public OffsetModel ParseOffsetData(ExifThumbnailDirectory exifThumbnailDir, string subPath)
{
if (exifThumbnailDir == null)
{
return new OffsetModel {
Success = false, Reason = "ExifThumbnailDirectory null"
}
}
;
long thumbnailOffset = long.Parse(exifThumbnailDir.GetDescription(
ExifThumbnailDirectory.TagThumbnailOffset).Split(' ')[0]);
const int maxIssue35Offset = 12;
int thumbnailLength = int.Parse(exifThumbnailDir.GetDescription(
ExifThumbnailDirectory.TagThumbnailLength).Split(' ')[0]) + maxIssue35Offset;
byte[] thumbnail = new byte[thumbnailLength];
using (var imageStream = _iStorage.ReadStream(subPath))
{
imageStream.Seek(thumbnailOffset, SeekOrigin.Begin);
imageStream.Read(thumbnail, 0, thumbnailLength);
}
// work around Metadata Extractor issue #35
if (thumbnailLength <= maxIssue35Offset + 1)
{
_logger.LogInformation($"[ParseOffsetData] thumbnailLength : {thumbnailLength} {maxIssue35Offset + 1}");
return(new OffsetModel {
Success = false, Reason = "offsetLength"
});
}
int issue35Offset = 0;
for (int offset = 0; offset <= maxIssue35Offset; ++offset)
{
// 0xffd8 is the JFIF start of image segment indicator
if ((thumbnail[offset] == 0xff) && (thumbnail[offset + 1] == 0xd8))
{
issue35Offset = offset;
break;
}
}
return(new OffsetModel
{
Success = true,
Index = issue35Offset,
Count = thumbnailLength - issue35Offset,
Data = thumbnail, // byte array
});
}
}
protected ImageSource ReadThumbnailFromExif(String filename, ExifThumbnailDirectory thumbnails)
{
if (thumbnails == null)
{
return(null);
}
//Assert.IsTrue(thumbnails.GetDescription(ExifThumbnailDirectory.TagCompression).StartsWith("JPEG"));
long thumbnailOffset = Int64.Parse(thumbnails.GetDescription(ExifThumbnailDirectory.TagThumbnailOffset).Split(' ')[0]);
const int maxIssue35Offset = 12;
int thumbnailLength = Int32.Parse(thumbnails.GetDescription(ExifThumbnailDirectory.TagThumbnailLength).Split(' ')[0]) + maxIssue35Offset;
byte[] thumbnail = new byte[thumbnailLength];
using (FileStream imageStream = new FileStream(filename, FileMode.Open, FileAccess.Read, FileShare.Read))
{
imageStream.Seek(thumbnailOffset, SeekOrigin.Begin);
imageStream.Read(thumbnail, 0, thumbnailLength);
}
// work around Metadata Extractor issue #35
//Assert.IsTrue(thumbnailLength > maxIssue35Offset + 1);
int issue35Offset = 0;
for (int offset = 0; offset <= maxIssue35Offset; ++offset)
{
// 0xffd8 is the JFIF start of image segment indicator
if ((thumbnail[offset] == 0xff) && (thumbnail[offset + 1] == 0xd8))
{
issue35Offset = offset;
break;
}
}
using (MemoryStream thumbnailStream = new MemoryStream(thumbnail, issue35Offset, thumbnailLength - issue35Offset, false))
{
JpegBitmapDecoder jpegDecoder = new JpegBitmapDecoder(thumbnailStream, BitmapCreateOptions.None, BitmapCacheOption.OnLoad);
WriteableBitmap writeableBitmap = new WriteableBitmap(jpegDecoder.Frames[0]);
writeableBitmap.Freeze();
return(writeableBitmap);
}
}