaderSizeInBytes)
{
throw new Exception($"Invalid file format. Size is too small.");
}
using (var fileStream = File.OpenRead(fileName)) {
using (var bReader = new SafeBinaryReader(fileStream)) {
var headerBytes = bReader.ReadBytes(BitmapFileHeader.BitmapFileHeaderSizeInBytes);
var fileHeader = BitmapFileHeader.GetHeaderFromBytes(headerBytes);
if (fileInfo.Length != fileHeader.FileSize)
{
throw new Exception($"File size is different than in header.");
}
var dibHeaderSize = bReader.ReadInt32();
fileStream.Seek(-4, SeekOrigin.Current);
var infoHeader = BitmapInfoHeader.GetHeaderFromBytes(bReader.ReadBytes(dibHeaderSize));
var width = infoHeader.Width;
var height = infoHeader.Height;
var bytesPerRow = Bitmap.RequiredBytesPerRow(infoHeader.Width, infoHeader.BitsPerPixel);
var bytesPerPixel = (int)infoHeader.BitsPerPixel / 8;
var paddingRequired = Bitmap.IsPaddingRequired(infoHeader.Width, infoHeader.BitsPerPixel,
bytesPerRow);
var pixelData = new byte[width * height * bytesPerPixel];
// seek to location where pixel data is
fileStream.Seek(fileHeader.PixelDataOffset, SeekOrigin.Begin);
if (paddingRequired)
{
var bytesToCopy = width * bytesPerPixel;
for (var counter = 0; counter < height; counter++)
{
var rowBuffer = bReader.ReadBytes(bytesPerRow);
Buffer.BlockCopy(src: rowBuffer, srcOffset: 0, dst: pixelData, dstOffset: counter * bytesToCopy, count: bytesToCopy);
}
}
else
{
var rowBuffer = bReader.ReadBytes(pixelData.Length);
rowBuffer.CopyTo(pixelData, 0);
}
var bitmap = new Bitmap(
width, height,
pixelData: pixelData,
bitsPerPixel: infoHeader.BitsPerPixel
);
return(bitmap);
}
}
}
