public static DecodedImage DecodeImage(ReadOnlySpan <byte> data)
{
var result = new DecodedImage();
result.info = DetectImageFormat(data);
switch (result.info.format)
{
case ImageFileFormat.BMP:
result.data = StbNative.DecodeBitmap(data);
break;
case ImageFileFormat.PNG:
result.data = StbNative.DecodePng(data);
break;
case ImageFileFormat.JPEG:
result.data = DecodeJpeg(data);
break;
case ImageFileFormat.TGA:
result.data = DecodeTga(data);
break;
case ImageFileFormat.FNTART:
return(DecodeFontArt(data));
default:
case ImageFileFormat.Unknown:
throw new ImageIOException("Unrecognized image format.");
}
return(result);
}
/// <summary>
/// Tries to detect the image format of the given data by
/// inspecting the header only.
/// </summary>
/// <param name="data"></param>
/// <returns></returns>
public static ImageFileInfo DetectImageFormat(ReadOnlySpan <byte> data)
{
ImageFileInfo info;
if (StbNative.GetPngInfo(data, out info.width, out info.height, out info.hasAlpha))
{
info.format = ImageFileFormat.PNG;
return(info);
}
if (StbNative.GetBitmapInfo(data, out info.width, out info.height, out info.hasAlpha))
{
info.format = ImageFileFormat.BMP;
return(info);
}
using var jpegDecompressor = new JpegDecompressor();
if (jpegDecompressor.ReadHeader(data, out info.width, out info.height))
{
info.hasAlpha = false;
info.format = ImageFileFormat.JPEG;
return(info);
}
if (TargaImage.DetectTga(data, out info))
{
return(info);
}
// Not a very good heuristic
if (data.Length == 256 * 256)
{
info.width = 256;
info.height = 256;
info.hasAlpha = true;
info.format = ImageFileFormat.FNTART;
return(info);
}
return(info);
}
