public bool GetThumbnail(Stream stream, int width, int height, bool cachedOnly, out byte[] imageData, out ImageType imageType)
{
imageData = null;
imageType = ImageType.Unknown;
// No support for cache
if (cachedOnly)
{
return(false);
}
Bitmap cachedBitmap = null; // used only for rotation
try
{
if (stream.CanSeek)
{
stream.Seek(0, SeekOrigin.Begin);
}
// open the image file for reading
using (var factory = new ImagingFactory2())
using (var inputStream = new WICStream(factory, stream))
using (var decoder = new BitmapDecoder(factory, inputStream, DecodeOptions.CacheOnLoad))
using (var rotator = new BitmapFlipRotator(factory))
using (var scaler = new BitmapScaler(factory))
using (var output = new MemoryStream())
{
// decode the loaded image to a format that can be consumed by D2D
BitmapSource source = decoder.GetFrame(0);
// Prefer PNG output for source PNG and for source formats with Alpha channel
var usePngOutput = decoder.DecoderInfo.FriendlyName.StartsWith("PNG") || PixelFormat.GetBitsPerPixel(source.PixelFormat) == 32;
BitmapTransformOptions bitmapTransformationOptions = BitmapTransformOptions.Rotate0;
BitmapFrameDecode frame = source as BitmapFrameDecode;
if (frame != null)
{
const string EXIF_ORIENTATION_TAG = "/app1/{ushort=0}/{ushort=274}";
ushort? orientation = null;
try
{
// Not supported on all input types, i.e. BMP will fail here
orientation = (ushort?)frame.MetadataQueryReader.TryGetMetadataByName(EXIF_ORIENTATION_TAG); //0x0112
}
catch { }
// If the EXIF orientation specifies that the image needs to be flipped or rotated before display, set that up to happen
if (orientation.HasValue)
{
switch (orientation.Value)
{
case 1: break; // No rotation required.
case 2: bitmapTransformationOptions = BitmapTransformOptions.Rotate0 | BitmapTransformOptions.FlipHorizontal; break;
case 3: bitmapTransformationOptions = BitmapTransformOptions.Rotate180; break;
case 4: bitmapTransformationOptions = BitmapTransformOptions.Rotate180 | BitmapTransformOptions.FlipHorizontal; break;
case 5: bitmapTransformationOptions = BitmapTransformOptions.Rotate270 | BitmapTransformOptions.FlipHorizontal; break;
case 6: bitmapTransformationOptions = BitmapTransformOptions.Rotate90; break;
case 7: bitmapTransformationOptions = BitmapTransformOptions.Rotate90 | BitmapTransformOptions.FlipHorizontal; break;
case 8: bitmapTransformationOptions = BitmapTransformOptions.Rotate270; break;
}
}
}
// Scale down larger images
int sourceWidth = source.Size.Width;
int sourceHeight = source.Size.Height;
if (width > 0 && height > 0 && (sourceWidth > width || sourceHeight > height))
{
if (sourceWidth <= height)
{
width = sourceWidth;
}
int newHeight = sourceHeight * height / sourceWidth;
if (newHeight > height)
{
// Resize with height instead
width = sourceWidth * height / sourceHeight;
newHeight = height;
}
scaler.Initialize(source, width, newHeight, BitmapInterpolationMode.Fant);
source = scaler;
}
// Rotate
if (bitmapTransformationOptions != BitmapTransformOptions.Rotate0)
{
// For fast rotation a cached bitmap is needed, otherwise only per-pixel-decoding happens which makes the process extremly slow.
// See https://social.msdn.microsoft.com/Forums/windowsdesktop/en-US/5ff2b52b-602f-4b22-9fb2-371539ff5ebb/hang-in-createbitmapfromwicbitmap-when-using-iwicbitmapfliprotator?forum=windowswic
cachedBitmap = new Bitmap(factory, source, BitmapCreateCacheOption.CacheOnLoad);
rotator.Initialize(cachedBitmap, bitmapTransformationOptions);
source = rotator;
}
Guid formatGuid = ContainerFormatGuids.Jpeg;
imageType = ImageType.Jpeg;
if (usePngOutput)
{
formatGuid = ContainerFormatGuids.Png;
imageType = ImageType.Png;
}
using (var encoder = new BitmapEncoder(factory, formatGuid))
{
encoder.Initialize(output);
using (var bitmapFrameEncode = new BitmapFrameEncode(encoder))
{
// Create image encoder
var wicPixelFormat = PixelFormat.FormatDontCare;
bitmapFrameEncode.Initialize();
bitmapFrameEncode.SetSize(source.Size.Width, source.Size.Height);
bitmapFrameEncode.SetPixelFormat(ref wicPixelFormat);
bitmapFrameEncode.WriteSource(source);
bitmapFrameEncode.Commit();
encoder.Commit();
}
}
imageData = output.ToArray();
return(true);
}
}
catch (Exception)
{
//ServiceRegistration.Get<ILogger>().Warn("WICThumbnailProvider: Error loading bitmapSource from file data stream", ex);
return(false);
}
finally
{
cachedBitmap?.Dispose();
}
}
public static IBitmapSource <TPixel> CreateBitmapFlipRotator <TPixel>(this IImagingFactory factory, IBitmapSource <TPixel> source, BitmapTransformOptions options) where TPixel : struct, INaturalPixelInfo => ((IBitmapSource <TPixel>)factory.CreateBitmapFlipRotator(source, options));
public IBitmapSource CreateBitmapFlipRotator(IBitmapSource source, BitmapTransformOptions options) => base.innerRefT.CreateBitmapFlipRotator(source, options);
