Re: Preserving thumbnail metadata - C# Discussion Boards

5-Jun-02 6:14

If I examine the propertyItems of a jpg file that was created using my digital camera I see that there is thumbnail related metadata. I have not been able to preserve the thumbnail data when using Image.Save(). Some metadata is preserved, but the thumbnail data is lost. Does anyone know what it takes to preserve the thumbnail metadata?

David

James T. Johnson5-Jun-02 12:59

5-Jun-02 12:59

Could you e-mail such a jpg to me?

I can only guess without one.

James

dsweet6-Jun-02 5:22

6-Jun-02 5:22

I emailed one to you this morning.
Let me know what you find.
Thanks. Smile | :)

James T. Johnson6-Jun-02 5:20

6-Jun-02 5:20

Yep, I got it this morning; I was very busy up until a few minutes ago so I just started looking in to it.

James

James T. Johnson6-Jun-02 5:50

6-Jun-02 5:50

I'm not getting that behavior at all.

If I open the image then save it the thumbnail data is preserved.

Just a guess, but perhaps some operation you are performing is creating a new image; and when you save the jpg it creates the other metadata; but not the thumbnail.

James

dsweet6-Jun-02 6:51

6-Jun-02 6:51

Interesting.

You found a propertyitem id indicating thumbnail data on the saved image?

The code is at home and I am at work so I can't give you more details until later. But I don't think there was much to it. It was something like:
Image myImage = Image.LoadFromFile("test.jpg");
myImage.Save("test_new.jpg"); and myImage.Save("test_new.jpg",ImageFormat.jpeg);

Both calls lost the propertyid items related to thumbnails.

I can post the exact code tonight.

David

James T. Johnson6-Jun-02 7:00

6-Jun-02 7:00

dsweet wrote:
You found a propertyitem id indicating thumbnail data on the saved image?

Yep, I've uploaded the source to my test program. It has no error checking, so you need to follow the order correctly Smile | :)

First load the image, then load the attributes; double click on the thumbnail data (has ~4K of data with it) to view the thumbnail; then click save to have it save the image as C:\test2.jpg.

Here is a test image to use for it if you don't have one with thumbnails...test.JPG (820.8 Kb)

James

dsweet6-Jun-02 7:22

6-Jun-02 7:22

Thanks a lot! I will run it on my PC tonight and see if I get the same results.

David

dsweet6-Jun-02 13:50

6-Jun-02 13:50

Bad News (for me).
The code you sent me did not produce the same results.
After saving test2.jpg and then reloading it, the tag (20507) was gone!
Do I need a new version or something?

Help-About states that I have .net framework 1.0.3705. What are you using?

David

James T. Johnson6-Jun-02 13:56

Call for help - Re: Preserving thumbnail metadata

6-Jun-02 13:56

Wow, this is too weird.... What OS are you on?

I'm running XP Pro with all the latest updates. I'll try my 2k server box in a second.

James

James T. Johnson6-Jun-02 14:01

Re: Call for help - Re: Preserving thumbnail metadata

6-Jun-02 14:01

Ok, just tried it on my 2k box and it is missing the thumbnail data. I think this qualifies for bug material.

Can anyone confirm what happens on 98/ME/NT4/XP Home? Follow the directions in this post.

James

dsweet6-Jun-02 14:22

Re: Call for help - Re: Preserving thumbnail metadata

6-Jun-02 14:22

Running winver I get :windows 2000 ver 5.0(build 2195: Service Pack 2)
.net framework: ver 1.0.3705.
No thumbnails. Cry | :((

dsweet7-Jun-02 7:13

7-Jun-02 7:13

On NT 4.0 sp6a there are no thumbnails either.

James T. Johnson10-Jun-02 8:58

10-Jun-02 8:58

Erick Ellis (MS) suggested installing this QFE.

Backup the gdiplus.dll in your %WINDIR%\Microsoft.NET\v1.0.3705\.

Now since the QFE is made for Windows XP you'll need to use Winzip to extract the files. Then place the new gdiplus.dll in the v1.0.3705 directory.

I'm hoping this is just a temporary fix until the updated gdiplus.dll is included with .NET SP2.

James

dsweet11-Jun-02 4:12

Converting from DateTime to UInt32 and back

11-Jun-02 4:12

That worked on my NT system here at work.

Thanks for your help.

David

5-Jun-02 5:19

I'm not sure why these functions were not included in the .NET release, they seem pretty important to me. They may be posted elsewhere, but I couldn't find them. I coded up these two functions (in C#), which I think should be public knowledge and this is the best place I could think of to post them. If you have any feedback, please reply.

---

// Time as represented by 32 (unsigned) bits is generally
// the number of seconds since midnight 01/01/1900.

// 1 tick = 100 nanoseconds ... 1 second = 10,000,000 ticks

static void ConvertInt32ToDateTime(UInt32 time32Bit, out DateTime time64bit)
{
// Convert an UInt32 representing seconds to an
// Int64 representing Timespan ticks

Int64 tempTimeSpan = Convert.ToInt64(time32Bit) * 10000000;
TimeSpan time32BitAsTimeSpan = new TimeSpan(tempTimeSpan);

DateTime baseTime32Bit = new DateTime(1900, 1, 1, 0, 0, 0);
time64bit = baseTime32Bit + time32BitAsTimeSpan;
}

static void ConvertDateTimeToInt32(DateTime time64bit, out UInt32 time32Bit)
{
DateTime baseTime32Bit = new DateTime(1900, 1, 1, 0, 0, 0);
TimeSpan time32BitAsTimeSpan = time64bit - baseTime32Bit;

time32Bit = Convert.ToUInt32(time32BitAsTimeSpan.TotalSeconds);
}

---

Thanks.

-Michael M

File Read in C#

Member 169775-Jun-02 1:33

Member 16977

5-Jun-02 1:33

Hi,
This may be very easy question but i am new to c#.
I want to read the file from start to end line by line,my code is:

FileStream myFileStream = new FileStream("temp.txt" , FileMode.Open , FileAccess.Read);

myFileStream.Seek(0, SeekOrigin.Begin);
StreamReader myReader = new StreamReader(myFileStream);
while(??)
{
myReader.ReadLine();
}

What is the equivalent of EOF here.I want to read each line upto the End of File is reached,how should i do that?

Thanx n Regards
Tushar

Mazdak5-Jun-02 2:32

Mazdak

5-Jun-02 2:32

I've not test this,but I think thats what you want.(its from MSDN)

StreamReader srReadLine = new StreamReader(
   (System.IO.Stream)File.OpenRead("C:\\Temp\\Test.txt"),
System.Text.Encoding.ASCII);
srReadLine.BaseStream.Seek(0, SeekOrigin.Begin);
while (srReadLine.Peek() > -1) {
   Console.WriteLine(srReadLine.ReadLine());
}
srReadLine.Close();

Mazy

"The more I search, the more my need
For you,
The more I bless, the more I bleed
For you."The Outlaw Torn-Metallica

Rickard Andersson²⁰5-Jun-02 2:47

Rickard Andersson²⁰

5-Jun-02 2:47

Tushar mahajan wrote:
while(??)
{
myReader.ReadLine();
}

change that code to:

string line = "";
while(line != null)
{
    if(line != null)
    {
       line = myReader.ReadLine();
    }
}

When you reach the end of file ReadLine retunrns null

Rickard Andersson@Suza Computing
C# and C++ programmer from SWEDEN!
UIN: 50302279
E-Mail: nikado@pc.nu
Speciality: I love C# and C++!

Daniel Turini5-Jun-02 15:10

Daniel Turini

5-Jun-02 15:10

Isn't the if (line != null) superfluous ?

Crivo
Automated Credit Assessment

Rickard Andersson²⁰5-Jun-02 21:35

Rickard Andersson²⁰

5-Jun-02 21:35

Nope, It will throw an exception if you don't check line if it's null.

Rickard Andersson@Suza Computing
C# and C++ programmer from SWEDEN!
UIN: 50302279
E-Mail: nikado@pc.nu
Speciality: I love C# and C++!

Daniel Turini5-Jun-02 22:33

Daniel Turini

5-Jun-02 22:33

That's not true. Probably, what you whant is this:

string line = "";
while(line != null)
{
    line = myReader.ReadLine();    
    if(line != null)
    {
        // Do something useful with line
    }
}

Crivo
Automated Credit Assessment

Rickard Andersson²⁰5-Jun-02 22:57

Rickard Andersson²⁰

5-Jun-02 22:57

Ofcourse will ReadLine not be inside the if statement!! Blush | :O

I did a little misstake there! Big Grin | :-D

Rickard Andersson@Suza Computing
C# and C++ programmer from SWEDEN!
UIN: 50302279
E-Mail: nikado@pc.nu
Speciality: I love C# and C++!