Add an EXIF/JPG thumbnail to a jpg

[tlhintoq]

I'd like to think I can work out most issues, but this one is kicking my butt.
What's worse, is that I know I can't be the first guy to want to add a thumbnail to jpg that doesn't already have one. I see it in plenty of other applications. Yet I can't seem to make it work despite being so very close.

I know the problem has to be in how I am making the PropertyItem of the thumbnail - because if I comment out lines 24-34 the JPG saves fine, just without a built-in thumbnail.

So I'm either wrong between lines 8-14 where I convert the bitmap NewThumbnail into a byte array, or I'm wrong in how I'm making the thumbnail property.

But for the life of me I can't seem to work it out.

Any assistance in this would be greatly appreciated.

        public static void WriteNewThumbnailInImage(string Filename, Bitmap NewThumbnail)
        {
            Bitmap Pic;
            PropertyItem[] PropertyItems;
            string FilenameTemp;
 
 
            #region Turn bitmap into an array of bytes
            MemoryStream thumbstream = new MemoryStream();
            NewThumbnail.Save(thumbstream, ImageFormat.Jpeg);
            byte[] Thumb = thumbstream.ToArray();
            //// copy thumbnail into byte array
            //for (i = 0; i < Thumb.Length; i++) Thumb[i] = (byte)Thumb[i];
            #endregion Turn bitmap into an array of bytes
 
 
            #region Read JPG from HDD - it was saved with no EXIF
            Image TempImage = Image.FromFile(Filename);
            Pic = (Bitmap)TempImage.Clone();
            TempImage.Dispose();
            #endregion Read JPG from HDD - it was saved with no EXIF
 
 
            #region If comment this out then the final image saves fine, but with no built-in thumbnail
            //put the new Thumbnail into the right property item
            PropertyItems = Pic.PropertyItems;
            //PropertyItems[0].Id = 0x010e; // 0x010e as specified in EXIF standard for DESCRIPTION
            PropertyItems[0].Id = 20507;// Every example uses this as the READ location for EXIF thumbnail.
            //PropertyItems[0].Type = 1; // 1 = Array of bytes
            PropertyItems[0].Type = 6; // 6 = Array of bytes that can hold any data type
            PropertyItems[0].Len = Thumb.Length;
            PropertyItems[0].Value = Thumb;
            Pic.SetPropertyItem(PropertyItems[0]);
            #endregion If comment this out then the final image saves fine, but with no built-in thumbnail
 
 
            // we cannot store in the same image, so use a temporary image instead
            FilenameTemp = Filename + ".temp";
            try
            {
                using (EncoderParameter qualityParam = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, (long)70))
                {// Encoder parameter for image quality
 
 
                    // Jpeg image codec
                    ImageCodecInfo jpegCodec = getEncoderInfo("image/jpeg");
 
                    if (jpegCodec == null)
                        return;
                    EncoderParameters encoderParams = new EncoderParameters(1);
                    encoderParams.Param[0] = qualityParam;
 
                    Pic.Save(FilenameTemp, jpegCodec, encoderParams);
 
                }
 
            }
            catch (Exception emg)
            {
                Console.WriteLine("EXIF #####################################################");
                Console.WriteLine(emg.Message);
                Console.WriteLine(emg.StackTrace);
            }
 
 
            return;
}

Of course error messages that don't tell you much don't help either.
Yippee, a generic error - let me track that right down.

A generic error occurred in GDI+.
   at System.Drawing.Image.Save(String filename, ImageCodecInfo encoder, EncoderParameters encoderParams)
   at WriteNewThumbnailInImage(String Filename, Bitmap NewThumbnail)
[...]
A first chance exception of type 'System.Runtime.InteropServices.ExternalException' occurred in System.Drawing.dll
The thread 0x15dc has exited with code 0 (0x0).

[tlhintoq]

I finally found an explanatin of property ID and propety type to use for. The EXIF 2.2 specification PDF. Imagine that. But geez these guys went out of the way to make that document hard to understand and still lacks a great deal of practical info.

ThumbnailCompre ssion according to the spec is merely set to 1 if not and 6 if jpg compression. No other description about it.

Right now I've gotten this to read and write JPEG thumbnail into EXIF data of a JPEG image. Hurray! The only part I am hesitant about is that it isn't in the property that I have always seen used for thumbnails: 20507. What is working is working in property 34675. The exact same code that works into 34675 does not work if I change the ID to 20507 and re-run it. Totally weird. By the way, no other property had to be set to anything. 34675 will accept the byte[] from Image.save(memo rystream). Which makes sense as the saved memory stream contains all the info needed to read and translate a compressed JPG.

[Plater]

Wierd, 34675 I have listed as PropertyTagICCP rofile

[tlhintoq]

yah... Exactly what I'm saying. It's weird, but it works. Right now this is intended for an in-house proprietary set of applications. So as long as application 'a' can find the thumb where application 'b' puts it, then all is good. But in the long run I would like to do it *right* and have things compatible with all other applications that actually follow industry standards.

[tlhintoq]

Ok. Finally got this working. Little tidbit that is hard to find: The maximum size allowed is 160x160 and must be in the same aspect ratio as the full size image.

#region Create a new standard thumbnail property.
//Max of 160x160 in same aspect ratio as main image
Image SmallThumb = tlhintoq.GDI.Graphics.CalculatedThumbnail(NewThumbnail, 160, 160);
MemoryStream MS = new MemoryStream();
SmallThumb.Save(MS, ImageFormat.Jpeg);
SmallThumb.Dispose();
MS.Position = 0;
byte[] smallthumbbytes = MS.ToArray();
 
PropertyItems = Pic.PropertyItems;
PropertyItems[0].Id = 0x501b; // PropertyTage ThumbnailData
PropertyItems[0].Type = 1;
PropertyItems[0].Len = smallthumbbytes.Length;
PropertyItems[0].Value = smallthumbbytes;
Pic.SetPropertyItem(PropertyItems[0]);
 
#region Create a new Thumbnail Compression property.
PropertyItems = Pic.PropertyItems;
PropertyItems[0].Id = 0x5023; // PropertyTagThumbnailCompression
PropertyItems[0].Type = (short)ImagePropertyTagValueTypes.ArrayOfUnisignedShort3;
PropertyItems[0].Len = 2;
PropertyItems[0].Value = new byte[] { 6, 0 };
Pic.SetPropertyItem(PropertyItems[0]);
#endregion

[Plater]

So now your thumbnails will be read by windows in the file explorer yes?

[tlhintoq]

They seem to be. SInce Windows7 tries to build new thumbs even if there is no EXIF included, then stick them in the thumbsdb I can only go by the speed. But it seems to be working.

I guess I should dig up a program that is known to load the industry standard thumb and display it.