GdPicture.NET.14~GdPicture14.GdPictureImaging~TagGetValueBytes - TagGetValueBytes Method (GdPictureImaging) -

public int TagGetValueBytes( 
   int ImageID,
   int TagNo,
   ref byte[] Data
)

public function TagGetValueBytes( 
    ImageID: Integer;
    TagNo: Integer;
   var  Data: Bytearray of
): Integer;

public function TagGetValueBytes( 
   ImageID : int,
   TagNo : int,
   Data : byte[]
) : int;

public: int TagGetValueBytes( 
   int ImageID,
   int TagNo,
   ref byte[]* Data
)

public:
int TagGetValueBytes( 
   int ImageID,
   int TagNo,
   array<byte>^% Data
)

'Declaration
 
Public Function TagGetValueBytes( _
   ByVal ImageID As Integer, _
   ByVal TagNo As Integer, _
   ByRef Data() As Byte _
) As Integer

Parameters

ImageID: GdPicture image identifier.
TagNo: Must be a value between 1 and the number of tags attached to a GdPicture image.
Data: Output parameter. Array where the tag value data will be stored.

Return Value

The length of the Data array.

Reading gps coordinates from the tags of a jpeg image.

C#

using (GdPictureImaging gdpictureImaging = new GdPictureImaging())
{
    int imageID = gdpictureImaging.CreateGdPictureImageFromFile("image.jpg", false);
 
    // Walk the list of tags to gather the gps coordinates.
 
    StringBuilder report = new StringBuilder();
    int tagCount = gdpictureImaging.TagCount(imageID);
 
    for (int tagNo = 1; tagNo <= tagCount; tagNo++)
    {
        Tags tag = gdpictureImaging.TagGetID(imageID, tagNo);
        switch (tag)
        {
            case Tags.TagGpsLatitudeRef:
                report.Append("LatitudeRef: ");
                report.AppendLine(gdpictureImaging.TagGetValueString(imageID, tagNo));
                break;
 
            case Tags.TagGpsLongitudeRef:
                report.Append("LongitudeRef: ");
                report.AppendLine(gdpictureImaging.TagGetValueString(imageID, tagNo));
                break;
 
            case Tags.TagGpsLatitude:
            case Tags.TagGpsLongitude:
                StringBuilder coordinate = new StringBuilder();
                if (gdpictureImaging.TagGetType(imageID, tagNo) == TagType.TagTypeRational)
                {
                    // Read the rationals for the coordinate, usually 3 floatting values, 8 bytes per value.
 
                    int dataLength = gdpictureImaging.TagGetLength(imageID, tagNo);
                    byte[] data = new byte[dataLength];
                    gdpictureImaging.TagGetValueBytes(imageID, tagNo, ref data);
 
                    int rationalsCount = dataLength / 8;
                    int readIndex = 0;
                    for (int rationalIndex = 0; rationalIndex < rationalsCount; rationalIndex++)
                    {
                        uint numerator = System.BitConverter.ToUInt32(data, readIndex);
                        uint denominator = System.BitConverter.ToUInt32(data, readIndex + 4);
                        double value = (double)numerator / (double)denominator;
                        coordinate.Append(value.ToString());
                        coordinate.Append(" ");
                        readIndex += 8;
                    }
                }
                else
                {
                    coordinate.Append(gdpictureImaging.TagGetValueString(imageID, tagNo));
                }
 
                report.Append(tag.ToString() + ": ");
                report.AppendLine(coordinate.ToString());
                break;
 
            default:
                break;
        }
    }
 
    gdpictureImaging.ReleaseGdPictureImage(imageID);
    MessageBox.Show(report.ToString(), "Coordinates", MessageBoxButtons.OK, MessageBoxIcon.Information);
}

Reference

GdPictureImaging Class
GdPictureImaging Members
TagCount Method
TagSetValueBytes Method