C # Image Processing: Obtain the EXIF information of a digital photo (2)

Let's talk about an instance. We will discuss some common exifpropertytagids and learn how to get their values. Remember that msdn is a good resource.

Open a picture of me and scan each EXIF property item as described last time.
The ID of the first item is 0x010f. Check msdn and find that it is "null-terminated character string that specifies the manufacturer of the equipment used to record the image.". It turns out to be the camera manufacturer. Again, type = 2. Well, there is no conflict. Call the function for resolving type = 2:
Private Static string getvalueoftype2 (byte [] B)
{
Return System. Text. encoding. ASCII. getstring (B );
}

The following text is obtained:
Eastman Kodak Company

Yes, I am Kodak. Continue to look down, the second item ID is 0x0110, the old rule msdn, found to be "null-terminated character string that specifies the model name or model number of the equipment used to record the image. ". It turns out to be a model. Type or 2. Continue to call the function. The result is:
Kodak z7590 zoom digital camera
Completely correct.

Next, we can see that the type of ID = 0x8827 (ISO speed) is 3. Check msdn to find that it is a 16-bit unsigned integer. Place the value [1] to the left before the value [0.
Private Static string getvalueoftype3 (byte [] B)
{
F (B. length! = 2) Return "invalid type (3 )";
Return convert. touint16 (B [1] <8 | B [0]). tostring ();
}
My value is 80. That's right. 0xa002 and 0xa003 describe the original size of the image together and can also be obtained using this method.

Type = 4 and type = 3 are similar, except that type = 4 represents a 32-bit unsigned integer.
Private Static string getvalueoftype4 (byte [] B)
{
If (B. length! = 4) Return "invalid type (4 )";
Return convert. touint32 (B [3] <24 | B [2] <16 | B [1] <8 | B [0]). tostring ();
}
Example: Id = 0x0202 (JPEG inter length)

Type = 5, for example, the exposure time (0x829a ).
This type contains two unsigned long integer numbers. But it is not difficult to handle it. Divide 8 bytes into two parts. value [0 ~ 3] is the denominator, value [4 ~ 7] is a molecule. But don't forget to shift.
Private Static string getvalueoftype5 (byte [] B)
{
If (B. length! = 8) Return "invalid type (5 )";

Uint32 FM, Fz;
Fm = 0;
FZ = 0;

FZ = convert. touint32 (B [7] <24 | B [6] <16 | B [5] <8 | B [4]);
Fm = convert. touint32 (B [3] <24 | B [2] <16 | B [1] <8 | B [0]);

Return FM. tostring () + "/" + FZ. tostring ();
}
The exposure time of my sample photo is 1/500. Commonly used IDs of the same type include 0x829d (F-number), 0x011a, 0x011b (representing the resolution in the x/y direction respectively), and 0x9202 (Lens Aperture.

Type = 7 is messy. At least my Kodak images cannot be decoded in a uniform way. 0x9000 (EXIF version), 0xa000 (EXIF fpx version) can be calculated as follows:
Private Static string getvalueoftype7a (byte [] B)
{
String RTN = "";

For (INT I = 0; I <B. length; I ++)
{

RTN + = (char) B [I]). tostring ();

}

Return RTN;
}

But 0x9101 (EXIF compression configuration) needs to be decoded so that it is correct:
Private Static string getvalueoftype7b (byte [] B)
{
String RTN = "";

For (INT I = 0; I <B. length; I ++)
{

RTN + = B [I]. tostring ();

}

Return RTN;
}

Don't understand. Please let me know.

Finally, let's take a look at type 10. In fact, it is similar to type 5, except that type 10 is signed, so there is not much here.