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).

[Plater]

I have never been able to modify/add PropertyItems to a Bitmap in .NET
I was just thinking about asking the other day if anyone knew how.
I always get the GDI+ error.


The thumbnail thing in particular I find interesting as I have some images whos thumbnails have no relation to the actual image. Which makes it very confusing.


Just looked up the constants, I think you need to supply more then just thumbnail data:
(From my ENUM)

PropertyTagThumbnailFormat = 0x5012,
            PropertyTagThumbnailWidth = 0x5013,
            PropertyTagThumbnailHeight = 0x5014,
            PropertyTagThumbnailColorDepth = 0x5015,
            PropertyTagThumbnailPlanes = 0x5016,
            PropertyTagThumbnailRawBytes = 0x5017,
            PropertyTagThumbnailSize = 0x5018,
            PropertyTagThumbnailCompressedSize = 0x5019,
            PropertyTagColorTransferFunction = 0x501A,
            PropertyTagThumbnailData = 0x501B,
            PropertyTagThumbnailImageWidth = 0x5020,
            PropertyTagThumbnailImageHeight = 0x5021,
            PropertyTagThumbnailBitsPerSample = 0x5022,
            PropertyTagThumbnailCompression = 0x5023,
            PropertyTagThumbnailPhotometricInterp = 0x5024,
            PropertyTagThumbnailImageDescription = 0x5025,
            PropertyTagThumbnailEquipMake = 0x5026,
            PropertyTagThumbnailEquipModel = 0x5027,
            PropertyTagThumbnailStripOffsets = 0x5028,
            PropertyTagThumbnailOrientation = 0x5029,
            PropertyTagThumbnailSamplesPerPixel = 0x502A,
            PropertyTagThumbnailRowsPerStrip = 0x502B,
            PropertyTagThumbnailStripBytesCount = 0x502C,
            PropertyTagThumbnailResolutionX = 0x502D,
            PropertyTagThumbnailResolutionY = 0x502E,
            PropertyTagThumbnailPlanarConfig = 0x502F,
            PropertyTagThumbnailResolutionUnit = 0x5030,
            PropertyTagThumbnailTransferFunction = 0x5031,
            PropertyTagThumbnailSoftwareUsed = 0x5032,
            PropertyTagThumbnailDateTime = 0x5033,
            PropertyTagThumbnailArtist = 0x5034,
            PropertyTagThumbnailWhitePoint = 0x5035,
            PropertyTagThumbnailPrimaryChromaticities = 0x5036,
            PropertyTagThumbnailYCbCrCoefficients = 0x5037,
            PropertyTagThumbnailYCbCrSubsampling = 0x5038,
            PropertyTagThumbnailYCbCrPositioning = 0x5039,
            PropertyTagThumbnailRefBlackWhite = 0x503A,
            PropertyTagThumbnailCopyRight = 0x503B,
 

[tlhintoq]

Just looked up the constants, I think you need to supply more then just thumbnail data:
(From my ENUM)

Yeah... I was kinda trying to bury my head in the sand about all of those.
I know many are optional, just as they are optional in the primary image the EXIF is a part of. EquipMake, EquipModel, Artist and so on.

Since I can read an exif thumbnail without having to look up any of the other properties I was expecting to be able to write it without any of the other properties.

Property 20507 (0x501B) is ThumnailData, which is all I use to get the EXIF thumbnail.

Hmm... I'm just out of ideas. I guess I'll walk away from this issue for a day then attack it fresh.

[Plater]

Well you might be able to read the byte[] in thumbnailData, but something else has to go on to know the dimensions of the bitmap for reconstruction right?

[tlhintoq]

The byte array created is the image saved to a memory stream. So it is a complete image including the file header, size, color depth etc, just as if it were a file saved to disk.

Then you read the complete byte array back, and turn it into an image again by reading the byte array from memory stream just as if reading from disc.

I'm still working the problem... slowly gaining on it. Though I am about to gain on it with my AR-15

[GaryTexmo]

@tlhintoq
Off topic, but...

I know I certainly feel like that some days, especially with my current work project. *sigh*

:)

[tlhintoq]

So after a day of beating on it I've made some progress. At this point I can successfully put a BMP in as a thumbnail and retrieve it. But not a jpg. And not to the property number that I have alway seen documented as the thumbnail property. (But it is the property number used by Apple's iPhoto for the thumbnail which I would have expected to follow industry specification since they helped design it)

Here's what I have learned so far:
You can add properties and give them values. The values will be seen and not show an error, but apparantly if they are not formed in a way that is expected for EXIF they won't be written and you won't get any error messages most times. Take this example. I added what I thought would be the thumbnail and a another property for 'description'. They can be seen pre-write to the HDD but when read back the description is still present but the thumbnail was not.

I can't find any documentation on how exactly to format the data for each property, or when one 'type' is used over another. "A property type of 1 is an array of bytes. A property type of 6 is an array of bytes that can be used for any purpose."

In this case the Compression tag value is set to "6" and tags in the 1st IFD (JPEGInterchangeFormat,
JPEGInterchangeFormatLength) are used to designate the location and size.

But the specifications document doesn't tell you if it should be a type 2 ascii "6", or a type 1 byte with a value of 6, or a type 6 byte of 6, or an int of 6 converted to a byte array.

So what I did was export a JPEG out of Apple's iPhoto with all the descriptions and other fields set to something. This gave me a total of 41 properties in the EXIF of the JPG. Now it's just a matter of reverse engineering what they do. But at least I have them, with their types and lengths and values. This will be my Rosetta Stone.

[Plater]

Have you checked out the msdn sections on exif? They seemed to be incomplete(possibly just old?) as I found another reference with an extra 100 or so id tag types.
I have enums for both the tagIDs and the value types

For value types, including the brief description of it

private enum ImagePropertyTagValueTypes
        {
            ArrayOfBytes=1,
            ASCIIString=2,//If you set the type data member to ASCII type, you should set the Len property to the length of the string including the null terminator. For example, the string "Hello" would have a length of 6.
            ArrayOfUnisignedShort=3,//16bit ints
            ArrayOfUnisignedLong=4,//32bit ints
            ArrayOfPairUnsignedLong=5,//(64bits) Each pair represents a fraction; the first integer is the numerator and the second integer is the denominator.
            ArrayOfObjectBytes=6,//bytes that can hold values of any data type.
            ArrayOfSignedLong=7,//32bit ints
            ArrayOfPairSignedLong=10,//(64bits) Each pair represents a fraction; the first integer is the numerator and the second integer is the denominator.
        }
 

[tlhintoq]

I have a very similar list from the MSDN page

        /// <remarks>             
        /// * Additionally, this MSDN page details more information, specifically that 
        ///     * JPEG images must have a width and height in multiples of 16 in order to have 
        ///     * completely "lossless" rotation:
        ///http://msdn.microsoft.com/library/default.asp?url=/library/en-us/gdicpp/GDIPlus/usingGDIPlus/usingimageencodersanddecoders/transformingajpegimagewithoutlossofinformation.asp
        ///The following table shows integers and the types they represent.
        ///1-Specifies that Value is an array of bytes.
        ///2-Specifies that Value is a null-terminated ASCII string. If you set the type data member to ASCII type, you should set the Len ///property to the length of the string including the null terminator. For example, the string "Hello" would have a length of 6.
        ///3-Specifies that Value is an array of unsigned short (16-bit) integers.
        ///4-Specifies that Value is an array of unsigned long (32-bit) integers.
        ///5-Specifies that Value data member is an array of pairs of unsigned long integers. Each pair represents a fraction; the first integer is the numerator and the second integer is the denominator.
        ///6-Specifies that Value is an array of bytes that can hold values of any data type.
        ///7-Specifies that Value is an array of signed long (32-bit) integers.
        ///10-Specifies that Value is an array of pairs of signed long integers. Each pair represents a fraction; the first integer is the numerator and the second integer is the denominator.
        ///For more information about property tags, see "Image Property Tag Constants" in the MSDN library at http://msdn.microsoft.com/library.
        ///</remarks>
 

But I like how your enum better spells out the intended use for each type.
Though I am still a little fuzzy how how they are differentiating their needs and uses. Based on the magic disappearing property experience I mentioned earlier I can only conclude that some validation is taking place before writing *based* on the type specified. No error gets returned if there is a problem: Just that the property doesn't get written into the file.

So I still wonder is there any documentation on when to use a given type for a given property? I mean, bytes are bytes: They hold values between 0-255.
So what makes type 1 bytes different from type 6 bytes. How are we supposed to know that if the property is a ThumbnailData you have to use type 6 bytes instead of type 1 bytes.

For the ThumbnailCompression property you are supposed to assign a value of "6". Ok, but in why type or manner?
I can write a 6 as an ASCII "6", that would be a type 1 string.
I can write a 6 as a short(3), long(4),ulong(7), or just a byte of value 6 would could be type 1 or type 6.

Through a lot of trial and error I was able to reverse engineer how to put in a non-compressed thumbnail in bitmap format. But it makes s 230kb jpg file into a 1,439 kb file. The uncompressed thumbnail data is actually larger than the compressed image.

A lot more trial and error and I will eventually have the magic combination for using a jpeg thumbnail inside a jpeg image. It just bothers me that I have to spend 2 days sussing this out when there should be rules and documentation available to developers for these types of things.

[Plater]

I understood type 6 to mean it was a serialization of an object
(Such as perhaps an "enum" as I would assume the ThumbnailCompression Property is)

[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.

ThumbnailCompression 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(memorystream). 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 PropertyTagICCProfile

[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.